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Energies 2016, 9(11), 953; doi:10.3390/en9110953

Retrofitted Solar Domestic Hot Water Systems for Swedish Single-Family Houses—Evaluation of a Prototype and Life-Cycle Cost Analysis

Department of Architecture and the Built Environment, Division of Energy and Building Design, Lund University, Box 118, 221 00 Lund, Sweden
Efficax Energy AB, Ideon Science Park, Scheelevägen 15, 223 70 Lund, Sweden
Author to whom correspondence should be addressed.
Academic Editor: Francesco Calise
Received: 30 August 2016 / Revised: 7 November 2016 / Accepted: 8 November 2016 / Published: 15 November 2016
(This article belongs to the Special Issue Solar Cooling and Heating)
View Full-Text   |   Download PDF [5852 KB, uploaded 15 November 2016]   |  


According to recent technology road maps, system cost reductions and development of standardised plug-and-function systems are some of the most important goals for solar heating technology development. Retrofitting hot water boilers in single-family houses when installing solar collectors has the potential to significantly reduce both material and installation costs. Previous studies have investigated such retrofitting, using theoretical simulations and laboratory tests, but no actual installations were made and tested in practice. This article describes the installation, measured performance and cost effectiveness of a retrofitting solution that converts existing domestic hot water heaters to a solar domestic hot water system. The measured performance is characterised by the monthly and annual solar fractions. The cost effectiveness is evaluated by a life-cycle cost analysis, comparing the retrofitted system to a conventional solar domestic hot water system and the case without any solar heating system. Measurements showed that approximately 50% of the 5000 kWh/year of domestic hot water consumption was saved by the retrofitted system in south Sweden. Such savings are in agreement with previous estimations and are comparable to the energy savings when using a conventional solar domestic hot water system. The life-cycle cost analysis showed that, according to the assumptions and given climate, the return on investment of the retrofitted system is approximately 17 years, while a conventional system does not reach profitability during its lifetime of 25 years. View Full-Text
Keywords: retrofit; solar thermal; single-family houses; life cycle cost; domestic hot water retrofit; solar thermal; single-family houses; life cycle cost; domestic hot water

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Bernardo, L.R.; Davidsson, H.; Andersson, E. Retrofitted Solar Domestic Hot Water Systems for Swedish Single-Family Houses—Evaluation of a Prototype and Life-Cycle Cost Analysis. Energies 2016, 9, 953.

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