In 2009, University of Luxembourg professor Phillip Dale gave a presentation at an academic conference and included a chart almost as an afterthought.
The chart showed that a new material for photovoltaic panels, despite some underwhelming initial results, had an efficiency that was comparable to a more established material’s performance at a similar early point in its development.
“The talk I gave was pretty awful, but people liked the graph,” Dale said this week.
In the years since, he and his frequent collaborator, University of Utah professor Michael Scarpulla, expanded this chart and found a pattern that held up across several solar power technologies: A key variable in the improvement of solar panel performance was the amount of effort, expressed as the number of research papers published.
This finding was a sign that improvements in solar technology were not just a matter of the passage of time or the intrinsic qualities of the materials, but that effort by researchers played an important role.
So what does efficiency mean in this context? The leading silicon solar panels, the technology that dominates today’s market, have efficiencies of more than 25 percent, which is the share of the solar energy they absorb that they are able to convert into electricity.
Dale and Scarpulla recently published their findings in the journal Solar Energy Materials and Solar Cells and I spoke with them together this week in a video interview, with Dale in Luxembourg and Scarpulla in Salt Lake City.
The key word, they said, is “effort.”
“It takes a lot of effort by a lot of people to make high-efficiency photovoltaics,” Scarpulla said. “There’s no free lunch.”
They found that different solar panel materials have similar increases in efficiency when based on the number of research publications about the materials. So, when a material goes from having, say, 100 papers written about it to having 10,000 papers written about it, the growth in efficiency is similar to its peers at the similar points in their histories.
The materials include silicon and cadmium telluride, which have been around for decades, and newer options, like halide perovskites and copper-indium-gallium-selenide, or CIGS. (Perovskites are being developed for use in tandem with silicon, which is one of several examples of materials being used together.)
“For me, the historical sweep of it was actually quite breathtaking,” Dale said.
The growth in efficiency is not a straight line. The early stages of research can result in large gains. Then, in later stages, additional improvements tend to be more difficult. This is a dynamic that exists across fields, showing that some of the hardest work is in eking out small gains in a well-developed technology.
One caveat: The authors acknowledge that using the quantity of research papers as a measure of effort has some shortcomings. For example, it doesn’t account for corporate research and development funding, which is a major driver of improvements in solar panels.
They chose to track research papers because this is something that can be quantified, while corporate R&D spending data is not widely available or comprehensive.
Also, it’s important to specify why they focus so much on growth in efficiency. Silicon solar panels have doubled in their efficiency since the 1970s, which, along with huge reductions in costs, have made the technology one of the most cost-effective sources of electricity.
Researchers are continually looking for other materials that can do the work of silicon but have other desirable qualities in terms of cost, availability, durability and other factors. But to compete, the alternatives will need to be highly efficient and affordable.
Dale and Scarpulla’s paper helps to give an idea what kind of improvements in efficiency can be expected based on what’s happened in the past. It also provides some context for understanding the efficiency levels of different materials. Some materials may have poor efficiency, but if they haven’t had as much research effort may still be worth a deeper look.
Does this mean any material can be used to make a solar panel, and will increase in efficiency with enough effort? Not exactly. Scientists work with silicon and its alternatives because those materials are well-suited to absorbing solar energy, and this work has a cumulative effect as researchers learn from each other. If a material has little or no promise, scientists aren’t going to bother with it and there will be little body of work on which to build.
The authors said they felt like often-cited resources for tracking efficiency of solar materials were leaving out some important factors.
Arguably the most cited chart for solar panel efficiency is the one maintained by the National Renewable Energy Laboratory. It tracks efficiency by year, showing slow growth in recent years for established materials and rapid growth for more recent ones.
But the NREL chart doesn’t show that there are some big differences in the amount of effort being expended to develop each technology, Scarpulla and Dale said.
By trying to understand the role of research effort, the authors are hoping to broaden awareness of the ability to increase progress in a targeted way.
I asked how this research informs their levels of optimism about the transition to clean energy.
