Optimization of a hybrid solar-geothermal energy system at building scale

Building sector decarbonisation involves large scale integration of renewable energy sources within the energy mix commonly used to fulfil the heat demand. For this, to combine several energy sources and to control conversion systems based on a systemic approach seems to be promising for making nearly zero energy buildings a standard. Such hybrid energy systems may be more reli- able and hence play a key role for grid interaction of variable energy sources. Many case studies have proven this already. However, the most of the analysis have often been made on specific building only. The present work aims to ad- dress the impact of hybrid renewable energy system use in a more general way. It prevents experts as decision makers from requiring large input information dataset regarding each individual building, on a given location. This enables to study more easily a whole area in terms of renewable energy potential and deduce energy-related information at urban scale. The district of Aire (GE) in Switzerland is selected as case study. Input datasets are based on national Swiss databases and studies previously performed at national scale. Simplified hydraulic model of space heating system is introduced at single building scale. Coefficient of performance temporal variation is included based on heat supply temperature evolution. Modelling of dynamic system behaviour is performed at monthly-mean-hourly temporal resolution. Energy performances are described throughout self-consumption and self-sufficiency ratio indicators. Furthermore, grid-based electricity use is monitored to compare performance of several sys- tem configurations with a reference case, that is without any coupling operation strategy in the frame of a hybrid system. Finally, an optimization procedure is applied for renewable energy based equipment sizing purposes. It appears that beyond a certain storage capacity limit, equipment sizing becomes less attractive in terms of energy performance and maximum surface area available for solar photovoltaic production should be harnessed.