Here comes the sun: Improving local use of electricity generated by rooftop photovoltaic systems

Abstract

Photovoltaic (PV) systems installed on buildings will be playing a major role in providing renewable energy and support the transition to a sustainable energy system. Rooftop PV systems will be mainly connected to the low voltage grid. Typically, these grids are not designed to accommodate large scale decentralized PV electricity production. This calls for research to effectively and efficiently integrate electricity generated by rooftop PV systems in our energy system. One of the possibilities for more integration of PV in the energy system is increasing the amount of directly consumed energy and consequently reducing feed-in PV power peaks to the electricity grid. The main objective of this thesis is the assessment of technical, economic and environmental benefits that can be obtained from the local use of energy generated by rooftop PV systems. The technical benefits include enhancing PV self-consumption and reducing PV feed-in peak power to the grid. This PV self-consumption is affected by the PV system design, electricity consumption patterns and energy technology used in the building, for example by using heat pumps. This thesis focussed on PV systems installed on residential and commercial buildings located in the Netherlands. About 33% of the PV generated energy of residential systems can be directly consumed by dwellings. This is 44% by commercial buildings. Stationary battery energy storage can charge surplus PV electricity and therefore increase self-consumption. A 1 kWh storage capacity per MWh of annual electricity consumption increases self-consumption by 23% for residential buildings and by 22% for commercial buildings. Only 4% of PV electricity during the systems lifetime is lost when a feed-in limit of 0.5 kW per kWp is imposed. This can be reduced to 0.2% using a 1 kWh storage capacity for each MWh of annual demand. Discounted payback times for PV systems are around 10 years for residential systems and 12 years for commercial systems. Dwellings with a PV capacity of 1 kWp for each MWh of annual demand contribute with about 17 tCO2eq to avoided life cycle greenhouse gas emissions. Recommendations for policy makers to support the growth PV systems on buildings were given for both short and medium term perspectives. Policies for the next five years should financially support PV systems larger than a 1 kWp per MWh annual electricity demand. When additional PV capacity is limited by the grid capacity, a feed-in limitation of 0.5 kW per kWp of PV is advisable to implement. Beyond 5 years, policies should provide rules and guidelines to enable new value streams from grid services provided by third parties. Also, a dynamic tax tariff based on marginal emissions factors could enable emission reduction by battery energy storage systems. Future research should focus on how storage and electrification can enable more variable renewable energy in our energy system. Therefore, methods to define dynamic electricity tariff structures and to assess the environmental impact of energy storage must be further developed.