This could potentially reduce heating costs to a significant extent, the ministry says.

A ground source heat pump or geothermal heat pump is a heating/cooling system for buildings which transfers heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through the seasons.

The arrangement can be both vertical ie. drilling deep down, or lateral, where the pump is installed at a shallower depth.

It is the first of these variants which are in focus here.

One fly in the ointment in Estonia is that drilling is very expensive here, more so than in neighboring Finland, as the subsoil and earth's crust in Estonia is of a different complexity.

Installing a ground source heat pump can cost tens of thousands of euros up front as a result, meaning support measures would likely be required in the case of most households and cooperatives, though at present no new such measure has been reported.

Head of the mineral resources department at the Ministry of Climate Ene Jürjens said that while initial tests are still underway, more comprehensive research could take three to four years or more.

Alvar Soesoo, adjunct professor at Tallinn University of Technology (TalTech), meanwhile said: "We are currently in a learning phase, and I believe that in ten years, it will definitely be used more extensively in Estonia, yet we wouldn't need a geology like Iceland's."

"If we had a crust similar to that in Iceland, we could also generate electricity. In Estonia, however, we certainly cannot produce electricity, but we can reduce our heating and cooling costs, two- to three-fold," Soesoo went on.

Using geothermal heat for heating homes is not a new concept in Estonia, but it is still relatively uncommon, Soesoo added

He said: "There are no very clear statistics, but we are talking about borehole-based usage. Over 2,500 installations have been installed, while groundwater is used at another 100-150 sites."

Soesoo's educated guess was that there are around 10,000 such installations in Estonia, with a population of around 1.3 million, which use horizontally installed underground pipes (see image), though this would not be comparable to the situation with neighbors to the north.

For example, in Sweden, population 10.5 million, 650,000 households use ground heat pumps, while for Finland, population 5.6 million, the figure is 200,000.

In short, the issue is not that the ground is "too cold," Soesoo said, though a lack of knowledge is also something which needs addressing.

Ene Jürjens at the Ministry of Climate said the state has begun researching vertical ground source heat pumps, which are drilled deep into the earth.

"We have even completed the first pilot project, a solution for an apartment building in Tiskre (just outside Tallinn – ed.) where we bored a 505-meter-deep hole, put in place a U-tube and some sensors, and now we are testing it out within the building's heating system," she outlined.

Ultimately the goal remains as one of determining, for example, to what depth it would be rational to drill, and how to use geothermal heat most effectively in Estonia.

"Using geothermal energy for energy production in this way is considered over twice as efficient as using air source heat pumps. It can save over half – up to 60 percent – on heating costs," Jürjens reiterated.

The method does not require burning anything to heat buildings, at least for as long as there is electricity available.

"In my view – and I am speaking as a geologist – this system is the most environmentally friendly solution available," Jürjens went on.

Other issues with vertical geothermal pumps may include regional variations inside Estonia, and considerations over permission to drill below certain levels, for instance due to groundwater concerns.

The thermal properties of the ground near the surface is usually divided into three layers, the surface layer (down to around a meter, most susceptible to changes in weather and sunlight), the shallow layer (anything from 8 to 20 meters in depth and which behind the surface temperature, so that the peak temperature comes about six months after the surface peak temperature) and the deep layer, where temperatures are more constant and where  geothermal energy plays a role."

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