Small scale electricity distribution grid
A mini-grid is an aggregation of electrical loads and one or more energy sources operating as a single system providing electricity and possibly heat, isolated from a main power grid. A modern mini-grid may include renewable- and fossil fuel-based power generation, energy storage, and load control. A mini grid can be fully isolated from the main grid (wide area synchronous grid) or interconnected to it. If it is interconnected to the main grid, it must also be able to isolate (“island”) from the main grid and continue to serve its customers while operating in an island or autonomous mode. Mini-grids are used as a cost-effective solution for electrifying rural communities where a grid connection is challenging in terms of transmission and cost for the end user population density, with mini-grids often used to electrify rural communities of a hundred or more households that are 10 km or more from the main grid. 
Mini grids and microgrids are similar, and the terms are sometimes used as synonyms. Both microgrids and mini grids include generation and distribution, and generally include electricity storage in the form of electrochemical batteries. Both can “island” in the event of a blackout or other disturbance or – common in mini grids – in the case that they were never connected to the main grid in the first place. In practice, the term “mini grid” is used more in a context common in low- and middle-income countries providing electricity to communities that were previously unelectrified, or sometimes used to provide reliable electricity in areas in which the national grid is present but where electricity is sporadic. Across Sub-Saharan Africa, more than half of households connected to the main grid reported receiving electricity less than half of the time. The African Mini Grid Developers Association (AMDA) reports that uptimes of mini grids of its members for which data was available averaged 99% across countries. In contrast, the term “microgrid” is used more in higher income countries to refer to systems that provide very high levels of reliability (for example, “five nines” or 99.999%) for critical loads like data centers, hospitals, corporate campuses or military bases generally in service areas that already have high levels of reliability (e.g. “three nines” or 99.9% reliability) by global standards.
Background.
History.
The electric grids of many developed, high-income countries once started out as mini-grids. These isolated electrical systems were then connected and integrated into a larger grid. This first generation of mini grids was pivotal to the early development and industrialization of most modern economies, including Brazil, China, Denmark, Italy, the Netherlands, Spain, Sweden, the United Kingdom, and the United States. Mini grid systems introduced in the late nineteenth and early twentieth centuries can be described as the first generation of mini grids. Starting in the 1980s and ramping up through the 1990s and early 2000s, a second generation of mini grids numbering in the tens of thousands was deployed in many low-income countries. These systems are typically small and isolated, powered by diesel or hydropower, and built by local communities or entrepreneurs primarily to provide rural households with access to electricity, especially in areas not yet served by the main grid. Many of these systems were overtaken by the national grids. Some that still exist are now prime candidates for hybridization with solar photovoltaic (PV) systems to reduce the fuel cost.
Contemporary mini grids.
Over the past few years, a third generation of solar mini grids has emerged. These mini grids, mostly solar PV hybrids, are owned and operated by private companies that leverage transformative technologies and innovative strategies to build portfolios of mini grids instead of one-off projects. The typical third-generation mini grid is ready for interconnection with the main grid, uses batteries for storage, and employs remote management systems and prepay smart meters. This third-generation mini grid also incorporates energy-efficient appliances for productive uses of electricity into its business model. These mini grids operate in more favorable business environments, taking advantage of cost reductions in the latest mini grid component technologies and regulations developed specifically for private-sector investment.
Rural electrification.
Many rural communities remain isolated from larger, traditional grids due to geographic and economic constraints. The electrification of the global off-grid rural population remains a major task of many developing and developed countries, and according to the International Energy Agency in the 2013 World Energy Outlook, mini-grids represent the most cost-effective way to provide universal electricity access to these populations. Due to new technology innovations that have resulted in declining costs both for mini-grids and energy generation sources, specifically solar and wind power, mini-grids have the potential to electrify remote areas that would otherwise remain outside of a grid connection. Mini-grids are a cost-effective and timely solution for more isolated areas in which connection to the main electric grid is unavailable, and represent a practical option for meeting the energy demand in Sub-Saharan Africa, South and East Asia, and Small Island Developing States.
Millions of people remain without access to electricity today, and the U.N. Sustainable Development Goals commit the global community to provide a solution. The map on the right demonstrates energy disparity between developed countries such as the US, China, and Europe while South America, Africa, and Southeast Asia still have many communities that lack reliable, sustainable, affordable energy. Mini-grids are currently being viewed as one of the most effective solutions to bringing energy to rural populations where the energy demands are such that individual stand-alone systems such as nano-grids are impractical but where the population is large enough to require a larger grid system. Because a grid must balance the supply of energy with the demand, the mini-grid's larger size and flexibility allows for safer and more affordable power.
Technical components.
Generation.
