The U.S. is a global production leader in energy and a major consumer of all types of energy. The Worldwatch Institute estimates that the U.S. has less than 5 percent of the world’s population yet consumes about 26 percent of the world’s energy. Also, the U.S. produces about 18 percent of the world’s total electricity from coal, second only to China. Although coal has long been a staple of electrical generation, the global power community is quickly moving to decrease coal in favor of renewable energy sources—wind, solar, geothermal, hydropower, biomass and biofuels.
The power industry is experiencing transformation of its fuel mix on a large scale. The major drivers of these changes are the U.S. Environmental Protection Agency’s tightening of the Clean Air Act and Clean Water Act, as well as the push to new renewable energy sources and more efficient power generation systems. As a result, the Electric Power Research Institute (EPRI) projects that power companies will decommission up to 90 gigawatts of coal-fired capacity during the next five to 10 years. These closings will be in addition to the decrease in fossil-burning capacity that has occurred during the past decade. According to SourceWatch, the number of power plants burning coal in the U.S. since 1988 has dropped approximately 20 percent, from 57 to 37 percent.
Today, utility companies are under increasing pressure to build new infrastructure that will drive better technical performance and economic returns while reducing environmental impact.
Another major issue facing the power industry is the lack of a comprehensive national energy policy. Investor-owned electric utilities, which constitute approximately 78 percent of all power generation in the U.S., are hesitant to invest in a new generating plant without knowing which fuel source, or mixture of sources, will be preferred based on market dynamics and regulatory requirements.
One solution is promoting energy conservation. This allows plants to meet current demand without investing in new types of power generators. In response, practically every major power company has a range of incentives and rebates to assist their consumers in reducing their electrical demand.
As power companies continue to retire base-loaded plants and replace them with intermittent power sources such as wind and solar, the level of uncertainly concerning a given utility’s ability to meet demand load in real time will increase. Plant operations are increasingly swinging their base-loaded, coal-fired boilers to meet frequent changes in demand. Because most of these units were not designed for these swings, equipment reliability has been negatively impacted.
While the distributed control systems are highly capable of handling load swings, the rotating assets and their actuators were designed around base-load specifications with fixed-speed operation. The new reality is the existing equipment must adapt to meet process changes in flow, pressure, temperature and level.
Significant load swings require flow rate changes across the affected pumps involved in the steam production process. Typically, the only pumps in a coal-fired power plant that operate under variable speed control are the boiler feed pumps. When the plant changes load based on demand, the circulating water, condensate, closed heater drain, closed cooling, makeup and blow-down pumps, among others, adjust flow rate. When these flow rates change, the pump system will either run closer to the maximum mechanical efficiency of the pump or will run further away from the best efficiency point (BEP).
During the last decade, in response to the U.S. Department of Energy’s 1998 report “United States Industrial Electric Motor Systems Market Opportunities Assessment,” there have been both a change in how motor system efficiency is viewed and a growing use of variable speed drives. The electric utility industry understandably was not focused on internal electrical energy savings but now realizes that variable speed operation of rotating assets has tremendous value in terms of flexible operation and process reliability.
Uptime and reliability are valuable in an industry that must adapt to rapidly changing load swings. While motor system efficiency will not solve all needs for flexibility, it can and should have an important role in enabling the power industry to reach a state of equilibrium between the uncertainty of intermittent power sources and economizing the remaining fossil-burning plants.
Reaching a Balance
Federal regulations will continue to cause the permanent shutdown of many coal-fired power generation plants. It may be initially difficult to attract the investment capital required to replace this base-load generation capability in an environment of increasing price uncertainty.
The industry will continue to develop solar and wind generation because of technology advances and relatively low capital cost when compared with traditional fossil sources.
Over time, a balance in regulations, technology and capital requirements should be reached, resulting in a new landscape of power generation with a mix of fuel sources that will meet the needs for a reliable supply of power from sources that are economical and sustainable.