text:
Renewable Energy - The Facts
Manuel Adrio González
saveSave Renewable Energy - The Facts For Later
Dieter Seifried and Walter Witzel
Renewable Energy – The Facts
London • Washington, DC
First published in 2010 by Earthscan
Copyright © Energieagentur Regio Freiburg Gmbh 2010
Original German version published as: Walter Witzel and Dieter Seifried (2007) Das Solarbuch. Fakten, Argumente und Strategien für den Klimaschutz, 3rd edition, Ökobuch Verlag.
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ISBN: 978-1-84971-159-3 hardback ISBN: 978-1-84971-160-9 paperback
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Seifried, Dieter. Renewable energy : the facts / Dieter Seifried and Walter Witzel. p. cm. Includes bibliographical references and index. ISBN 978-1-84971-159-3 (hardback) – ISBN 978-1-84971-160-9 (pbk.) 1. Renewable energy sources. I. Witzel, Walter. II Title.
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Foreword by Rainer Griesshammer
New Paths to the Future by Luiz Ramalho
Our climate is at stake
The inevitable fight for limited oil reserves
Addiction to energy imports
Nuclear energy is not an alternative
Renewables are the way of the future
We have enough sun
Scenario for the solar future
The solar strategy requires conservation
Cogeneration – an indispensable part of our energy transition
Liberalization of the German energy market
Solar collectors
Hot water from the sun
Solar heating in district heating networks
Cooling with the sun
Solar drying – air collectors
Solar Electric: Photovoltaics
The heart of a PV array – the solar cell
Grid-connected PV arrays
Off-grid PV arrays
Solar energy as part of sustainable development
The outlook for PV – lower costs from new technologies and mass production
Solar Architecture
A third of the pie – space heating
Passive solar energy
The solar optimization of urban planning
Solar thermal and PV in renovation
The wall as a heater – transparent insulation
Homes without heaters – passive houses
The off-grid solar house – a model for the Solar Age?
Plus-energy houses
Fields and forests as solar collectors
Biogas cogeneration units
Wood as a source of energy
District heating networks with woodchip systems
Fuel from the field – biodiesel
Fuel from the plantation – ethanol
Synthetic fuels (BTL)
Is there enough land for biofuels?
Wind power comes of age
Wind power and nature conservation
Wind velocity is key
The success story of wind power since the 1990s
The success story of wind power – the advantage of being first
Wind power worldwide
Wind power prospects – offshore turbines
Wind power prospects – less is more through repowering
Water Power, Geothermal and Other Perspectives
Water power – the largest source of renewable energy
Expanding hydropower – the example of Germany
Hydropower and nature conservation
The world's largest hydropower plants
Geothermal worldwide
Underground heat
Hot dry rock – power from underground
Other possible sources of renewable energy
New Energy Technologies
Solar hydrogen
How fuel cells work
Stationary fuel cells
Fuel cells in mobile applications
Current Use and Potential
The potential in Germany
The future has already begun in Germany
EU votes for renewables
Expanding renewables in the EU
Renewables worldwide
A long-term solar scenario for Germany
The 100 per cent target
What do we do when the sun isn't shining?
How can we store large amounts of electricity?
Can carbon emissions not be avoided less expensively?
What is the energy payback?
Are renewables job killers?
Is the Solar Age the end of power monopolies?
Promoting Renewable Energy
Research funding – not much money for the sun
Start-up financing is needed
Internalizing external costs
Ecological taxation reform – protecting jobs and the environment
Ecological taxation reform in increments
Investment bonuses for solar thermal systems
Solar energy in rental apartments – a problem child
Compensation for solar power with a return on investment
From the Feed-in Act to the Renewable Energy Act (EEG)
The Renewable Energy Act (EEG)
The EEG as a model for other countries
Photovoltaic arrays as a 'blight' on the landscape
Quotas and requests for proposals
Solar thermal arrays required on new buildings
Feed-in tariffs for heat in Germany?
A cornucopia of instruments
Phasing out nuclear
Renewable energy here and in the developing world
Good Marketing – Successful Projects
Everyone loves the sun
'Green electricity'
Not everyone owns the roof over their head – community solar arrays
Solar brokers
Service brings in new customers for all-in-one packages
Investing in climate protection
Utilizing new leeway
Using new technologies
Oil reserves: The gap between new discoveries and production widens
Global oil and gas reserves (2005) are restricted to a few regions
Nuclear power is not an option
The sun is the future
We have enough sun: The land needed for a 100 per cent solar energy supply
The Institute of Applied Ecology's Energy Transition study (1980): Growth and prosperity without oil and uranium
Solar strategy requires energy conservation
Cogeneration: An indispensible part of our energy tradition
Rising power prices: Profits at the expense of households and small consumers
The economic benefits of energy efficiency and renewables
Design of flat-plate collectors
Solar thermal with long-term heat storage
(1) Solar drying: How air collectors work
(2) Solar drying: Solar tunnel dryer for agricultural products
The heart of a photovoltaic array: The silicon solar cell
Grid-connected photovoltaic arrays
Off-grid photovoltaic arrays
A Cuban village school with solar power
Prospects for photovoltaics: Lower costs from new technologies and mass production
Space heating: A comparison of key energy figures in various building standards
Passive solar energy: South-facing windows and roof overhangs instead of heaters and air conditioners
Solar optimization of urban planning
Solar arrays as a component of renovation: Reducing energy consumption with and without solar arrays
Walls as heaters: Transparent insulation
Homes without heaters: Passive houses
The Energy-Autonomous Solar House, Freiburg, Germany
Plus-energy homes
Forests and fields as solar collectors: The many ways of using biomass
Diagram of a biomass unit
Biogas cogeneration unit lowers CO 2 by offsetting other CO 2 -intensive generation sources
Getting energy from wood
District heating systems with woodchip heaters: A comparison on emissions
The potential energy yield of different energy crops in Germany
A comparison of alternative fuels and conventional systems
The energy payback of various fuels
How much a hectare can produce
Fuels from biomass take up a lot of land
Wind power takes off: The performance of wind turbines increases
Wind power and landscape conservation
Wind velocity is crucial
The success story of wind power: Trends in Germany since the 1990s
The success story of wind power: The importance of being a first mover
The installed capacity of wind turbines worldwide
Tremendous potential for offshore wind
Repowering: Less is more
Water power: Global potential, used and untapped
Hydropower in Germany
Hydropower and nature conservation: Fish bypasses
Giant hydropower: The Three Gorges Dam in China
Geothermal: Installed capacity of a select group of countries
Geothermal heat: How a hydro geothermal heat plant works
Power from hard rock: How the hot-dry-rock method works
(1) New power plant technologies: Solar chimneys
(2) New power plant technologies: Seaflow
The efficiency of fuel cells for domestic power
Mobile applications: Will hydrogen fuel cells help the climate?
Technical potential of renewables in Germany and ecologically optimized scenario
Germany, the transition has begun: Power and heat from renewables
The EU's dependence on energy imports is growing
Expanding renewables in Europe: Power generation in EU-15
A long-term scenario for Germany: Renewables as a part of primary energy consumption
Bioenergy village of Jühnde: 100 per cent biomass
What do you do when the sun isn't shining? Annual solar and wind patterns
How much energy can be stored? Energy storage with compressed air systems
Can CO 2 be offset less expensively in some other way? CO 2 avoidance costs (in euros per ton)
Comparison of service life with energy payback
85,000 wind power jobs
The Solar Age: The end of power monopolies? The share of private power generators as of 2004 in Germany
Federal funding for energy research in Germany
Annual subsidies in the energy sector
External costs of nuclear energy
How ecological tax reform works
Eco-taxes reduce start-up financing for renewable energy
Upfront bonuses for solar thermal more effective than loans
The problem child: Solar energy for tenants
Feed-in rates for solar power get photovoltaics started in Germany
From the Feed-in Act to the Renewable Energy Act
The Renewable Energy Act: Feed-in rates for new systems connected to the grid in 2007
German feed-in rates abroad: Countries with feed-in rates for renewable electricity
Solar on disused land
Quota systems and feed in rates: Which is more effective?
The success of mandatory solar arrays in Barcelona
Proposal for feed-in rates for Germany: Heat providers receive bonus for environmental service
How emissions trading works
How the Clean Development Mechanism works: An example
Using different policy instruments
Renewables for off-grid applications
Public support for renewables
Green power from utilities
Community projects for solar power
Solar brokers: The example of Zürich
Service wins over new customers: All-in-one packages
Climate protection as a good investment
Renovation of Willibrord School as a community project: Carbon emissions were reduced by 85 per cent 2005
Solar lamps replace oil lamps: Benefits for people, environment and climate
There are dark clouds on the horizon. Climate change – long researched, discussed and denied – is increasingly making its pres- ence felt. Drawn up by more than 2000 climate researchers from around the globe, the International Panel on Climate Change's (IPCC) 2007 report has a clear message: the Earth will inevitably heat up by more than 2°C above the temperature of the preindus- trial age. Additional warming would have enormous consequences for mankind and the environment, and a global economic crisis can only be avoided if the global community works closely together.
'The time for half measures is over', former French President Jacques Chirac once said, commenting on the challenges of climate protection. 'It is time for a revolution – an awareness revolution, an economic revolu- tion, and a revolution of political action.'
Unlike the three industrial revolutions (the first with the steam engine, loom and rail- ways; the second with crude oil, cars and chemistry; and the third with information technology and biotechnology), the fourth industrial revolution will have to be part and parcel of a transition to a solar economy – and it will have to be a global revolution.
Despite all the talk, global energy consump- tion continues to rise from one year to the next. Industrial nations have only adopted modest climate protection policies, and energy consumption is skyrocketing in the most populous developing nations of China and India. We are called on to cut global greenhouse gas emissions in half by 2050; at the same time, poor countries continue to
fight for their right to economic develop- ment. Therefore, our global switch to a renewable energy supply must be based on a dual strategy: greater energy efficiency and the fast development of renewable energy.
The dark clouds on the horizon do indeed have a silver lining of sorts. Behind them is a blue sky and a shining sun. The fourth indus- trial revolution of efficiency and solar power will make our energy supply safer. No longer will we fight for oil, and the battle against poverty will be won. Millions of new jobs will be created, and national economies and consumers will face less of a financial burden. The only thing to fear is inaction.
But the fear of inaction should be taken seri- ously. The main energy efficiency technologies and eco-efficient products – from cars that get 80 miles per gallon to cogeneration systems and homes that produce more energy than they consume – are already available. Seifried and Witzel show a wide range of these convincing options in practice and discuss the political reasons for society's reluctance to become more efficient.
