Image: Juicy ripe tomatoes and thriving plants at Grob Gemüse

Both shallow and deep geothermal systems have many commercial applications, including greenhouses, warehouses and farm buildings. Michael MacKenzie, of GEMINI partner Geological Survey of Northern Ireland, has personally tasted the benefits geothermal energy has brought to a Swiss farm.

Michael visited the farm in Schlattingen, northern Switzerland: “In October 2025, as part of the European Geothermal Congress, I got the opportunity to visit Grob Gemüse, a family-run vegetable farm using geothermal energy to heat the greenhouses their crops are grown in.”

On the farm, two deep boreholes extract water at around 62°C which is transferred for direct use (no heat pump required) in the greenhouse heating system. The first borehole was drilled vertically to 1.5 km depth, while the second deviates to a near horizontal position at 1.1 km. One borehole produces sufficient thermal energy to meet the system base load requirements, the second being brought online during peak demand times. Unusually, both are abstraction boreholes: but here, instead of a more typical re-injection configuration, the thermally spent, cool water is treated and discharged to a local surface water body.

Michael says, “What made the tour so special was getting to meet the Grobs themselves and hear their experiences with getting the system installed and operational. The family began the farm nearly 70 years ago, and each of the three generations has expanded and innovated their operation. Since 2022, they’ve enjoyed a CO2 emissions reduction of 1,662 tonnes per year, and heating oil savings of 692,500 litres annually.” 

Geothermal greenhouses exist in multiple countries across Europe, and Ireland has massive potential for similar applications. “One thing is for certain,” recalls Michael,  “the tomatoes grown in Grob Gemüse’s geothermal greenhouses tasted fantastic.”

Image: Arka and colleague (below ground) measure up in Leeds

Individual public buildings, such as sports centres and swimming pools, can make use of thermal energy from shallow boreholes to provide heating in winter and cooling in summer. Dr Arka Dyuti Sarkar, now working with GEMINI partner Queen’s University Belfast, has been involved in developing the University of Leeds Geothermal Campus geo-observatory installation.

The university has drilled a series of boreholes to test the potential for a shallow geothermal heating system for part of its campus. A network of ten boreholes has been drilled at depths between 150-250 m, comprising open loop, closed loop and fully cored pilot wells, currently being used for scientific monitoring and testing.

Arka contributed substantially to the work there: “Alongside Geosolutions Leeds colleagues, I helped design the on-site borehole well completions, both the open loop and the pilot boreholes. I’ve also been involved in collecting geophysical data using fibre optic monitoring and data loggers. The latter part of my research was spent logging and analysing more than 500 m of core, as well as doing data management for all the campus data. The aim of this work was to create subsurface models that could de-risk energy projects in the UK and beyond.”

Permanently installed fibre optic cables can measure temperature and vibrations in the subsurface for long-term monitoring. This is useful to see how the system responds over time to changes in temperature and pressure. Combined with data from the core samples, the geophysical findings can be used by scientists and engineers using computer simulations to help forecast the impact of using the resource over time.

“I’m looking to bring the very same skills I honed in Leeds to the island of Ireland. The GEMINI demonstration sites will show how we can explore for and utilise geothermal energy across the island, and do so in a sustainable way where the heat resource is responsibly managed. I’m very much looking forward to bringing those skills to GEMINI.”

Image: The extraction well head in Riehen

Deep geothermal systems can use ground source heat pumps or direct heat exchange to heat and cool multiple and larger buildings via district heating networks. Nicola Noller, of GEMINI partner RML, was impressed by the versatility of an award-winning district heating system she viewed near the Swiss border.

Riehen, a pretty suburb of Basel, has been supplying 10,000 of its residents with sustainable geothermal heat for over thirty years. So successful has it been, that the municipality was the first to receive the European Energy Gold Award and is currently planning to extend capacity to reach more than half of its population through the ‘geo2riehen’ project.

“What’s interesting is the way in which they combine geothermal energy with other energy sources. Geothermal energy has very low operating costs and is a reliable ‘always on’ resource, so it’s ideal for supplying the base load. This is then supplemented by other energy sources including wood, waste heat from incineration plants and, at the moment, natural gas - though that’s set to change.”

The geothermal system at Riehen features two boreholes. An extraction well drilled to about 1.5 km withdraws deep fluids with temperatures up to 67°C. The thermal energy is transferred via a heat exchanger to a district heating network, and the cooled fluid – now approximately 25°C – is returned to the same geological layer underground via the second well. The system saves 2.2 million litres of heating oil and 5,750 tonnes of CO2 annually, as well as providing cleaner local air compared to burning fossil fuels.

“As well as the substantial savings in emissions and costs, another bonus is the low impact of the resource infrastructure above ground,” says Nicola. “Our tour comprised visiting a rather ordinary pipe feeding into a small, underground plant room, and the district heating network centre was compact and pristine. My job is to communicate the benefits of geothermal energy and it’s an exciting creative challenge to bring to life something that works so quietly and efficiently behind the scenes!”