Kingston project uses the Thames for heating

An innovative heat pump system that harvests energy from the River Thames to heat a £70m housing scheme is a first for the UK and could have a major impact on future developments in towns and cities, its creator claims.

The water source heat pump system has now been switched on at the Kingston Heights mixed-use development being built by United House for NHP Leisure Developments on the site of a former power station in the heart of Kingston upon Thames, just 200 metres from the banks of the river.

The project is due for completion next year and will feature 137 apartments, including 81 luxury homes, and 56 affordable homes for social landlord Affinity Sutton. The scheme will be expanded next year to include a four-star 142-bedroom hotel.

The system utilises Japanese heat pump technology from Mitsubishi Electric to harness heat stored in the river water to generate a constant supply of energy for underfloor heating and hot water used by residents. It works on the principle that two metres below the surface of the water the temperature averages 9°C and never falls below 7°C, making it a constant source of renewable energy.

Water is first sucked up from the river bed through a two-stage filtration system designed to ensure that no fish or other marine life can enter. An average of 75 litres per second will be abstracted from, and later returned to, the Thames.

The official launch of the heat pump system was attended by Edward Davey, the secretary of state for energy and climate change

Water then passes through a high-efficiency heat exchanger, which transfers the low grade heat from the river water to an internal “closed” water system that links to a plant room on the fifth floor in the apartment block 200 metres away.

Here, 41 Mitsubishi Electric Ecodan water source heat pumps increase the temperature of the low grade heat up to 45°C, before sending it to mini plant rooms right across the development. The river water that has passed through the system is then returned to the river.

The Ecodan heat pumps work by using what is known as the “vapour compression cycle” to upgrade low temperature heat and raise it to usable temperatures for the home.

Inside sealed copper piping within each unit, refrigerant vapour is compressed to raise both the pressure and the temperature. This hot, pressurised vapour is then passed through a condenser, where it liquefies and gives off usable heat that is passed to the apartment’s hot water supply and underfloor heating.

Mike Spenser-Morris, managing director of NHP Leisure Developments, believes it paves the way for other developments taking place near open bodies of water, reducing the need for traditional combustion boilers and related carbon emissions.

“This heat pump system will be capable of producing over two megawatts of thermal energy for this development and will provide it 24/7, 365 days a year, regardless of the weather or air temperature, even in the depths of winter,” he said. “Almost every major city in this country is close to a river, lake, reservoir, canal or the sea. There will be thousands of homes and businesses that can benefit from this most energy-efficient technology and in the process prevent thousands, even millions of tons of harmful carbon being released into the atmosphere from now on."

Spencer-Morris claims that if gas boilers had been fitted instead, the site would be dumping around 500 additional tonnes of carbon into the atmosphere each year. In addition, because of this system’s exceptional energy efficiency, the equivalent heating cost for a couple living in a one-bedroom apartment would be 18% more. "For an average home, this would mean hundreds of pounds extra,” he said.

Kingston Heights’ apartments are due for completion in December and towards the end of 2014 a new 142-bedroom hotel, with meeting, banqueting and conference facilities will be completed at the site, further increasing the efficiency of the heating scheme.