In Renewable Energy – The Facts, the authors concentrate on the second major challenge we face: covering all of our (dras- tically reduced) global energy consumption with renewables. They convincingly show the great technical and economic potential of solar energy alongside that of wind, water and biomass, each of which can be considered indirect solar energy.
And that's not all. They also show that a narrow focus on technical potential is near- sighted. The drastic structural change in our energy sector and society will only come about if society undergoes an innovation process. In addition to technologies, this process requires the will to march on into sunnier days. It also requires proper institu- tional and market conditions – and different consumer behaviour, both in terms of purchases and product use.
The questions seem to be endless, but the answers are provided in the book you hold in your hands. Renewable Energy – The Facts is a manual for the fourth industrial revolu- tion.
Rainer Griesshammer Rainer Griesshammer is a member of the board at the Institute of Applied Ecology and a member of the German Advisory Council on Global Change.
'Renewables are the way of the future' – 20 years ago, this was a minority opinion. Back then, our energy supply came from fossil sources (coal, oil and gas) and from nuclear power. Power providers did not believe that solar energy could ever make up a large share of the pie and merely spoke of it as the 'spare tyre', which was good to have on board, but not something you would want to rely on all the time.
Over the past few years, opinions have begun to change. Markets for renewable energy sources are booming around the world. At the same time, the negative effects of our fossil-nuclear energy supply become clearer all the time:
• The dramatic impact on the climate of our uninhibited consumption of fossil energy is causing glaciers and polar ice to melt at rates previously unimagined. Ironically, the deserts are also expanding. Higher temperatures foster the spread of malaria and cholera, and extreme weather events, such as the European heatwave in the summer of 2003 and Hurricane Katrina in 2005, are becoming common. The warnings from researchers about the catastrophic consequences and the tremendous costs of climate change are only becoming more urgent. For instance, in a study published in October 2006, Nicholas Stern, the former chief economist at the World Bank, argued that climate protection is the best economic policy. While a lack of effective climate policies could cause damage amounting to up to 20 per cent of global gross domestic product (GDP),
Stern calculated that proper climate protection would only cost 1 per cent of global GDP. 1
• Crude oil and natural gas are becoming scarcer. Prices skyrocketed in 2008 leading up to the economic crisis, while the war in Iraq was a reminder that most of the world's oil reserves are in an unstable part of the world.
• The reactor disaster in Chernobyl (1986) tragically demonstrated that there is no such thing as safe nuclear power. Indeed, mishaps continue to this day, such as in the summer of 2006 in Forsmark, Sweden, and Biblis, Germany. Furthermore, we still do not know how to safely dispose of nuclear waste, which is why we need to stop making it as soon as possible.
These and other reasons clearly illustrate that our fossil/nuclear energy supply is not sustainable and has no future. At the same time, we are currently witnessing the begin- ning of the Solar Age and a boom in renewables, though perhaps 'witnessing' is not the right word – we are bringing this change about ourselves. Obviously, solar power is not a marginal player. Instead, it is the only sustainable energy source we have and will be a central pillar of our future energy economy alongside prudent energy consumption.
The trends over the past few years leave room for no other conclusion; solar energy is no longer a marginal player. 2 In 2006, the number of solar arrays installed in Germany crossed the threshold of 1 million. In only seven years, from 1999 to 2005, the industry
increased its sales more than tenfold, equiva- lent to average annual growth of around 50 per cent. In 2005, 45,000 people were employed in the solar sector, which posted €3.7 billion in revenue. By 2020, that figure is expected to increase another sevenfold.
Wind power has grown even faster. Policies in the 1990s got things going, bringing about increasingly powerful wind turbines. For many years, Germany was the world's leader in wind power and was only over- taken by the US in 2008. At the end of 2008, Germany had installed a total capacity of 23,903 megawatts (MW) of wind power. The 20,301 wind turbines in the country generated 40.4 terawatt-hours (TWh) of wind power that year, equivalent to 7.5 per cent of Germany's power consumption. The figure from 2006, only two years earlier, was 5.7 per cent; that year, wind power overtook hydropower as the biggest source of renew- able energy.
Nowadays, the payback from policies to promote wind power is clear. German firms are global market leaders. Modern wind turbines are being exported in large numbers because in good locations wind power is cheaper than power from conven- tional central plants. At the end of 2007, some 90,000 people were employed in the German wind power sector.
Long overlooked, biomass recently moved to centre stage. A number of communities heat new buildings with renewable wood, and wood pellets ovens for detached homes and multi-family units have become genuine competitors for oil and gas heaters. Within just three years, the number of these envi- ronmentally friendly boilers rose tenfold. In addition, a growing number of farmers are now growing energy crops. Plantations of rapeseed are a source of additional income alongside biogas digesters.
All of these steps go in the right direction in our opinion, and they are all the results of government policy, such as Germany's Renewable Energy Act (EEG). But Germany is not a special case. A number of countries have adopted similar policies, called feed-in tariffs (FITs). Some 60 countries worldwide have adopted FITs, making it the leading policy instrument to promote renewables worldwide.
Wind power continues to boom worldwide (see www.ewea.org/fileadmin/ewea_docu-
ments/documents/press_releases/2009/GWE
C_Press_Release_-_tables_and_statis-
tics_2008.pdf). For instance, in 2008, installed wind power capacity rose by some 30 per cent, while the grid-connected photovoltaics (PV) capacity grew by more than 70 per cent. 3 Overall, a total investment of €120 billion (2008) underscores the growing economic importance of the sector.
Crucially, China, the most populous country in the world, has set some ambitious targets for itself. By 2020, renewables are to make up 15 per cent of the country's power consumption. In particular, China installed some 13 gigawatts (GW) of wind capacity in 2009 alone, bringing it more than halfway to its target of 20GW by 2020 – and making China the global wind leader for that year. 4 China also has ambitious plans for other renewable sources of energy, which all goes to show that renewables are a genuine option for developing and newly industrial- ized countries.
Though the US did not ratify the Kyoto Protocol, more than 300 mayors – from Chicago to New York, Los Angeles and New Orleans – have stated their support for the treaty. 5 And though former President George W. Bush came from the oil sector and was surrounded by consultants from the oil industry, renewables boomed during his
administration more than ever before as the country worked to make itself less depend- ent on foreign energy imports.
Clearly, energy policy is in a transitional period. Renewables are quickly becoming more important. In this book, we navigate our readers through this process and provide them with facts and good reasons for this change. We also present strategies for the quick transition to the Solar Age:
• The book first provides information about the many ways that solar energy can be used. We start with the direct use of solar energy: solar thermal and PV. The former creates heat; the latter, elec- tricity (Chapters 2–4). The sun is also the engine behind our climate; wind, clouds and rain are the result of insolation. Likewise, plants (biomass) could not exist without light. Biomass, wind power and hydropower are therefore thought of as indirect ways of using solar energy. Finally, geothermal is yet another renew- able source of energy (Chapters 5–7). We round off this presentation of energy sources with an overview of new energy technologies often mentioned in the context of renewable energy, such as fuel cells (Chapter 8).
• The second part of the book focuses on the overall potential of solar energy. We discuss not only the possibilities of various types of solar energy, but also how they are currently used in Germany, Europe and worldwide. A scenario for the expansion of renewables illustrates our future prospects (Chapter 9). A number of arguments against the expan- sion of renewables are also repeatedly voiced in the debate about our future energy supply. In Chapter 10, we respond to some of the most common charges with some basic facts.
• The last two chapters concern how the
solar energy future we describe can become a reality. Chapter 11 provides an overview and assessment of various types of policies. Largely considered the best policy, feed-in tariffs are the focal point. But the long-term expansion of renewables will have to include addi- tional instruments, such as for the heating sector. We also briefly present the history of the concept behind feed-in tariffs, which go back to the Aachen Model of 'cost-covering compensation'. Finally, in Chapter 12 we present a number of examples of creative market- ing strategies that have successfully sped up the implementation of renewable energy (mainly in communities). In doing so, we hope to provide some ideas of how people and communities can become involved in addition to actions taken by big energy players.
Renewable Energy – The Facts has a special design: each page of text has a chart juxta- posed. The concept is intended to give readers a quick overview of the topic. At the same time, we as authors are forced to cover each issue on exactly one page. In some cases, some ancillary ideas had to be deleted and moved into footnotes. To facilitate read- ability, we have also added a glossary of technical terms. Interested readers will also want to consult the list of important publi- cations and websites to help them keep up with current events and find additional information on special topics.
This book is a translation of the third edition of the German publication; some of the data in the German book were updated for the English publication.
We hope that you enjoy the English version of this book and find that it provides you with the basic knowledge you need to get involved in sustainable energy policy. There
may be many setbacks to come, but one thing is also certain: the course of the sun cannot be stopped.
Dieter Seifried and Walter Witzel Freiburg, March 2010
PS All the figures in this book can be downloaded at www.earthscan.co.uk/ onlineresources. We hope they prove useful to you in your presentations and awareness- raising.
New Paths to the Future
In the battle against climate change, practi- cal expertise in energy efficiency and renewables is in higher demand than ever. After all, renewable energy represents a truly long-term alternative compared to finite, environmentally unfriendly fossil energy sources – which are also unsafe in terms of security. The inexhaustible power of the sun is not the only way to fulfil our responsibility to future generations; wind, water and renewable bioenergy are of help and can be used as well.
Renewables offer genuine hope for develop- ment because they can provide decentralized energy in developing coun-
tries; therefore, they are used wherever poverty and a lack of energy would go hand- in-hand. They are also useful wherever people already have a lack of means to deal with the consequences of the wrong energy policy and environmental disasters such as droughts, floods and hurricanes.
Renewable Energy – The Facts provides a number of important answers to a lot of such urgent questions. It offers the latest information and technical explanations, including interesting examples and how to put guidance into practice. An agency of German development cooperation, InWEnt (Capacity Building International, Germany)
supports this publication. The promotion of renewable energies and energy efficiency for developing countries is at the core of Germany's policies to combat climate change and to foster climate adaptation.
Climate and energy policy is not simply a matter for national governments. Politicians, even at the most local level, are also concerned as are the private sector and indi- viduals. After all, energy consumption and climate change make themselves felt in indi- vidual homes and businesses. Roughly 75 per cent of energy consumption takes place in cities, which is why sustainable energy policy has to be implemented there. Furthermore, the avoidance of carbon emis- sions and climate adjustments has to focus on urban areas. Worldwide, megacities and metropolises have the greatest need for action. These are the places where climate change is caused – and where the changes are felt the most. In particular, the fast- growing Asian megacities are often located on rivers and coasts, where the rising sea level caused by climate change is not an abstract idea but an everyday reality – along with increasingly frequent typhoons and floods. The poor people in shanty towns
with the least money will pay the highest price.
