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The Watt-Sun Program Is Poised to Improve Weather Forecasting for Solar Energy

A 20 megawatt solar farm in Tucson, Arizona, is one of the test sites for Watt-Sun.

Solar-power panels seem to be popping up on both residential and commercial rooftops like Morel mushrooms in the spring. And massive solar farms are being built in sun-friendly areas of the world. This is great news for renewable-energy proponents, who see solar—along with wind, waves and tides—as a way to wean the world off fossil fuels.

Germany has at times more than 20% renewable-energy penetration, but no one can rely on it because no accurate forecasting technologies or approaches are available

For grid operators, however, some major issues must be addressed to make all of these newly commercial energy sources viable as part of the overall energy-producing strategy. This is particularly true when it comes to solar energy, which depends on blue skies and a bright sun to generate energy. The grid must be able to nondisruptively incorporate solar power without going down.

Currently, modern forecasting methods can’t effectively predict exactly when the clouds will break so grid operators can power up plants to accommodate a sudden influx of energy—and the storage of such energy remains a challenge. However, thanks to the Watt-Sun program, this forecasting issue may soon be a thing of the past. Hendrik Hamann, IBM research manager for Physical Analytics and Watt-Sun project leader, says IBM Research and the U.S. Department of Energy are working together to significantly improve both short- and long-term weather forecasting, which will make the sun a much more viable means of adding energy to the grid.

Q. Solar energy seems like a great renewable-energy concept. Why do we have issues with it when it’s introduced into the grid?
One of the hardest things to do with energy is store it. That is an unsolved challenge. Of course, people are making progress with that, but any storage of energy is associated with some loss and additional cost.

What utilities are doing today is predicting the load. They match this load using conventional resources with a mix of different energy sources, but all of these energy sources are what they call “dispatchable.” So whenever they want, whenever they feel right in a load, they can just dispatch the energy. That’s how the grid works. If this gets out of balance, then there are big issues within the grid, all the way to blackouts.

“When it comes to solar, you need to be able to predict the clouds quite well —and there’s nothing more complex than clouds.”
—Hendrik Hamann, IBM research manager for Physical Analytics and Watt-Sun project leader

With the emergence of renewable energy, a lot of energy- producing sources on the grid come on and off whenever the weather supports it—whenever the sun shines, whenever the wind blows. That of course changes everything. Until recently, renewable energy as part of the energy mix was a tiny percent so it could essentially be ignored. Now, with wind and solar approaching high levels—10 percent, 15 percent—this starts to become a big problem.

Germany, for example, has at times more than 20 percent renewable-energy penetration, and a significant portion of that is produced by solar energy. However, no one can rely on it because there are no accurate forecasting technologies or forecasting approaches available. A good analogy for what we’re tying to do is similar to looking at different projections of the path of a hurricane.

Will it go south, to the west, to the northeast? I refer to different approaches to forecast the weather with different models as “expert systems.” Each approach may include different aspects of physics, which may or may not work well for particular weather situations but are part of the working model or paradigm.v But working models or paradigms actually tell us how difficult it is to conduct simple weather predictions. That speaks to the challenge of the problem. For example, when it comes to solar, you need to be able to predict the clouds quite well—and there’s nothing more complex than clouds.

Jim Utsler, IBM Systems Magazine senior writer, has been covering the technology field for more than a decade. Jim can be reached at

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