INNOVAL
The hot climate at Le Port led the team in charge of the INNOVAL project to prepare a cooling strategy for different seasons. During the winter, natural ventilation is sufficient to cool offices and during the mid-season between the winter and the summer, natural ventilation is completed with ceiling fans. However, during the summer, natural ventilation coupled with ceiling fans are not sufficient, consequently, air conditioning has to be used. In buildings in Reunion Island, a significant percentage of the energy consumed is due to air conditioning, therefore, the air conditioning system selected here is an efficient one with a Variable Refrigerant Flow ensuring reliability and energy savings. Moreover, a software tool automatically regulates the power of cooling in relation to office use. Finally, while in Reunion Island, people are used to cooling below 24 °C, the air conditioning of the building cannot cool below 26 °C which is adequate with ceiling fans and natural ventilation. Indeed, with the assistance of ceiling fans, the felt temperature is reduced by 5 °C allowing a final felt temperature of 21 to 22 °C. In order to optimize the refrigerated unit power, the temperature adjustment consists of applying a difference of 5 °C between the outside and the inside. For example, if the outside temperature is 34 °C, the temperature adjustment will be 29 °C. All these choices in operation have led to a decrease from 100 kW to 30 kW in the power required by the refrigerated unit.
Hashem Akbari
The UHI group in LBNL have monitored buildings in the California central valley with lightly colored, more reflective roofs and found that these buildings used up to 40% less energy for cooling than buildings with darker roofs. In a study funded by the U.S. Environmental Protection Agency, they carried out a detailed analysis of energy-saving potential of light-colored roofs in 11 U.S. metropolitan areas, with resulting estimated savings potential of about $175 million per year (1998 USD) for the 11 cities. Extrapolated national energy savings from air conditioning was estimated at $750 (1998 USD) million per year. The savings from shade trees and vegetation is also estimated at $1B per year. The impacts of savings in health and lost work time owing to a projected 12% O3 reduction are three times larger than that cited for air conditioning above. Heat island mitigation technologies apply all around the world in both developed and developing countries. They estimate that the potential energy savings and health benefits from a worldwide implementation of heat-island mitigation technologies can save over $10B per year. They are working with manufacturers of roofing and paving materials to develop ‘colored’ solar-reflective materials for the marketplace, including both dark and light-colored cool shingles with reflectivity of up to 60%.