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Geothermal energy: CNIM pioneer in the valorization of 38°C water
In Lituania, the city of Klaipėda operated for nearly 20 years a large geothermal heating plant. Initially built to house a demonstrator funded by the World Bank in the early 2000’s, the plant was equipped with four CNIM’s absorption heat pumps, supplying 50 MW of energy to the city’s district heating system.
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geothermal shafts in operation between 2000 and 2018
Comprehensive heat recovery system
Heat produced by cooling groundwater
The Baltic port city of Klaipėda (population: 190,000) operated a geothermal energy-powered district heating system for nearly 20 years. Heat was produced by cooling groundwater. In the 2000’s, a demonstrator financed by the World Bank was tested using CNIM equipment to equip a plant with the absorption heat pumps required for extraction and cooling. (Picture: Port of Klaipèda, Lituania)
4 x 12.5 MW supplied by absorption heat pumps
The absorption heat pumps produced energy. They used water from geothermal wells drilled into an aquifer* situated 1,100 m below the surface. The system operated in a closed circuit: water was reinjected into the aquifer when it has cooled.* An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt). Groundwater can be extracted using a water well. (source: Wikipedia)
This geothermal source was too cold to be used directly to heat the district heating water and required the use of heat pumps to raise their temperature.Each four CNIM’s machines supplied 12.5 MW of energy, extracted from 38°C groundwater, injecting a total of 50 MW of energy into the city’s district heating system.
Picture: Four CNIM absorption heat pumps
High-performance materials to combat corrosion
A number of technological challenges had to be tackled. Difficulties involving corrosion of the subsystems in direct contact with water were encountered, due to gypsum precipitation fouling tubes in the surface loop and heat pumps. These problems were overcome using special materials such as titanium.
Environmentally friendly facility
The environmental impacts were positive: decreased use of fossil fuels and lower annual carbon dioxide (CO2) and nitrous oxide (NOx) emissions, at 52,000 and 270 tons, respectively (source: Proceedings of the World Geothermal Congress).