Case Study:  Hot in the City

Energy supplier E.ON is installing high temperature heat pumps in a district cooling and heating network in the City of London. The heat pumps running the HFO R1234ze are part of a bid to cut carbon by up to 50 per cent and to enhance air quality in the city by reducing emissions.

The project is part of a multi-million-pound programme by E.ON to improve and upgrade the Citigen energy centre, supporting efforts to decarbonise the city and transform how connected buildings in the Square Mile are heated and cooled. The refrigerant used in the selected heat pumps, R1234ze, has a GWP of less than 1, which is significantly lower than the previous refrigerant, and therefore has only a tiny fraction of the environmental impact, the heat pumps’ manufacturer Carrier says.

Three of the firm’s AquaForce heat pumps will extract thermal energy from water extracted from an aquifer 200 m beneath the capital. They will also harness waste heat from the existing Combined Heat and Power plant that would otherwise be lost to atmosphere, the manufacturer notes.

The Carrier units produce hot water at 80 deg C. This will be used to provide up to 4 MW of heating and 2.8 MW of cooling to residential and business customers via a 10 km district-wide network. Among the customers connected to E.ON’s heating and cooling network are the Barbican arts and residential complex, the Guildhall arts centre and the Museum of London.

“Tackling the environmental impact of heating, especially in densely populated areas, will be key to meeting the UK’s 2050 net zero targets,” says Antony Meanwell, head of Low Carbon Solutions – City Energy Solutions at E.ON, “By installing heat pump and geothermal technology at Citigen we’re making a powerful statement of what can be done to reduce carbon usage on a large scale. No project on this scale – or as pioneering in its vision – simply happens. It has required a huge team effort to develop the ideas, translate them into plans and finally make our project a reality on the ground.”

The heat pumps are based on Carrier’s twin-rotor screw compressor, which has bearings with oversized rollers, oil-pressure lubricated, and a motor cooled by suction gas for extended operation, even at maximum load.

In addition, the heat pump is designed to be quick and easy to install for contractors, requiring only an electrical supply and water source. Streamlined electrical and hydraulic connections ensure quick set-up and commissioning, the manufacturer says.

“The high temperatures required by the project are normally very challenging to achieve. However, AquaForce heat pumps are designed specifically to generate high-temperature hot water from relatively low-grade energy sources, “ says John Foster, project lead for Carrier, “In addition, the way the units are multiplexed in the overall system ensures their capacity is fully utilised.”

The manufacturer claims that the significantly reduced capital outlay and maintenance costs makes the HFO heat pumps around 20 per cent cheaper than comparable natural refrigerant models.

Mr Foster notes an apt historical twist: the Citigen plant room once housed the ice-store for Smithfield Market. “It is a happy coincidence that the site is being reborn as a centre for modern, cutting-edge low-carbon cooling and heating.”