Phase Change Heatstorage
Traditionally solar thermal has only been used in the UK for water heating.
Though it is of course possible to oversize a system to enable space heating via radiators or underfloor heating, the problem has always been the same:
When excess heat energy is available (during the summer months) there is little or no requirement for room heat and when room heating is required (during the winter) there is little or no extra heat energy available.
The solution is to install a quantity of phase change material with a very high latent heat capacity storing a relatively large quantity of heat during the solar rich months so this heat can be given off when required.
The temperature that the heat is stored at can be varied by the use of different PCMs (phase change material) and for space heating would typically be between 21°- 28°C.
Whist there is a huge marketing push on electrical domestic storage batteries, heat batteries are still relatively uncommon. The principals of PCM storage have been understood for many years, but only recently has a safe and practical Heat Battery been launched.
Heat has traditionally been stored in water. This has been very successful due to the natural high specific heat capacity of water. (Water can store 10 times as much heat as the equivalent mass of Copper).
However, despite of it’s efficiency, where relatively little space is available, there are materials that can be used to store over 4 times as much heat as water of the same volume.
Furthermore, they benefit from being packaged in square or rectangular containers that can further use space efficiently.
How Phase Change Materials (PCMs) work
Traditionally heat is stored in water by gradually adding energy until it achieves a safe maximum temperature (usually 75°C if a blending valve can be used). At this point it is no longer possible to store any more energy.
PCMs are solid at room temperature, it then takes energy to melt them at varying temperatures (usually in excess of 58℃). Typically, this could be 4 x the energy that could be stored in water of the same volume.
Energy can be added in the following ways:
- Solar Thermal energy via liquid flowing through a heat exchanger (the most efficient system).
- Electricity generated from solar PV during the day.
- Cheap off-peak electricity.
Heat can then be extracted:
- As hot water direct to the outlets.
- As space heat via radiators or an underfloor heating system.
Typical applications can be homes with limited space, yachts, narrow boats and vehicles.
Installed products start at around £2000.