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Could a water source heat pump work for you?

house by canal

A waterway might not spring to mind as a way to get heating and hot water for your home or business – but it’s certainly an option for some.

Water source heat pumps (WSHPs) work by extracting heat from a body of water and converting it into useful energy to heat your home. They use a series of submerged pipes to extract the heat from a river, lake, large pond or borehole and compress the water to increase the temperature.

Admittedly, they are a more niche renewable technology, given they need a considerable quantity of water to work. The most popular type of heat pump by far are air source heat pumps – which are naturally suitable for more homes, and, perhaps even more importantly, involve less equipment.

Why invest in a water source heat pump?

Water source heat pumps are often more efficient than ground and air source devices. This is because heat transfers better in water, while water temperatures are generally more stable throughout the year (between 7 and 12 degrees on average), which is higher than the average air and ground temperature in winter.

It is possible to access financial support for installing a water source heat pump through the Renewable Heat Incentive scheme, which pays a rate for units of heat generated. In Scotland, water source heat pumps may also qualify for funding through the Scottish Government funded Home Energy Scotland Loan.

Both these schemes require that the installer and product installed are certified under the Microgeneration Certification Scheme (MCS), and all MCS installers must be members of a consumer code and work must adhere to their code’s standards.

Before installation

houses by a lake

When you install a water source heat pump, you might need to install underfloor heating and larger radiators to get the best performance out of the technology, similar to when you install an air or ground source heat pump. Overall, this could represent an expensive undertaking.

There are other factors to consider that are specific to water source heat pumps:

1. Have you got enough water for the system?  

Without sufficient water, the heat pump will lower the temperature of the water to the point where the system is not running very efficiently or, worse still, the water freezes. You need a river or lake near your home – the more heat you need to generate, the larger the water source you’ll need.

2. How compatible is a water source heat pump with your home?

Your home must be near a water source, with enough space to lay pipes between the water source and the building. Indoors, you need room for the system’s compressor – preferably away from where its low humming noise, made when switching on and off, won’t annoy anyone.

3. Is a heat pump compatible with your existing heating distribution system?

If you’re going to to see the maximum heat and financial benefit from a water source heat pump, your home needs to be well-insulated. You should also check with an installer whether it will work with your current distribution system (radiators, storage heaters etc).

Heat pumps are generally more cost effective when they replace electric or coal heating systems. They are not generally such an economical replacement for gas central heating systems – although they do have lower carbon emissions.

4. Will you need planning permission?

In most cases, planning authorities will consider water source heat pumps as ‘permitted developments’, so they can be installed without specific planning permission if they’re within the boundaries of your land. However, there are some restrictions, so it’s important to check with your local planning department whether you require permission before you install one.

Types of water source heat pump

Closed loop systems

These water source heat pumps have sealed pipes filled with fluid (antifreeze), which are submerged beneath the water, never coming into contact with water directly. As the fluid flows through the pipes it is heated by the water body and returns to the heat pump.

Open loop systems

Water flows through the pump to extract its heat in an open loop system, before being discharged back to its source. These can be more efficient than closed loop pumps, but you need to gain consent from either the Environment Agency, for England or Wales, or the Scottish Environment Protection Agency (SEPA) in Scotland to discharge the water, and possibly additional permission to extract it.

Hybrid heat pumps

These involve a second heating source running alongside the water source heat pump system. These are particularly suited to older homes, where it’s not possible to insulate the property sufficiently to optimise the pump’s performance.  

Solar assisted pumps

These water source heat pumps combine a solar thermal panel with the water source heat pump.

Choosing the right system is no simple matter, so it’s important to research your options and consult with the experts before, quite literally, taking the plunge.

Heating up, on a larger scale

Water source heat pump technology could come into play on a larger scale, as part of community energy projects. In 2015, the UK government drew up a map for water source heat pump suitability, recommending that urban areas on fast-flowing rivers were the most promising areas for the technology.

The government’s research largely focused on the potential of larger schemes, suggesting that over 100 local council-led projects were in consultation with government experts. Speaking to the powers that be is a sound strategy: in contrast to domestic projects, a sizable community-based scheme would almost certainly require planning permission.

The report pointed to a number of small urban areas on rivers, with relatively low heat demand, that could have all of their heat needs satisfied by WSHPs. This is clearly a technology that can deliver good results, in the right circumstances. In total, a generation capacity of 6GW was mooted for rivers, with canals a more modest 84MW.

For people living on waterways and interested in green energy options, hydropower is another option. Rather than generating heat, a hydropower system takes the potential energy from moving water and turns it into kinetic energy, which in turn generates electricity. Great for lighting up a home and powering appliances.

All in all, while water source heat pumps are not a technology for everyone, there is plenty of untapped potential in this often-overlooked and novel approach to keeping warm. 

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Gary Hartley's picture
Gary Hartley is Energy Saving Trust's expert blogger. He has extensive experience researching and writing on a number of topics, with particular expertise in sustainable energy, policy, literature and sport. As well as providing regular blog content, Gary has also been published in numerous magazines and journals.