Optimal dimensioning of a solar PV plant with measured electrical load curves in Finland

The optimized system sizes for the grocery store, dairy farm, and domestic house with direct electric space heating were 89 kWp, 28 kWp, and 5.2 kWp, respectively. The solar modules of the grocery store and the domestic house were facing south whereas the optimal module orientation in the dairy farm was 50-50% east-west. It was found that in the case of the grocery store and the dairy farm, the PV system size could be increased without the internal rate of return decreasing significantly, and thus, a larger system could be justified. Using the self-consumption ratio to optimize the PV power system size leads to undersizing of the system. It was found that the subsidies for the PV power systems have a significant impact on profitability. In the cases of optimized sizes, the grocery store would be economically viable even if the electricity price decreased annually by 3.6% with subsidies and 1.0% without subsidies. The optimized PV power system of the dairy farm would be economically viable if the electricity price decreased by 3.3% annually; however, without subsidies the electricity price would have to increase by 1.0% annually to remain viable. Considering a residential house, the annual increase in electricity price should be 0.6% with subsidies and 1.9% without subsidies.