Facade-integrated massive solar-thermal collectors combined with long-term underground heat storage for space heating

This work shows how facades of industrial buildings can be used as a heat source for a heat pump heating system. Opaque sections of the building skin are formed by facade-integrated massive solar-thermal collectors (FMSC) in order to collect solar radiation and heat from the ambient air. By means of a building-integrated long-term storage (BLTS), the heat collected during the summer period is conserved for utilization during the heating season. Depending on the current ambient conditions and the actual heat demand, different operating modes are to be applied: In part load with favorable external conditions the space heating demand is covered by direct use of the FMSC heat output. With rising heat demand and lower heat gain from ambient, heating is accomplished by a heat pump with FMSC or BLTS as heat source. With regard to architectural restrictions, FMSC surfaces have to be operated at temperatures above the dew point, avoiding formation of condensate or frost at the building surface. The performance of the system is modeled by means of TRNSYS, relying to available model types for the system components. The model of the core component, i.e. the FMSC, has been validated by a laboratory measurement. A design study has been carried out for an industrial building with a foot print of 1,300 m(2) and an annual heating demand of 82,000 kWh. Key aspect of the investigation is the identification of the most efficient system composition, characterized by the required size of collector area and heat storage volume. (C) 2015 The Authors. Published by Elsevier Ltd.