Net energy analysis of domestic solar water heating installations in operation

摘要

The potential of solar water heating systems to reduce domestic energy use is frequently acknowledged.However there are two factors that are rarely discussed when studying this technology. Firstly the realperformance of the installed systems in operation, and secondly a life cycle perspective of its energy use.These two issues are reviewed in this paper, and a field study in Ireland is also presented. In the review,some studies show that measured real performance of domestic solar water heating systems can belower than expectations. Concerning their life cycle energy performance, existing studies show that theinitial energy investment for the systems (their embodied energy) is a small portion of the energy savingsover their lifetime with calculation paybacks generally lower than 2 years. On the field study carried inIreland, representative of a maritime north European climate, the ‘energy payback’ based on the expectedenergy savings is between 1.2 and 3.5 years, values comparable to previous studies considering theless favourable climate and installation characteristics. However the measured energy savings generallyworsened the life cycle energy performance of this technology and thus increased the energy paybackperiod. The study concludes that while there is a real potential for life cycle energy savings throughdomestic solar water heating installations, devising mechanisms to ensure proper design, installationand operation of systems is essential for this technology.