Solar air Cooling

Using the sun's energy for residential cooling is possible, and a challenging solution. Solar air cooling (or solar air conditioning) is an emergent and promising technology with some novelties....

Solar air cooling with absorption chiller air conditioners

The solar absorption technology used in solar air cooling demands high temperatures and solar panels capable of producing them (tube solar panels, in the case of home applications). The energy generated by the solar panels is used to separate a tank liquid mixture that includes an absorbent (lithium bromide salt, for instance) and a refrigerant fluid (often water). The refrigerant (water vapor) is then condensed and eventually evaporated to produce the desired cooling effect. In the Audubon Nature Center case, cited in this page, solar panels are used to heat the water in a gigantic 1,200-gallon tank. When the tank water reaches the right temperature (180º F) it is pumped into a chiller containing a lithium bromide salt (the absorbent) which yields water vapor (the refrigerant) that is subsequently condensed to produce chilled water - used to cool the indoor air of the facility through a system of coils. Other technologies use desiccant cooling systems in very similar terms.

The most traditional solar air cooling units are based on the absorption chiller technology (absorption chillers can also be fueled by gas or other fossil fuels).

These units are common in some Asian countries, namely in Japan, where the high cost of power makes these gas and solar air cooling units a competitive alternative (they were mostly used, till recently, in commercial and industrial buildings).

This technology - when involving solar energy - is environmentally-friendly and relatively simple to implement, and there are some practical examples of its implementation worldwide.

In USA, for instance, the Los Angeles Audubon Nature Center - a 5,026-square-foot facility for enjoyment and education – has a fully solar-powered air cooling system (see box).

Some corporations - namely Yazaki - have invested strongly in this technology and is now offering tested absorption chillers that can be integrated in hybrid and solar air cooling systems.

Competitiveness

The maintenance and the running costs of absorption chiller solar air cooling technology are low, but the prices of these solutions are still relatively high.

Besides, reduced levels of sunlight (mostly during nighttime...) can also be a problem. They reduce the performance of the system and may require a backup system...

A newer offer of solar air cooling systems for homeowners

But there are also a new line of products, very different from the chiller solar air cooling technology. Big corporations like Lennox or LG are now offering a new type of solar air cooling solutions...

In fact, that's just a new combination, and not exactly a new technology...

LG's solar air cooling units are just a PV solar panel on top of a thousand watt air conditioner, while Lennox (image at left) solar air cooling units are "solar-ready heat pumps and air conditioners", that is, heat pumps and air conditioners integrated with a solar photovoltaic panel (used for both heating and cooling purposes).

These hybrid solar systems have some obvious advantages, and can benefit from tax credits for renewable-energy systems... They involve very basic and well tested technologies able to work under adverse weather conditions.

In fact, their central pieces - the heat pump/air conditioner in their core - can either be fueled by solar and common grid-electricity...

Anyway, some questions remain, concerning the alternatives, the energy savings and the true environmental impact...