Net energy analysis of domestic solar water heating installations in operation

Abstract

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 real performance 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 be lower than expectations. Concerning their life cycle energy performance, existing studies show that the initial energy investment for the systems (their embodied energy) is a small portion of the energy savings over their lifetime with calculation paybacks generally lower than 2 years. On the field study carried in Ireland, representative of a maritime north European climate, the 'energy payback' based on the expected energy savings is between 1.2 and 3.5 years, values comparable to previous studies considering the less favourable climate and installation characteristics. However the measured energy savings generally worsened the life cycle energy performance of this technology and thus increased the energy payback period. The study concludes that while there is a real potential for life cycle energy savings through domestic solar water heating installations, devising mechanisms to ensure proper design, installation and operation of systems is essential for this technology. Introduction: the potential of domestic solar water heatingEnergy consumption in residential buildings represents a large portion of global energy use, approximately 25% of total primary energy use in the European Union [1]. Water heating was responsible for around a quarter of that energy use [2]. Domestic Solar Water Heating (DSWH) is a well-proven technology used to reduce the energy demand for providing domestic hot water, and its potential to largely reduce domestic energy use is frequently acknowledged [3][4][5][6].

An integrated supply-demand model for the optimization of energy flow in the urban system

“…Further models, which build on exergy analysis have examined the efficiency of the heating and cooling systems using solar energy (Bayrak et al, 2013;Hernandez and Kenny, 2012;Borge et al, 2011) and ground source heat pumps (Li et al, 2014b;Ally et al, 2013). Application of these models allows for a better understanding and more effective design of thermal energy supplier technologies.…”

Review and perspectives on Life Cycle Analysis of solar technologies with emphasis on building-integrated solar thermal systems

“…Hernandez et al [28] conducted a study about the net energy analysis of domestic solar water heating installations (flat-plate and ETC collectors) in operation. The final conclusion was that for a correctly properly performing installation, embodied energy is generally a small part of the life-cycle energy savings, and energy paybacks as low as 3 years are possible even in a maritime climate such as Ireland.…”

Modelling and simulation of Building-Integrated solar thermal systems: Behaviour of the coupled building/system configuration

“…It should be noted that there are also few LCA studies about BA solar thermal systems: BA flat-plate solar collectors/active systems [75][76][77][78][79]; BA flat-plate solar collectors/ passive systems [80][81][82]; evacuated-tube solar collectors [83][84][85][86]; integrated collector/storage systems [87][88][89]. On the other hand, a small number of LCA works are reported on BIPVT systems [90][91][92] and BI concentrating PV [93].…”