Solution: Heat from Finland’s Deepest Hole

No fuel is required for geothermal heat production and therefore the new plant is completely emission-free. Photo: St1 Deep Heat Oy.

The first geothermal plant in Finland will produce entirely emission-free district heating.

A historical step in Finnish heating production is set to be taken this month in Otaniemi, Espoo: the energy company St1 is drilling two wells into the bedrock, both seven kilometres deep, to generate geothermal heating for houses in the area. Last summer a separate trial well was drilled down to two kilometres, and everything has gone well. With its depth of seven kilometres, the actual plant will have the deepest wells in Finland.

On the surface, the wells are one metre in diameter, and as they descend they taper to a diameter of about 20 cm. Water is routed down one well, and after heating it then ascends the other well to Fortum’s heating plant.

At the bottom of the wells, the temperature of the rock is about 120 degrees Celsius. This raises the water temperature enough to make geothermal heat pumps unnecessary in district heating. And since no fuel is required for heat production, the plant is completely emission-free.

The trial run of the plant is scheduled for February 2017. After the plant becomes operational, it is expected to produce a maximum of 40 megawatts of energy, which is enough to cover ten percent of the district heating demand in Espoo.

1) Which energy challenge will the St1 geothermal plant solve, Tero Saarno, St1 Deep Heat Ltd. Production Manager?

“The plant will introduce an entirely new, clean method for district heating production. The solution replaces imported fossil fuels, such as gas, oil and coal and thereby promotes the energy self-sufficiency of Finland.”

2) How will it improve quality of life?

“As energy self-sufficiency increases, less money flows across borders. Atmospheric pollution decreases, and the solution also helps combat climate change, as there are no carbon dioxide emissions.”

3) How does the innovation support sustainable development?

“The plant uses no fuel at all.”

“The plant uses no fuel at all, which eliminates heating production emissions from polluting the air, water and landfills. A conventional power plant pollutes the air with its chimney and also produces ash, which is put in landfills. A geothermal plant has no such emissions. Moreover, the drill used to bore the wells is powered by electricity, and even that operates without emission-producing fuels.”

4) How, in your view, will Finnish geothermal energy technology have developed in ten years’ time?

“The first plant that is now underway will allow us to test the concept and the technology. Hopefully, in ten years similar plants will be under planning or even construction elsewhere in Finland. In addition to district heating, future production will most likely also include district cooling energy and perhaps even electricity. The basic technology remains the same, and in the future the biggest development will be lower construction costs and shorter construction time.”

St1 is drilling two 7-kilometer deep wells into the bedrock to generate geothermal energy. Photo: St1 Deep Heat Oy.
St1 is drilling two 7-kilometer deep wells into the bedrock to generate geothermal energy. Photo: St1 Deep Heat Oy.


5) Have similar experiments been done elsewhere in the world?

“There are not many plants that have been drilled as deep, and moreover not into hard granite. Similar facilities exist in France, Germany and Australia, but the difference is that they only produce electricity. In the cold climate of Finland, it makes sense to produce district heating.

“However, shallower wells of two to two and a half kilometres in depth already exist in over 20 countries; there are about 40 of them in the Paris district heating network alone. The rock there is different, however, as it is soft sediment. In warmer countries, it is not necessary to drill as deep as in Finland, where you have to go very deep to find rock that is warm enough.”

Text: Laura Manas

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