Solar-plus-storage benefits for end-users placed at radial and meshed grids: An economic and resiliency analysis

Abstract

A resilient photovoltaic system, which comprises from the joint use of photovoltaic solar panels and electrochemical storage that is able to operate both with and without grid connection, is capable of providing an added service both during normal grid-connected operation and when a blackout occurs (as opposed to a traditional solar system). When the conventional power grid is in normal operation, resilient photovoltaic systems are able to generate revenue and/or reduce the electricity bill. During blackouts, resilient photovoltaic systems are capable of providing critical emergency power to help backup diesel generator systems. The research presented here evaluates the technical and economic feasibility of systems based on photovoltaic solar energy and electrochemical storage in three critical infrastructures which have to account with a typical backup diesel generator. To this end, the research presented here assigns a monetary value to the cost of avoiding a blackout. Thus, the REopt Lite software has been used to optimally select and dimension different resilient schemes. For each of the cases evaluated the resilient systems were able to obtain benefits associated with the substitution of the energy use of the electricity grid, the reduction of charges for the use of energy during peak energy periods, and the modification of energy purchase periods from periods of high cost to periods of low cost. For all cases the model found the optimal combination of technologies capable of minimizing the cost of energy throughout the life cycle of the project. The obtained results show that assigning a value to the cost of blackouts can have a major impact on the economic viability of a resilient solution. For all cases the net present value of a system was always higher when a value was assigned to resilience. The values assigned to resilience were higher for users plugged to radial networks, which are more prone to blackouts, and lower for users connected to meshed grids, usually more reliable. Despite the fact that for the investigation presented here only three types of infrastructures were assessed, similar results could be expected for other critical infrastructures with similar loads and electricity tariffs. Resilient systems using photovoltaic solar installations that are limited in size could provide both economic savings during normal grid-connected operation and limited emergency power during blackouts. When these systems based on photovoltaic solar energy and electrochemical storage are used in conjunction with an emergency diesel generator, these resilient “hybrid” systems are capable of satisfying critical loads during short- and long-term blackouts.