What Keeps the Lights On?

BY AMY SPIVEY, PROFESSOR OF PHYSICS

When was the last time you recall being somewhere when the power went out? Were you at home? Or on campus? It doesn’t happen very often, right? We are fortunate to live in a part of the world where homes and businesses have electricity close to 100% of the time. Our electrical power is so reliable that we forget to think about where it comes from. In fact, electrical power generation is complicated and constantly evolving, and it’s worth considering both how our electricity is generated and the scientific innovations involved in the process.

Figure 1 shows the percentage of electrical power in the U.S. generated by utilities using different energy sources (1). Nationwide, we get about 61% of our electricity from fossil fuels (coal, natural gas, and petroleum combined), 17% from renewables (solar, hydroelectric, and wind energy), and 20% from nuclear power, which is emissions-free but not technically renewable. The “Other” category in Figure 1 includes geothermal energy, wood and wood fuels, and other less-prevalent sources.

Although Figure 1 shows the energy mix used in the entire U.S., there is wide variability in the sources used depending on geography and local resource availability. For example, in 2020 Hawaii generated 68% of its electrical power by burning imported petroleum, while in Iowa 57% of the electrical power was generated using wind turbines (1). Our local public utility, Tacoma Power, generated about 80% of its electricity in 2020 using four hydroelectric dams in western Washington, with the rest coming from nuclear power and wind (2).

The energy sources used for electrical power generation are constantly evolving. Figure 2 shows the percentage of U.S. electricity generated nationwide using different sources over the past 20 years (1). While the fraction of electricity generated using nuclear or hydroelectric power has stayed relatively constant, Figure 2 shows that natural gas has gradually replaced much of the coal-fired electrical power generation. Much of this change has been driven by low-cost natural gas obtained through fracking, but it also may reflect efforts to lower CO₂ emissions. (For each kilowatt hour of electricity generated, burning natural gas releases about half as much CO₂ as burning coal (3).) Figure 2 also demonstrates that the fraction of U.S. electricity generated using wind or solar energy has been on the rise during this time.

Along with university researchers, federal agencies in the U.S. (such as the National Renewable Energy Laboratory) and companies such as BP (formerly British Petroleum) and General Electric are tackling energy-related problems. Efforts include studies of new photovoltaic solar cell materials (4), research on more efficient and cost-effective battery storage for large-scale wind and solar generation projects (5), and the development of cheaper, safer nuclear power sources (6). Scientists and engineers around the world continue to develop technologies that could help move electricity generation away from fossil fuels and toward emissions-free and/or renewable sources.

FIGURE 1 - Energy sources used for electrical power generation by utilities in the United States in 2020. Data provided by the Energy Information Administration, a division of the U.S. Department of Energy (1).

As a student at the University of Puget Sound and a future scientist and problem-solver, perhaps you, too, will work in one of these areas someday -helping us keep the lights on!

FIGURE 2 - Percentage of U.S. electricity generated by utilities over time for the most common energy sources. Data from the Energy Information Administration (1).