Cities are strong and flexible enough to implement a new energy policy that will take them in the right direction; national govern- ments, in contrast, often have sluggish governmental procedures, and resolutions take time to be adopted. But thanks to their close contact with citizens and the private sector, city governments are more able to raise awareness and implement innovative policies.
Renewable Energy – The Facts contains a number of useful ideas easy to apply. It is a must-read for anyone who wants to act responsibly and take advantage of the opportunities which the future offers.
Luiz Ramalho Director of the Department of Sustainable Economy InWEnt
1.1 Our climate is at stake
Climate change is already making itself felt. Over the last century, the average global temperature rose by 0.7°C. Glaciers in the Alps are retreating, as is the Arctic ice shelf. The frequency and strength of hurricanes has increased, and extreme weather events – such as Hurricane Katrina in 2005 and the heatwave in Europe in 2003 – are becoming more common.
The causes are well known. When fossil energy is burned, carbon dioxide (CO 2 ) is released. Its concentration is increasing in the atmosphere, strengthening the green- house effect. Since the pre-industrial age, the concentration of CO 2 , the most impor- tant heat-trapping gas, has risen from roughly 280 parts per million (ppm) to the current level of almost 390ppm. But CO 2 is not the only heat-trapping gas emitted by civilization. For example, large amounts of methane are released by farm animals and in coal and natural gas extraction. Likewise, laughing gas (nitrous oxide, N 2 O) is a heat- trapping gas from agricultural fertilizers.
These gases change the amount of energy trapped in the atmosphere and the amount reflected back into space. Shortwave sunlight penetrates the atmosphere and is reflected from the Earth's surface. Reflected waves are generally longer and cannot penetrate the atmosphere as well; heat-trap- ping gases partially absorb them. This natural phenomenon (the greenhouse effect) is vital for our planet; without this effect, the Earth would have an average temperature of –18°C. The increasing concentration of these heat-trapping gases is gradually disturbing this ecological equilib-
rium. Land and oceans are heating up faster, more water vapour evaporates from the seas, and hurricanes and typhoons are becoming more common. The overall amount of energy input into the atmosphere
is increasing. As a result, extreme weather
events such as droughts, floods and heat- waves are becoming more common.
A decade ago, the idea that climate change
was man-made was still controversial, but today there is a widespread consensus:
'Nowadays, no serious scientific publication disputes the threat that emissions of green- house gases from the burning of fossil fuels poses to the climate', says Professor Mojib Latif from the Leibniz Institute of Marine Sciences at the University of Kiel, Germany. 1
Nonetheless, there is still some resistance to efficient climate protection policy, though this opposition is not the result of honest doubts about climate change. Rather, some industrial sectors simply have an eye on their bottom line and are concerned that their profits may suffer, as some countries and lobby groups would have us believe.
Concentration of carbon dioxide in the atmosphere*
*Measured at the Mauna Loa Observatory
Increase in the average temperature on the Earth
Annual average temperature in degrees Celsius
Linear trend
Figure 1.1 Our climate is at stake
Source: Al Gore, An Inconvenient Truth, 2006; BMU
1 1.2 The inevitable fight for limited oil reserves
At the beginning of the 1970s, the Club of Rome's Limits to Growth raised awareness about the idea that exponential growth on Earth is not possible in the long term. It also stated that crude oil reserves would be depleted in 30 years under a specific set of assumptions. Today, oil reserves are reported to be 1200 billion barrels (a barrel contains 159 litres), and the statistical range is reported as 42 years. 2 Those may sound like reassuring figures, but they are not. And there are several reasons why.
Statistical range is an indication of how many years current reserves – economically extractable oil using current technology and assuming that consumption remains constant – will last. But of course, if oil consumption continues to increase as in the past, then the statistical range will be much shorter.
While new sources of oil were found regu- larly up to the beginning of the 1980s, no major discoveries were reported in the 1990s. Since then, far more oil has been consumed than discovered (see Figure 1.2).
Our current oil fields cannot be drained at any rate we wish. Once an oil field has been tapped, it quickly reaches a point where production cannot be increased. Once it has been half emptied, one speaks of a 'deple- tion midpoint'. After that, it is practically impossible to speed up production. And because most current oil fields have already reached that midpoint, the production capacity of all oil fields in the world will begin to fall sooner or later – even though the range may statistically hold out for a few more decades. A number of oil-producing countries – such as the US, Mexico, Norway,
Egypt, Venezuela, Oman and the UK – have already passed their production peak, and others are soon to follow. A number of experts are therefore talking about peak oil production for the world – called 'peak oil' – which some say may have already been reached or may happen soon. 3 When production is likely to decrease as demand increases, prices can be expected to skyrocket, as indeed they did before the recent economic crisis.
One more crucial factor has to be kept in mind: the remaining oil reserves are largely found in a small number of countries. In 2005, OPEC members had three quarters of all proven reserves. Indeed, five countries of the volatile region of the Persian Gulf – Saudi Arabia, Iraq, Kuwait, the United Arab Emirates and Iran – alone make up 60 per cent of global oil reserves. 4 Instability there- fore not only results from the absolute scarcity of oil reserves, but also from unequal distribution.
An energy policy based on renewables and energy efficiency will therefore not only protect the climate, but also make us less dependent on fossil energy, thereby reduc- ing the potential for armed conflict over scarce reserves and resources.
Billions of barrels of oil
New discoveries per year
Figure 1.2 Oil reserves: The gap between new discoveries and production widens
Source: BP, IEA, Aspo, taken from SZ Wissen 1/2005
1 1.3 Addiction to energy imports
Though Germany is sometimes touted as a global leader in renewables, the country imported 59 per cent of its primary energy consumption as oil or gas in 2005. And even when it comes to nuclear energy (12.5 per cent of primary energy consumption) and hard coal (12.9 per cent), Germany is hardly independent; 100 per cent of its nuclear fuel rods are imported, and more than 50 per cent of the coal burned in Germany comes from abroad.
The situation overall in the European Union (EU) is hardly better. The 25 member states currently import around half of their energy. If consumption and domestic production were to continue in line with the current trend, the share of imports would soon exceed two thirds. Domestic production continues to drop within Europe, but energy consumption is increasing considerably. As a result, the share of domestic energy will continue to drop if energy policy fails to change these trends.
Rising prices on the global crude oil market woke up energy politicians both in Germany and the EU a few years ago. In the autumn of 2005, oil prices began to skyrocket,
reaching prices that surprised many; a barrel of crude oil (159 litres) was being sold for more than US$70. But even that price would double before the economic crisis suddenly brought prices back down. The effects of this price hike made themselves felt in consumer prices. While a family that consumes 3000 litres of heating oil a year only had to pay around €1000 in Germany in 2003, that figure had doubled by 2005/2006 and would double again by
Oil and gas imports to Germany rose to €66 billion in 2005, a 27 per cent increase over the previous year. 5
Dependence upon energy imports not only means a heavy outflow of capital, but also narrows political leeway 6 and, as we have seen over the past few years, increases the likelihood of armed combat over scarce resources.
Sustainable energy policy based on energy efficiency and renewables therefore strengthens local markets by redirecting capital that would have left the area to pay for energy imports into domestic energy sources. But such a policy also helps keep the peace by making battles for scarce resources unnecessary to begin with.
Oil in millions of tons
Gas in billions of cubic metres
5,100 1.490
700 1,100 China
Roughly 60 per cent of global oil reserves is located in a few countries in the near East: Saudi Arabia, Iran, Iraq, Kuwait and the United Arab Emirates.
Figure 1.3 Global oil and gas reserves (2005) are restricted to a few regions
Source: BP Statistical Review 2006
1 1.4 Nuclear energy is not an alternative
A number of issues pertaining to nuclear
energy have yet to be resolved and may be irresolvable: 7
• The danger of a reactor meltdown like the one in Chernobyl (1986) remains, as events in July 2006 at Sweden's Forsmark nuclear plant revealed. 8
• There is still no final repository for highly radioactive waste.
• The 'peaceful' use of nuclear energy cannot be completely separated from military applications.
• There is no perfect way to protect nuclear plants from terrorist attacks.
Germany, therefore, recently resolved to phase out its nuclear plants. 9 In 2005, the Obrigheim plant was the first to be decom- missioned. Since then, nuclear plant operators have been attempting to overturn the agreement they themselves signed in order to have longer commissions for their nuclear plants. They have discovered a new argument: climate protection. They claim that nuclear power would have to be replaced by coal plants and gas turbines, which produce more CO 2 emissions than nuclear plants, thereby running contrary to current efforts to reduce these emissions.
Nonetheless, longer commissions for nuclear plants are the wrong way to get out of our climate trap, as would be newly constructed nuclear power plants. For instance, if we want to use nuclear power to ensure that we reach the German goal of an 80 per cent
reduction in CO 2 emissions below the level
of 1990 by 2050, Germany would have to
construct and operate some 60–80 new nuclear plants, roughly 4–5 times more than the current 17 nuclear plants in Germany. 10
Globally, several hundred new nuclear plants would need to go on line to reduce CO 2 emissions considerably; some 440 are currently in operation. In turn, nuclear risks would increase significantly.
At the same time, the supply of nuclear fuel rods is hardly ensured. At current rates of consumption, uranium reserves will only last for another 40–65 years. 11 If we build new nuclear plants, the uranium would not even last that long.
In addition, investments made in the energy sector clearly revealed that nuclear power is now considered too expensive. Since the disaster at Chernobyl, very few new nuclear plants have been ordered, and the ones that were built generally received generous subsi- dies. 12
The nuclear industry would have us believe that nuclear power is undergoing a renais- sance. Lobbyists like to point out that a few plants are currently under construction, but those figures include discontinued projects abandoned years ago. And because so many nuclear plants will be decommissioned over the next few years worldwide even under the normal schedule, the number of nuclear plants will decrease. 13
At the beginning of 2007, for example, seven nuclear plants in Europe were taken off the grid for good – four of them in the UK, two in Bulgaria and one in Slovakia. 14 The risks of nuclear power can be prevented if we switch to renewables, which are an environmentally friendly alternative (see
11.18).
Number of reactors in operation worldwide
Over the next decade, the number of nuclear power plants in operation will drop, as will the amount of nuclear power produced.
