Air Source Heat Pumps are a proven and efficient way of generating hot water ands are 3 to 4 times more efficient than using an electric element to heat water and are ideal to couple with solar PV panels as a sun powered option.
Heat Pumps Supplied by The Green Power Company
We have a range of the most efficient and highly regarded heat pumps from the following brands.
Heat Pump Operating Principle
Mechanical Heat Pumps compress refrigerant to generate heat, which is absorbed by the hot water circuit via a heat exchanger.
The refrigerant in its gaseous state is pressurised and the working fluid is circulated through the heat pump by a compressor. The Discharge side of the compressor has highly pressurised vapour which is cooled in a heat exchanger that is known as a condenser. The condensed refrigerant then passes through a pressure- lowering device known as a metering device. The metering device may be a capillary tube, expansion valve, or a work extracting device such as a mechanical turbine. The low pressure liquid refrigerant enters another heat exchanger known as the evaporator where the liquid is heated and boils. The refrigerant returns back to the compressor where the cycle is repeated.
The refrigerant inside the heat pump has to reach a sufficiently high temperature so when compressed, the refrigerant would release heat through the condenser. To allow heat to be transferred from the ambient cold region into the fluid in the evaporator, the fluid must be at lower temperature for fluid expansion. In terms of the pressure difference, pressure must be great enough for the fluid to condense at the hot end and evaporate in the lower pressure region at the cold end. Heat pumps have coefficient of performance that decreases with increasing temperature difference between output temperature and ambient air temperature.
Heat pumps have built in insulation that reduces the work and energy required to achieve a low temperature in the region to be cooled.
Coefficient of Performance of Heat Pump
The Coefficient of Performance of a mechanical heat pump varies with regards to temperature difference. When the ambient air temperature decreases, the Coefficient of Performance of the heat pump increases and vice- versa. Coefficient of Performance could be maximised at a design time by choosing a heating system that requires only a low final water temperature and a heat source with a high average temperature. Conventional heating radiators and domestic hot water system require higher temperatures which reduces the Coefficient of Performance of the system that would affect the choice of a heat pump.
Heat Pump Refrigerants
Different refrigerants are used in heat pumps, depending on the heating requirements of heat pump. Generally, domestic heat pumps with moderate heat output requirements of around 60 degrees Celcius, use Carbon Dioxide ozone-friendly R744 (CO2) refrigerant which has been widely used since the 2000’s. R744 utilizes a transcritical cycle that requires much higher working pressure and as a natural refrigerant gas, it does not contribute to global warming.
Refrigerants were often known as chlorofluorocarbon such as R-12 (dichlorodifluoromethane) in the 1990’s. R12 refrigerant was banned because of the damage that the CFCs cause to the ozone layer, if released to the atmosphere.
Heat Pump Noise Level
The ground source heat pump has no outdoor mechanical unit so there is no external noise pollution produced.
Air source heat pumps has mechanical components like fans that produces noise in the range of 30 – 505db depending on the type and brand of unit.
Air Source Heat Pumps (Air to Water)
Air Source or Air to Water Heat Pumps, generate hot water by drawing energy from the surrounding air and converting it to heat via compressed refrigerants. The Ozone friendly refrigerant inside the Heat Pump absorbs heat from the ambient air, then the warm gaseous refrigerant flows to the compressor where it is converted into a high pressure and high temperature gas. The hot low pressure refrigerant passes through a heat exchanger, evaporator which heats the water before it is pumped to the stainless steel storage tank.