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

Abstract

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.

Numerical and Experimental Study on a Solar Water Heating System in Lhasa

“…Buker et al [10] reviewed the solar thermal applications in buildings, addressed the important issues related to architectural barriers, system design and installation and revealed the trend of solar thermal technologies required in the future. As solar energy is unstable and discontinuous, a heat storage unit is an indispensable component to ensure the reliable and efficient operation of the solar heating systems [11,12]. Solar water storage tanks are widely used for solar heating systems due to their low cost and convenience [13][14][15].…”