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Heat from the soil sourced to provide clean green energy for buildings

An EU-funded initiative has exploited near-surface geothermal energy to increase the share of renewable energy used for providing heating and cooling in buildings.

Energy

Currently, space and water heating accounts for around 47 % of Europe’s total energy consumption. Hence, the greatest potential for significantly reducing CO2 emissions lies within the heating sector. One prospect for major energy savings is near-surface geothermal energy, which is heat from the sun stored in the earth down to a depth of 10 metres. The GeoCollector project developed an innovative geothermal heat absorber system that uses near-surface geothermal energy as a cost-effective heat source. “The initiative plays an important role in developing and producing new, permanent solutions using geothermal energy systems to establish clean and sustainable heating and cooling systems in Europe and worldwide,” says project coordinator Ludwig Eichenseher. Project partners exploited a renewable energy source for heating, hot water production and/or cooling at low cost and with little effort. In contrast to the majority of existing geothermal technologies, the absorber system uses geothermal energy that is already available just below just below the earth’s surface. “Unlike other systems, trenches only 1.5 metre deep and 0.7 metre wide are sufficient for laying the GeoCollect-Absorber-System,” Eichenseher explains.

Heat from the soil

Researchers developed a high-performance system that makes it possible to absorb even low-temperature heat from the ground. The robust modules are made from soil resistant plastic and comprise 12 collectors welded together in a row. The pre-assembled module is then lowered into the excavated trench, which is backfilled. A water/glycol mixture is used to transfer the heat from the soil to the heat pump, where it is prepared for the heating system. According to Eichenseher: “A continuous influx of energy is supplied by the warmer soil surrounding the absorber module.” An important challenge facing near-surface geothermal energy technologies is the large area required by the heat source system. The GeoCollect-Absorber-System is therefore designed for a significantly higher surface extraction than with conventional surface collectors or geothermal probes.

Multiple benefits

The greater heat removal performance means the system is extremely space saving, requiring only one seventh of the land area needed by conventional ground collector systems. “This means installation is possible on smaller plots, thereby enabling the large-scale use of geothermal energy in heavily urbanised areas,” comments Eichenseher. Once the system is installed and paid for, all it needs is minimal electrical power to keep the heat pump-system in operation. Little effort is therefore required to install the GeoCollect-Absorber-System and help future proof both newly built and retrofitted buildings. The innovative system is thus easy to maintain and operate and can be combined with photovoltaic systems to provide heating and hot water. Furthermore, as no deep drilling is involved no approval process is necessary prior to installation. “Since the system uses an inexhaustible climate friendly energy source and therefore not dependent on oil or gas supplies, it is not affected by increases in fuel prices,” Eichenseher points out.

Keywords

GeoCollector, heating, soil, near-surface geothermal energy, space, GeoCollect-Absorber-System, heat pump, space saving, water heating

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