We are all familiar with heat pumps, even if we don’t realise it. The most common application of heat pump technology is the refrigerator at our home and also air conditioning units in offices.
There are three basic types of heat pumps:
· ground-source heat pumps, which get their heat from ground below the frost line;
· air-source heat pumps, which get heat from the outdoor air; and
· water-source heat pumps, which get heat from water.
Heat pumps offer the most sustainable way to provide heating and cooling in many applications, as they can use renewable heat sources in our surroundings. Even at temperatures we consider to be cold, air, ground and water contain useful heat that's continuously replenished by the sun.
A heat pump can be used where there is a low temperature source of heat and by applying a little more energy, a heat pump is able to raise the temperature of this source to the level needed, typically at 45 to 50ºC.
Similarly, heat pumps can also use waste heat sources, such as from industrial processes, cooling equipment or ventilation air extracted from buildings.
Heat pumps are very energy efficient as they supply more energy than they consume, by extracting heat from their surroundings. For every unit of electricity used to pump the heat, 3-4 units of heat are produced.
Applications include space heating and cooling, pre-heating domestic hot water, heat recovery and dehumidification in both domestic and industrial sectors.
Most heat pumps have two main parts: the outdoor unit and the indoor unit. The outdoor unit includes the outdoor heat exchanger, the compressor and a fan. This is where the heat from outside is picked up during the heating season, and where the heat from inside the house is rejected during the cooling season.
The indoor unit contains the indoor heat exchanger and the fan that distributes heated or cooled air to the distribution system. Some systems have a second indoor cabinet that contains the compressor. By reversing the heat pump it can also be used for cooling.
Heat pumps access renewable or waste energy and so displace consumption of conventional fossil fuels (gas, oil, coal). Because heat pumps consume less primary energy than conventional heating systems, they are an important technology for reducing gas emissions that harm the environment, such as carbon dioxide (CO2), sulphur dioxide (SO2) and nitrogen oxides (NOx).
Heat pumps have relatively low CO2 emissions due to the efficiency of the system e.g. 300-400%. It is estimated that the total CO2 reduction potential for heat pumps is about 6% of the global emissions! This is one of the largest amounts a single technology can offer.
The running costs of a heat pump can be less than those of a traditional gas boiler heating system and definitely less than some other forms of heating (LPG, oil, electricity), although the initial capital cost is usually higher than other conventional heating systems. The ‘whole-life’ cost, combining the capital and running costs, can be favourable for heat pumps compared to fossil fuelled systems, especially compared with other forms of electric heating.
In addition to providing domestic heating, heat pump systems are used in commercial premises (offices, hotels, supermarkets) often providing heating and cooling – and also in some industrial processes and applications.
Low Carbon Buildings Programme offers a £1,200 grant regardless of system size.
Links for Further Information