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Stanford at CERAWeek: energy storage, net-zero GHG, radiative cooling and perovskite solar cells

Mar 30, 2021
Precourt Institute

By Mark Golden

Four Stanford University faculty members discussed their work to make energy systems more sustainable, affordable and reliable at the annual energy sector conference CERAWeek, held during the first week of March.

Normally, more than 5,000 energy executives in business, government and research from around the world attend the conference. Last year, CERAWeek was canceled due to the Covid-19 pandemic. Held virtually this year, the conference attracted more than 20,000 viewers.

Yi Cui, director of Stanford’s Precourt Institute for Energy and professor in the Department of Materials Science & Engineering, discussed new horizons for energy and climate research as part of a panel. To Cui, the big issue is energy storage to enable greater use of intermittent solar and wind power.

“In about 10 years, the battery industry will be about 10 times bigger than it is today,” said Cui. “Battery life could go up to 5,000 cycles in 15 years,” he added. That would nearly double the lifetime of electric vehicles.

However, Cui said, batteries – which is the primary focus of his research – may not be the most economical solution for grid-scale electricity storage, which covers sustaining a constrained grid for days and storing excess power supplies in summer for winter months.

“For seasonal, I’m not seeing that batteries can do the job. Cost needs to be much lower, like $20 per kilowatt-hour. This is where hydrogen may come in to play a large role,” he said.

When pressed by moderator Atul Arya of CERAWeek if hydrogen has an affordable path for long-term storage, Cui said simply, “Yes.”

Meanwhile, he added, research on technology innovations, policies, finance, and social and environmental impact must work together. “If we can put people together to work on this holistically,” Cui said, “then when we get a technology innovation maybe the policies are in place to scale up fast.”

Getting to net-zero

Arun Majumdar, professor of mechanical engineering and former co-director of the Precourt Institute, discussed gigaton-scale solutions for getting to zero greenhouse gas emissions globally from human activity. A tectonic shift, he said, is that electric vehicles will be comparable in cost and range with gasoline vehicles in five years due to lower costs for lithium-ion batteries.

“But, that doesn’t mean that we have addressed climate change,” Majumdar said. “If you really want to limit the global average temperature rise and thereby limit some of the weather extremes we are seeing, we will have to get to net-zero at some point. We don’t have the technology to decarbonize cement and steel. The food and agricultural sector produces more emissions than the transportation sector globally, and we need technologies for that.”

“I think people may become complacent if they think wind, solar and batteries are going to get us out of climate change,” he added. “I don’t think they will.”

Nevertheless, Majumdar is impressed that almost half of Fortune 500 companies and many countries have committed publicly to operate with zero emissions in the coming decades. That commitment, he said, could provide the commercial path for new technologies to scale up and, eventually, become broadly cost-competitive due to economies of scale. At the same time, he said, the world also needs technologies that remove carbon dioxide from the atmosphere at the gigaton scale.

Radiative cooling

Shanhui Fan, a professor of electrical engineering, explained how his latest advances in radiative cooling, which harvests electricity from the coldness of the universe, can be harvested on Earth for several renewable energy applications. For millennia, humans in regions where the ambient temperature never falls below freezing have used the concept to make ice by burying water at night.

Radiative cooling could have a significant impact on lowering electricity use and boosting output of renewables, but it will require advances in blackbody emitters, materials that absorb heat and radiate the heat at frequencies that send it into space.

“This requires a good blackbody emitter,” said Fan, “but we can cool objects to a temperature 13 degrees Celsius (55 degrees Fahrenheit) below the ambient temperature with no electricity,” said Fan. “It’s purely passive cooling.”

Radiative cooling systems could, for example, reduce the electricity required for air conditioning by 10 percent to 15 percent, he said. Such systems at night could also generate enough electricity for LED lighting in homes, which would be a significant development for the billion humans without electricity.

Spray-on solar cells

Reinhold Dauskardt, professor of materials science and engineering, explained his recent work on the rapid and inexpensive manufacture of perovskite solar cells at industrial scale. The efficiency of devices, including solar modules, declines when they are manufactured on a large scale, Dauskardt said. To date, the efficiency penalty here for perovskite cells has been quite pronounced compared with silicon cells.

Dauskardt’s team on March 1 published very encouraging results of their coating technologies, which improve uniformity and reduce defects to improve reliability in manufacturing. The process is done in the open air at ambient temperature and pressure, which should greatly reduce manufacturing costs, though humidity is controlled and clean-room quality air is required.

“Rapid spray plasma processing is significantly faster than other techniques, like gravure and inkjet,” Dauskardt said, “and very low cost.”

His team has done extensive cost modeling for a 100-megawatt factory manufacturing process, and the technology should be competitive with silicon in around five years, he said.