Use the suns rays to stay cool this summer

Solar air conditioners make very good business and environment sense for India.

Solar air conditioners make very good business and environment sense for India. We are blessed over 300 days of sun in a year in most places across our vast land. The increasing use of air conditioners at home and office has led to massive demands on electric power. This results in power outages by utility companies when maximum demand is exceeded on a hot summers day. This time is just right to capitalise on the source of infinite energy the Sun to satisfy our quest to remain cool and soothe frayed tempers when the electric supply fails.

The obvious benefit of using a solar air conditioner is savings on electricity costs. Currently,over 40 per cent of energy consumed in commercial buildings is due to air conditioning and this proportion is rapidly increasing in homes too. The second benefit is for the environment in the form of reduced carbon emissions.

There are two types of solar air conditioners. One uses a photo voltaic PV panel to power the air conditioner. The other type uses a desiccant moisture absorbing compound and a heat recovery wheel to achieve cooling and dehumidification. The latter technology is more suited for dry climates and does not lend itself for practical application in domestic air conditioners.

Internationally,PV panel powered cooling has been the popular technology for residential applications. A PV system uses an inverter to convert the DC power generated by the panels into AC power. The AC power provides the electricity to power a conventional air conditioner.

Nowadays,air conditioners running on DC power are being manufactured. In this case,there is no need for an inverter. So air conditioners designed to run on DC power say at a DC input voltage of 48 volts can then run from batteries that are charged by a PV panel or from other alternate energy sources such as wind power. The other alternative is the air conditioner that can run on dual power,i.e. both DC and AC supply that comes from the power grid.

So how does a solar powered air conditioner differ from a conventional air conditioner? A typical home solar air conditioner would look just like a standard split air conditioner. It differs in the method by which it receives electric power,which we have seen earlier. Solar-powered air conditioners switch back to conventional grid power when solar power is not available on cloudy or rainy days or when the sun goes down.

A typical solar air conditioner would have a PV panel mounted on the roof of the building or the balcony of the flat that faces the sun at most times. The installation would be as simple as that of a dish antenna for a television set.

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Now the prices. There are manufacturers focusing exclusively on hybrid solar air conditioners that work on both conventional and renewable power. A 0.75 tonne unit would typically be in the range of Rs 45,000. A 1 tonne unit would range between Rs 52,000-55,000 and a 1.5 tonne unit would cost between Rs 70,000-75,000. The solar mode would work on all sunny days and can save 30 per cent or even more on your electricity bill. Assuming a monthly electricity bill of Rs 2,500,the capital cost for a 1 tonne unit can be recovered in under three years.

Vikram Murthy is former president,Indian Society of Heating,Refrigerating amp; Air Conditioning Engineers,Mumbai Chapter