What is Evaporative cooling?
Methods of cooling a building
Many buildings require cooling either for the comfort of the occupants or to protect the processes or equipment they contain. Three methods are usually employed to cool buildings: ventilation, evaporative cooling, or refrigerant-based air conditioning. The choice of system can dramatically affect the total carbon emissions of the building and the energy consumed due to their different electrical demands.
When to use evaporative cooling?
Ventilation systems can provide comfortable levels of cooling for most of the year. However, during prolonged periods of high temperatures, they are unable to maintain internal temperatures below 25°C. Refrigerant-based air conditioning systems are effective but can be expensive to install and operate and require frequent maintenance. Evaporative cooling, which can consistently produce air below 22°C in the UK climate, provides an intermediate solution that offers superior cooling performance than ventilation at a fraction of the cost of refrigerant-based air conditioning.
Principles of evaporative cooling
To understand how an evaporative cooler works, it is first necessary to understand a little about heat. There are two types of heat: sensible heat (that you can feel or “sense”) and latent heat (hidden heat that cannot be detected with a thermometer). During evaporative cooling, the sensible heat you can feel in the air is changed into latent heat (the heat you can’t feel), leading to a cooling effect. This occurs due to evaporative heat exchange: as liquid water in the atmosphere changes its state into vapour, it absorbs heat from its surroundings. An evaporative cooler works on the principle of accelerating this natural heat exchange process.
Why is evaporative cooling cheaper than air conditioning?
Typically, an evaporative cooling system is 75% cheaper to install and has 90% lower running costs than a refrigerant-based industrial air conditioning system. These low installation costs are because evaporative coolers need fewer moving parts to function than refrigerant-based air conditioners. In addition, evaporative coolers typically use 85% less energy than air conditioning units. Using a control system to bring in ambient air, we can keep a building cool most of the year. The only significant energy use is in the fan for the air movement.