New technology could turn ground heat into cheap alternative to fossil fuels

Washington(ANI): Researchers and entrepreneurs in Slovenia and Serbia are developing a heat pump technology that would make ground-source heat a cost-effective alternative to fossil fuels-a feat that could cut CO2 emissions and improve energy security.

Across Europe, there are plentiful sources of geothermal energy- heat stored in the ground which can be tapped to provide a renewable and inexhaustible energy supply.  

The small spa-town of Lendava, Slovenia, draws on a deep geothermal well 1,500 metres below the ground to supply its district heating network.

The 70 degrees Celsius water is used to heat schools, sports centres, shops, businesses and apartment buildings.

However, once used, the water is still around 50 degrees Celsius: too cool to re-use for space heating but too warm to re-inject into the well (or dispose of in the local environment).

Nafta Geoterm, the firm that manages the well, was convinced it could make better use of its resource and reuse this 'waste' water.

The solution, proposed by Professor Darko Goricanec at the nearby University of Maribor's faculty of chemistry and chemical engineering, was to devise a high-temperature heat pump that could reheat geothermal source water from around 40 degrees up to 80 degrees, at which point it could be reused for space heating.

While many heat pumps on the market could heat water from around 25 degrees to 60 degrees, none could deliver the high temperatures (80-90 degrees) required for the type of heating system that is most common in Europe's older housing stock- high-temperature radiators designed to be run from fossil fuel boilers.

The heat from the heat pump is cheaper than natural gas. People have cheaper heating.

"If it's possible to heat groundsource water from 15 degrees to 50 or 60 degrees, we thought, why isn't it possible to heat water of 50 degrees to reach 60 or 70 degrees?" said Evgen Torhac of Nafta Geoterm.

The project has a broader potential-it could open a new market for the wider exploitation of geothermal energy sources and waste industrial heat.

To succeed, the pump would have to provide heat more cheaply than using fossil fuels, which was Lendava's fall-back option during cold weather periods.

Maribor University's Laboratory for Thermal Energy developed software to model the structure of heat pumps and the influence of different temperatures; and conducted simulations to assess the impact of different types of coolant on the pump's running costs and efficiency.

This enabled them to specify and simulate the type of compressor and heat exchanger required to achieve optimal efficiency.

Not only is the development and production of HTH pumps an achievement, but indirect benefits are targeting the environment protection sector as well as the building industry.

The prototype heat pump does not just heat water to 85 degrees Celcius, but it can also be used in reverse, to cool water for reinjection into the ground.

The technology has already proved its worth in Lendava.

"The heat from the heat pump is cheaper than natural gas. People have cheaper heating," said Evgen Torhac.

Rather than relying on a reserve of fossil fuels to supplement the heat supplied from the town's geothermal well, now it can action the heat pump first, and only use fossil fuels as a last resort.