Air conditioning

Domestic air conditioning is common in climates where high temperatures or high humidity occur, and the energy demands of air conditioning systems in summer can be comparable to those for heating in winter. In countries such as the USA and India, units consuming 10 to 20 kW are not uncommon. In automobiles, a significant proportion of fuel consumption can go to power the air conditioning: 5 to 10 per cent is common in the USA.

In general, air conditioning consists of several stages. First, air drawn from within the building (or vehicle) is mixed with some fresh air from outside and is filtered to remove dust. To control humidity, moisture may be added to or removed from the air: in the latter case the air is cooled considerably to precipitate out the excess moisture. Before the air is recirculated, some final cooling or heating may be needed to achieve the desired temperature.

Because air conditioning is most needed under strong sunlight, it is recognised as an ideal application of solar energy, and numerous designs for solar air-conditioning systems have been made and tested. As energy prices in real terms rise, solar air conditioning may be- come increasingly competitive with electrically-powered units.