Heat pumps are machines that work on the Carnot cycle. This transfers heat from the source of heat to a heat sink via a cycle of vapour compression. Refrigerators use heat pumps to move heat out of the unit. Industrial heat pumps are used to move heat from external sources through to a building.
Heat can be obtained from a source of air, ground or water. The heat pump is capable of concentrating low-grade heat into higher grade heat so it can be used for space heating or hot water in homes.
Ground Source Heat Pump.
A ground source heat pump or GSHP heats from the ground. According to GroundSun ground temperature is warmer than the air in the winter and cooler in the summer. This is the reason that they are more efficient than air source heat pumps even in extremely cold weather when they are needed most. They also do not make much noise and can last for years without much maintenance.
A practical way of extracting this energy is via pipes in the ground. The pipes in the ground are in a loop laid out from horizontal trenches that go as deep as two metres. Vertical boreholes are the alternative to achieving results. They are more expensive, but they are ideal when there is not enough space to lay horizontal pipes.
When depths go below six metres, the temperature in the ground does not differ much from the Mean Annual Air Temperatures which is about 9 degrees C -11 degrees C in the UK. Below a depth of two metres, there is a vast amount of warmth that gets tapped for wintertime heating. The temperature here, however, drops quickly when a heat pump extracts a good deal of heat from the ground loop. This is why it is important that the size of the ground loop equals the heat load of the building. The way to achieve this is by a full thermal modelling.
Advantages and Disadvantages of Ground Source Heat Pumps.
As with anything, there are pros and cons to heat pumps. One of the advantages is that they save money. They are cheaper to operate than direct electric heaters are. They are also cheaper than oil burners and can be cheaper than gas boilers. Heat pumps are fully automatic so they also demand less than biomass boilers do.
Heat pumps reduce carbon emissions. This is unlike LPG, oil, gas, or biomass. Heat pumps do not produce carbon emissions on a site and, if renewable electric sources power them, they do not emit them at all.
Heat pumps can save space. There are never any fuel storage requirements.
They are safe because they do not need any combustion. No dangerous gasses emit and no flues are needed.
Heat pumps need less maintenance than combustion heating systems.
A well-made ground source heat pump system will increase the value of your property.
Heat pumps can both cool in the summer and heat in the winter.
Planning authorities like ground source systems because they are safe and silent. They are also invisible and have a low impact on the environment.
The Government likes them, as well. It offers better Renewable Heat Incentives than other renewable technologies do.
As for the disadvantages, there are few. They are more expensive to install than air source heat pumps are. This is because a ground heat exchanger needs to be installed, too. This connection to the ground helps the GSHP operate more efficiently than ASHP. This is true especially when the outside air is lower in the winter when heating is needed most.