UK could become ‘world leader’ in seabed heating technology

An international study involving Nottingham Trent University (NTU) 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.

The study shows that during winter when the seawater temperature is only 3.7 deg C – the heat exchangers can produce up to 60 watts per square metre of heat energy to nearby coastal properties. The amount required to heat an average UK home is 100 W/sq m.

The research, undertaken with Beijing University of Technology, Zhengzhou University of Light Industry and Beijing Municipal Institute of Labour Protection, builds on the development of heat pumps, delivering the heat to homes through standard heat pump units. The same technology naturally be used to cool properties in hot countries by utilising the cooler seabed temperatures.

Researchers noted that more than 5.3 million people live in coastal towns in England and Wales, according to the Office for National Statistics.

Senior Lecturer Hua Zhong, an expert in applied energy and environmental engineering at Nottingham Trent, said: “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.”

The technology works by a capillary heat exchanger, featuring capillary tubes of only 4.3 mm in external diameter – extracting heat or cooling energy from the shallows of the seabed. Heat or cooling energy is then transferred to an indoor heat exchanger by pump. The indoor heat exchanger then heats or cools the indoor air of the property via an indoor heat pump unit.

A hotel in Qingdao, China, was used to pilot test the technology, with 250 square metres of capillary laid 5m deep in the shallows, 50 m offshore. The total distance from the hotel to the capillary was 300 m. On test, the water exiting the seabed in the capillary was heated to 40.6 C, before it was pumped to the hotel.

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.”

The study also involved Alan Fewkes, of NTU; Yanfeng Li, of Beijing University of Technology; Jin Zhang, of Beijing Municipal Institute of Labour Protection. The findings are set to be presented at an NTU research conference during the summer of 2022