Renewable electricity and energy storage to permit retirement of coal-fired generators in Nova Scotia

In August 2011 Canada's Environment Minister proposed performance standards aimed at retiring coal-fired electricity generators. In this study, an evaluation is made of future renewable electricity generation and gross electricity demand in Nova Scotia, Canada. These are coupled with an energy storage model for peak shaving and increased ramp-rate capabilities sufficient to retire coal-fired generation. The proposed storage system represents a feasible method to not only displace coal use, but to displace the need for fossil-fueled generating capacity as backup for renewable generators. Within the model, an aggregate electrical system load timeseries at 1 h intervals is developed for Renewable Energy Standard years 2015 and 2020 using publicly available historical data and existing load growth projections. This is compared to renewable energy generation projections, with the difference between generation and demand used as the input to an energy storage model wherein storage augments dispatchable generating capacity. The model estimates energy storage characteristics required to limit peak conventional generation capacity and ramp-rates. A storage system comprised of 500 MWh of energy storage, coupled to the projected effects of efficiency improvements is found to be adequate to insure reliability while retiring 600 MW of coal generation capacity.