Water Source

Heat Pumps

Harnessing energy from a body of water

As the name suggests a water source heat pump WSHP, works by extracting heat from a body of water and converting it into useful energy to provide hot water and to heat your home. It uses a series of submerged pipes containing a special refrigerant fluid to absorb the heat from a river, lake or large pond.

How do they work?

Water source heat pumps are often more efficient than ground and air source units as heat transfers better between the water and the collector loops submerged within it, than heat transfers between the earth and ground loops. This is a closed loop system.

The warmed mixture in the submerged collector loops then passes through a heat exchanger and heats a refrigerant. The process of compressing the warmed refrigerant without allowing it to occupy a greater volume increases both its pressure and, most importantly, its temperature! This compressed and heated refrigerant then passes through a heat exchanger where it transfers its thermal energy to the system inside the house.

An open loop system can prove more efficient as raw water is pumped straight into the compressor rather than relying upon conduction through the submerged collector pipes. Once the water has passed through the heat exchanger it is discharged straight back into the body of water.


A closed loop water source heat pump.

Internal Requirements

As with all heat pumps you will typically, by comparison to a gas-fired boiler, require a little more space within the building itself. This is to house a water cylinder and a buffer tank for heating water. The size of these components depends very much upon the size of the space to be heated and the anticipated occupancy of the building.

The water cylinder is just that and provides water to your taps and showers when called for.

The buffer tank serves to satisfy the heat pumps requirements for minimum flow-rates and total volume of water in the circuit. Keeping the heat pump happy in this way increases its efficiency and lifespan.

External Requirements

You will need a body of water within a couple of hundred metres of the building to be heated. The shorter the distance, the lower the running costs as a reduced amount of energy will be required to pump the water to the unit inside.

The size of the body of water required is proportional to the size of the space you are trying to heat and how well insulated it is. The more energy required to heat the building, the colder the body of water becomes and so the heat pump becomes less effective in much the same way as an ASHP becomes less effective in colder weather.

A useful video by the Energy Saving Trust explains Ground Source Heat Pumps in more detail. The principal is exactly the same with a Water Source Heat Pump but for the fact that the thermal energy is collected from a body of water instead.

What if I don't have the space?

Your best option is an Air Source Heat Pump. Specifying an advanced MasterTherm heat pump by Jupiter ensures that you will benefit from an outstanding co-efficient of performance not drastically dissimilar to that of a ground source heat pump.