Fukushima Pref. Farmer Grows Strawberries Using Groundwater Thermal Energy; Innovative Method Produces Especially Sweet Fruit

By Ryuichi Nakagawa / Yomiuri Shimbun Staff Writer

13:16 JST, March 31, 2026

KORIYAMA, Fukushima — A woman who became a farmer in recent years has now taken up the challenge of growing strawberries in a greenhouse using thermal energy from groundwater, in collaboration with a local startup in Koriyama, Fukushima Prefecture.

With fuel costs rising, cultivation using groundwater thermal energy incurs lower maintenance costs than the conventional heavy-oil-based approach. Yasuda Farm owner Sayuri Yasuda, 45, hopes that, in addition to this, her use of renewable energy also contributes to decarbonization.

Yasuda has been growing strawberries in Koriyama since autumn 2024, when she took up farming after working for about 15 years at a telecommunications construction company run by her husband.

In autumn last year, when Yasuda added a fourth greenhouse to her three existing ones, expanding her total cultivated area from 850 square meters to 950 square meters, she also introduced a heat pump system that uses heat from water extracted from the ground.

The system works on the same basic principle as an air conditioner: pressure on a refrigerant is increased to raise the temperature and decreased to lower it.

The system is said to provide efficient heating and cooling by taking advantage of the temperature differential between the groundwater, which stays at 15 C to 16 C throughout the year, and the outside air.

The system was designed and developed by Shintaro Tamura, 44, president of Link-F Co., a startup headquartered at Nihon University’s engineering department campus in Koriyama. Tamura founded Link-F in February 2023 after leaving a machinery manufacturer and participating in a geothermal research and development project at the university.

At a demonstration greenhouse on Yasuda Farm, liquid heated by equipment designed by Tamura flows through pipes running along ridges of Tochiotome strawberries, warming the surrounding soil and air. The fruits and leaves of the strawberries cultivated in these ridges apparently grow better than a control group cultivated in soil without such pipes.

It was warm enough to make one sweat inside the demonstration greenhouse when The Yomiuri Shimbun visited, thanks to the system producing an effect like that of underfloor heating.

Although the system uses electricity, maintenance and management costs are said to be about 60% lower than those for conventional heavy-oil-based greenhouse cultivation. Strawberries grown in the special ridges are also sweeter than those harvested from an adjacent conventional ridge.

Yasuda speculates it is because, thanks to the surrounding soil being slowly warmed, the period between flowering and fruiting is extended by about five to 10 days, causing the fruit to develop a higher sugar content. She said now it is important to find ways to maintain the balance between the strawberries’ characteristic tartness and sweetness.

The groundwater thermal energy system still only produces a small crop of strawberries, so the farm only sells them on an irregular basis.

Yasuda is mulling selling the strawberries as unique products under her farm’s brand name, allowing customers to compare their taste with that of strawberries from conventional greenhouses. Yasuda said one name she is considering giving them is “Geoberries,” which evokes images of the Earth and the soil.

While strawberries are usually shipped from autumn to spring, Yasuda said she might be able to market hers as “summer strawberries” if she is able to grow them in summer, using the heat pump system for cooling.