Figure 1.4 Nuclear power is not an option
Source: IAEA
1 1.5 Renewables are the way of the future
While the share of renewables in Germany has been increasing drastically over the past ten years, the country still gets around 85 per cent of its energy from fossil sources. Oil makes up the largest share of the pie at 36 per cent, followed by coal at 24 per cent and gas at 23 per cent. 15
Up until the 18th century, civilization got all of its energy from such renewable sources as wood, wind, water and muscle. Coal – and later oil and gas – only took off at the begin- ning of industrialization. Today, we admittedly do not face any acute shortage of fossil energy, but reserves are nonetheless finite. Estimates are that, under current consump- tion, known reserves of oil will be depleted in some 40 years and brown coal in 220 years. 16 And while new resources may yet be discov- ered, these resources remain finite. Figure 1.5 clearly shows that the age of fossil energy will only appear as a blip on the screen of energy consumption over a 4000 year period.
When coal, oil and gas are combusted, CO 2 is released. CO 2 is the main reason why the Earth's atmosphere is heating up – and why the climate is in danger. Back in 1990, the German Parliament's Commission on Protecting the Earth therefore called for an 80 per cent reduction in CO 2 emissions within Germany by 2050.
Nuclear power currently covers some 30 per cent of electricity consumption in Germany, roughly 13 per cent of the country's total energy consumption. However, the risk of a major reactor meltdown like the one in Chernobyl in 1986 and the unsolved problem of waste disposal rules out this high-risk technology as part of a sustainable energy supply.
So we are left with one major source of energy over the long term: the sun. 17 It can be used both to generate heat and electric- ity (solar thermal and solar power). At the same time, however, the sun is also the reason plants (biomass) grow and the weather changes. Different amounts of sunlight hit the Earth's surface in different locations, bringing about wind. 18 And when the sun shines, ocean water evaporates, creating clouds and rain – hydropower. Biomass, wind power and hydropower are therefore indirect ways of using solar energy. And because the sun, wind, water and biomass are inexhaustible in human terms, they are called 'renewable' types of energy.
There are a number of ways to use solar energy directly and indirectly, and all of them are constantly being further developed. Along with greater efficiency in energy consumption (see 1.8), indirect and direct solar energy will provide a reliable, sustain- able energy supply.
Renewables are the way of the future. The Solar Age will arrive one way or the other. The question is only whether we will manage that transition without crises and major conflicts.
Global fossil energy
1st Solar Age
2nd Solar Age
Date (Year)
Range of fossil energy sources
Hard coal
˜ 150 years
˜ 63 years
Petroleum ˜ 40 years
Figure 1.5 The sun is the future
Source: Goetzberger and Wittwer, Sonnenergie; Bundesamt für Geowissenschaften und Rohstoffe, 2006
1 1.6 We have enough sun
The sun is our planet's main source of energy. Each year, the sun provides the Earth with 7000 times our current global energy consumption – a figure that does not vary much. Although roughly 70 per cent of that energy falls onto the ocean, there is still enough solar energy left. For instance, an area of the Sahara 200km by 200km – roughly the size of Kentucky or twice the size of Wales – would suffice to cover current global energy consumption. But even if this sunlight could only be used at an efficiency of 10 per cent, we would still only need an area roughly 700km by 700km to cover our current global energy demand with solar power. 19
Of course, the sun only reaches Germany at half the strength of sunlight in the Sahara – roughly 1000–1100kWh per square metre, equivalent to the amount of energy in approximately 100 litres of heating oil. In other words, the sun pours roughly the energy equivalent of 100 litres of oil on each square metre of Germany each year in the form of sunlight. Overall, Germany receives more than 80 times more solar energy than it currently consumes from all energy sources.
Sunlight comes in two varieties: direct and diffuse. The latter occurs when sunlight is reflected, such as in clouds. The light then reaches the surface from various directions. Some solar energy systems need direct sunlight (see 2.6), but most can utilize both direct and diffuse sunlight.
These figures clearly show:
1 Insolation, even in northern Europe, is still roughly half as strong as in the tropics and subtropics. It therefore makes sense to use solar energy even at such latitudes. While the solar yield is then lower, there are no transport costs.
2 Even in an industrial country such as Germany, the sun still provides several times the energy needed.
The benefits of solar energy are clear, but low 'energy density' is a crucial drawback. While 1000W of solar power may reach a square metre of northern Europe under full sunlight, the annual average is only around 100W per square metre. Large areas are therefore required for solar arrays. But if we limit ourselves to available roof space, we see that Germany has some 3500km 2 , approximately 800km 2 of which could be used for solar energy. 20 With current tech- nology, Germany could therefore get some
16 per cent of its current power consump-
tion from solar on such roofs – and much more if power is used more efficiently. In addition, facades, bridges, noise barriers, etc. are also available. And then we have wind power, hydropower and biomass to round off our future renewable solar energy supply.
The land needed to cover our current global energy consumption with solar power (10 per cent efficiency)
Figure 1.6 We have enough sun: The land needed for a 100 per cent solar energy supply
Source: The authors
1 1.7. Scenario for the solar future
If we are to change our economy so that we can get most, and possibly all, of our energy from the sun and other renewables, we need to change our energy policy first. Back in 1980, the Institute of Applied Ecology in Freiburg, Germany, worked up a scenario for this transition. 21 The main thing that we have to change is our minds: the focus does not need to be on greater energy consumption, but on greater prosperity. Entitled 'Energiewende' (Energy Transition), the Institute's study therefore took a look at society's needs for energy services, such as lighting, transportation and heated build- ings. The energy required for these tasks not only depends upon the scope of these serv- ices, but also on energy efficiency. If, for instance, gas mileage can be tripled, people could then drive three times as far with the same amount of energy – or 50 per cent further with half as much fuel. The study demonstrated such efficiency potential in a number of fields. It concludes that we can reduce our primary energy consumption by nearly 50 per cent over the next 40–50 years even as our standard of living continues to increase.
These findings have been confirmed again and again since:
• The 11th German Parliament's Commission on Protecting the Earth's Atmosphere found that energy savings of 35–40 per cent are feasible. 22 • In Factor Four, 23 Ulrich von Weizsäcker, Amory Lovins and Hunter Lovins tell the Club of Rome that the efficiency gains are so great that standards of living could be doubled even as energy consumption is cut in half.
• Another study in Germany, entitled 'Lead Study 2007 – Update and reassessment of the use of renewable energies in Germany' showed the potential and costs of this transition. 24
In addition to demonstrating the great savings potential, the Energy Transition study conducted by the Institute of Applied Ecology also includes a scenario for the solar future. For example, solar energy can provide low-temperature heat. A greater share of wind and hydropower would cover our electricity consumption. Waste from the timber and agricultural sectors would provide heat, electricity and motor fuels. If the conservation potential is fully exploited, our energy supply could be redesigned so that solar, wind, hydropower and biomass cover roughly half of our energy consump- tion by 2030. The other half would then mainly come from coal in highly efficient, and therefore environmentally friendly, cogeneration plants.
The Energy Transition study does not specif- ically talk about a solar economy as a goal, but it does emphasize three important steps on the path towards a solar economy:
1 Conservation should be exploited when- ever possible.
2 Cogeneration should be used as a bridge technology.
3 Renewables must be expanded.
Millions of tons of
hard coal equivalent
Energy transition means:
• Consistently tapping conservation potential
• Using cogeneration
• Expanding renewables
Figure 1.7 The Institute of Applied Ecology's Energy Transaction study (1980): Growth and prosperity without oil and uranium
1 1.8 The solar strategy requires conservation
Let us now focus on the three examples of energy conservation and energy efficiency for the solar strategy explained in the previ- ous section.
Example 1: Standby power consumption
In Germany, electrical appliances in offices and homes consume some 22 billion kilo- watt-hours of electricity each year, 25 roughly the amount generated by four nuclear power plants. If this electricity had to be provided by solar panels, more than 200km 2 would be needed. In light of the costs and materials required, the effort would be absurd, especially when we realize that this standby consumption could already be reduced by more than 80 per cent today if we replaced our current appliances with newer ones that consume less standby power. The Eco-design Directive for Energy- using Products (2005/32/EC) was adopted in 2005 and came into force in August 2007. It establishes a framework under which manu- facturers of energy-using products (EuP) will, at the design stage, be obliged to reduce the energy consumption and other negative environmental impacts that occur during the product's life cycle. From the beginning of 2010, the 'off mode' electricity consumption of all appliances sold in Europe is not allowed to exceed 1W and the stand-by mode is limited to 2W.
And if we switch appliances off completely (i.e., do without standby mode), we can reduce our consumption even further.
Example 2: Space heating
The average German single-family detached house with 120m 2 of floor space consumes some 30,000kWh per year for heating and hot water. A large solar hot water system
(12m 2 ) can produce some 13 per cent of the energy required for that task. To increase that share considerably, consumption has to be reduced by means of good insulation and effi- cient windows. Such 'low-energy buildings' (see 4.1) make do with around 10,600kWh per year. But a 12m 2 solar thermal array would then cover 28 per cent of peak demand (see Figure 1.8). The greater the efficiency, the greater the share of solar energy. 26
Example 3: Efficient pumps
More efficient pumps and pump controls would save many billions of kilowatt-hours of electricity and heat in homes, businesses and industrial plants. But this change would require decision-makers to be better informed and tradespeople better trained; in addition, we would need an investment philosophy that accepts higher investment costs in return for lower operating costs. 27
These three examples make it clear that a solar energy supply is easier to reach and less expensive if conservation measures are simultaneously exploited.
Towards the goal of 100 per cent solar energy, Example 2 does not seem that convincing. If we want to go further, we can do the following:
• Use more solar energy. A larger solar array would cover a larger share of heating demand (see 2.3).
• Use greater efficiency. By further improv- ing insulation and ventilation systems, we can do without heaters altogether (see 4.6).
• Use other types of renewable energy. A combination of solar collectors and wood heating can provide renewable heat all year round (see 4.8 and 5.4).
These options represent a good starting point for the transition to the Solar Age.
Greater efficiency helps increase the share of solar:
Normal house
(poor energy efficiency)
Low energy house
(great energy efficiency)
31,000kWh
10,6600kWh
Solar share
Solar share (per cent) of total house energy demand
13 per cent of energy requirements
met by a 12m 2 solar array
Figure 1.8 Solar strategy requires energy conservation
1 1.9 Cogeneration – an indispensable part of our energy transition
Today, the generation of electricity is the cause of more than a third of all carbon emissions in Germany. The reason is the low efficiency at which power plants convert fuels into power. On average, fossil power plants run at efficiencies far below 40 per cent. If we then deduct the power needed by the plant itself and transport losses on the grid, we see that only a third of the primary energy fed into the plant actually arrives at your wall socket. 28
The alternative to conventional power generation is called cogeneration. Here, waste heat from the power generation process in conventional steam turbines is used. For the waste heat to be used in resi- dential areas, hospitals or commercial units, the power has to be generated close to consumers.
