Optimizing the size of a fully renewable power system to meet energy demand

Abstract

In electricity grids, demand and generation must be balanced at all times. Modern electricity is primarily generated by baseload power sources, such as nuclear and coal, and quickly dispatchable sources, such as gas fired power plants. As anthropogenic total CO2 emissions already make up almost 75% of the atmosphere's total carbon content, governments are increasingly implementing renewable energy mandates. Therefore future electricity generation markets will ultimately require variable, renewable power sources that emit no CO2. Two of the most widely used renewable power sources, wind and solar, cannot always provide energy when there is demand. In order to address this mismatch, either a third dispatchable energy source or an energy storage system has to be included to fully meet demand. This study examines and optimizes a purely renewable energy system to fully meet demand for the town of Minot, North Dakota. The renewable system studied combines wind and solar with CO2 Plume Geothermal as both a third power source and a method of of energy storage. I find that the renewable power system without energy storage has to be oversized by 400% of maximum demand in order to meet demand for the few constraining hours of the year. Once CO2 Plume Geothermal Energy Storage is introduced, system costs due to over-installation are reduced by 80% compared to the system without energy storage. Additionally, when using CO2 Plume Geothermal Energy Storage both characteristic demand curves are met with zero CO2 emission. The systems with CO2 Plume Geothermal Energy Storage are currently more expensive than dispatchable, fossil-fuel power sources, but as CO2 costs are introduced the systems become economical.