15 years of R&D in central solar heating in Denmark

Danish R&D activities during the last two decades in the field of Central S olar Heating Plants and Thermal Energy Storage Technologies are presented. The most relevant central solar heating plants (CSHPs), with and without se asonal storage, are examined and essential experiences highlighted. The Sal tum and Ry plants represent the type of CSHPs with preheating the return st ream of a district heating net and no storage involved. The Marstal plant r epresents an alternative approach, connecting the CSHP to the delivery pipe for summer operation. Here the plant involves short-term storage and the a pplication of variable flow that lead to novelties in the control strategy. The plant is described and experiences are analysed. The presented cases s how that the technology, under special conditions, can be economically comp etitive with other heating technologies. Under normal conditions, public fu nding and acceptance of higher energy price are necessary. Further technica l development and push towards a market is required. Especially the develop ment of economical storage technologies is decisive. Work with steel tanks, concrete tanks, aquifer storage, bore hole storage and most importantly, f rom a Danish view, pit water storage is presented and conclusions are drawn . R&D in the field of CSHPs call for international co-operation, knowledge transfer and not least financing. The structural and political climate that shapes the boundaries of the R&D activities and also makes up the dominant barrier for the dissemination of CSHPs is discussed. Conclusions are drawn and future work outlined. (C) 2000 Elsevier Science Ltd. All rights reserv ed.