The overall efficiency of cogeneration units ranges from 85–95 per cent.
Because of this high rate of efficiency, cogeneration units are not only much better ecologically, but also economically. Nonetheless, cogeneration plants make up less than 10 per cent of installed capacity in Germany because large utilities have consis- tently attempted to stamp out cogeneration efforts by communities and industry, which would have cut into the sales revenue of util- ities. 29
The liberalization of the power market made the efforts to stamp out cogeneration even fiercer. Large power producers, all of whom suffered from overcapacity, lowered their prices to cutthroat rates so that the already installed fleet of cogeneration units was no
longer profitable. With prices at 2–3 euro- cents per kilowatt-hour – below the cost of production – even highly efficient cogenera- tion cannot compete.
To take account of the negative effects of liberalization on cogeneration, Germany passed its Cogeneration Act in March 2002. The goal was to reduce carbon emissions by 23 million tons annually by 2010 through cogeneration. In all likelihood, this target will not be reached. One of the goals of the new governing coalition in Germany is therefore to respond to calls by the cogener- ation sector and improve legislation. 30 The UK has also come up with some proposals for proper compensation of heat in its Energy Bill.
We need only look elsewhere in Europe to see how effectively cogeneration can be used. In Denmark, Finland and The Netherlands, the share of cogeneration in power production is between 40–50 per cent. 31
For the next few decades, we will still have fossil power plants generating electricity. It is therefore crucial that we use these power plants as efficiently as possible in order to reduce the environmental impact. Like energy conservation, cogeneration is there- fore a crucial part of our transition to the Solar Age.
Separate generation
Fuel input
Energy made
Separate generation (cogeneration)
Elec-
Cogeneration reduces primary energy consumption by around 40 per cent
Figure 1.9 Cogeneration: An indispensable part of our energy tradition
1 1.10 Liberalization of the German energy market
On 29 April 1998, the German energy market was 'liberalized'. From one day to the next, former monopoly power providers saw their markets opened up to the compe- tition; after 60 years of monopoly service, customers could now (temporarily) look forward to competition. They could choose their own power provider.
The effects of liberalization were drastic. Power prices initially fell, providers merged and the big fish acquired the small fish. Power providers have increasingly focused on what they see as their core business: increas- ing sales revenue. In particular, overcapacity and predatory pricing put more and more pressure on community cogeneration plants, some of which were decommissioned. Drawn up at the beginning and middle of the 1990s, least cost planning schemes 32 to increase the efficiency of electricity consump- tion were put on ice or discontinued.
Competition temporarily made it cheaper for families to consume electricity. Initially, experts expected retail rates to remain basi- cally stable in the wake of liberalization, but something surprising happened in the fall of 1999, when RWE and EnBW – two of Germany's Big Four power providers – began cutting prices to gain market share. Only a few years later, the battle for a larger share of the retail market died down. Indeed, retail rates are currently much higher than they were before liberalization and continue to rise far faster than inflation. 33
From 2002–2007, for example, retail rates rose by around a third without any increase in taxes on power. 34 The main reason for these price hikes is the market power of the Big Four and the lack of competition. After a brief phase of fierce competition (1998 to
2000), E.ON, EnBW, RWE and Vattenfall realized that the best strategy was to divide up the pie among themselves rather than compete for a bigger slice. Their strategy is working quite well; after all, the four oligop- olists run 96 per cent of all baseload plants and account for 80 per cent of all power generated in Germany. 35
In 2005, politicians responded to increasing power prices and the lack of competition by creating the German Federal Network Agency. The Agency has already succeeded in lowering excessively high power transit fees in a number of cases. But even the Agency can only go so far in creating true competition between companies. Alois Rhiel, Economics Minister in the State of Hessen, thus called for antitrust law to be made stricter in order to demonstrate that the government can make a difference. As he put it: 'Otherwise, the state will have to do away with the oligopoly of power producers and force the Big Four to sell power plants.' His goal was to increase the number of power producers until competi- tion could get a foothold, the goal being to reduce retail rates. He argued that high power prices were bringing down the German economy. 36
In October 2006, the German government took another step to ensure competition by making it easier for retail customers to switch power and gas providers. Now, customers need only give one month's notice.
At this point, it is up to customers to demand competition. Unfortunately, they have been reluctant to do so up to now. From 1998 (the beginning of liberalization) to the end of 2006, fewer than 5 per cent of household customers switched power providers even though they could have saved a lot of money by moving to a provider with lower rates. 37
Profits in billions of euros
Power price in cents/kWh
Profits of the Big Four (E.on, RW E., Vattenfall and EnBW)
Retail electricity rate in Germany (average annual consumption
of 3,500 kWh)
Figure 1.10 Rising power prices: Profits at the expense of households and small consumers
1 The changing market has also endangered municipal power companies. A number of them have responded proactively out of fear of competition and sold shares to the Big Four. In doing so, they generally also sold their leeway to design community energy policy. Experience has shown that the busi- ness and sales interests of the Big Four then take precedent, even if they only hold a minority of shares in the municipals.
Yet, the prospects for municipal energy service providers are quite good. 38 On the one hand, they can pick and choose a power provider; on the other, they know their customers well and have the expertise to offer the kinds of energy services in demand. But they will only be able to justify their exis- tence if their services differ from the ones offered by firms motivated solely by profits.
The next few years will show whether munic- ipal utilities will succeed even if their prices are not the lowest provided if they offer the energy services customers demand. 39
One of those services is a commitment to renewables. But merely providing 'green power' is not enough; rather, municipal util- ities should help construct and finance systems owned by their customers and promote community projects.
Two main pillars of the energy transition have been crippled by the liberalization of energy markets:
1 Power generation in municipal cogener- ation units and industry has been ramped down. Because the Big Four have used their overcapacity to pursue predatory pricing, cogeneration no longer pays for itself. The German government reacted to the inevitable with a special law to promote cogenera- tion, but the goal of reducing emissions
by 23 million tons of CO 2 by 2010 will not be reached under current legislation. Improved legislation is therefore needed quickly; after all, an energy supply based on solar energy cannot do without efficient power plant capacity, exactly what cogeneration provides. Indeed, cogeneration plants can not only help cover the baseload, but also compensate for fluctuations in intermit- tent renewable power (see 10.1).
2 Since the beginning of liberalization, the Big Four have focused even more on sales of kilowatt-hours. Yet, what customers need is inexpensive energy services. After some success stories in the mid-1990s, energy conservation campaigns have become rare among utilities. And while customers benefited from lower power prices initially, today they can only defend themselves by switching providers, which they largely fail to do. 40
Our experience with liberalization demon- strates that the market has to be changed if the environment and the climate are to be protected. The market needs guidelines so it will develop in the desired direction. If these changes are not made, liberalization will have a tremendous environmental impact and be a tremendous burden on the German economy. So where do we go from here?
• Our tax system has to be systematically redesigned to increase the tax burden on energy consumption and resource consumption and lessen the burden on labour. What we need is the kind of envi- ronmental tax reform that Germany began ten years ago with its 'eco-tax' on fossil fuels. But the current tax rates on energy consumption and private homes, businesses and industrial plants are not yet high enough to ensure that energy is
consumed efficiently. Further steps are necessary. 41
with an eye on long-term success. 44
• New regulations are needed to allow
We need a tradable quota for cogenera-
grid operators to pass on the cost of
tion. Utilities should be required to cover
investments in energy conservation
certain share of the power they sell
campaigns to their customers, which
with cogeneration units. The utilities
they are currently not able to do.
could then decide whether they want to generate that power themselves or purchase it. Current German law, based
on a floor price (feed-in tariff) for kilo- watts of electricity exported to the grid, cannot ensure the success of cogenera- tion as well.
• Renewable energy sources should receive assistance for market launch, and feed-in tariffs must be offered for renew- able power exported to the grid. This is where governments can make the great- est difference (see 11.9–11.12).
special fund 42 for energy conservation
• Nuclear power has to be phased out as quickly as possible (see 1.4 and 11.18)
and/or energy efficiency should be created, and further steps should be taken to promote efficient technologies (demonstration projects, training programmes, better labelling on large electronic devices, energy ratings for buildings, stricter efficiency standards, etc.). An energy efficiency fund would publish competitive requests for energy conservation proposals. The company that can provide the required energy conservation at the lowest cost would be awarded the contract. Such energy effi- ciency funds have already proven successful in a number of countries. 43 The efficiency fund could be financed by means of a surcharge on the retail elec- tricity rate or on the other energy carriers.
and energy policy has to be restructured accordingly. Here, it is crucial that the EU, member states and regional govern- ments state specific targets and pursue a reliable energy and transport policy to provide a stable business environment for investors, manufacturers of efficiency technology and producers of renewables technology over the long term. A number of new market players will be required in the process: energy agencies, contracting firms, 45 and academic centres that offer degrees in energy. Companies focusing on efficiency technology could step up energy and electricity conservation. These firms will, however, only be successful if the business environment fosters the kind of work they do.
Stricter energy conservation require- ments for new buildings and renovation projects.
Clear signals set by reliable taxation and incentives for consumers are equally impor-
We already know that a sustainable energy
Utilities must be forced to compete for
tant. Indeed, they are indispensable if
customers to a greater extent so that utilities will change the services they offer. The price per kilowatt-hour should not be the only reason to switch utilities. Rather, customers should also take other economic, ecological and social aspects into account. To this end, the perform- ance of utilities should be rated. Such ratings would provide benefits not only to customers, but also to companies
consumers are to take energy costs into greater consideration when purchasing items with long service lives, such as cars and refrigerators.
supply is not a pipe dream, but a feasible alternative. 46 It is also affordable and would provide significant economic and social benefits.
1 1.11 Economic benefits
Considerable investments will have to be made for our energy supply system to become sustainable; renewables will have to make up a large share of our supply, and energy applications will have to become much more efficient. These upfront invest- ments are offset over the long term by lower energy costs and independence from fossil energy sources, which are only going to become more expensive.
