Wind power and solar cells may seem like best friends to environmentalists, but in a very real sense, they are “fair weather friends.”
Most Austinites remember waking up to the bitterly cold morning of Jan. 17, when temperatures plummeted to 18 degrees. Austin’s utility hit a new winter demand record. When this occurred, Austin’s wind power operated at only 22 percent of its rated capacity, and its solar cells operated at only 1.5 percent of capacity.
Defenders of fossil fuels never fail to fault wind and solar cells as intermittent and not “dispatchable,” that is, these power sources cannot be turned on or off on demand. The many cities, states and countries trying to increase consumption of renewable energy confront this problem.
The city of Georgetown, just north of Austin, purchases 100 percent of its electricity from wind and solar cells. But it can only do this on paper. Its dispatchable balancing power came from the Texas grid known as ERCOT, operated by the Electric Reliability Council of Texas. In 2017, ERCOT received only 18 percent of its electricity from wind and solar.
Denmark, a clean energy champion, got 46 percent of its electricity from wind and solar cells in 2017. But the tiny country trades electricity every minute of the year with its neighbors in Germany, Norway and Sweden. The region collectively generates only 18 percent of its electricity from intermittent renewable power.
Some academics suggest that intermittent wind and solar can be woven together from different regions to form virtual dispatchability, with little or no conventional power needed. When one region is not producing power, another will. However, there is no place in the world where this has been done at scale. Even if it could be done, long distance transmission lines are expensive.
Some clean energy advocates believe electric batteries will create dispatchability. But at this point in time, they are not economic for daily storage in the mainstream United States. They are only economic for niche markets.
Austin has been a leader in clean energy for decades. We need to take the next step and develop dispatchable renewable options available for Texas.
Concentrating Solar Power, which has existed since the 1980s, uses mirrors or lenses to focus high-temperature heat to the top of a tower or the center of a trough to boil water or refrigerant to generate electricity. Just six-tenths of 1 percent of the land in Texas could provide all of its total 2017 electric consumption. Its onsite heat storage is relatively inexpensive compared to electric batteries.
Compressed Air Energy Storage uses intermittent or low-cost power to produce compressed air in geologic formations like old gas wells. When stored energy is needed, the air is heated in a combustion turbine, which operates at greater efficiency due to increased pressure. This process still needs natural gas, albeit greatly reduced amounts of it. In the future, waste heat from the compression process itself might replace gas altogether.
Thermal Energy Storage uses intermittent or low-cost power to produce ice, cold water, or hot water in tanks inside or near buildings for later use. It is cost effective today for many large buildings and grocery stores. Austin has barely scratched the surface of its potential.
Concentrating Solar Power and Compressed Air Energy Storage have not been built in Texas. The first plants will be more expensive because they have not reached economies of scale. To mitigate costs, Austin should become the charter member of a partnership with other Texas cities and utilities to share the expense. Austin could also use funding from the utility’s GreenChoice program, which allows customers to voluntarily pay more to support renewable energy.
Thermal Storage could be mandated and incentivized for new large buildings and grocery stores when appropriate.
Real leaders in clean energy today are confronting dispatchability. If Austin wants to continue to lead in this field, we need to rise to this challenge.
Robbins is an environmental activist, consumer advocate, and editor of the Austin Environmental Directory .