Water Source Heat Pumps

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Nowadays, renewable sources of energy are needed more than ever. Water source heat pumps can be a great way to generate your own renewable energy. Which can not only save the planet, but can save you money.

How do Water Source Heat Pumps Work?

Water source heat pumps (WSHP’s) are similar to ground source and air source heat pumps, except they take heat out of a body of water, rather than the ground or air.

Water source heat pumps work by the running of a low-temperature, low pressure refrigerant fluid in heat exchanger coils through a water source.

Heat is taken from the relatively consistent temperatures that are found in a body of water via a series of flexible pipework. This pipework is completely submerged in the body of water, whether that be a lake, river or stream.

The heat pump pushes working fluid through the network of piping, and this fluid absorbs the heat from the surrounding water. An electric compressor then compresses the fluid, raising the temperature. The heat in the working fluid this then transferred into your property using a heat exchanger, which provides you with hot water and central heating.

Water source heat pumps can be two to three times more energy efficient than more convention methods of heating because it takes heat from one source and moves it to another, rather than producing heat on its own.

Water source heat pumps can be used in bodies of water such as;

  • Lakes
  • Streams/Rivers
  • Larger Rivers
  • Aquifers
  • Sea Water
  • Wells

Water source heat pumps benefit those who have a simultaneous need for heating and cooling throughout the year.

Types of Water Source Heat Pumps

Closed-Loop System

This option will see the lowest cost if your property is situated next to a body of water. These systems use a refrigerant in a closed loop to transfer heat and energy from a water supply, such as a lake.

A supply pipeline is run through the ground, starting at your home and ending in the water. The pipe will supply water from at least 8 feet under ground level to avoid freezing in the winter. The liquid refrigerant then absorbs heat from the water and transfers this heat into your property.
Coils must also be put in the water to ensure that it meets minimum requirements for volume, depth and quality.

Open-Loop System

This type of system uses ground water from a lake or a well. Water is extracted and fed directly into the heat pump. The energy raised through compressions is then extracted by heat. The increased heat is then transferred by the fluid in the heat exchange. Which runs through the heat pump system, returning the water to the ground via a well, recharge well, or the surface discharge. This option is only suitable where there is a reasonable and consistent supply of clean water. All rules and regulations regarding groundwater discharge must be adhered to.

Hybrid System

Hybrid systems tend to be installed when a property has more need for a cooling system rather than a heating one. These systems tend to use geothermal resources or a combination of geothermal resources and air from outside.


Costs and Savings

The main factors that will affect the cost of running a water source heat pump include;

  • Size of property
  • Amount of energy needed to heat the property
  • Operating efficiency of the water source heat pump
  • Temperature of the water source

A water source heat pump will cost on average £10k to install, and this will be dependent on the size of property and the type of WSHP that is used.

You may be entitled to the Renewable Heat Incentive (RHI) scheme set up by the government to give people money back on the installation of renewable energy sources. Thanks to this scheme you may start to earn money on the system after only a few years.

WSHP’s reduce monthly heating and cooling bills, with utility bills falling by approximately 15% after installation.

The most common reasons for unreasonably high running costs of a WSHP are faulty installation, and installation that is not suited to the type of property.


How Green Are Water Source Heat Pumps?

WSHP’s can be one of the highest coefficient performances (COP) of any heat pump system. With water source heat pumps producing as much as COP 5, compared to other heat pump systems that product on average 3.0 to 4.3.

The efficiency of a WSHP is dependent on how hard it needs to work to achieve the desired results. The smaller the gap between water temperature and desired property/water temperature, the more efficient the system will be.

WSHP’s are fairly green, and even though they use energy, they have the potential to make between 2-4 units of heat for every unit of electricity used to power them. This makes them much more efficient than conventional heating systems.

Important Legislation

Before installation can take place there may be some legislation that needs to be addressed.


Environmental Legislation

Open loop systems alter the temperature of the groundwater, whilst thermal plumes will affect hydrochemistry and bacteriology. You may also require a licence, depending on the types of system you want to install. You can get the correct licence through the Environment Authority and you will need to check with them what actions are required before installation is carried out.


Other Legislation

You may also need planning permission before installing a heat pump of any kind so it’s always best to check and make sure. You may also need permission depending on who owns the body of water.


Installing a Water Source Heat Pump

The extent of installing a water source heat pump depends on the type of building and size of the project. For most domestic WSHP’s the installation, only a small body of water will be required as the property will not need that much heat and energy.

Larger domestic and commercial projects often require a bigger and more substantial water intake because the system needs to use more water to achieve the same results. For these sorts of projects in-river construction work will probably be required, for this it is essential to hire experienced professionals.


Benefits of Using a Water Source Heat Pump

  • They generate less CO2 emissions compared to conventional heating systems, reducing your carbon footprint
  • Relatively easy to install if your property is near a body of water
  • Little visual impact to the property as all pipework is submerged in the water
  • You may be entitled to government funding which could reduce the cost
  • Heat transfer rate is far larger than ground source or air source heat pumps
  • Reduces the need for digging and drilling compared to ground source heat pumps
  • Return temperature is usually higher than ground source heat pumps by about 5-6°C