Stony Brook’s Minghao Qiu Helps Uncover Where Clean Energy Delivers the Biggest Impact
A new research study co-authored by Stony Brook University Assistant Professor Minghao Qiu reveals that the climate benefits of solar power vary widely across the United States, and that location matters just as much as capacity when it comes to reducing greenhouse gas emissions.
Published in Science Advances, the American Association for the Advancement of Science’s open access multidisciplinary journal, the study found that increasing solar power generation in the U.S. by 15 percent could lead to an annual reduction of 8.54 million metric tons of carbon dioxide (CO₂) emissions. But the biggest takeaway, Qiu said, is how those benefits play out differently across regions, and how data-driven placement of solar investments could yield much larger climate benefits.
“We wanted to go beyond the national average and understand the finer details of how solar generation affects carbon emissions hour by hour, region by region,” said Qiu, an assistant professor jointly appointed between the School of Marine and Atmospheric Sciences and the Program in Public Health. “It’s about producing clean electricity, but also about knowing when and where that electricity replaces the dirtiest generation sources.”
The study, led by Rutgers University and conducted in collaboration with the Harvard T.H. Chan School of Public Health, analyzed five years of hourly electricity generation, demand and emissions data from the U.S. Energy Information Administration. The team divided the country into 13 geographic regions and modeled how increasing solar output at different times of day would affect CO₂ emissions both locally and in neighboring regions.
The results revealed remarkable contrasts: in areas such as California, Florida, the mid-Atlantic, the Midwest, Texas and the Southwest, small boosts in solar power were linked to substantial emissions reductions. In other areas, including New England, Tennessee and the central U.S., increases in solar generation by similar levels had relatively smaller impacts.
This serves as critical information for climate policy. “If you have limited resources to invest in solar, you want to place those resources where they displace the most fossil-fuel-based electricity,” Qiu said. “That’s where you get the biggest bang for your buck, both for emissions reductions and for public health benefits from improved air quality.”
The study also highlighted the spillover effects of solar adoption. In many cases, clean energy produced in one region reduces fossil fuel use in another, due to the interconnected nature of the U.S. power grid. A 15 percent increase in California’s solar capacity was associated with daily CO₂ reductions of more than 900 metric tons in the northwest and nearly 2,000 metric tons in the southwest.
“This interconnectedness means that clean energy investments can have benefits far beyond the state or region where they’re installed,” Qiu explained. “It shows the value of coordinated efforts between regions and across state lines.”
For Qiu, who specializes in studying the environmental and air quality impacts of energy and climate policies, the project was a chance to bring advanced computational tools to a growing climate problem. The research team developed a statistical model that could capture the immediate reductions in emissions when solar displaces fossil fuels, and also the delayed effects several hours later.
In California, a 15 percent solar boost at noon was associated with a drop of 147 metric tons of CO₂ in the first hour, and another 16 metric tons eight hours later. That delayed impact, Qiu said, is the result of complex interactions in the electricity system, such as changes in how power plants are ramped up or down over the course of a day.
“Electricity systems are dynamic,” he said. “When you add solar in the middle of the day, it doesn’t just reduce emissions right away, it can also affect which power plants are running in the evening, which changes the emissions profile later on. Our model was able to capture those subtler, downstream effects.”
Those downstream effects matter for health, in addition to climate. Fossil fuel combustion is a major source of fine particulate matter, which has been linked to asthma, heart disease and premature death. By indicating where solar displaces the most polluting generation, policymakers can target investments that deliver both cleaner air and a healthier population.
Qiu explained that the findings can inform federal and state energy policy and also private-sector decisions. “Utilities, grid operators, and investors all have a stake in making solar deployment as effective as possible,” he said. “This kind of analysis provides a roadmap for where investments will have the highest returns in terms of CO₂ reduction.”
While many of the discussions surrounding renewable energy focus on building greater capacity, Qiu emphasized that efficiency in deployment is equally important. “We’re going to need a lot more clean energy to meet our climate targets, but we also need to be strategic,” he said. “The same amount of solar power can have dramatically different impacts depending on where and when it’s generated.”
Large companies with sustainability targets often invest in renewable energy projects through power purchase agreements. “If those companies want their investments to have the maximum climate benefit, our data can help guide them to the right regions,” Qiu said.
Another key takeaway from the study is the role of transmission infrastructure in maximizing solar’s benefits. In some cases, Qiu noted, a region might generate more clean electricity than it can use during peak sunlight hours, leading to curtailment, when renewable energy goes unused because it can’t be delivered to where it’s needed. “Strengthening the grid and building more transmission capacity could allow regions to export that clean energy to neighbors, increasing the total emissions reductions,” he said.
The research also shows the value of timing in solar generation. Solar panels naturally produce power during daylight hours, but researchers have observed increased usage of peak fossil fuel in the late afternoon when solar output starts to decrease. In some regions, Qiu said, pairing solar with battery storage could allow clean energy to replace fossil fuel generation during high-demand evening hours.
“These findings are directly applicable to decisions being made right now about where to put solar farms, how to design energy storage systems, and how to coordinate clean energy policies across regions,” Qiu explained, and he sees this study as just the beginning: the same approach could be applied to wind energy, hydropower and emerging technologies like green hydrogen. It could also be used to model the combined impact of multiple clean energy sources working together.
“As the energy transition accelerates, we need tools that can help us navigate complexity,” he said. “Our work demonstrates how big data and computational modeling can provide the clarity needed to make informed, impactful choices.”
“This study is about making sure we get the most out of every solar panel we build,” Qiu said. “If we can target our investments to the places where they make the biggest difference, we can accelerate the transition to a cleaner, healthier, more sustainable energy future.”
— Beth Squire