Interdependence of Renewable and Conventional Fossil Power Generation

The current economic climate and energy policies are forcing significant change on the bulk of the US power generation fleet. Specifically, the rapid increase in renewable power generation and in environmental requirements will have a direct impact on the conventional fossil-fuel fired power plants. The likely outcome will be the shuttering of smaller coal generating units, older boilers, and units where environmental-related capital investment is not economically viable. Many of the surviving plants will face the addition of environmental-related equipment and a change in operation from base-loaded to more cyclical duty. While some coal plants will continue to operate as base-load generation due to the specific energy market served, it is forecast that much of the US coal fleet will in some way be required to balance the intermittent and variable production characteristics of renewable generation when those sources (wind, solar, hydro) are not available. As the renewable portfolio standards are currently estimated to range from 15–33% (1) of a utilities annual generation, this balancing role is critical to match the electricity demands of the US market. The resultant increase in cycling of the existing fossil fleet that will occur when this balancing occurs is expected to have extremely deleterious effects on the fleet of aging plants. Specifically, the impact will be felt in the areas of serviceability of the critical systems, emissions of fossil plants, and operational efficiencies. This paper is intended to identify some of the major issues that are expected to occur to the existing conventional fossil-fuel fleet as the renewable generation increases. These issues include the degradation in serviceability and reliability in light of increased cyclic operation, reductions in plant thermal efficiency, and impact on plant emissions.