THERMAL energy trapped in the sewer system could be used to heat our homes, a University of Bradford professor has argued.

Professor Mostafa Mohamed is researching technology that could dramatically improve the efficiency of heat pumps, and claimed that heat trapped in sewers could be used.

He wants to lower the cost of energy for heating homes and improve our carbon footprint.

“It’s not something the UK is doing enough of at the moment, but it certainly has potential,” he said.

“We can recover heat from the soil, from tunnels and even sewers. But the technology needs to become more efficient and competitive to increase its adoption.”

The idea of recovering heat from sewers is discussed in a 2018 research paper, in which the University of Bradford was a partner.

It looked at heat recovery from the sewer network in Antwerp, and found that there is enough energy to provide between seven and 18 per cent of the catchment’s need.

Professor Mohamed also looked at how heat exchange in the soil is affected after it is saturated by rainwater.

He has already run trials on three houses in Dewsbury, each of which is fitted with an underground compact heat exchanger, and are the first houses in the UK to have this technology.

His team looked at ways to further enhance the efficiency of heat recovery using rainwater, for example by funnelling roof run-off into soakaway areas.

Initial experiments found that rainwater enhanced the recovery of energy from the soil by up to five times compared to when it was dry.

“We are working on a novel material that could be used to store heat energy in the ground, say during the summer months, and release it when it’s needed,” Professor Mohamed explained.

“This heat exchanger technology could be incorporated into the piles used to build houses, it could be incorporated into the foundations of a building, we could even use it to recover energy from sewers and tunnels.”

His work on ground source heat recovery found that heat exchanger pipes encapsulated in heat store material had an increased heat transfer efficiency rate of 75 per cent, compared with standard heat exchangers.

“We are focusing on how we can store heat when there is no demand and extract it when we need it,” Professor Mohamed added.

“If we can enhance performance, we will lower the cost of energy for heating homes, it will be part of decarbonising and we will reduce our carbon footprint.”