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.
Highlights
Buildings account for approximately 40% of the total energy use in Europe [1] where 79% of that energy demand is heat for domestic hot water and space heating [2]
Solarnot energy savings could the provided by the was combination of energy from the electric heater and not energy be calculated, since theexisting energy storage provided bya the existing storage was a combination of energy solar two months excluded from themonths energy were savings becausefrom the system was from collectors
If one follows measurements performed on domestic hot water in accordance with the rule of thumb of 4500–4800 kWh/year mentioned by the Swedish Energy consumption, the expected hot water load for a Swedish single-family house with five inhabitants
Summary
Buildings account for approximately 40% of the total energy use in Europe [1] where 79% of that energy demand is heat for domestic hot water and space heating [2]. In order to reach the European energy and climate goals for 2020 [3], the existing building stock should be addressed [1]. This includes passive energy efficient measures to decrease the building’s energy consumption and local energy production by means of renewable energy, especially when moving towards net-zero energy buildings. Solar thermal has the potential to have an important role in achieving the European Union’s 20% renewable energy target for the year 2020 with scenarios predicting its contribution to be between 2.4% and 6.3% [4]. Beyond the previously mentioned national goals, several local communities and cities are setting ambitious targets for energy sustainability
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