At current oil and gas prices, a wide range of investments in energy efficiency already pay for themselves and provide both macro and microeconomic benefits without any subsi- dies. 47 In contrast, renewable energy sources require further support, such as from feed-in tariffs, which ensure a return on investments in renewables (see 11.10). But the surcharges that feed-in tariffs entail do not simply increase the price of electricity for consumers; rather, the growing share of renewable energy sources has brought power prices down on power exchanges, as recent independent studies have demon- strated. 48 While this may seem surprising at first glance, it makes complete sense. Prices on power exchanges are sorted in ascending order. The greater the demand for power, the more power plants with low efficiency rates and higher fuel costs are used. But if a large amount of renewable power is being generated, the worst power plants are no longer used. Supply and demand converge to produce lower exchange prices. On average, power prices in Germany have fallen as a result by as much as 0.76 euro- cents per kilowatt-hour. 49
In particular, such macroeconomic benefits are the main reason why we should restruc- ture our energy supply:
• External costs in our current energy supply – from air pollution, climate change, the risk of nuclear disaster and the cost of securing access to raw mate- rials – are by definition not included in monthly power bills. Instead, they are incurred outside of our energy supply as external costs that society must cover. A sustainable energy supply largely avoids such external costs. Furthermore, there is the increasing damage caused by extreme weather. These costs have risen to nearly €2 billion per year on average for Germany alone, but the German Institute for Economic Research (DIW) estimates that that figure could rise to €27 billion by 2050. 50
• A sustainable energy supply would create hundreds of thousands of jobs. In the renewables sector alone, 280,000 new jobs had been created by 2008 in Germany, and that figure could rise to 500,000 by 2020 (see http://bee- ev.de/Energieversorgung/Wirtschaftlichk eit/Arbeitsplaetze.php). Every new job is not only valuable from the social stand- point, but it also reduces expenditures for unemployment benefits.
Energy efficiency and renewables
– Less dependence
on energy sources
and security
– Less damage to
the climate and
– Lower societal
costs from
– New jobs
– Export markets
– No wars over
– Greater tax revenue
– Lower social costs
– Greater international
Figure 1.11 The economic benefits of energy efficiency and renewables
2.1 Solar collectors
When sunlight hits a dark object, that object heats up. This well known effect is behind solar thermal systems. Solar collectors convert sunlight into usable heat. The absorber – a black plate made of copper, aluminium or sometimes even plastic in simple systems – is exposed to the sun, which heats the plate up. The heated plate then passes the heat on to a fluid (heat carrier) flowing through tubes embedded in the plate, and this fluid flows to the consumer device (to provide heated service water). Various technologies are imple- mented to reduce heat losses: 1
• Flat-plate collectors, the most common type, have an absorber within a frame. The cover facing the sun is transparent, and the cover is well insulated to the sides and on the back. Such solar collec- tors are 50–60 per cent efficient at a temperature of 50˚ Celsius. They can, however, reach temperatures of up to 80˚C under direct sunlight.
• Evacuated tube collectors have their absorbers inside a sort of thermos bottle that is transparent on the side facing the sun. The vacuum reduces heat losses greatly. These evacuated collectors there- fore have greater efficiencies, especially when the temperature difference is great between the absorber and the ambient air. If the difference is 70K (= 70 degrees), evacuated tube collectors are around 15 per cent more efficient than flat-plate collectors. But that figure drops to only 5 per cent if the difference is 40K. The benefits of evacuated tube collectors thus make themselves felt especially during the cold season. It
therefore makes sense to use them to support heating systems. • When outdoor swimming pools are heated, heat loss is not that great an issue, so no insulation is generally used. The water is pumped through black absorber hoses to absorb the solar heat. Such systems are, however, only useful in applications where only a few degrees of heat is required, such as in outdoor pools.
Solar collectors also have to be properly oriented to be efficient. In Germany, roof angles are optimally 45 degrees and facing due south. Fortunately, efficiencies drop only slightly if these ideal values are missed; collectors still produce around 90 per cent of their rated output if the collectors have an angle between 0 degrees and 50 degrees and face anywhere from southeast to south- west. It is therefore possible to use a slightly larger collector surface to compensate for suboptimal orientation. Some evacuated tube collectors even allow you to compen- sate by slightly turning the absorber within the tube.
Glass cover
Figure 2.1 Design of flat-plate collectors
Source: Schüle, Ufheil and Neumann: Thermische Solaranlagen, 1997
2.2 Hot water from the sun
2 The heat from solar collectors is generally used to provide heated service water, but the hot water can also be used in heating systems. The solar thermal system is then combined with the heating system; gener- ally, the solar heat suffices to cover all heating demand in the warm season and part of heating demand in the cold season.
Systems for single-family homes and duplexes are the most common today. They generally have a dual circuit system (see Figure 2.2). The solar circuit (solar collector, bottom heat exchanger and pump) contains a frost-proof fluid (a mixture of water and glycol) that transports heat to the heating circuit. Once the sun starts shining, the temperature in the collector rises several degrees above the temperature in the lower part of the tank, setting off the pump in the solar circuit by means of an electronic control. The solar heat then passes from the lower heat exchanger into the service water tank, which should be large enough to provide hot water for around two days.
Because hot water is lighter than cold water, the water heated with solar energy rises in the tank. The water thus separates into layers, with the lighter hot water at the top and the colder water at the bottom. Hot water is then drawn from the top of the tank, where the stored water is always the hottest. If the sun ever fails to provide enough heat, the auxiliary heater can provide extra heat via the top exchanger.
A solar thermal system with some 6m 2 of flat-plate collectors and a 300 litre storage tank can generally cover hot water demand during the warm season in a four-person
household. But even the solar heat during the cold season offsets the consumption of around 300 litres of heating oil per year in Germany. The net investment cost of around €5000. 2
Decisive benefit
Solar thermal systems that provide hot service water not only replace the consump- tion of fossil fuels with solar energy, but also very effectively reduce pollution. Because oil and gas heaters run at low levels during the warm season, they are especially inefficient then and emit more pollution; the heaters generally only come on briefly and therefore do not run in their optimal range. But if solar heat is used during the summer to heat service water, you can leave your boiler off altogether.
In addition to providing hot service water, larger solar thermal arrays can also provide heat for space heating during the spring and autumn. In such cases, the building should be properly insulated and have a heating system running at a low temperature. A 12m 2 solar thermal array can then reduce fuel consumption by 20 per cent. This combined use is becoming increasingly common on the market. 3
Solar station
with pump +
Pipes to transport
solar heat to the
Storage tank with
enough capacity to
store solar hot water
for a few days
Figure 2.2 Solar hot water
2.3 Solar heating in district heating networks
2 If you want to get a lot of your heating energy from solar heat, you have to take two factors into consideration:
1 Far more heat is required for space heating than to heat service water. In old buildings, 5–10 times as much energy can be required for space heating than to provide hot tap water. But even in well insulated homes, space heating can require two to three times more energy. For solar heat, the first goal is therefore to reduce the building's requirements for heating energy; in addition, far greater collector areas are required when space heating is to be covered in addition to hot service water.
2 In the winter, when you need the most space heating, you have the least solar energy. In January, the sun only provides a sixth of the energy it supplies in July at Northern European latitudes.
The main problem with solar heating is getting the excess heat from the summer stored for the winter. Long-term heat storage tanks play a crucial role. Specific heat losses and specific costs both decrease as the size of these storage tanks increases. Therefore, subterranean storage tanks are generally the best option. 4 District heating networks can then provide heat to adjacent buildings from these underground tanks.
In other words, more solar heat can be provided when buildings are well insulated, collector fields are large, a long-term storage tank is available and a district heating network can be connected to it.
In the 1980s, Sweden set up the first district heating networks with solar heat. Germany followed suit in 1996, with its first two solar pilot systems that included long-term storage.
In a pilot project in Hamburg-Bramfeld, a total of 3000m 2 of collectors was installed on the roofs of 124 row houses in a new neighbourhood. The solar heat collected was stored centrally and distributed to consumers via a district heating network. Any heat not used was fed to the long-term storage tank, a 4500m 3 concrete tank with a stainless steel lining. The tank was insulated on the outside to reduce heat loss. It filled up with heat in the summer, reaching its highest temperature of around 80˚C in August. It then provided heat for space heating well into December. A condensation boiler was used to provide heat for the rest of winter. The goal was to cover 50 per cent of energy demand for heating and hot water, and that goal was reached.
The cost of this solar heat (without subsidies) in the Hamburg project is 26 euro cents per kilowatt-hour, but another project in Friedrichshafen, which was larger and had a larger storage tank, provided heat at a price of 16 euro cents per kilowatt-hour. By 2005, five other solar district heating networks had been set up in Germany. 5
Collector field of 5,600 m 2
Central heating unit
Condensation boiler
storage tank,
12,000 m 3
Share of solar heat in overall heat consumption
Building with a 12 m 2 solar array
Building with connection
to district heating network
with solar support
Figure 2.3 Solar thermal with long-term heat storage
Source: BINE, Solar Nahwärmekonzepte
2.4 Cooling with the sun
2 At present, most air-conditioning and refrig- eration devices are vapour-compression machines. The refrigerants used, even though they do not contain CFCs, are not exactly environmentally friendly. And, of course, these units consume a lot of power. Here, solar energy can also help offset the consumption of fossil energy, reduce pollu- tion and reduce peak power demand. It turns out that the most solar power is avail- able right when air-conditioning is needed most. Buildings are not only mainly air- conditioned in the summer, but also during the day, which makes the costly long-term storage required for solar heat unnecessary here.
There are various types of solar cooling based on solar thermal heat. 6 Those based on low-temperature heat are especially useful for solar applications. Below, we discuss Desiccant Evaporative Cooling (DEC).
DEC is based on the principle that evaporat- ing water cools down its surroundings. 7 A humidifier cools down the air by taking out the heat as water evaporates from the previ- ously dried air. 8 The dehumidifier contains silica gel that removes moisture from the incoming air by absorbing the moisture in its own molecular structure. The silica gel there- fore has to be 'regenerated' (dried) for reuse, so when the outgoing air passes by, it takes some of the moisture with it. The heat required in the process comes from solar collectors, but it could also come from a short-term storage tank with an auxiliary heater.
In 1996, a solar DEC system went into oper- ation as an air-conditioning system at a startup park in Saxony, Germany. Its 20m 2 of collectors cover 75–80 per cent of the air- conditioning required. 9
There have already been a number of successful demonstration projects pertaining to solar air-conditioning. Serial production is getting underway, but solar cooling still cannot compete at current energy prices. Cost reductions are expected, 10 and less expensive air collectors (see 2.5) are expected to help bring down prices further. Such air collectors are especially useful towards the equator. Properly planned build- ings in central Europe generally do not need air-conditioning, though special-purpose rooms – such as for technology or assem- blies – are an exception. Here, it would make sense to have the collectors used all year round. In the summer, they could provide air-conditioning; in the winter, space heating. In tropical countries, solar cooling can help store food. Clearly, solar air-condi- tioning and cooling systems have considerable potential.
