In previous weeks I reviewed ground and air source heat pumps as a way to generate energy to heat your home. Staying on the heat pump theme, this week I review water source heat pumps. Whilst the least common of the heat pumps, provided that your property fits the bill (and you live close to a suitable water source), water source heat pumps are worth considering.
How do water source heat pumps work?
Water source heat pumps come in 2 types:
- Open loop systems: where the water is taken from the source (see below*) and then flows around a heat exchanger to generate heat. The water is then released back to the water source.
- Closed loop systems: these work like ground source heat pumps, but instead of the pipes extracting heat energy from the ground, the pipes (or panels) are submerged in the water source to extract heat energy from the water.
*Water sources can be in the form of rivers, streams, lakes, large ponds, wells or boreholes.
How much energy will water source heat pump generate?
Most water source heat pump systems will deliver in excess of 4kW of heat energy (and will typically expend 1 kW of electricity to generate this heat energy).
What are the advantages of water source heat pumps?
Water source heat pumps are more efficient than other types of heat pump because the heat transfer rate from water is far higher than the heat transfer rate from the ground or air. This is especially the case in the winter, when heat energy is most needed.
The installation of water source heat pumps will usually be much less expensive and much less intrusive than the installation of ground source heat pumps (you won't have to dig up your garden).
Water source heat pumps are an ideal option for heating domestic swimming pools.
Are there any constraints?
If the water source dries up then no heat can be created.
Open loop systems, whilst more efficient than closed loop systems, pose a number of challenges. Open loop systems generally require greater maintenance, especially if the water quality is poor. The pipes within open loop systems can freeze at very low temperatures. Plus there is the cost and red-tape associated with acquiring the Environment Agency extraction licence to consider (see below).
What consents will I need?
The installation of a water source heat pump is usually considered to be "permitted development", which means that planning permission is not required subject to certain conditions and exclusions. Check out the Planning Portal Website for further advice.
Water source heat pumps will have to comply with the Building Regulations.
With respect to open loop systems, an Environmental Agency "extraction licence" is usually needed where water is being extracted at any scale. A discharge consent will also be needed to release the water back into the water source.
The Green Deal scheme may be able to help you pay for the upfront costs of the installation through Green Deal financing. The installation costs will then be paid back over time, with interest, through your electricity bill.
You may qualify for payments from the Government under their Renewable Heat Incentive scheme.
- Given their greater efficiency, water source heat pumps are recommended over ground source heat pumps if you live close to a suitable water source.
- Water source heat pumps are an ideal option for supplying heated water to domestic swimming pools.
- You may qualify for payments under the Renewable Heat Incentive scheme.