Novel load matching indicators for photovoltaic system sizing and evaluation
László Zsolt Gergely, Tamás Csoknyai, Miklós Horváth
Abstract
Integration of renewable energy sources in energy systems is crucial in achieving climate goals. Transformation of the power system – decentralization and prosumerism has led to the spread of domestic power plants taking part in the process. Mismatch problem of these predominantly grid-connected systems are typically described with load matching indicators. Most commonly used self-consumption and self-sufficiency metrics, though come with limits. One of the greatest is that they are monotone as the function of the capacity of photovoltaics implemented, making them uncapable of suggesting a technical optimum for system size. The scope of this study is to introduce two novel indicators with technical optima those can serve as a sizing principle for domestic photovoltaic plants for different approaches. First, self-production metric is introduced which allocates photovoltaic capacity that delivers maximum renewable utilization on-site and second, grid-liability reveals an optimum from the perspective of minimizing grid usage. A reference building is studied with two control approaches to observe both the existing and indicators. As a base scenario, a water heater with classical control is simulated, while in the second case, demand side management is achieved via improved rule-based control, aiming to store surplus photovoltaic power production. Simulations reveal that the optimum capacity of the photovoltaics from the perspective of both self-production and grid-liability is much lower than the capacity (of 6.57 kWp) that would cover the annual electricity demands of the observed household. In case of the traditional control, self-production leads to an optimal photovoltaic capacity of 4.38 kWp, while grid-liability to a 0.73 kWp. With improved control, optimal capacities are much closer, 2.92 and 2.19 kWp respectively.