Adsorption air-conditioning
Cool, dry
Hot, moist
incoming air
outgoing air
• No climate impact from refrigerants
• Demand for cooling is greatest when the most solar energy is available
• 70–80 per cent solar coverage possible
Figure 2.4 Cooling with the sun
Source: Sonnenenergie 1/99
2.5 Solar drying – air collectors
2 Solar collectors containing fluids are fairly low-tech, but air collectors allow solar energy to be used for heating purposes in an even simpler way. Here, a sheet that lets through light is pulled taut across a frame just 2.5cm or so above a black plate. When sunlight hits this air collector, the air between the plate and the foil heats up. If the collector is set up at an angle, the hot air rises, automatically creating air flow. If the collector is completely horizontal, a ventila- tor is required, though it could run on solar power.
Air collectors allow solar energy to be used in drying applications. In many rural areas in the tropics and subtropics, farmers only have the wind and the sun to help them dry their harvests to conserve produce. Often, they simply spread fruits and vegetables out under an open sky. Some of the harvest is generally lost to rodents and birds, while dust, microorganisms, mildew, etc. reduce quality. As a result, part of the harvest is lost or no longer marketable. Solar tunnel dryers 11 are an inexpensive way of conserv- ing such products without great losses or poorer quality (see Figure 2.5). On an area some 2m by 18m long and slightly raised off the ground, a foil can be stretched across like a pitched roof. Roughly half of the area serves solely as an air collector, with the other half containing the products to be dried by the air heated up in the collector. Small ventilators powered by solar energy can be used to ensure that the air circulates. This process not only reduces harvest losses, but also cuts the time required for drying roughly in half. Furthermore, the dried goods are protected from precipitation, which is common in tropical countries; the drying process continues without interrup- tion during rain. And if the rain continues
long enough to discontinue the supply of solar heat, a gas burner could provide auxil- iary heat. Such a tunnel dryer can provide up to 60kWh of solar energy per day, equivalent to the energy contained in some 15kg of firewood.
Air collectors can also be used in temperate zones. 12 The energy yield is even higher than with flat-plate collectors for space heating. In energy-efficient buildings, air collectors and ventilation systems can be combined in a number of interesting ways. 13 For instance, at an indoor pool in Wiesbaden, Germany, a 420m 2 air collector heats the air inside, saving some 50,000m 3 of natural gas each year. 14 In Göttingen, Germany, a 343m 2 air collector on the wall of a heating plant pre- heats the combustion air with solar energy, reducing the amount of energy that the plant itself consumes.
Transparent foil
Cold air
Air exit
Drying area
Expansion chamber
Air collector
Solar module
Air entrance
Figure 2.5 (1) Solar drying: How air collectors work Figure 2.5 (2) Solar drying: Solar tunnel dryer for agricultural products
Source: W. Mühlbauer and A. Esper, 'Solare Trocknung', in Sonnenenergie 6/1997
2.6 Solar thermal power plants
2 Solar collectors can heat up to around 80˚C. But much higher temperatures can be reached when sunlight is concentrated. This concentrated heat can then boil water and steam can be used to drive a turbine to generate electricity. In such cases, one speaks of solar thermal power plants or concentrated solar power (CSP).
In CSP plants, mirror systems track the sun and concentrate reflected light on a single focal point, where temperatures can reach up to 800˚C. There, a fluid is heated to create steam. The steam can then drive a conventional turbine like the ones used in coal and oil power plants. Unlike photo- voltaics (see Chapter 3), sunlight is not directly converted into electricity here, but rather indirectly via steam and a turbine. There are basically three types of CSP plants.
The most common type is parabolic trough plants. This technology has moved out of the pilot phase. In California's Mohave Desert, nine such power plants have been built with a total mirror surface area of 2.3 million square metres and a cumulative output of 354MW. The mirrors curve around a central tube at the focal point of the para- bolic trough. The fluid inside these tubes is heated up to 400˚C and used to generate electricity. Such commercial systems have been under construction since 2002, when Spain adopted special feed-in tariffs for solar thermal electricity. In mid-2006, construc- tion began on a 50MW parabolic trough plant, and dozens more were planned. 15 In other Mediterranean countries and the US, large concentrating solar power plants are under construction or planned. 16 In the DESERTEC project, giant parabolic power plants are to be built in the Sahara to supply
electricity to the north African countries and to Europe. 17
In dish Stirling systems, a large dish- shaped mirror focuses sunlight on a Stirling engine, which uses the heat to generate electricity. With mirror diameters ranging from 7–17m, power output ranges from
10–50kW.
Solar tower plants concentrate sunlight on a single focal point like a dish Stirling system does, but they do so with a large number of mirrors that track the sun and concentrate it on the top of a tower, where steam is produced. Pilot systems currently have outputs of 1–10MW. 18
CSP plants can generate up to 200MW of electricity per plant. A study conducted by the German Aerospace Centre found that the potential for Mediterranean countries alone was up to 1500TWh, equivalent to roughly half of all power currently consumed in Europe. 19
And when the heat-carrying medium is stored, electricity can also be produced from solar energy even in the evening when the sun is not shining.
Parabolic trough power plant (concentration along an axis)
Solar rays
Absorber tube
Solar tower power plant (concentration on a point)
Figure 2.6 Solar thermal power plants
Source: The authors, Triolog
3.1 The heart of a PV array – the
3 solar cell
As described in Chapter 2, solar thermal energy converts solar rays into heat. Photovoltaics is another way of using solar energy. This technology is based on a well known effect in physics: some semiconduc- tors convert light directly into electrical current. This chapter focuses on the main applications and the future of photovoltaics as seen from today.
Just as the absorber is the heart – the part that converts sunlight into heat – of a solar thermal array (see 2.1), the solar cell is the heart of a photovoltaic array. Spread out thinly over the largest possible area, this semiconductor converts incident light directly into electrical current.
The first solar cell was made using silicon in 1954, and 90 per cent of all solar cells currently made worldwide are still manufac- tured using this basic semiconductor material.
To reach voltage levels commonly used (such
as 12V of direct current), multiple solar cells are 'switched in parallel' (connected in rows). When the cells are laminated into a sandwich between a glass pane on the top
and a plastic foil on the back, you have a finished solar panel.
The efficiency of crystalline solar cells commonly sold on the market is generally around 15 per cent under standard test conditions. As temperatures rise, the power yield drops; ensuring that panels have some air underneath them to cool them off (natural ventilation) is therefore a good idea.
In addition to the silicon wafers described
here, thin film has grown to cover roughly 10 per cent of the market. Thin-film cells generally consist of either amorphous silicon or some combination of copper, indium, gallium and selenium (CIS and CIGS), which will be discussed further in 3.5. Thin-film cells are much thinner than traditional crys- talline silicon solar cells, and the production methods are also very different.
In a process called 'doping', impurities (generally boron and phosphor) are intro- duced to a wafer generally thinner than 0.2mm consisting of highly pure silicon to create two layers with different electric prop- erties. When light reaches the solar cell, the charge carriers (electrons) from one layer flow to the other layer, creating a voltage of 0.5V at the contacts. This voltage within the solar cell remains relatively constant, but the current that comes out of the cell varies depending on the size of the cell and the intensity of incident light.
A number of other cell types are also being
developed or in pilot production. The goal of this research and development is to make photovoltaics, which is currently relatively expensive, cheaper by using less material or less expensive material. 1
doped silicon
Border layer
Positively doped
Figure 3.1 The heart of a photovoltaic array: The silicon solar cell
Source: Leuchtner and Preiser, Photovoltaik-Marktübersicht, 1994
3.2 Grid-connected PV arrays
Power generated from photovoltaics offers a number of benefits:
• Emissions – PV arrays are silent and emit no waste gases.
• Service life – since there are no moving parts, solar arrays have very long service lives. Manufacturers offer warranties of 20 years and longer for solar panels.
• Environmental impact – silicon solar cells are environmentally friendly during oper- ation and can be recycled without any environmental impact. 2
• Resources – silicon is the second most common element on the Earth's crust, so it is hard to imagine us running out of the raw material.
• Wide range of applications – photo- voltaics can be used in a large number of applications from pocket calculators and wristwatches to large solar power plants.
Thanks to these benefits and a number of governmental policies to promote photo- voltaics, grid-connected arrays have become a common sight on residential buildings in many countries (see Figure 3.2). Generally, they have a rated output ranging from 1–10 kilowatts-peak. 3 Solar panels produce direct current, which an inverter converts into alternating current so that the power can be exported to the grid. When solar power is metered separately from consumption (double metering), compensation for solar power can be decoupled from the retail rate (feed-in tariffs, see 11.10); this approach also allows solar power generation to be measured for carbon trading and towards renewables targets, which net-metering (with a single meter) does not.
A PV array with a peak output of around 2kW will take up some 20m 2 of roof space. Depending on local conditions and the array's orientation, that array will generate some 1700–2000kWh per year at German latitudes, roughly as much power as a four- person household that conserves energy would consume. In 2010, such an array would cost less than €8000, with prices falling rapidly (see 3.5).
When feed-in rates were offered for photo- voltaics, businesses began to become interested. They began to set up much larger arrays with lower specific costs on multi- family dwellings, roofs of commercial facilities and farms. In 2006, arrays with a rated output ranging from 10 kilowatts- peak to 1 megawatt-peak made up around half of the German market. 4
Today, the largest PV power plants have a peak capacity of dozens of megawatts. A 60MW array was completed in Olmedilla, Spain, in 2009 and there are plans to break the 100MW threshold in the US.
From Q4 2008 to Q3 2009, some 2.4GW of photovoltaics was installed in Germany, equivalent to the amount consumed by 720,000 German households.
Figure 3.2 Grid-connected photovoltaic arrays
3.3 Off-grid PV arrays
Roughly 2 billion people worldwide – a third of the world's population – have to make do without a power grid. Distributed electricity
3 supply to cover the basics would improve the lives of these people considerably. Artificial lighting at night allows people on farms and in shops to work later; schools and community centres can also offer more flexible services. Radio, telephones and tele- vision provide information and means of communication to remote regions. The power needed for such applications can be provided less expensively and often faster with off-grid PV arrays than with grid expan- sion. 5 Indeed, photovoltaics is often even less expensive than small diesel generators.
