Water Source Heat Pumps

By | May 23, 2015

Although we mostly only hear of either the Air Source or Ground Source Heat Pumps, water is another way that you can generate energy that can be used for heat pumps to help warm up the temperatures inside your home.

There are numerous advantages for using a Water Source Heat Pump, they include:

  • The heat transfer rate from Water Source Heat Pumps are much higher than traditional Air and Ground Source Heat Pumps
  • The flow of water means that the energy source is constantly replaced due to the circulation within the system.
  • You won’t need to dig any trenches to install a Water Source Heat Pump, which directly saves you money on the installation cost when compared to Geothermal Heat Pumps.
  • The CoP (coefficient of performance) of a Water Source Heat Pump is much higher than that of other sources due to the fact that the return temperature to the heat pump is usually higher than the ground and outside air temperatures.

So what water sources can be used?

  • Lakes
  • Ponds
  • Rivers
  • Springs
  • Wells
  • Boreholes

Two different ways in which Water Source Heat Pumps work:

Open Source System

The water gets extracted from the source and is then flowed around the heat pump’s intermediate heat exchanger (also known as an open loop rated heat exchanger) and is then discharged.

You’ll need an extraction license from the Environmental Agency if you aim at extracting more than 20m3 per day of water from the source. Basically, if you’re using anything bigger than a 4kW Water Source Heat Pump for 24 hours per day, you’ll need a license.

You’ll also need to obtain a discharge consent and make sure that the water that gets discharged isn’t just dumped somewhere.

Advantages of Open Source systems:

  • Due to the fact that no ground heat exchanger is present, there’s no temperature drop, which makes it a little more efficient than closed loop systems.

Concerns with Open Source Systems:

  • The risk of freezing does exist if the water temperature drops below 8 degrees Celsius, which will cause the pump to stop working.
  • If the pH level of the water isn’t neutral, you’ll need corrosion resistant pumps, pies and heat exchangers. You’ll also need to make sure the filter is changed regularly and might have to treat the water to prevent algae deposits. In general, the maintenance requirements of an Open Source System are much higher than a closed loop system.

Closed Loop System

Similar to Ground Source Heat Pump systems, pipes (or sometimes heat exchange panels) or panels called pond mats, are placed in the water source and then water and antifreeze mixture passes through the pipes, which then absorbs the energy from the water.

Advantages of a Close Loop System:

  • No corrosion risk
  • Much lower pumping energy loss levels
  • You won’t need to obtain any licenses because you’re not extracting any water
  • Because the system uses anti-freeze in the loop, the risk of freezing water is almost eliminated.

Concerns with Closed Loop Systems:

  • You’ll have to carefully place the pipes or panels to avoid boat traffic and debris.

A problem with ALL Water Source Heat Pumps

It comes as no surprise really, but if the water source gets depleted, it automatically means that without water there is no heat.