EnergyCalculating emissions, costs of increased wind, solar in the West

New research from the Energy Department’s National Renewable Energy Laboratory (NREL) quantifies the potential impacts of increasing wind and solar power generation on the operators of fossil-fueled power plants in the West. To accommodate higher amounts of wind and solar power on the electric grid, utilities must ramp down and ramp up or stop and start conventional generators more frequently to provide reliable power for their customers — a practice called cycling.

An NREL release reports that the study finds that the carbon emissions induced by more frequent cycling are negligible (<0.2 percent) compared with the carbon reductions achieved through the wind and solar power generation evaluated in the study. Sulfur dioxide emissions reductions from wind and solar are 5 percent less than expected because of cycling of fossil-fueled generators. Emissions of nitrogen oxides are reduced 2 percent more than expected. The study also finds that high levels of wind and solar power would reduce fossil fuel costs by approximately $7 billion per year across the West, while incurring cycling costs of $35 million to $157 million per year. For the average fossil-fueled plant, this results in an increase in operations and maintenance costs of $0.47 to $1.28 per megawatt-hour (MWh) of generation.

“Grid operators have always cycled power plants to accommodate fluctuations in electricity demand as well as abrupt outages at conventional power plants, and grid operators use the same tool to accommodate high levels of wind and solar generation,” said Debra Lew, NREL project manager for the study. “Increased cycling to accommodate high levels of wind and solar generation increases operating costs by 2 percent to 5 percent for the average fossil-fueled plant. However, our simulations show that from a system perspective, avoided fuel costs are far greater than the increased cycling costs for fossil-fueled plants.”

Phase 2 of the Western Wind and Solar Integration Study (WWSIS-2) is a follow up to the WWSIS released in May 2010, which examined the viability, benefits, and challenges of integrating high levels of wind and solar power into the western electricity grid. WWSIS found it to be technically feasible if certain operational changes could be made, but the first study raised questions about the impact of cycling on wear-and-tear costs and emissions.