Why modern cooling systems are so much cheaper than air conditioning

October 11, 2012

Modern evaporative air cooling systems take air from outside a building and pass it over filter pads soaked in water, which cool it before pumping it into the building. Simultaneously, warm air is vented from the building, allowing the cooled, fresh air to circulate inside.

Air conditioning, on the other hand, takes a gas refrigerant, compresses it to a liquid, and pumps this around the cooling system. The heat from the air flowing over the pipes is absorbed into the liquid, which expands back to a gas so it has to be recompressed to start the cycle again. It doesn’t take long to realise that this cycle of compression requires an eye-watering amount of energy.

How much energy? Your organisation could save as much as 90% if it switched from air conditioners to evaporative air-cooling systems for cooling your data centre.

Imagine a 100kW council data centre. Now, the efficiency of data centres varies. The best ones have a COP (Coefficient of Performance) of around 3.7. Older ones can have a COP as low as 1. But at a COP of, say, 2, the operating costs look like this:


Electricity per kWh Typical air con system Typical evaporative air cooling system Savings
                  9p £39,400 £3,300 £36,100
                12p £52,600 £4,400 £48,100
COproduction 235 tonnes 20 tonnes 215 tonnes


That’s a saving of 215 tonnes of CO2, which means you’re well on your way to reducing your carbon emissions.