DHE Holding harvests geothermal energy  through deep hole drilling. A new, patented drilling method cuts through the bedrock ten times as fast as competing technologies, and can reach greater depths where the temperature is higher. This makes the energy source viable and competitive at new locations.

”DHE is employing a brand new drilling method which makes it possible to drill deeper and faster than before. We can reach more than 5 km below the earth’s surface for geothermal energy, producing electricity, district heating and cooling at places where it was not possible earlier”, says Petri Laukkanen, CEO of DHE Holding.

Geothermal energy is harvested by pumping up hot water to a heat exchanger. The cooled down water is brought back underground, forming a closed system. Illustration: DHE Holding.

DHE Holding was nominated for “Innovation of the Year 2016” in Södertälje, and received an honourable mention: ”DHE Holding has made an amazing international innovation available in Sweden and in Europe, with great social and economical implications – a commercially interesting deep hole drilling method which can be used to produce district heating and electricity”.

Large scale geothermal energy systems

The temperature increases further down in the bedrock. This has been used as a source of energy for thousands of years, and today about twenty countries include geothermal in their energy mix. The energy source is very well suited to power large scale district heating systems, but it can also generate electricity. The best conditions are found where the temperature is relatively high close to the earth’s surface, such as areas with volcanic activity.

”In Sweden, the temperature gradient in the bedrock is 15 – 30 °C per km. This means that you have to drill 5 – 7 km to reach sufficient temperatures. It has been both complicated and time-consuming to drill to those depths, and such projects have rarely been profitable. We are now using a new technology which can drill deeper and faster. One advantage of the new technology is that the power and drill speed remain the same even several kilometers down. This gives us a good opportunity to become a leading geothermal energy producer in Europe”, Petri Laukkanen says.

Harvesting geothermal energy

The geothermal energy is harvested by water circulating in the system. The heat is transferred in a heat exchanger, and the system is a closed loop. The cooled down water is injected back in a second, equally deep well. The holes are lined to a depth of two kilometers to prevent ground water fouling. Since the system is a pressurized, closed loop, no salts or chemical substances are deposited. Neither are there emissions of gases solved in the water.

Patented new drilling method

”The drilling method, called waterhammer, has been developed and patented by our associate Hanjin D&B. DHE has the sole right to use the technology in Europe. Compared to the traditional Tricon Bit technology, based on rotational movement, the waterhammer is based on a hammering motion created by a high air- and water pressure. The result is a ten times faster progress through granite bedrock. The drill, D&B 450W, is designed to drill deeper and more efficient. At a depth of 2 500 meters, the progress is 15 meters per hour, and at 3 500 meters it remains steadily above 10 meters per hour”, Petri says.

New technology makes it possible to drill deeper and faster for geothermal energy. The W D&B 450 drill, from Hanjin D&B, is capable of reaching depths of more than 5 km. Illustration: DHE Holding.

”The drill is constructed with five drill heads that are worn out and has to be replaced after about 150 meters. Once they are resharpened, they can be used again. The entire rig can be loaded on 36 lorries, and that includes all the pipes required to reach more than 5 km below ground. Some of the environmental advantages of the technology, according to DHE, are that fewer holes need to be drilled, that the heat pumps are water powered, that the footprint is reduced thanks to horizontal drilling, and that it puts higher temperature waters within reach”.

”A geothermal facility has less impact on the environment and the climate than a fossil fueled power plant. Instead of just providing heat for a couple of houses, DHE can contribute to sustainable energy systems for malls, airports, residential districts or parts of cities. The new technology can help municipalities and regions to reach their climate goals. For instance, DHE has conducted a pre-study for E.ON regarding district heating in Malmö City. We hope that the project will generate 120 MW of district heating, and to gather sufficient energy we are planning to drill about ten holes to a depth of 6000 meters”, Petri Laukkanen says.

The article was published in December 2016.