DECC water source heat pump map EnglandLondon could heat itself using the River Thames, and Bristol could be warmed by the River Avon in the future, if the potential identified by a new heat map of England is unleashed. It identifies 39 English cities that could take advantage of heat pumps and nearby bodies of water to deliver low carbon heat via district networks.

The British government is keen on using water source heat pumps to help reduce the nation's greenhouse gas emissions and has published a map (click on the map on the right for a larger version) of the country which identifies areas of high heat demand that are adjacent to the sea and to rivers with sufficiently high flow rates to contribute to meeting this demand.

There are now two shining examples of this technology in practice in the UK: a 2MW installation at Kingston Heights on the River Thames in London and a 300kW one at Plas Newydd on the Menai Straits in north Wales.

How heat pumps work

The technology, which is proven and not expensive, works by concentrating heat from a large volume into a small one, in much the same way – but in reverse – that heat is pumped from inside your fridge to the outside. Although the water may feel cold to the touch, it still contains some heat energy (as does any substance at a temperature greater than absolute zero).

Naturally, the pump consumes some electricity, but systems are typically designed so that around three times more useful energy is extracted than is put in. Heat pumps can also take heat from the ground and the air, but water is more reliable as a heat store. It rarely drops below freezing, unlike the air and the ground.

Many settlements are located alongside rivers and coastlines, and so will be able to take advantage of this free heat and thereby displace the use of gas or other fuel sources for heating space and water. This provides a reliable source of heat for many years into the future at a much more predictable price than reliance on fossil fuels.

District heat networks

Heat pump map water source, SE EnglandThe Government's purpose in publishing the map is to raise awareness of this untapped potentional, to encourage local authorities, community groups and private developers to consider using it when planning local, sustainable energy solutions.

The Department of Energy and Climate Change hopes that the heat will be distributed in local heat networks as this is the most efficient means of exploiting it. A typical capacity required for large network schemes is 20 MW; to meet this the pumps would have to be 1 km apart, say the technicians who compiled the report.

A further constraint on designing the map was that only areas with a heat demand greater than between 5 and 10 kWh per square meter were considered. Another consideration was that the return water should not be more than 2°C lower in temperature, to avoid negative impacts on water life.

The 39 cities

Key urban areas identified in the map are listed below. 

Additionally, it is possible to use estuary and coastal sites. On the south coast the suggested cities are: Southend-on-Sea, Brighton, Portsmouth, Southampton, Bournemouth and Plymouth. Elsewhere, Grimsby, Liverpool, Blackpool and Hull are possible candidates.

  • Barnsley (Dearne)
  • Bedford (Ouse)
  • Birmingham (Cole)
  • Bournemouth (Stour)
  • Bradford/Leeds (Aire)
  • Bristol (Frome, Avon & Chew)
  • Burton-on-Trent (Trent)
  • Cambridge (Cam)
  • Chelmsford (Chelmer & Can)
  • Chesterfield (Rother)
  • Colchester (Colne)
  • Derby (Derwent)
  • Doncaster (Don)
  • East Greater London (Lee)
  • Gillingham (Len & Medway)
  • Huddersfield (Calder)
  • Hull (Hull)
  • Ipswich (Gipping)
  • Lancaster (Lune)
  • Leicester (Soar)
  • London (Thames)
  • Manchester (Irwell)
  • Middlesbrough (Tees)
  • Newcastle-Upon-Tyne (Tyne)
  • Northampton (Wootton Brook & Nene/Brampton & Nene/Kislingbury)
  • Norwich (Wensum & Tud) 
  • Nottingham (Trent)
  • Oxford (Thames & Evenlode)
  • Peterbourgh (Nene)
  • Preston (Ribble & Darwen)
  • Reading (Thames & Kennet)
  • Sheffield (Don)
  • Southampton (Itchen)
  • Stockport (Tame)
  • Stoke-on-Trent (Trent)
  • Sunderland (Wear)
  • Warrington (Mersey)
  • Windsor (Thames)
  • York (Ouse).

DECC says it will publish a more detailed water source heat map in the winter, that will be part of a new National Heat Map, which is currently being further developed. This is in the fulfilment of its policy paper The Future of Heating, Meeting the Challenge, which wants to see more district heat networks, combined heat and power and improved building energy efficiency. 

It's also trialing prototypes of novel compact heat stores which can be integrated with low carbon technologies (such as heat pumps) to help balance peak loads on the electricity grid.