A Promising Outlook for Solar Energy Forecasting
Solar energy continues to grow in the United States, but its relative unpredictability remains a hurdle in deploying it on the grid. Now a research team is working to create detailed 36-hour forecasts of incoming energy from the sun.
The three-year effort, led by the National Center for Atmospheric Research (NCAR), is funded by a $4.1 million grant from the U.S. Department of Energy. NCAR is working with universities, utilities and other energy companies, as well as commercial forecast providers, to predict with far more accuracy and specificity when cloud cover could reduce the amount of energy coming from the sun.
More than half of all states in the U.S. have required that utilities increase their use of renewable energy, but renewables are inherently variable. The hope is that solar can follow the example of wind, which now has far more reliable forecasts from a previous NCAR effort. (Related post: “Focusing on Facts: Can We Get All of Our Energy from Renewables?“)
The team is designing a prototype system that would forecast sunlight and the resulting power every 15 minutes over specific solar facilities.
One of the biggest challenges energy companies face with solar power is the ability to anticipate how much of it will be available — and when — so that they can reliably work it into the grid. (See related: “The Big Energy Question: What to Develop Next?“)
If an incorrect forecast shows that there will be more solar energy available than there is, a utility has to buy more on the wholesale market to make up for it — likely at a higher price than they would pay if they could plan ahead for it.
“What happens when a cloud comes over and cuts the production in half, and we as an ISO [independent system operator] have to go out and procure that energy? Then when you go to buy that energy it’s like buying an airline ticket” at the last minute, so it’s more expensive, explained Jim Blatchford, who helps integrate renewable energy into the smart grid for the California ISO, one of NCAR’s partners in the project.
“If we can predict what’s going on and we can line up that generation and buy it in the future instead of in real time,” the company can save money, he said.
Likewise, if more sun than is expected produces excess solar power, that extra energy can go to waste because currently there is no cost-effective way to store it.
“It’s critical for utility managers to know how much sunlight will be reaching solar energy plants in order to have confidence that they can supply sufficient power when their customers need it,” said Sue Ellen Haupt, director of NCAR’s Weather Systems and Assessment Program and the lead researcher on the solar energy project, in a statement. “These detailed cloud and irradiance forecasts are a vital step in using more energy from the sun.”
Nick Depmer, one of the managers on the trade floor at Xcel Energy in Colorado, knows that firsthand.
“You have to be able to unload or load up other assets to fill in that void,” he said. “If you can anticipate that issue, then you can react to it. The more accurate your forecast, the better.”
NCAR worked with Xcel to create a detailed wind energy forecast that saved Xcel ratepayers an estimated $6 million in a year. But determining cloud cover accurately and specifically always has been a challenge for meteorologists, because there are different types of clouds, and they’re affected by so many factors, including wind, humidity, surface heat, atmospheric gases, and more.
Russ Bigley, a meteorologist with Xcel, said the NCAR-led research team will start with the same atmospheric model that was used for wind, and tweak it to work for solar. He said solar forecasts that look further out might be easier than those for wind, but “solar on a five-minute basis is probably going to be a lot more difficult than the wind.”
Both Bigley and Depmer said that wind forecasting had come a long way with the NCAR project, in large part because information that companies might otherwise have kept to themselves was released. They’re hopeful the same will be true for solar, but they’re not convinced better forecasting will be the ultimate game changer because of solar’s cost.
Utilities do currently use solar forecasting, but they are looking for more detail.
“We do use computer models and we push that into a solar forecast based on cloud cover,” Bigley said. “I think right now … the state of the forecasting is probably in its infancy, and that’s partly because the penetration level of solar is not that great compared with other generation assets.”
The California ISO uses some solar forecasts in the two-hour range, but “we want to get it in closer to real time,” Blatchford said.
The research team will put in place a range of observing instruments, including lidars (laser-based technology that takes measurements in the atmosphere); specialized computer models; and mathematical and artificial intelligence techniques, according to a press release. A key part of the system will be placing groups of three sky imagers in each of several locations. They will observe the whole sky, triangulate the height and depth of clouds, and trace their paths across the sky.
Researchers plan to test the system in several geographic areas and during different weather patterns throughout the year.
The forecasts would then be able to predict when, where and what type of clouds would form over a specific area, as all of those factors have a varying impact on the amount of sunlight that gets through.
The utilities and ISOs can then look at the forecast and determine, “Where’s the sun in relation to those clouds? How’s it going to hit my solar farm?” said Blatchford. “This is all really just in its infancy. We’re [becoming] a little bit smarter, a little bit more advanced.”
Related Topics
Go Further
Animals
- Octopuses have a lot of secrets. Can you guess 8 of them?
- Animals
- Feature
Octopuses have a lot of secrets. Can you guess 8 of them? - This biologist and her rescue dog help protect bears in the AndesThis biologist and her rescue dog help protect bears in the Andes
- An octopus invited this writer into her tank—and her secret worldAn octopus invited this writer into her tank—and her secret world
- Peace-loving bonobos are more aggressive than we thoughtPeace-loving bonobos are more aggressive than we thought
Environment
- Listen to 30 years of climate change transformed into haunting musicListen to 30 years of climate change transformed into haunting music
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- U.S. plans to clean its drinking water. What does that mean?U.S. plans to clean its drinking water. What does that mean?
- Food systems: supporting the triangle of food security, Video Story
- Paid Content
Food systems: supporting the triangle of food security - Will we ever solve the mystery of the Mima mounds?Will we ever solve the mystery of the Mima mounds?
History & Culture
- Strange clues in a Maya temple reveal a fiery political dramaStrange clues in a Maya temple reveal a fiery political drama
- How technology is revealing secrets in these ancient scrollsHow technology is revealing secrets in these ancient scrolls
- Pilgrimages aren’t just spiritual anymore. They’re a workout.Pilgrimages aren’t just spiritual anymore. They’re a workout.
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- This ancient cure was just revived in a lab. Does it work?This ancient cure was just revived in a lab. Does it work?
Science
- The unexpected health benefits of Ozempic and MounjaroThe unexpected health benefits of Ozempic and Mounjaro
- Do you have an inner monologue? Here’s what it reveals about you.Do you have an inner monologue? Here’s what it reveals about you.
- Jupiter’s volcanic moon Io has been erupting for billions of yearsJupiter’s volcanic moon Io has been erupting for billions of years
- This 80-foot-long sea monster was the killer whale of its timeThis 80-foot-long sea monster was the killer whale of its time
Travel
- How to plan an epic summer trip to a national parkHow to plan an epic summer trip to a national park
- This town is the Alps' first European Capital of CultureThis town is the Alps' first European Capital of Culture
- This royal city lies in the shadow of Kuala LumpurThis royal city lies in the shadow of Kuala Lumpur
- This author tells the story of crypto-trading Mongolian nomadsThis author tells the story of crypto-trading Mongolian nomads