Cameron Potter is a power prediction engineer, a snappy way of saying that he works on improved methods for forecasting the watts generated by wind farms.

You may recall from the post Forecasting 101 that, while we expend a lot of effort predicting the weather, we’re ultimately informing wind farm operators and utilities about the power output they can expect from their turbines. That way, they can plan accordingly by selling all the power they generate, or by buying power from other sources to compensate for becalmed turbines.

How to Decipher a Power Curve

An important element in predicting energy output is the power curve — either provided by a wind turbine manufacturer or derived by observation — that describes the energy generated by a turbine at various wind speeds.

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In a little-used 3TIER conference room — the one where old desk chairs go to live out their twilight years — sit two stacks of cardboard boxes containing more boxes: slick, nearly featureless black boxes. One pile stores new CPUs awaiting introduction to the computing cluster.

The other pile stores hard drives shipped to us from the Space Science and Engineering Center at the University of Wisconsin-Madison. Although 3TIER is located in the most wired building in the Pacific Northwest, we calculated that it’s more bandwidth-savvy to ship empty hard drives to Madison and receive full hard drives back. The data acquisition team unpacks them one by one and joins their contents to a massive collection: 12 terabytes of satellite pictures of the planet. These images are the beginnings of the REmapping the World global solar map.

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Now that you’ve got the 411 on our assessments, you’re probably wondering how that’s different from forecasting, the other thing on which we spend a lot of time and computing power.

In short, an assessment analyzes lots of past data to tell you what the weather was like, whereas a forecast tells you what the weather will be like. “Assessment is ‘hindcasting,’” Scott Eichelberger says. Which means forecasting is … well, you know what it is. Scott didn’t give me a pithy one-liner for forecasting.

Who uses our assessments? Developers who are prospecting for sites for new installations, financiers wanting to know the power-producing potential of a site, and builders who want weather data to help guide which equipment and technology they use. FirstLook assessments are available for wind and solar, whereas the more detailed FullView assessments cover wind.

Who wants forecasts? Usually, energy site and utilities operators who need to plan which sources of power they will call upon in order to ensure a steady supply to the grid. We currently forecast for wind and hydro. I’ll cover forecasting in much more detail in upcoming posts.

In the post “Assessment 101,” I mentioned that Scott Eichelberger and his ilk get a lot of grilling while staffing the 3TIER booth, and not just about the location of the restrooms, or which booths give away the best tchotchkes. People want to know how our method, numerical weather prediction (NWP), compares to other techniques. Many of our competitors are using a method called measure, correlate, predict, or MCP. Here’s the skinny on some key differences between the two.

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Unlike many tech firms, which keep the brains of their operations sequestered in dimly lit cubicle farms veneered with the orange dust of long-gone Cheetos stuck to spilled Mountain Dew, 3TIER lets its scientists out in public. Many of the questions Scott Eichelberger, our assessment tsar, fields when he’s staffing the 3TIER booth at meetings have to do with how we perform our weather modeling magic, and where the data comes from. In fact, I had the same questions. Lucky for me, Scott is a kind and patient person, and a gifted explainer.

The most surprising thing I learned from Scott is that the computer model 3TIER uses for assessment, the Weather Research and Forecasting (WRF) model, is a free program produced and constantly improved by government and research institutions. I could download a copy for my laptop. The data set with which we begin each model run also is freely available, a gift to the planet’s people from the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP-NCAR).

Of course, amateur that I am, the output from my Home Wind Assessment Kit would be useless hokum, indicating that glaciers had just retreated from my yard. (more…)