Heat under our feet, Cardiff groundwater study reveals

Natural water in the ground could be used as a low-carbon heat source in many towns and cities, according to research from the British Geological Survey (BGS).

Data gathered from a natural ground-water system below Cardiff has resulted in the BGS calling for more research to see if similar technology can be used on a larger scale.

The findings are based on data from a three-year-long study at one of the UK Geoenergy Observatories, a network of sites being created across the country to research new and alternative energy supplies in the subsurface.

The £300 000 study was funded by Innovate UK, the BGS, WDS Green Energy Ltd and, more recently, the European Commission, to examine the environmental impact of a pilot groundwater heating scheme that heats a school building in the Welsh capital using the warmth stored in the natural water system below ground (an aquifer) and electric heat pumps.

Natural system

Data from the natural groundwater system below Cardiff is being collected by the Urban Geo Observatory, a network of 61 boreholes equipped with temperature and water-level sensors, to build up a picture of the groundwater temperatures in the aquifer found just ten metres below the ground surface.

BGS research lead David Boon said: “We knew that the use of ground-source heat pumps changes the ground temperature by several degrees Celsius. What we didn’t know was by how much.”

A study of the data collected between 2015 and 2018 indicates that the large heat resources stored in the UK’s underground water systems could sustain ‘shallow open-loop ground-source heat pump systems’, which are a low-carbon heating approach widely used in European cities that are being used more frequently for heating the UK’s building stock.

Low-carbon

Boon added: “Our findings prove that groundwater-source heat pumps are a technically viable, low-carbon heating solution in many towns and cities across the UK, providing the geology beneath the surface is favourable.

“Of course, regulation and long-term planning will be needed to manage this emerging energy technology so that larger and more complex schemes can be rolled out in our cities without “draining” the underground heat source.”

While there are physical limits to how much water and heat can be abstracted and reinjected, and regulatory legal limits on temperature drops, the BGS’s findings confirm that even a small quantity of heat from a very large volume of water provides a low-carbon heating solution for many UK towns and cities.

The solution could be applied in district-wide heat networks, homes or commercial buildings.

How could it be used to heat our homes and workplaces?

  • Hot water and steam from deep underground can be used to drive turbines
  • It can also be used to heat buildings directly
  • Potentially a source of renewable energy with no carbon footprint

Mr Boon added: “A well-balanced combination of groundwater-source heat pumps in tandem with vertical, closed-loop ground-source heat pumps and air-source heat pumps will maximise the options for decarbonising heating in UK homes and businesses.”

Image by Roegger from Pixabay