Modelling of hybrid renewable energy system consisting of microcogeneration unit and photovoltaic installation

In the wake of much needed energy transformation, European Union urges member states to take action for supporting microgeneration. As Poland introduced novel to Renewable Energy Act in mid-2018, microgeneration systems of up to 50 kWe installed can benefit from a prosumer scheme. This paper investigates scenarios for installation of a hybrid system composed of a microcogeneration unit and a photovoltaic installation, applied to an existing public building located in northern Poland. The building is heated by a 32 kW oil-fired boiler and gets all it’s 60.9 MWh of the annual electricity needs from the distribution system operator grid. The actual state was assumed as a reference scenario. The microgeneration unit is composed of a wood pellet-fired boiler of 25 kW nameplate capacity and the linear free piston Stirling engine of 1 kW electric nameplate power. The microcogeneration unit works together with 24 kWp rooftop photovoltaic system, configured in East-West setup. Modelling heat and power demand and production via the energy conversion units was conducted in the commercial modelling software package. The models were built based on the actual data and time series for external weather conditions. Two scenarios were analysed – one where the basic setup of microcogeneration unit and photovoltaic system is topped up with 3 m3 buffer tank and another, where instead of buffer, 10 kW electrical boiler is used for peak loads. Relevant simplified investment and operation expenditures were calculated over a period of 10 years. Calculations proved that despite very little electricity surpluses available for the prosumer support scheme, both scenarios bring positive cash flows within 5.5 and 7.1 years, respectively.