Scratching the surface: the potential of surface water heat pumps

With the take up of low-carbon heating at a low level Phil Jones, independent energy consultant and chairman of the CIBSE CHP-DH Group, looks at the huge potential of surface water heat pumps and wonders what can be done to promote their increased use in the UK.

Take-up of existing low carbon heating technology is below 2.5 per cent of demand, a problem caused largely by a lack of confidence in its use. As problems go, lack of confidence is a tricky one to solve, and it’s an issue that has plagued ground, air and water source heat pumps for many years.

In a chicken and egg type scenario, low take-up of surface water source heat pump (SWSHP) technology caused by lack of confidence means that (no matter how effective the technology) there is a shortage of examples of the technology in action. If there are few examples, there is very little information about how they perform. If there isn’t much information, few technical documents or best-practice manuals can be created. If these don’t exist, it is less attractive to train to install the technology. And if few people are trained to install it, potential investors won’t be confident enough in the technology to buy it – and the cycle goes round again.

By producing this SWSHP Code of Practice CIBSE, the Heat Pump Association (HPA) and the Ground Source Heat Pump Association (GSHPA) are trying to break that cycle by filling the void with information and training. By using a practical best practice guide investors can be confident that installers are working to the best wisdom on the topic available, and standards across this part of the industry can be improved.

One innovation which is a key part of the new Code is the Water Source Heat Map, produced by the former DECC, which shows locations throughout the UK that are suitable for a SWSHP system. This is the first of its kind, and it reveals just how great the untapped potential of the technology is in the UK. We are blessed with thousands of miles of waterways, from rivers to canals to coastlines, which have the potential to produce low carbon heat from urban areas to the wildest of countryside.

Water naturally sits at a higher temperature than the ground or the air, giving SWSHPs an inherent advantage over other kinds, and the technology is more versatile. It can heat and cool as well as do both simultaneously, for example, and it can do so at a range of temperatures from 35 to 95oC. It is this versatility which also makes it an attractive long-term investment, providing financial and sustainability benefits through the whole life of the building with proper maintenance.

This is also where guidance comes in. SWSHPs have the potential to provide low-cost, low-carbon heat to a building throughout its working life, but in order to do this most effectively they need to be specified, installed, commissioned and maintained correctly in the first place in order to get the most out of the system. The industry has been crying out for concrete guidance so that clients have a measurable standard to hold their projects to, which is what we’ve been working towards.

Each potential application has its own challenges and opportunities and the final design adopted can have a substantial impact on the civil and mechanical engineering required. Depending on the project this can increase or reduce the capital and operational costs. The civil engineering costs of structures for open loop abstraction and discharging water, for example, can often be a significant part of the capex, particularly on larger schemes. The level of heat abstraction/discharge capacity can be an important determining factor when considering the suitability of a smaller river or a slow flowing canal or particularly a static body of water like a lake or reservoir.

These are just a few of the many considerations that need to be taken into account when specifying the system, never mind the actual process of installing it and the (hopefully!) decades long process of keeping it maintained. As more systems are installed around the country and we get more data about their performance, confidence in SWSHP technology will grow on its own. In the meantime, the most important thing is to spread best practice and minimum standards throughout the industry using documents like the Code of Practice in conjunction with training, to demonstrate to engineers what is possible with a SWSHP system.

This type of heat pump takes advantage of a natural resource that Britain has in abundance, and will be a vital part of the UK’s heating plans going forward. With the benefit of saving British homes and businesses money in bills and maintenance along the way, this technology can help shelter them from fuel insecurity and attracting investment in the form of Government grants.

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