Thermal scout hunts for hot spots at solar plants

The National Renewable Energy Lab combined GPS, an infrared camera and sophisticated software to make a device that can quickly spot trouble at concentrating solar power plants.

Pinpointing a problem within a concentrating solar power plant -- which can contain thousands of mirrors sprawled over dozens, even hundreds of acres -- has typically involved guesswork, a lot of time and money.

The U.S. Department of Energy's National Renewable Energy Laboratory has come up with a speedier solution by combining GPS, an infrared camera, some fancy software, and then loading it all onto the back of a pickup truck. The so-called Thermal Scout can identify and analyze bad receiver tubes, which typically number in the thousands, as fast as a truck can drive between the rows of mirrors at a CSP plant.

CSP plants use mirrors or lenses to concentrate sunlight on fluid-filled receiver tubes that heat up water to create steam and drive a turbine to power an electrical generator. There are about 40 multi-megawatt CSP plants in the world today, and 28 new ones slated to be built by 2014, the NREL said.

The efficiency of the tubes, and the CSP plant as a whole, can be affected by thermal loss caused by air and hydrogen leaks or damage from rocks. CSP operators typically look at the entire output and roughly guess that if the plant seems to be operating at 4 percent under capacity, it may have about 400 bad tubes, the NREL said. Operators also can check each tube by hand -- a costly and months-long endeavor.

NREL Senior Engineer Tim Wendelin developed the basic concept behind the thermal scout a decade ago. He combined an infrared camera with a precise GPS unit and software to create a device that provided a few shortcuts to the old-school labor-intensive method of manually checking each tube.

It wasn't until NREL colleagues Allison Gray and Benjamin Ihas embedded real-time analytics and a user-friendly interface that the Thermal Scout was born. The data analysis component allows users to click for a row report, which generates a web page that can be shared with anyone at the plant. Users can retrieve a complete data analysis for a row, a series of rows or the entire plant. The CSP plant operator can quickly pinpoint trouble and determine when and if they need to replace the receivers.

Photos by Dennis Schroeder/NREL


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