GE ECOmagination Contest Displays Refreshing Concepts For Energy Conservation, Including Solar A/C

Solar AC

Space heating and cooling, together with solar tap water are the most energy hungry users. Optimal efficiency will be offered by solar water heating based systems for space cooling and heating. The energy usage of pure solar air conditioning is extremely low as they only require small pumps and fans. As a lower cost alternative for geothermal storage there is seasonal thermal storage, that will further increase the efficiency of such systems.

During the summer, all excess thermal capacity may be used to store hot water in well insulated tanks. Even in autumn -before the heating season begins- excess capacity is to be used to maintain the temperature of the water in the storage tank. This hot water can then be used for space heating during the heating season, either supplementaryto or as replacement of the thermal capacity on the solar collector during less sunshine. After the seasonal tank's temperature has dropped below a useful level (typically in the middle of winter) the water can be cooled by circulating water from the seasonal storage tank to a heat exchanger underground outside. The temperature will then (gradually) go down to 1° C/34° F. In the cooling season this water can be used to cool the green home by pumping the cold water to wall or floor radiators or water based AC airhandlers. Alternatively, the hot or cold water can be sent to a fluid to air converter (think of a car radiator where the water circulates and a fan blows through it), which is the solution for central AC systems.

Limitations of solar air conditioning

During overcast winter days it may not be possible to heat the house on solar alone. Seasonal thermal storage as described above can nicely compensate that. Therefore, if you plan to build a new green residence, integrate seasonal /thermal storage under the house. During hot days, the solar cooling system will work perfectly, but once the sun sets you can only rely on the stored capacity. Even if you have only 1 big tank (200 Gallon = 760 liter) you should be able to maintain the desired temperature during the evening (but only when the house is well insulated. During the night the efficiency of the solar A/C will gradually drop and the temperature will slowly get higher. For most people however, this is not a problem at all as during your sleep you don't experience minor changes in temperature. In heating mode the system works exactlythe other way around. Mission critical applications such as data centers will generally require a backup system.

Use the solar heated water also for your washing machine and dishwashing machine. If they don't have separate connections for cold and hot water, connect the hot water to the regular input, but make sure that the piping can withstand the high temperature. Solar dryers are coming too and will have a good impact as they use a lot of energy. Now that solar water heating is becoming more popular, developers will come with solutions. In Israel it is against the law to build a residence without a solar water heater!. In China many houses have solar water heaters In Germany they are installed at 15% of houses and a far higher percentage in new construction but in North America solar water heaters are not yet so common, but that will likely change quickly, now that people realize that we must work towards green houses that are energy neutral. Another important consideration remains is to construct very well insulated houses.

Is a zero energy home becoming a reality soon? Absolutely; and the cost goes down. A energy neutral residence is the total of energy conservation, good insulation and renewable energy. Look at the GE ECOmagination challenge website at the link hereunder; that will give you a good idea what is going on.


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James Post is a Dutch national living in Grenada. A strong conceptual designer, he is now a top participant at the GE technology competition and welcomes votes and comments from readers. Link to the Ecomagination website (signup required): http://tinyurl.com/smartsolar . He also owns a small ECO resort: http://www.paradisebayresort.net/html/eco.html ;the first hotel in the world that installed a utility class wind turbine.