An Innovative Use of Renewable Ground Heat for Insulation in Low Exergy Building Systems

• Published in: Energies (Basel) 2012-08, Vol.5 (8), p.3149-3166
• Main Authors: Meggers, Forrest, Baldini, Luca, Leibundgut, Hansjürg
• Format: Article
• Language: English
• Subjects: buildings; Concrete construction; exergy; geothermal; Geothermal power; ground heat; Heat exchangers; heat pumps; insulation; Temperature; Ventilation
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en5083149

Ground heat is a renewable resource that is readily available for buildings in cool climates, but its relatively low temperature requires the use of a heat pump to extract it for heating. We developed a system that uses low temperature ground heat directly in a building wall to reduce transmission heat losses. The Active Low Exergy Geothermal Insulation Systems (ALEGIS) minimizes exergy demand and maximizes the use of renewable geothermal heat from the ground. A fluid is pumped into a small pipe network in an external layer of a wall construction that is linked to a ground heat source. This decouples the building from the outside temperature, therefore eliminating large peak demands and reducing the primary energy demand. Our steady-state analysis shows that at a design temperature of −10 °C the 6 cm thick active insulation system has equivalent performance to 11 cm of passive insulation. Our comparison of heating performance of a building with our active insulation system versus a building with static insulation of the same thickness shows a 15% reduction in annual electricity demand, and thus exergy input. We present an overview of the operation and analysis of our low exergy concept and its modeled performance.