The equipment used for such purposes is known as Solar Home Systems (see Figure 3.3), these consist of a solar panel roughly 0.5m 2 in size (around 50 watts-peak), a battery, a charge controller and three compact fluorescent light bulbs (12/24V). Under five hours of full sunlight per day, such as systems can power a radio, the three lights, a black-and-white television and other small devices for several hours. While that may not sound like much by European standards, it marks a crucial increase in the standard of living for many people in devel- oping countries. Solar Home Systems for a basic power supply are available starting at around US$500 – a lot of money for the target group. Suppliers have therefore come up with suitable financing models.
For instance, Shell has the following strat- egy: 'You cannot expect a shepherd in Inner Mongolia to pay €500 or €1000 for a solar array. We have therefore come up with a kind of lease. We finance the system and install it. Customers then pay for monthly usage with a chip card that costs €7 for 30 days. They then have to recharge it, for instance at a Shell station or at their commu- nity centre. In this way, we get our investment costs back.'
The benefits of these PV systems are so obvious that this market is growing quickly without any subsidies. In 2005, more than 2 million households worldwide in developing countries received new Solar Home Systems. In China alone, some 10,000 new systems were installed per month in 2005. 6
There are even situations in industrial coun- tries where off-grid PV systems are the best option. For instance, PV-powered parking ticket meters are cheaper than the ones that run solely on batteries or require a grid connection. PV panels also make lighting possible for remote bus stops (with motion detectors to conserve electricity) to provide greater comfort and safety in public trans- port for rural areas. Farmers have also found that small PV arrays provide the cheapest power sometimes, such as to power a fishing pond aerator, an electrical fence and an irrigation pump. 7
Solar Home Systems enable an economical supply of electricity in off-grid regions
Figure 3.3 Off-grid photovoltaic arrays
3.4 Solar energy as part of sustainable development
Solar energy is by no means the only require- ment for sustainable development, but
3 energy supply does have to be extended if standards of living in rural areas of develop- ing countries are to be improved. Cuba provides an interesting example of how solar energy can raise standards of living for entire villages.
Comprehensive rural electrification began shortly after the Cuban revolution in 1959. From 1960 to 1992, the share of rural households with electricity rose from 4 per cent to 79 per cent. Because it would be very expensive to expand the grid to cover the remainder, some 500,000 remote homes still did not have electricity in the 1990s. In 1987, the Cuban government launched an ambitious programme to provide electricity to even the most remote villages.
In the first phase, all health clinics in these
regions received solar power systems. Every
village has such a health clinic staffed by one doctor and one nurse. This service is one of the reasons why Cuba's health care system is
a model for Latin America. The solar array
with an output of 400W powers a refrigera- tor for medicine and a small television. It also ensures that the clinic, which is often the main village meeting place, has sufficient light. By the summer of 2002, 320 such health clinics had received such solar power systems.
In a second phase, schools in remote villages received solar power systems. The Cuban government installed a 165W panel on 1900 schools – enough power to light classrooms and power a colour television and VCR. The cost per school was US$1480. Local people were trained to service the solar array, the battery and the devices. This solar electrifica- tion programme for schools was completed in 2002. 8
In the third phase, which began in 2003, all homes were to receive power within five years. Most of them were to receive Solar Home Systems, with the panels produced locally in Cuba. In areas where wind power, hydropower or biomass could be used inex- pensively, expansion into microgrids 9 was considered.
All schools in rural regions of Cuba use solar power
Figure 3.4 A Cuban village school with solar power
Source: BMU, Sustainable Energy Policy Concepts (SePco). Photo: Dorothee Reinmüller
3.5 The outlook for PV – lower costs from new technologies and mass production
Silicon-based photovoltaics is a well devel-
3 oped technology that reliably produces environmentally friendly solar power. At present, however, solar power from grid- connected arrays still costs around 30–40 eurocents in Germany per kilowatt-hour (depending on system size), roughly six to eight times as expensive as power from coal plants, though the price of solar power is a fraction of that in prime locations in places like Arizona. Research and development in photovoltaics has therefore mainly focused on lowering costs, mainly by means of two approaches that go hand-in-hand: new technologies and mass production.
New technologies will provide greater effi- ciencies and make do with less material or less expensive material. Various approaches are currently being pursued: 10
Thinner cells
Over the past ten years, cells have become increasingly thinner – from 300 to 180 microns of expensive, highly pure silicon. But thin-film cells – mainly copper-indium- selenide (CIS) and cadmium telluride (CdTe) – make do with far thinner layers; CIS layers are only five microns thick, which represents a considerable reduction in material consump- tion. And because these layers are applied to a substrate by means of vapour deposition, manufacturing costs are also lower. Experts nonetheless believe that silicon cells will remain the main workhorse of photovoltaics.
Advanced designs
The surface structure can be optimized, for instance, to capture more light by reflecting less of it back outside the cell. The result would be greater efficiency.
Concentrator systems
If three types of semiconductor, each of which absorbs a different part of the light spectrum, are stacked on top of each other, efficiency increases dramatically. Such cells are, however, much more expensive. But if simple optical mirrors and lenses are used to concentrate light on such small cells, the energy yield increases even as material costs decrease.
Market development is also crucial in lower- ing costs. Industry will only be able to set up the large production capacity required for economies of scale if markets are sufficiently large to absorb output. The last decade clearly shows that greater solar panel production leads to lower panel prices (see Figure 3.5). Germany's 100,000 Roofs Programme, which ran from 1999–2003, and the more recent Renewable Energy Act (see 11.9) set off this development in Germany by providing a safe investment environment; the former with upfront funding, the latter with feed-in tariffs. Admittedly, the skyrocketing demand for solar panels led to a bottleneck in the supply of silicon in 2005, which temporarily kept
module prices high. 11 But the silicon shortfall has been overcome, and prices for silicon solar panels fell by around 25 per cent in
2009 alone. Experts believe that grid parity –
when solar power will cost the same as
power from the grid – is already being reached in parts of southern Europe and the southwestern US, but even Germany is expected to reach grid parity by around
2013 because of its relatively high electricity
prices. 12 German PV success is the direct result of its feed-in rates for solar power.
Installed capacity in MW p
Power costs in euros/kWh
Power costs
Figure 3.5 Prospects for photovoltaics: Lower costs from new technologies and mass production
Source: BMU, Erneuerbare Energien, 2006
4.1 A third of the pie – space heating
4 The construction sector plays a special role in our solar strategy because roughly a third of the final energy consumed in industrial countries such as Germany is used to heat buildings. Indeed, more energy is used to heat apartments, offices, public buildings, etc. than in the entire transport sector. Yet, there are many ways to use solar energy for these purposes (low-temperature heat). We will discuss these solar options in this chapter.
The average German building requires some 220kWh of heat per square metre per year, equivalent to 22 litres of heating oil or 22m 3 of natural gas. Most of this energy would not be required if buildings were properly insulated. In the past few years, legislators have fortunately begun setting up require- ments for insulation. For instance, Germany required all new buildings to make do with 100kWh per square metre a year in 1995. 1
'Low-energy buildings' make do with much less. Here, ventilation systems are added to improved insulation so that homes (in Germany) only need around 50–70kWh per square metre a year for heating – roughly 5–7 litres of oil, only a quarter of the average for buildings constructed before 1995. In Sweden, the low-energy standard was made mandatory for all new buildings at the beginning of the 1990s. Germany did not implement this standard until 2002. 2
In its revised Energy Performance of Buildings Directive, the EU requires all new buildings to be 'nearly zero-energy' by 2020. Though that may sound like an ambitious target, zero-energy buildings have been around since at least the 1990s. The off-grid solar home (4.7) was opened in 1992 as a pilot project, but zero-energy homes, numerous passive houses (4.6) and plus- energy homes (4.8) constructed over the past two decades show that homes can do without conventional heating systems without any loss of comfort even at German latitudes. Such homes are becoming increas- ingly attractive for buyers; they will have to become the standard for the transition to the Solar Age.
But standards for new buildings will not take us far. The greatest energy conservation potential comes from renovations of old buildings. A solar strategy that focuses solely on new buildings will therefore fall short of the mark. Rather, the insights gained from progressive building standards must be used for renovation projects as well. Solar thermal systems and transparent insulation will play an important role here (4.4 and 4.5).
Energy consumption in kWh/m 2 /a
Plus-
WSchVo
Figure 4.1 Space heating: A comparison of key energy figures in various building standards
4.2 Passive solar energy
'Passive' solar energy means that solar energy is used to help heat a building in the winter without any complicated technology, such as pumps, heating circuits, etc. There are basically two ways to use solar energy
4 passively: 3
1 Special components, such as windows, glass façades and transparent insulation.
The type and design of the windows used are especially important because every house has them. The technology in this field has made significant progress over the past few decades. At the end of the 1970s, insu- lated double glazing was considered a good standard. By adding a coating that reflects heat and by filling the space between the panes with a noble gas, modern insulating windows can reduce heat loss by around 60 per cent (U g = 1.2 instead of 2.8 for 'normal' insulating glazing 4 ); triple glazing (U g = 0.7) even increases that reduction to 75 per cent.
But if we are to use solar energy, we not only need to make sure that as little heat as possi- ble passes out of the building in the winter through the windows; we also want as much solar energy as possible to enter the house through the windows. As the insula- tion of windows becomes better, the solar input is also reduced even as heat losses out of the building drop considerably. Nonetheless, south-facing, insulated windows have a positive energy payback. These windows allow more heat to enter the house than they allow to exit over the year.
Solar architecture takes advantage of this effect by reducing the building's energy demand with a greater share of south-facing glazing (in the northern hemisphere). North- facing windows cannot provide such heat
input owing to a lack of direct sunlight. Therefore, windows on the north side of the building are kept as small as possible if a building is to be heated.
Likewise, in the southern hemisphere, windows on the north side would be made larger to allow more heat to come into the building. And wherever a building is to be kept cool, the windows on the side with the most sunlight would be made smaller.
2 Solar architecture, such as selecting the proper location and orientation for a building, adapting the shape of the building, using the roof to provide shading, and planting trees to provide shading.
The use of the roof to provide shading for south-facing windows is especially interest- ing (see Figure 4.2). In many buildings, sunlight in the summer creates excessive heat indoors, requiring energy-intensive air conditioning. To prevent this, solar energy input has to be reduced passively, i.e. without much technology. By having the roof eaves extend out over the façade, the roof itself provides a simple, but effective shading mechanism when the sun is high up in the sky during the summer. At the same time, the eaves should not extend out so far as to prevent direct sunlight from entering the building in the winter.
This example shows how traditional types of architecture use the sun. In the age of cheap oil, we have simply lost sight of a lot of these options. For the transition to the Solar Age, we need to fall back on this knowledge and combine it with new materials and tech- nologies.