In what is being called the “largest U.K. mine-water heat recovery project to date,” the Gateshead (U.K) Council and Gateshead Energy Company (GEC) are extracting heat from water in abandoned coal mines to provide low-carbon district heating using two 3MW (853TR) GEA ammonia (R717) heat pumps.
The mine water – with a natural temperature of 15°C (59°F) – is pumped 150m (492ft) from the old mine to the heat pump platform, filtered and run through titanium plate heat exchangers, after which it is returned to the mine at 8°C (46.4°F), says GEA in an article on its website.
Following the mine-water heat exchange, the heat pumps use a two-stage compression cycle with screw compressors to provide 80°C (176°F) hot water for distribution to the borough. Several heat exchangers, connected in series on the heating side of the system, optimize heat pump efficiency.
“For every 1 unit of power used by the heat pump, 3 units of renewable heat are generated,” says GEA, giving the system a COP of 3.
Using a refrigerant with no GWP, ammonia-based heat pumps offer the best efficiencies for this application, GEA said. “Under the given conditions in Gateshead, ammonia heat pumps are 10 to 20 percent more efficient than F-gas solutions (HFC/HFO).”
Newly built solar parks – on the field adjacent to the system – provide green power to run the heat pumps on surplus power days. Therefore, at certain times with the heat pumps, “GEC can produce 100% zero carbon heat” for the existing network, serving 18 public and private buildings and 350 households, with the ability to extend the heating district.
“Working alongside our partners, we can make use of the naturally heated mine water and generate valuable, low carbon energy,” said Martin Gannon, leader of Gateshead Council. “We are proud to have successfully delivered the largest mine-water project in the U.K.”
“We have a low-carbon, secure, U.K.-owned heat source in the form of mine water in Gateshead, which is also an excellent option for many other coalfield communities,” said Richard Bond, Director of Innovation and Engagement at the Coal Authority.
GEC and the Gateshead Council seek to achieve zero carbon emission by 2030. The mine-water heat extraction helps fulfill its “zero carbon heat strategy,” providing cheaper heat energy with a lower carbon footprint for borough residents.
“GEA’s highly innovative heat pump technology has been used in other district heating projects in the U.K. and around the world,” said John Burden, Director of Project Sales Heating & Refrigeration Solutions at GEA UK. “We expect to see many more new and ambitious projects in the coming years,” he added, citing the U.K.’s ambitious targets to increase district heating.
Energy efficient heat pumps
“Heat pumps [can] generate up to five times more heat energy per kWh usage of primary energy (electricity) compared to burning gas or direct electrical boilers,” said Kenneth Hoffmann, Product Manager of Heat Pumps at GEA HRT, in a GEA article. Heat pumps help mitigate climate change, especially with electricity increasingly generated from renewable sources.
In Malmö, Sweden, heat reclaimed from wastewater and waste incineration supplies district heating to 10,000 homes with four ammonia-based GEA heat pumps. “Each [heat pump] has a COP above 3.5, so for each 1kWh of electricity used, 3.5 kWh of heat is produced for the city,” Hoffmann said.
“Natural refrigerants offer double-digit percentage points better performance compared to synthetic refrigerants,” said GEA, adding, on its website, that heat pumps offer over ten times better efficiency than conventional boiler/chiller installations in applications supplying both heating and cooling.
Headquartered in Düsseldorf, Germany, GEA Heating and Refrigeration Technologies provides global commercial and industrial heating and cooling solutions.
“Working alongside our partners, we can make use of the naturally heated mine water and generate valuable, low carbon energy.”Martin Gannon, Gateshead Council