Choosing the Right Technology – Optimized Design of Renewable Supply Systems for Residential Houses

The use of renewable energy sources (RES) has continuously increased throughout the last decade. In the residential building sector the trend goes towards energy supply systems based on multiple RES. This is mainly due to political requirements, governmental subsidies and fuel price development. These systems not only require an optimal design with respect to the installed capacities but also the right choice in combining the available technologies assuring a cost-effective solution. The aim of this paper is to present an optimization methodology for residential on-site energy supply systems based on mixed integer linear programming. The methodology chooses the right combination of technologies and sizes the components based on on-site weather data and expected consumption profiles. Through this approach the fluctuations of RES as well as the user behavior are taken into account already during the planning process. The methodology allows for specifying a level of Net Zero Energy Building (Net ZEB) performance to investigate cost reductions when allowing shares of fossil fuel consumption. The outcome is an optimal supply technology combination and optimal installed capacities in terms of the overall costs including system installation and operating expenses. The approach is applied to a case study of a residential single family house under Danish conditions. It delivers rapidly site-specific solutions and can easily be used as an extension for common building energy simulation software.In the case study several levels of Net ZEB performance have been investigated. The results show that supply systems based solely on renewable sources are still considerably more expensive than standard solutions and that substantial cost reductions can be reached by allowing a certain share of primary energy consumption.