Solar house space cooling & Solar home air conditioning

STOP GLOBAL WARMING
Save energy and money

Solar air conditioning & House Space Cooling

Solar air conditioning: cooling your house with solar energy?

Until now the applications of solar energy are mostly limited to heating purposes and to PV solar electricity, and it may sound strange to use the sun energy in house cooling purposes. And yet it’s possible.

Solar home space cooling systems are part of the Thermally Activated Cooling Systems (TACS), and for some enthusiasts of solar energy, they are an environmentally-friendly technique with a promising future.

Some gigantic facilities as the Los Angeles Audubon Nature Center - a 5,026-square-foot facility devoted to enjoyment and education – has a fully solar-powered air conditioning system (heating and also cooling).

Solar air cooling systems: possible but expensive

Today’s solar air conditioning systems aren’t competitive, mainly in stand-alone applications. Solar cooling is rarely used because of the high initial costs of the system implementation.

Only when combined with solar home water heaters and space heating systems they may become more competitive. Most stand-alone solar cooling systems are quite expensive investments: solutions of $4000 - $8000 per ton are very common.

Implementing a solar house cooling solution

Once solar cooling systems demand expensive investments, a possibility is to develop combined air conditioning systems (dual systems) using the same basic equipment/collectors. This solution - serving more than just the cooling needs – allows the use of the installed equipment in the parts of the year when cooling is not required.

Manufacturers and suppliers of solar air conditioning

There isn’t a specific offer of solar space cooling equipment on a national basis, and there aren’t local suppliers either, contrasting with other solar equipment… Solar home space cooling solutions have to be studied and implemented in conjunction with solar heating technicians and experts on common gas cooling systems.

A partial solution

Most solar air conditioning solar systems solutions are sized to provide 40% - 70% of house cooling requirements (the remainder are usually fueled by natural gas or other means).

Technologies available

Technologies available for solar-driven cooling include 1) advanced absorption systems and 2) desiccant cooling systems.

Solar absorption technology

Absorption technology demand high temperatures and collectors capable of producing them: evacuated-tube and concentrating type solar collectors… The energy from these solar collectors is used to separate a tank liquid mixture that includes an absorbent (lithium bromide salt, for instance) and a refrigerant fluid (often the water). The refrigerant (water vapor) is then condensed and eventually evaporated to produce the desired cooling effect.

In the Audubon Nature Center case, cited above, the thermal energy from the solar collectors is driven to a 1,200-gallon insulated high-temperature hot water storage tank. When the stored hot water reaches the right temperature (180 degrees F…), it is pumped through a generator into a chiller containing a lithium bromide salt (the absorbent) which yields water vapor (the refrigerant) that subsequently is condensed to produce chilled water. In its terminal phase, the system use fan coil units to drive the indoor building air across the coils containing the chilled water, causing its cooling.

Solar desiccant technology

Solar desiccant technologies use… desiccants - substances like silica gel, calcium sulfate, etc. to absorb the air humidity and to cool it. Desiccants are commonly solids, but may also be liquids. Both technologies are very similar in their implementation.

In the case of the solid desiccant system, as the air passes through the desiccant (usually located on a wheel rotating into the air stream going into the house rooms) the moisture is removed from the air, causing the humidity level and the temperature of the air to drop. At the same time the thermal energy from the solar collectors is used to dry the desiccant, driving off the absorbed water (as it rotates out of the air stream).

Heat pumps and other alternatives for solar air conditioning and cooling

Since solar cooling systems demand expensive investments and aren't a well established technology with a wide offer, you should consider other environmentally-friendly options, namely:

- a combination of a correct insulation with energy-efficient doors and windows, shading and ventilation; this combination will keep homes cool with a minimal use of energy (except in the hottest climates, where ventilation is usually a bad option).

- ground (or geothermal) heat pumps: they are an excellent solution for home heating but also for home cooling.

- ventilation (though not in hot humid climates): natural ventilation and a good fan system (combined with approaches as insulation) will reduce dramatically the need to use air conditioning.

- evaporative coolers (also called swamp coolers): in dry climates, this very cheap alternative produce very good cooling results at very low low costs. Evaporative cooler are cooling devices in which a blower forces air through over water-saturated pads, cooling it and pushing warmer air out through windows.