With the rapid decline in the cost of solar photovoltaics, there is a strong and accelerating trend towards the use of solar electricity in mini grids. According to a 2022 study by the World Bank's ESMAP, approximately 51 percent of installed mini grids are solar or solar hybrid (generally solar + diesel), followed by those powered only by hydro (35%), fossil fuel (10%), and other generation technologies such as wind (5%). The trend is accelerating: more than 10 times as many solar mini grids were built per year from 2016 to 2020 than fossil fuel mini grids. Almost 99 percent of all planned mini grids are solar or solar hybrid. Solar hybrid mini grids include one or more other sources of electricity generation, typically a diesel generator or sometimes a generator powered by biomass fuel to a provide a dispatchable source of electricity in the event of extended cloudily periods. Most solar mini grids are hybridized with a diesel generator that provides backup power in the event of extended cloudy periods. The diesel generator typically generates less than 10% of the energy consumed by mini grid customers on an annual basis. In areas where agricultural residues such as rice husk or animal manure are plentiful, biomass or biogas generators can take the place of diesel backup generation.
Where suitable sites allow, small scale hydroelectricity (micro- or mini-hydropower) provide cost-effective 24-hour a day electricity generation. In areas where windspeeds are consistently high and/or sunlight is very restricted seasonally, wind is used to power mini grids, often in a hybrid configuration with solar or diesel or both. 
A vital component of a mini-grid electric system is on-site, reliable source of energy generation. Traditional mini-grid generation for remote areas came from diesel engine alternators, which incurred high running costs, low efficiency and high maintenance. To obtain the reliability of a fossil fuel powered grid with greater sustainability, hybrid energy systems can be used to integrate renewable energy technologies with diesel generators, batteries, and inverters. The main concern with generation is the fluctuation in load demand that imposes varied power requirements from the generation system. These fluctuations can vary throughout a single day, from day to day, or even on the scale of weeks to months, which necessitates flexible mini-grid generation. In the case of limited power generation without a source of energy storage, peak loads can demand more power than the mini-grid generation is capable of supplying, which results in brownouts or blackouts.
Energy storage.
In renewable energy mini-grids, storage plays a crucial role by balancing the intermittency of sources like solar and wind, ensuring a consistent and reliable supply of electricity, especially during periods when generation is low or demand is high. Electricity in third generation mini grids is stored in electrochemical batteries. Prior to 2018, most mini grids were installed with lead acid batteries, however the rapid cost decline and superior lifetimes and performance of lithium-ion batteries has led to most new mini grids using lithium-ion batteries. In a World Bank ESMAP survey of 211 mini grids under commissioned in 2020 and 2021, 69% used Li-ion batteries and 31% used lead-acid batteries.
Power conversion and management.
In most mini grids, inverters convert the direct current (DC) electricity stored in batteries and produced by solar panels into alternating current (AC) power that powers appliances used in households and businesses.
In some particularly small communities with low loads, DC mesh mini grids are used. Mesh grids—or “skinny grids”—distribute DC electricity for lighting, electronics, and small appliances like fans and even efficient refrigerators or electric rickshaws. They take the form of clusters of solar home systems made up of solar panels affixed to customers' premises and connected in a mesh network. Specialized controllers allow surpluses to be shared and households can upgrade to AC appliances by purchasing an inverter.
Energy management systems (EMS) optimize the balance between dispatching the diesel generator and drawing on energy storage, taking into account expected load and near future opportunities for solar charging. Many mini grids, even in remote areas, have cell-phone carrier based remote monitoring capabilities that monitor power production and consumption, battery state-of-charge, and voltage levels and upload information to the internet several times per hour. Remote monitoring can help operators to identify and address small problems early before they cascade and become larger problems.
Distribution.
A mini-grid distribution system carries the energy produced by the generation source to the end users. It consists of poles and low voltage ( ;1000 V) distribution wires as well as protection equipment necessary to enable safe and effective energy distribution. If a feeder in the distribution system is longer than roughly 1 km in distance, then it is generally necessary to use transformers to step up the electricity to medium voltage (35 kV or below) to reduce ohmic losses. Depending on the load requirements, a distribution system can be in AC single or three phase power or DC. 
If there is the prospect that the main grid may someday arrive, the mini grid distribution network is often built to utility standards so that the distribution network can be easily integrated into the national grid. If the mini grid is certain to remain disconnected from the main grid (for example, if it is located on an island distant from shore) distribution networks are sometimes built to standards that are lower than the national grid, but still ensure safety and efficiency.
Electricity is sold to customers using either pre-pay or postpay meters. Pre-pay meters are more common and work like pre-paid phone plans, automatically disconnecting customes when the amount of purchased electricity is consumed. Because electricity consumed during sunny hours is less costly to produce than electricity that must be stored in batteries or generated from a diesel generator, mini grids metering systems sometimes provide lower tariffs for daytime consumption, or the ability to curtail lower-priority customers in the event of energy shortages.
The use of a pre-made switchboard (sometimes referred to as a ready-board) with a few light switches and outlets can eliminate the costs of internal household wiring.
Benefits.
There are many potential benefits of mini-grids ranging from technical and environmental to social and financial advantages. Mini-grids can be used in rural areas and are often more efficient and cost-effective than other types of power systems. They can also strengthen the community while having less impact on the environment.
Technical benefits.
The technology used in mini-grids provides various benefits. Mini-grids are relatively quick and easy to implement in areas without electricity. They can also be used to improve existing electrical grids that are ineffective or unreliable by providing additional power or by replacing them completely. Mini-grids are also more efficient because they can provide a low