Warm water pumped from redundant coal-mines is among the potential sources of waste heat that could be exploited for commercial protected cropping or by projects where greenhouses form part of a social or training enterprise, according to studies by consultancy and development company District Eating.
In a feasibility study for Durham County Council at Horden Colliery, which closed in the 1980s, the company concluded that around 1.3MW of heat could be available from the water which the Coal Authority has to continue to pump from the mine in order to treat it to prevent pollution. “In this case the volume of heat available is unlikely to be enough for a modern commercial-scale greenhouse but could support something under 2ha,” said District Eating founder Faye Tomson.
She says Durham County Council is interested in establishing a small commercial or ‘social or training’ project greenhouse. “There are other mine sites, though, which could be viable to heat greenhouses up to about 5ha,” she said.
“The water is not warm enough to use directly but you could use a heat pump to extract the energy with reasonable efficiency.”
According to the Coal Authority, depending on the location and geology, mine water is pumped out at temperatures of between 10 and 20°C – though it can reach 40°C at depths of 1km. However, the lack of energy decarbonisation incentives currently available for heat pumps means the capital cost of energy from mine water makes it unviable for growers. “The equivalent of a new renewable heat incentive for heat pumps – or other mechanism to reduce the cost of electricity for operating heat pumps – would really change the economics,” said Ms Tomson.
Durham County Council councillor Mark Wilkes says the council is leading the way on mine-water heat networks. “There are some fantastic opportunities to explore the possibility of using low carbon to heat businesses or to grow food in the area,” he said.
Meanwhile, Ms Tomson believes there are other ‘lower-hanging fruits’ in terms of waste energy sources which could benefit greenhouse production.
“We are working on potential projects for co-location at energy-from-waste plants or industrial sites which could be cost-competitive for growers and provide an opportunity to decarbonise,” she said.
“We have about 10 large sites with land and an energy supply, buy-in from the owners and some interest from investors. We plan to develop a small-scale pilot project in the coming years and hope to develop the larger sites with partners.”
Read more news and features from the protected crop industry in our monthly publication The Commercial Greenhouse Grower.