Solid absorbers are vertically arranged external components made of concrete , mostly as prefabricated parts , into which thin plastic circulation pipes are concreted. They are mostly in an energy exchange with the ambient air, but also with the ground, groundwater, ponds or rivers (mainly heat and radiation energy ) and make this environmental energy usable for heating purposes with the help of a heat pump . The energy is temporarily stored in the concrete element and, when the heating starts, fed to the heat pump and thus to the heating circuit via the brine flowing in the circulation pipes . When the heat pump is idle, the massive absorber that has been cooled down by the extraction of heat regenerates itself.
Solid absorbers and heat pumps use techniques and principles similar to those used in heat pump systems with geothermal probes or geothermal registers . The performance of the solid absorber results from the good thermal conductivity and the good thermal capacity of concrete. The thermal conductivity of 2.1 W / (m · K) exceeds that of water with 0.56 W / (m · K) several times. The heat capacity of concrete is 0.720 kWh / (m³ · K), that of water (the cheapest and most commonly used heat storage device) 1.166 kWh / (m³ · K), while that of air is only 0.00035 kWh / (m³ · K). Thanks to good heat conduction , the heat flowing into the surface penetrates the absorber element and warms up the concrete mass. The ambient heat arriving during the day is thus stored and given to the heat pump heating system if required. The direct as well as the diffuse solar radiation can warm up the concrete element well above the ambient temperature, so that the heat pump has an attractive temperature level available.
Above-ground concrete components are preferably used and quality-monitored and produced in the manufacturing plant. Proven solid absorbers have an area of approx. 10 m² and contain around 80 m of circulation pipes. Preferred solid absorbers are vertically arranged concrete components that are required anyway and that are in contact with the outside air: z. B. concrete walls, concrete retaining walls, noise protection and privacy screens, balcony parapets or parapet elements for parking garages, pilaster strips , curtain walls and sandwich elements made of concrete, energy garages, carports , pergolas , concrete sculptures such as the "energy star", vertical concrete slabs on flat roofs, concrete piles, etc.
The first buildings that are heated exclusively (monovalently) with massive absorber heating were built as early as 1979. In 1995 a complete housing estate, the so-called solar thermal housing complex in Oberhausen-Rheinhausen , each of the 22 single-family houses separately, was equipped with monovalent massive absorber heating. We have experience with the systems in operation for over 25 years. An annual performance factor of 3.3 has been verified by measurement in the solar thermal housing complex. Higher annual performance figures are achievable.
Solid absorbers and heat pumps use techniques and principles similar to those used in heat pump systems with geothermal probes or geothermal registers. The particular advantages over other heat pump heat sources are fewer approval problems, better accessibility, the double use of the solid absorber prefabricated parts as a component and absorber and shorter charging periods .
- ^ Roy Jastrow: Optimization of a heat pump heating system with concrete absorbers. Measurements in the solar thermal housing complex Oberhausen-Rheinhausen and mathematical model . Dissertation Universität Karlsruhe 1997, VDI progress reports, series 19, no.104 , VDI Verlag, Düsseldorf, 1997, ISBN 3-18-310419-9 .
- Bernhard Schwarz: warmth from concrete. Systems for the use of solar energy , Bau + Technik, 1987. ISBN 978-3764002213 .
- Illo F. Primus, et al. a .: Massive absorber: The heat source for the heat pump , Bau + Technik, 1995. ISBN 978-3764003272 .