Evaporative Cooling Saves Energy Costs | Breezair Evaporative Cooling UK

Evaporative Cooling Saves Energy Costs
By Mike Sullivan, Director COSAF Environments

Evaporative air-cooling (EAC) can provide excellent cooling and ventilation with minimal energy consumption using water as a working fluid and avoiding the use of global warming HFCs (hydrofluorocarbons) as used by compressor type systems as used by compressor type systems. Compressor systems also remove essential moisture whereas evaporative systems add health-giving moisture inside a building. EAC technology is simple, functional, can be used in both industrial and commercial applications and consumes less than a quarter of the energy of refrigerative air-conditioning systems.

WHAT IS HEAT?

Heat exists in two forms Sensible heat and Latent heat. Sensible heat is the heat you can feel, or “sense”. It is a property in Nature that can be detected with a thermometer. A pavement heated by the sun, a stove burner, or a hair dryer, are examples of sensible heat. Latent heat is hidden heat that cannot be detected with a thermometer.

The heat used to evaporate water into water vapour is called “Latent Heat of Evaporation”. For example, it is the heat from the hot pavement that is given up to evaporate the water after a summer rainstorm. As the liquid water changes its state into vapour, it absorbs heat from its surroundings; the temperature does not change but the amount of heat or energy it absorbs is contained in the molecular structure of the vapour.
Evaporative Air Conditioning is only possible because of this natural phenomenon of Latent Heat.

Total Heat is the sum of latent heat and sensible heat. It is the total amount of heat in a room, made up of heat you can feel and heat you can’t feel. Total heat is measured in kilojoules (kJ). 1000kJ is approximately 1000 BTU’s. The complete evaporation of one litre of water absorbs about 2000kJ of heat energy and that occurs within the process without any external energy input. In this way evaporative air conditioners use a very small amount of electrical power to operate.

Until recently, companies have discounted the use of EAC through lack of knowledge. Instead, they have either had to put up with no cooling at all or have installed extremely expensive refrigerative air conditioning systems. This is unfortunate both for the user and the global environment.

The reason evaporative systems use less energy is that unlike refrigerative systems, they do not have to an energy-consuming compressor to compress vapour and condense it back into liquid to repeat the cooling cycle. Instead, evaporative coolers just use fresh water to achieve high efficiency cooling. According to the World Bank report, 4 million EAC units in operation in the United States provide an estimated annual energy savings equivalent to 12 million barrels of oil in addition to an annual reduction of 5.4 billion pounds of CO2 emissions.

In industrial applications, EAC may be used to moderate the effects of an additional internal heat source that does not depend on the climate or the time of the year. For example, temperatures may rise inside warehouses or buildings because of the operations of ovens, machines or the presence of people or livestock. These heat sources exacerbate already high ambient temperatures and may need cooling year-round. In many of these cases EAC is the only practical solution as air conditioning cannot function or compete effectively because of high installation and operating costs. Historically in applications such as hotels, restaurants and offices air conditioning has been the first choice, now due to cost savings, the added advantages of “air washing” (to avoid sick building syndrome) and forced ventilation, many commercial establishments are finding EAC the most cost effective solution.

Advantages of Evaporative Versus Air Conditioning

Evaporation is a highly efficient natural heat exchange process because there is no third element in the exchanger. As the air is in direct contact with the refrigerant, in this case water, the heat is transferred extremely efficiently.

In compressor systems, the exchangers involve a third element – the metal coil in the "evaporator", which interferes with the efficiency of the heat transfer. With compressor systems there are two heat exchangers, the evaporator and the condenser, so there is a double negative effect.

The only power-consuming components of a direct evaporative cooler are the fan and small water pump. The energy savings of EAC systems vary with humidity levels and temperatures, however, typically in the UK; EAC systems will yield 50 to 70 percent energy savings compared to conventional air conditioning. For example in a typical hourly cycle a three and a half ton refrigeration unit consumes 8698 watt of electricity compared to an equivalent evaporative cooler, which consumes 1360 watts of electricity.

Benefits of Evaporative Air-Cooling Versus Air-Conditioning

Evaporative air conditioning uses between 25 and 70% less energy than air conditioning, brings in 100% outside air and utilises water for cooling instead of HCFC's. In addition maintenance is minimal requiring just an annual pad clean, or change, compared to air-conditioning which requires a bi-annual filter change. Last but not least, there are no HCFC pollutant emissions from evaporative air conditioning and water consumption is moderate. That all adds up to very responsible environment and energy saving behaviour.

Conventional air-conditioning impacts significantly on a building’s operating costs as it uses in excess of 25% of the building's energy consumption. It therefore makes sense to create a pleasant environment for workers to maximise productivity whilst at the same time minimising energy costs. Evaporative cooling enhances the well being of individuals in areas where ambient temperatures are high, providing comfort cooling in buildings such as schools, libraries and offices. It is also the best, and often the only solution for commercial and industrial applications such as greenhouses, laundries, warehouses, factories and commercial kitchens.