Residential buildings claim a significant share of the total energy use worldwide. In order to have more realistic energy performance predictions, increased attention is paid to the analysis of the building’s energy use through comprehensive, transient detailed numerical simulations. In this article, the self-consumption and self-sufficiency values of three detached residential buildings are assessed through numerical models made in the programming language Modelica and software tool Dymola. The three buildings have the same structure and different space heating energy demands of 15 kWh/m2year, 30 kWh/m2year and 45 kWh/m2year. The energy use of the buildings coincides with the occupancy profile where domestic hot water use dominates over the space heating demand provided by an air to water heat pump. The discrepancy between renewable energy production and energy consumption is mitigated by means of thermal load shifting and electrical energy storage. In this research, the self-consumption and self-sufficiency of the studied buildings have been analysed as a function of the economically favourable energy storage sizing. For the use of an electrical battery with the installed capacity of 2.5 kWh and thermal energy storage of 250 l, the self-sufficiency results to be 40%, 38.5% and 37% for the three buildings respectively at the specific simulated energy demand conditions.
An optimized inverter sizing depends on the installed photovoltaic capacity, the azimuth and zenith of the panels, the latitude and the efficiency curve of the inverter. Simplified inverter sizing rules are generally used and can be narrowed to two rules of thumb. The first rule aims a maximum PV-production and uses an inverter according to the PV power, the second rule aims a maximum self-sufficiency and uses an inverter size ratio of 0.7. Simulations are performed to quantify the production loss or self-sufficiency loss when the rule of thumb is used instead of the optimized inverter power for a load profile with only household appliances. In a second part, the energy system is extended with a heat pump, a battery or both combined. This study checks if the refurbishment of residential PV systems with heat pump and/or battery still can use the same rules of thumb or is a new sizing method preferred to replace the inverter. Detailed models for load, PV-inverter, battery and battery-converter are developed. The PV-production and the self-sufficiency are determined for 6 azimuths and 7 zenith positions. A final evaluation of the rules of thumb is made.
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