“What I really take heart from is (the potential for) accelerated learning when we all work together,” Dale said.
Other stories about the energy transition to take note of this week:
Korea’s Hanwha Q Cells Makes Major Investment in US Solar Supply Chain: Qcells, the South Korean solar energy company, made a long-awaited announcement on Wednesday that it will spend $2.5 billion to expand manufacturing capacity at an existing plant in Georgia and open an additional plant in the state. The announcement is one of the largest corporate manufacturing commitments since last year’s passage of the Inflation Reduction act, a law that encourages domestic manufacturing of clean energy components, as Nichola Groom reports for Reuters. Qcells, which is part of the conglomerate Hanwha, has said the expansion will lead to the hiring of up to 2,500 workers. “I think it’s fair to say that this deal is President Biden’s vision come to life,” said John Podesta, a White House climate adviser, in a call with reporters. “A major global business chose America as the place to invest in to help build our clean energy future and create thousands of good paying middle class jobs in the process.”
FERC approves Duke Energy Florida, Tampa Electric membership in Southeast Energy Exchange Market: The Federal Energy Regulatory Commission has given the go-ahead for two florida utilities—Duke Energy Florida and Tampa Electric—to join a regional partnership for sharing resources. The partnership, called the Southeast Energy Exchange Market, now includes 21 members, as Diana DiGangi reports for Utility Dive. The group has been controversial because it has some attributes of organizations that run regional grids, but is not an open market. The result, according to critics, is a partnership that favors the utilities that are members and does not foster the kind of competition that would be good for consumers. The debate has implications for the transition to clean energy because one of the barriers for renewable energy in parts of the southeast is that utilities are able to limit the ability of competitors to enter the market.
Critic of Fossil Fuels to Lead Key Offshore Energy Agency for Biden: The Biden administration named Elizabeth Klein to be director of the Interior Department’s Bureau of Ocean Energy Management, the office that oversees offshore oil, gas, mineral and wind power. Klein, a senior advisor to Interior Secretary Deb Haaland, is a strong supporter of renewable energy who had worked at Interior during the Clinton and Obama administrations, as Timothy Puko reports for The Washington Post. The White House had intended to nominate Klein to serve as deputy head of Interior, but changed those plans because of objections from Sens. Joe Manchin, D-West Virginia, and Lisa Murkowski, R-Alaska, about how the combination of Haaland and Klein would relate to fossil fuel industries, Puko reports. Klein will be replacing Amanda Lefton, who is stepping down, who has led the office during a period of rapid acceleration of offshore wind permitting activity.
To Get Off Fossil Fuels, America Is Going to Need a Lot More Electricians: To cut greenhouse gas emissions on pace with the best available science, the United States needs to reduce the burning of fossil fuels in buildings. But to convert buildings to run exclusively on electricity is going to require a big increase in the number of electricians, as Emily Pontecorvo reports for Grist in partnership with Canary Media and Post Script Media. “Customers are literally looking for electricians every single day,” said Borin Reyes, owner of Boyes Electric in Oakland, California, which has a staff of 12 electricians. “We’re not taking emergency calls anymore because we don’t have the manpower. All of our current technicians are out on the field, they’re busy trying to get jobs done.” Adding to the problem, many electricians are near retirement age, so there is a need to ramp up apprenticeship and training programs to fill the gap.
Inside Clean Energy is ICN’s weekly bulletin of news and analysis about the energy transition. Send news tips and questions to [email protected].
Dan Gearino
Reporter, Clean Energy
Dan Gearino covers the midwestern United States, part of ICN’s National Environment Reporting Network. His coverage deals with the business side of the clean-energy transition and he writes ICN’s Inside Clean Energy newsletter. He came to ICN in 2018 after a nine-year tenure at The Columbus Dispatch, where he covered the business of energy. Before that, he covered politics and business in Iowa and in New Hampshire. He grew up in Warren County, Iowa, just south of Des Moines, and lives in Columbus, Ohio.
