Air Conditioning

Air conditioning (A/C) is more expensive than heating and can use more energy. It is important to recognize the difference between A/C and simple ventilation: Natural ventilation is cheaper and, when properly controlled, can greatly reduce A/C loads.

Air conditioning is a chiller by another name, and therefore all A/C uses a compressor of some type in the A/C unit. Some A/C units have free cooling coils that operate in the same way as free cooling for chillers, and these can considerably reduce the cost of A/C.

Poorly controlled A/C can double the energy costs of an office, and a key issue is to avoid heating and A/C competing with one another. Even when well controlled, A/C will make up approximately 35% of the energy demand of the average office. Poorly controlled A/C will use much more energy and can be over 50% of the energy use. In temperate climates there is no reason for A/C in production areas.

Action:

Investigate free cooling for A/C units.
Turning thermostats down does not cool the building quicker. An A/C unit has a fixed output and cannot cool faster than this.
Cooling levels should be adjusted to the outside temperature.
Reducing the delivered air volumes can reduce costs.
Leaving A/C on overnight does not save energy. Use controls to turn A/C off overnight.

Note: Dr. Robin Kent is the author of Energy Management in Plastics Processing, published by Plastics Information Direct, and managing director of Tangram Technology Ltd., consulting engineers specializing in energy management in plastics processing. rkent@tangram.co.uk.