Even allowing for the vagaries of the British weather, many properties in the United Kingdom still require some means of artificial air conditioning to maintain indoor temperatures and humidity levels at a comfortable level. Indeed this may become increasingly true in the future if predictions regarding global warming are to be believed. Evaporative air conditioning systems require no compressor making them quiet and highly energy efficient – increasingly so as ambient temperatures rise – and no potentially damaging refrigerant chemicals. Furthermore, evaporative air conditioning systems provide a supply of fresh moist air which can be more comfortable than the dry air provided by refrigerated systems and of benefit to asthma and allergy sufferers.
How Evaporative Air Conditioning Works
All evaporative air conditioning systems work on the basic scientific principle that the evaporation of water from a damp surface is always accompanied by cooling. Actually this is the very same principle that allows perspiration to cool the human body and relies on the exceptionally high latent heat of vaporisation of water. Approximately five times more heat energy is required to evaporate a given volume of water than to raise its temperature from 0°C to 100°C so the evaporation process – on the skin or in an evaporative air conditioning system – absorbs huge amounts of heat.
In the case of an evaporative air conditioning system, a fan draws warm air into the system and propels it through a filter or membrane saturated with water. Heat energy is extracted from the air evaporating the water and the air, itself, is cooled – by anything up to 15°C – and humidified. Unlike a refrigerated air conditioning system which dehumidifies the air – in other words removes excess moisture – an evaporative air conditioning system actually increases the moisture content.
Pros & Cons of Evaporative Air Conditioning
Evaporative air conditioning systems are simple in design with fewer moving parts than refrigerated air conditioning systems. This means that they are typically up to 50% cheaper to buy and up to 80% cheaper to run than comparable refrigerated systems making the far more environmentally friendly. Not only that but their sheer simplicity also makes them more reliable.
Refrigerated systems rely on refrigerant chemicals which may result in the depletion of ozone in the atmosphere and are also responsible for increased carbon dioxide (CO2) emissions when compared to evaporative air conditioning systems. Refrigerated systems also circulate the same air, over and over again, throughout your home. Evaporative air conditioning systems, however provide constant fresh air, replenished every 2 minutes or so.
Evaporative air conditioning systems do, of course, require a constant supply of water – possibly up to 15 litres, or 3½ Imperial gallons per hour – and are dependent on humidity levels outdoors. Their performance on a hot, humid day is markedly different to that on a hot, dry day. If humidity is high the level of evaporation that is possible decreases in turn decreasing the cooling capacity of an evaporative air conditioning system.