AGILE GAS-BASED POWER PLANTS FOR AFFORDABLE, RELIABLE AND SUSTAINABLE POWER.
Great amounts of renewable energy are installed into power systems at state, regional and national level, often due to fulfill legislated mandates or renewable portfolio standards (RPS). While renewable energy is a means for reducing reliance on fossil fuels and decreasing greenhouse gas emissions, it is increasingly evident that there is need for flexible thermal fleet to help balance the renewables. The primary fuel considered for new builds is natural gas, and the default technology to meet capacity and flexibility needs is gas turbines in simple or combined cycle. In this work we show the substantial system benefits of increased flexibility and improved dynamic dispatch capability. This is achieved by exchanging traditional gas turbine based plants in the planning process to gas-fired combustion engine plants. The combustion engine plants have zero start costs and faster start and ramp rates than comparable state-of-the-art gas turbine based plants.
We use the California Independent System Operator (CAISO) as representative of a large system implementing an aggressive 33% RPS by the year 2020. Through simulation of the year 2022, we compare reliability, operational costs, water consumption and CO2 emissions for the CAISO system assuming 5.6 GW of newbuild gas turbine-based capacity against a 5.6 GW scenario of combustion engine generation. For modelling, we use PLEXOSTM, a dispatch simulation software by Energy Exemplar.
The rapid start times, superior efficiency and flexibility of gas-fired combustion engines are shown to increase the entire fleet efficiency within the CAISO system, by reducing cycling and starts/stops on existing combined cycles and optimizing provision of ancillary services. Flexibility combined with the superior reliability of multishaft engine plants are shown to reduce the number of hours of ancillary service shortfalls by 70%, and the magnitude (MW) of ancillary service shortfalls by more than 50%. The Combustion Engine Alternative scenario shows estimated ratepayer savings of 4–6%, compared to Base Case scenario with gas turbine plants. Water consumption is reduced by 25 million gallons per year, and CO2 emissions are curtailed by 1.1% (> 500,000 short tons per year).