Potential assessment of coupling PV electricity with district heating supply of building
Keywords:district heating, sector coupling, photovoltaic, renewable energies, carbon footprint, model predictive control, residential building forecasts, operation of HVAC-systems
The energy transition in Germany is leading to an increasing decentralized generation of electrical energy. In Fact, the feed-in of electrical surplus of PV systems causes a higher load on the electrical grid. Increased local use prevents this. Significant potential for the integration of produced electrical power of PV plants for this purpose exists in the heat supply. This paper describes the development and evaluation of a system solution from the cross-sectoral use of surpluses from PV plants and district heating. The latter is often used to supply urban apartment buildings. According to research on the market situation, independently controlled heating rods are available for converting electrical power of PV plants into heat. However, a coordinated operation of these heating rods with district heating is not possible so far. In this paper different approaches for combining these two heat sources with various hydraulic concepts and system controllers will be developed and evaluated. As a potential assessment, a parameter study on influencing factors (e.g. user behaviour, power size of the components, building characteristics) was carried out by numerical simulations. As one result, the highest potentials arise from the use of a forecast-based charging control of a combi-storage tank. The charging control can be realised with different techniques, either through simple if-then decisions or a model predictive control. This can only use slightly more produced electrical power of PV plants, as it is limited due to the time lag between PV surpluses and heat demand. Predictions of future energy flows are necessary for both approaches but these have relatively high errors for individual consumers and PV systems. The results of the paper shows, that more complex forecast approaches (demanding large data sets) do not perform significantly better than simple forecast approaches (which can deal with smaller data sets). Model predictive control requires a higher forecast resolution and is therefore also more error-prone, thus it is not recommended. The desired relief of the electrical grids can be achieved through local consumption. In addition, the economic implementation and the carbon footprint of such a concept are analysed under local and global (whole energy-system) aspects.
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