Renewable energy achieved a significant milestone in April, surpassing coal as the greater source of power for electric generation in the United States. This record may not persist as April is a windy month and because of mild weather less energy is needed for heating or cooling. Regardless, it is a milestone that portends the future.
Electric power from burning coal has been in decline for over a decade. Nuclear power is flat and renewable energy is ascendant. Of the renewable energy sources, wind is the leader followed by solar. Hydropower, geothermal and biomass are relatively static.
Technological advances and economies of scale are responsible for the lower cost and therefore greater penetration of renewables in the electric power production marketplace. Wind turbines are getting larger and taller which makes them more cost-effective in both production costs and efficiency as taller turbines reach windier levels of the atmosphere. As for solar arrays, the advances are mainly in cost reductions due to economies of scale rather than greater efficiency at capturing sunlight.
About seventeen percent of the energy mix is now renewable, and that is dominated by hydroelectric dam generation. In absolute terms, wind produces about seven percent and solar a little under two percent. These numbers are small but the two sources have the greatest potential for growth. Wind energy production has increased a phenomenal thirty-fold since 2000. When it comes to growth, solar is the champ having grown one hundred times faster than wind; that is, a three thousand-fold increase in installed capacity between the year 2000 and today.
One of the beauties of solar is its scalability. Practical installations range from small home systems providing most if not all of an individual homeowners electric power needs up to utility-scale monsters that cover hundreds of acres. Slightly larger than home size installations are those for schools and churches. Even larger installations include power for businesses such as Walmart Supercenters. The real growth, however, is in utility-scale solar arrays.
Entergy, the main supplier for electricity in Arkansas is now producing power from a giant installation near Stuttgart. This facility has 350,000 panels covering 475 acres. It produces enough energy for 13,000 homes. Using this scale of production suggests that every home in Arkansas could be powered from an area less than ten percent of Lafayette County, the smallest county in Arkansas.
Wait just a minute you say, what about when the sun goes down? Not to worry, at least for a couple of decades. Power grid managers won’t worry until intermittent sources reach somewhere between thirty and fifty percent of the total load. Right now wind and solar represent less than ten percent. Two factors are important, source management and grid size. Although wind and solar are intermittent, they are also predictable, and increasingly so.
Utility grid managers have become quite good at wind and sun forecasting. They know about how much wind and solar power will be available in the short term and can effectively plan for alternate sources during those times. The total size of the US power grid adds to the stability. Power can be shipped for one region to another with the flip of a switch – well, that and a more robust national grid of transmission and distribution lines.
Dr. Bob Allen, Ph.D., is Emeritus Professor of Chemistry at Arkansas Tech University.