Can Renewables Power An Entire City?
More than 170 cities across the United States have set goals to power their communities with 100% renewable electricity, according to the Sierra Club.
How realistic would it be to generate electricity for an entire city solely with sources such as solar, wind, geothermal, and hydropower? Based on a sampling of responses from some renewables market-watchers, perhaps the most optimistic answer is “it depends.”
For starters, gauging a city’s electricity demand hinges on a variety of factors. Paulina Jaramillo, professor of engineering and public policy, Scott Institute Energy Fellow, and co-director of the Green Design Institute at Carnegie Mellon University, told Rigzone that the electricity needs of major cities can vary greatly within a single country. She cited as examples cities in the Northern and Southern United States.
To illustrate, Jaramillo pointed out the average residential utility customer in New Orleans, La., needs significantly more electricity per year than a similar customer in Pittsburgh, Pa. – largely on account of differences in air conditioning demand. According to the U.S. Energy Information Administration (EIA), the average U.S. residential customer needed 10,649 kilowatt-hours (kWh) of electricity in 2019. Louisiana took the top spot among states in terms of average annual residential consumption (14,787 kWh) and Hawaii (6,296 kWh) showed the lowest usage for the period, EIA stated.
Jaramillo also observed that isolating the electricity demand for a single city is difficult.
“That’s tricky because we have an interconnected grid that doesn’t just power one city,” she said, referencing the Eastern Interconnect, the Western Interconnect, and Texas major electrical grids. “You can build enough renewable for a city, but we can’t just say that Pittsburgh is buying 100% renewables.”
Although a city could buy all of its power from wind farms, for instance, that power is still going to the grid, Jaramillo continued. She noted that grids could be built 100% renewable but added the economic feasibility of doing so – despite ongoing cost reductions – remains a challenge. Along those same lines, she said that high costs represent hurdles to storing power via electric batteries or hydrogen.
Power and Storage
“It would be tough for renewables to provide 100% of electricity,” remarked Mary Anne Sullivan, senior counsel in the Washington, D.C., office of law firm Hogan Lovells and a U.S. Department of Energy general counsel during the Clinton administration. “Because of the intermittent nature of solar and wind, to provide consistent reliable power, they depend on storage, whether from batteries or other forms of electricity storage, such as pumped storage.”
Sullivan pointed out that pumped storage (associated with hydroelectric power) is not an option in many locations, adding that maintaining the intermittency of wind and solar power demand an “enormous” amount of battery storage. For example, she cited a plan by the utility Southern California Edison (NYSE: EIX) to contract with a large battery project capable of storing 400 megawatt-hours (MWh) (400,000 kWh) of electricity yet insufficient for covering an entire city.
“Wind and solar still produce intermittently and we do not have a reliable, cost-effective battery solution,” said Fernando Valle, senior oil and gas analyst with Bloomberg Intelligence. “Wind and solar can generate a significant portion of electricity demand at peak times.”
What About Nuclear?
“Many new nuclear technologies are much more passively safe and less capital-intensive, and they can be part of a carbon-free power solution,” Sullivan said.
Sullivan’s reference to nuclear power generation provides an opportunity to compare the capacity factors of various energy sources. A power plant’s capacity factor gauges how often the plant runs at maximum power, according to EIA. The statistical arm of the U.S. Department of Energy explains on its website that a facility with a 100% capacity factor constantly generates power.
In 2019 nuclear power boasted a 93.5% capacity factor – well above any other energy source that year, EIA stated. Natural gas-fired plans, with a 56.8% capacity factor, ranked second in the EIA’s comparison for the period. EIA noted that other capacity factors by source for 2019 include:
- Coal: 47.5%
- Hydropower: 39.1%
- Wind: 34.8%
- Solar: 24.5%
“Wind in the U.S. generally has a capacity factor of less than 50%, and solar has a capacity factor usually below 30%,” said Tom McNulty, Houston-based Principal and Energy Practice leader with Valuescope, Inc. “It is not consistent enough to be able to be a baseload source of power for now. This might change, if there are significant breakthroughs in storage technology and capacity, but right now the answer (to whether renewables alone can power a city) is no.”
To be sure, McNulty acknowledged that exceptions exist in places with substantial hydro resources – such as Brazil, New Zealand, and Norway.
Vicki Knott, CEO with the control room automation firm Crux OCM, said that a city’s suitability for full renewable electricity potential depends largely on its geographical location.
“For example, if you are located in the mountains with an abundance of hydro dams, then the answer is likely yes,” she explained. “This is not the case for most cities in the world, introducing a need for a diversified energy grid to ensure base and peak electricity demand can be met.”
Acknowledging the goal of 100% renewables, Knott expressed her view that “we are not even close” to reaching the global generation infrastructure necessary for meeting base and peak electrical loads.
“Combining that with continually increasing global population and energy demand, we are chasing a bar that is getting higher and higher,” Knott said. “The only way to build the renewable infrastructure needed for the growing global demand is to use fossil fuels as an energy source to manufacture the renewable infrastructure – impacting the actual cradle-to-grave environmental impact of renewable infrastructure.”
The alternative to the challenge of finding sufficient space for a utility-scale solar plant or wind farm near a city is to install new power transmission lines for long distances to deliver electricity from renewable sources, noted Sullivan. However, she observed that such projects lack universal support.
“There is a lot of recent history that shows that is a very tough sell to those who will look at the lines every day and get no benefit from them,” she said.
Going beyond the city level, some European countries have managed to generate enough renewable energy at certain periods of time to enable grid operators to shut down non-renewable generation, noted Christopher Goncalves, chair and managing director of Energy and Climate practice with consulting firm Berkeley Research Group, LLC (BRG). However, he added that he knows of no instance yet where renewable energy supplies 100% of a country’s needs.
“This is a good long-term question that may still seem a bit academic given how little renewable energy has penetrated the power grids of most countries worldwide,” Goncalves said. “We are far from 100%.”
Goncalves added there is no reason to advance the goal of 100% renewables when it is possible to achieve net-zero power generation with substantial renewable energy usage ranging from, say, 60% to 80% – under one or more of the following conditions:
- an adequate baseload supply of nuclear generation, which exists
- ample low-cost battery storage to manage intermittency and load swings, which he said is technically possible but still moving along the technology cost-reduction curve
- a material marginal supply of green hydrogen electrolysis for power generation, which he also said is technically possible but faces a similar cost-reduction curve hurdle
- sophisticated smart-grid technology and artificial intelligence solutions to instantaneous load management, which he said are under development.
“In short, we have the technologies to achieve net-zero power generation based primarily – not exclusively – on renewable energy generation, but we might be 5-10 years away from beginning to deploy those technologies at a massive scale and competitive economic cost,” concluded Goncalves.
To contact the author, email email@example.com. The Sierra Club’s “Ready for 100” website provides a map of U.S. cities that seek to obtain 100% of their electricity from renewables. The EIA’s website provides additional information about capacity factors.
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