Heat pumps are, in essence, powered entirely by solar energy. The electrical input could be as simple as solar photovoltaic energy, or as energy from the sun harvested by plants and creatures millions of years ago, which are made into fossil fuels. The sun also heats up the ground and the water lying on it. The ground will then heat up the air above it, so we can then use an air source heat pump to extract this heat for use in our homes. Believe it or not, there is heat energy in air even below 0°C; in fact there is energy all the way down to -274°C (absolute zero). Most air source heat pumps will work down to -20°C.
Heat will also be drawn down into the ground via natural conduction and precipitation. This heat can be extracted by a ground source heat pump, which has a more reliable performance factor season to season, as the ground temperature changes very little throughout the year. Go into any cave in the UK and the temperature should be a static 11°C summer or winter.
Heat pumps use refrigeration to move and upgrade heat energy, from one place to another. The physics are quite simple: refrigerant is a vapour that can exist in two states.
The process starts at the compressor, where a low-pressure vapour is compressed to a higher pressure, – this produces heat. You can feel this process when using a bicycle pump to inflate a tire, the harder you work the hotter the end of the pump gets. The high-pressure hot vapour flows through a heat exchanger, passing the heat into another medium for use in heating. The hot vapour condenses into a liquid at this stage, having exchanged its’ heat energy. The liquid passes along a pipe to a reservoir, known as a liquid receiver. The liquid is then sprayed through a small hole known as an expansion valve, where the pressure drops dramatically. The liquid passes through another heat exchanger where it evaporates, and changes state to become a vapour again. This part of the cycle is very cold, similar to using an aerosol deodorant; you feel the spray as cold on your skin. Energy is required to complete this change in state, usually extracted directly from the air (as in ‘air source’) or indirectly from the ground (as in ‘ground source’). The low-pressure vapour moves onto the compressor where the process starts again.
As a heat pump extracts the majority of its’ energy from natural resources, it is quiet and very clean. It can be combined with multiple heat sources and can serve almost any application. We can install, maintain and service any system from basic heating only, or heating and hot water to large scale district systems incorporating multiple heat sources and applications including swimming pools.
Whatever your heating requirement, get in touch to talk about what we can do for you to keep you running efficiently for longer.