Water Source Heat Pumps – How They Work

Water Source Heat Pump Gif

 

A water source heat pump system extracts heat energy from a water source such as a lake, river or even the sea and uses it to provide hot water and heating to a property. It is an alternative to other systems such as gas, oil or electric central heating – but it’s far more efficient and sustainable. Water source heat pumps are the most efficient type of heat pump - approx. 4-5% more efficient than a ground source heat pump which can achieve efficiencies of 400%. Water source heat pumps can be installed in a variety of buildings, whether their purpose is residential, commercial or agricultural.

 

How is a Water Source Heat Pump System Installed?

The installation of a water source heat pump involves installing the heat pump inside a property or external building. Pipes run from the heat pump to the edge of a water source buried in a trench around 0.5 metres deep and around 40cm wide. When the pipes reach the edge of the water they connect to a lake collector or a pond mat (these are loops of pipe used to circulate a mixture of water and refrigerant referred to as brine). The collectors are constructed outside of the water and when ready, they are floated out onto the surface before sinking to the bottom where they are held in place by weights. Pond mats differ slightly, they are coils of slinky pipe attached to a corrosion resistant stainless-steel frame, this keeps the pipes in a tighter formation which can help if the water source is smaller. The heat pump generates energy by circulating the brine through the collector, absorbing the heat energy from the surrounding water. The heat energy is then passed through a compressor which raises the temperature to a usable level and circulates it on to your heat distribution system (radiators, underfloor heating, hot water cylinder) to provide heating and hot water.

 

Water Source Heat Pump Pipe Installation Water Source Heat Pump Trench

 

Water Source Heat Pump Design

Just like any other heat pump, water source heat pump systems need to be designed before they are installed. This involves carrying out heat loss reports for the property to check if any extra insulation is required and conducting a heat load report to ensure that an appropriate heat pump model is selected which can achieve the required output for your property. There are two types of water source heat pump systems, open loop and closed loop.

What is an Open Loop Water Source Heat Pump?

An open loop system will extract and filter the water from the water source and circulate it through the system. It’s then released back into another section of the water source or other acceptable alternative such as a water well or borehole. Open loop systems differ to closed loop collectors as they don’t use a heat transfer fluid, the water itself is the fluid. They can be the more efficient option but due to the hydraulic performance needed, system lifespan can decrease and even with the best design they can be prone to clogging.

What is a Closed Loop Water Source Heat Pump?

A closed loop system will circulate a mixture of water and refrigerant (often referred to as brine) through the collectors submerged in the water source. The water from the source cannot get into the pipes, the energy is collected through the brine and circulated to the heat pump.

 

How are water source heat pumps controlled?

We install MasterTherm heat pumps which can be controlled via internet browser, smartphone app or with a display unit installed on a wall in your property. MasterTherm heat pumps are also compatible with Homely Energy Smart Meters which enable you to set heating schedules and access variable tariffs such as Octopus Agile. This set-up can improve your efficiency even further as your heat pump will automatically optimise to meet your desired temperatures whilst also considering weather forecasts and the half-hourly pricing of electricity a variable tariff provides, saving you money. The Octopus Agile tariff also uses renewable electricity so your system would be 100% clean and carbon free.

 

Which Water Sources Can be Used with a Heat Pump?

  • Lakes
  • Rivers and streams
  • Mine water
  • Sea water
  • Aquifiers – an aquifier is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt). Groundwater can be extracted using a water well.

 

Why Choose a Water Source Heat Pump?

• Most efficient type of heat pump, making them particularly advantageous if you’re considering claiming the Renewable Heat Incentive (RHI) as the higher the efficiency the higher the payments you’re eligible to receive.

• Considerably less groundwork required than a ground source heat pump, reducing installation cost and time.

• Heat pump lifespan of 20+ years.

• Lake collector lifespan of 100+ years.

• Improved efficiency will reduce utility bills, particularly when connected to a variable tariff.

• Lower carbon footprint (if used with renewable electricity the system is 100% carbon free)

• Combustion free

 

Considerations for Installing a Water Source Heat Pump

• Licenses – Some water source heat pump installations will require licenses from bodies such as the Environment Agency. If you’d like to know more about this get in touch with us on 01269 833 100.

• Freezing/Tides – We recommend using a water source that is deep enough that it avoids freezing. If the water source is prone to strong tides we’ll also factor this into the design so that we can ensure the collector remains secure.

• Maintenance – Open loop systems require regular maintenance such as cleaning of the filtration. This helps to avoid bacteria build and prevent water fouling. The frequency of system cleaning depends on the water quality but regular services may be something your want to factor in to the annual cost of running your system.

• Other Uses – If the water source is used for other purposes such as boating, fishing etc, then extra precautions should be taken to ensure the collectors are not damaged. It’s also worth considering if the water source might be used by other properties for the same system as this could reduce the efficiency of your system.

 

Water Source Heat Pump Case Study

If you’re interested in seeing one of our water source heat pump projects, take a look at our a lake collector case study on a property in Carmarthenshire which provides heat and hot water to two residential properties, each equipped with their own heat pump so that residents can set their preferred heating schedules and temperatures.

 

Water Source Heat Pump Case Study

 


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