A heat pump collects energy from the outside world, and deposits it inside. It transfers heat from a cold source to a warm room using three components:
- an array of pipes that transfers heat from the source, e.g. ground, to a volatile liquid,
- a compressor, which concentrates the liquid and the heat it contains, and
- a system in the warmed space to distribute the heat – normally underfloor pipes.
Ground-source heat pumps – GSHPs
The ground is a rich source of heat. A GSHP uses buried pipes to extract this heat and feed it to the compressor. The pipes are placed at a relatively shallow depth of about 2m, so the sun’s heat is the source of energy. The temperature is close to constant throughout the year at this depth – about 10°C in the UK. This gives an inherent advantage over air-source heat pumps (ASHPs), since the machines work more efficiently with higher source temperatures (the air gets much colder than 10°C in winter!), and the design of the heat pump can be optimised for a very narrow temperature range. Photo by Kensa Heat Pumps
The efficiency of a heat pump is expressed in its coefficient of performance – CoP. This is the ratio of heat energy moved to electrical energy used in the process (by the compressor). The best heat pumps achieve a CoP of around 4, meaning they can move 4kWh of heat with every 1kWh of electrical input.
For a good explanation of how heat pumps work and the advantages of using land as a heat source, visit Kensa Heat Pumps’ website.
We have installed many ground-source heat pumps. They are very long-lasting and require little or no maintenance. Provided the house is suitable, they are cheap to run and very effective. They run on electricity and make good use of the input energy. The government’s Boiler Upgrade Scheme (BUS) offers a grant of up to £7,500 for the installation of either type of heat pump. The scheme is administered by Ofgem and is accepting applications until the end of 2027.
Kensa Shoebox, which is a ground source heat pump. It is small enough to fit inside a cupboard.
Picture courtesy of Kensa.
Air-source heat pumps – ASHPs
An air-source heat pump extracts heat from the outside air, even in cold temperatures and uses it to warm your home and your water supply. It is basically a refrigerator that is working in reverse. It takes ambient heat and boosts it to a usable temperature for heating. They are considered a renewable energy source because they use heat from the air, a naturally replenishing resource.
Daikin Altherma air source heat pump.
Picture courtesy of Daikin.
