Proportioning wind, solar, and in-stream tidal electricity generating capacity to co-optimize multiple grid integration metrics

With an increasing amount of electricity generation coming from renewable sources, integrating that variable output is of concern for electricity system reliability. This study investigates the proportioning of generating capacity between three co-located but uncorrelated variable renewable resources; wind, solar, and in-stream tidal, so that they complement each other and reduce grid integration costs. One year of resource data from various sites in the province of Nova Scotia, Canada was used. These data were analysed with respect to four metrics of importance to grid operators and electric utilities; coincident minimum and maximum power production, average power output, and ramp rates. These metrics were then combined, on an equal weighting basis, to find an “optimal” combination of generating capacities. The results were also compared to electrical load during the same year to determine the impact that increasing amounts of renewable generating capacity have on the required conventional dispatchable generating capacity. It was determined that a mix of installed generating capacities of 61% wind, 27% solar, and 12% in-stream tidal optimizes the energy, power, and ramp rate metrics. However, even with three independently varying resources, a large increase in renewable generating capacity results in only a small decrease in required dispatchable generation, due to a few coincident low renewable resources occurrences throughout the year.