A team of businesses and researchers in Serbia and Slovenia, with support from the Eureka Network, has developed a heat pump technology which makes use of ground source heat as a climate-friendly, cost-effective alternative to fossil fuels. The forces of nature that exist underground are no secret, given what we have seen from the recent volcanic eruptions. The exploitation of this geothermal energy source had been underdeveloped until recently. Now, thanks to Nafta Geoterm and the University of Maribor, both based in Slovenia, Serbian business partner Klima and its parent company Mayekawa in Belgium, an alternative means of heating ground water has been developed so that this largely neglected heat source may be used for space heating to remarkable effect.
A deep geothermal well supplies the town of Lendava, Slovenia with water for heating various types of buildings. The water temperature of 70°C falls to 50°C once used - this is not warm enough to be re-used for space heating yet is too warm to be put back into the well. It was evident that better use of this water made ecological sense. Professor Darko Goricanec from the University of Maribor proposed a solution which was to come up with a high-temperature heat pump that can reheat geothermal source water from 40°C to 80°C - hot enough to be reused for space heating. Heat pumps previously available on the market fell short, since none could reheat the water to up to 90°C, the required temperature for the type of heating system commonly used in Europe's older housing - that being, high-temperature radiators designed to run from fossil fuel-fired boilers.
Professor Zoran Stevanovic, head of the Hydrogeology Department at Belgrade University in Serbia, worked in close collaboration with Professor Goricanec and his Maribor colleague Professor Jurij Krope to develop software that can model the structure of heat pumps. Simulations were conducted to assess how different types of coolant impact the pump's running costs and efficiency. A breakthrough measure suggested by Klima was to use ammonia as the coolant for the heat pump. This is an optimal choice since unlike isobutene, it is not explosive and unlike Freon, it does not pose a threat to the ozone layer. Since ammonia provides maximum cooling capacity per kilo the cost of the unit was reduced and the pump can use a lower-volume compressor. Besides being able to heat water to 85°C, the prototype heat pump can also do the reverse: cool water for reinsertion into the ground. Since heat from the heat pump is less costly than natural gas, people have the option of less expensive heating. 'Not only is the development and production of the chemical centrifugal pump (HTH type) an achievement, but indirect benefits are targeting the environment protection sector as well as the building industry,' says Professor Zoran Stevanovic.
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, Nafta Geoterm