UK: The UK could be a world leader in the utilisation of geothermal energy from the seabed if it could tap the rich potential of its 12,000km of coastline, a new report finds.
An international study by researchers from Nottingham Trent University (NTU), Beijing University of Technology, Zhengzhou University of Light Industry and Beijing Municipal Institute of Labour Protection has shown the potential for using capillary heat exchangers for heat pumps in the shallows of the seabed, with the potential to provide homes with an infinite supply of heating and cooling.
The study shows that during winter – with a seawater temperature of only 3.7°C – it can produce up to 60W/m2 of heat energy to nearby coastal properties. The amount required to heat an average UK home is 100W/m2. The same technology could be used to cool properties by utilising the cooler seabed temperatures to supply cold air.
The technology works by a capillary heat exchanger – featuring 4.3mm diameter capillary tubes with an internal diameter of 2.8mm – extracting heat or cooling energy from the shallows of the seabed. According to the actual conditions in coastal areas, capillaries can be assembled both horizontally and vertically, which forms a three-dimensional heat exchange network.
As part of the study, a hotel in Qingdao, China, was used to pilot test the technology. A 250m2 capillary was laid 5m deep in the shallows, 50m offshore. The total distance from the hotel to the capillary was 300m.
Tests showed that the water exiting the seabed in the capillary was heated to 40.6ºC, before it was pumped to the hotel and used to warm the air in the building.
Zhenpeng Bai, a researcher in energy saving technology from Beijing University of Technology and Zhengzhou University of Light Industry, said: “The heat capacity of the seabed is infinite – making this an extremely impressive potential source of renewable energy.
“Unlike ground-source heat pumps which can require extensive excavation work, a capillary seabed heat pump requires very little set up and causes minimal damage to the seabed.
“It can have a large heat exchanger area, is less susceptible to corrosion from seawater, is more affordable than other technologies, and does not need auxiliary equipment such as filtration and water treatment,” he added.
“This technology has the potential to become a new and significant addition to the way in which homes around the world can reduce their carbon footprint. Due to their proportionately large coastlines, and rich sources of shallow geothermal energy in coastal areas, the UK, US and China have the potential to pioneer this under-researched renewable energy source,” said Hua Zhong, a senior lecturer and expert in applied energy and environmental engineering at NTU.
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