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Water heater schematic
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Water heater location
Locating the heat pump in the under build protects the unit from the weather, corrosion is non-existent. The wooden structure protects the chilled air which is blown out of the heat pump to atmosphere, being blown back into the under build, which would then reduce the efficiency of the heat pump.

Air to water heat pump

air to water heat pump

There are several types of heat technologies on the market. If you are near a large water source you can use a water to water heat pump. This is regarded as the most efficient of all heat pumps. However, it can be expensive to install and may need additional pumps to supply the water to the heat pump.

Geo thermal heat pumps take the stored heat from the ground either through a buried piping loop, or a borehole.  Both of these heat pump technologies can be expensive to install if you are unable to do the groundwork yourself. If a ground loop is not installed correctly, this can cause permafrost. Not all building sites are suitable for these technologies, due to either bedrock issues or space - but they are very efficient.

The air to water heat pump was chosen for the project as it demonstrates a virtual plug and use technology.  Very little site work is required other than a base for the unit. Some form of shelter in an environment like Shetland is advisable.

An air to water heat pump extracts heat from the ambient air temperature and the heat exchangers remove the heat as this is passed through heat exchangers - the reverse of the refrigeration process. An air to water heat pump can be sited in a small urban garden or even built into balconies in high rise structures, apartments for private developments or social housing units where a shared system would lead to energy efficiencies.

The project is also incorporating heat recovery. This is a system that evacuates all the air within the house over a given period and passes the exhausted air through a filter - recovering 90 per cent of the heat. The pre-heated air is again passed through a filter and is distributed through louves in the ceiling throughout the house. This requires ducting to be installed but Villavent produce a retro fit product for existing housing. This system has an override and, in summer, can switch automatically to air conditioning.

The 10 per cent heat loss is being recovered directly through the air to water heat pump through insulated ducting plugged into the inlet louvre of the heat pump. We should be able to recover six per cent of this, leaving 4 per cent that is spilled. This may increase to 8 to 9 per cent but, with any system like this, there are some inbuilt deficiencies.

Puffin on Unst
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