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Thermal cameras assist solar contractors

Photonics Spectra
Jul 2010
Lisa Bell, !%FLIR Commercial Systems Inc.%!

Solar service and installation companies have known for some time that high-performance thermal cameras, capable of detecting very small temperature differences and of creating crystal clear images or video of problem areas, had enormous potential to diagnose problems on solar installation sites.

Their drawback had been that they were prohibitively expensive for smaller businesses. The past few years, however, have seen the cost of high-quality thermal cameras drop dramatically, with models now available for less than $3000, greatly expanding their use in building and maintenance applications, including solar energy.

Innovative solar contractors are rapidly adding this tool to their diagnostic and preventive maintenance programs. Pro-active thermal imaging surveys of solar modules can identify problem areas quickly and efficiently, preventing offline incidents and reducing operation costs.

In addition, solar contractors report that adding thermal images and temperature data to inspection reports significantly increases the value of these reports and generates more work opportunities.

Halcyon Solar Construction of Cottonwood, Calif., installs, maintains and troubleshoots megawatt photovoltaic (PV) systems, both residential and commercial. Co-owner Andrew Begley has been using a thermal imager to identify problem areas in solar modules for more than a year – initially at the request of a client familiar with the technology.

After renting a handheld thermal camera for close to a year and becoming familiar with infrared technology and its possibilities, Begley was so pleased with the results that his company purchased a camera at the start of this year.

Thermal imaging is now a key component in Halcyon’s preventive maintenance program. The camera, a Flir T300, offers extremely high quality images and advanced features in an affordable, lightweight, tough and versatile handheld package. Over the past three months, Halcyon has regularly used it to identify bad modules and to mitigate system risk.


Halcyon Solar Contractors in California uses a Flir T300 thermal imager to detect problems in solar cells. Top center, a hot solar cell is revealed by thermal imaging. Top right, a hot splice box is found at the back of a module where wires connect. Right, a solar module with broken glass and damaged cells is imaged. Images courtesy of Flir Commercial Systems Inc.

Begley uses the camera to create a composite electrical reading across the output curve of the entire solar module, to evaluate the quality of power output, to identify bad connections and to understand overall thermal patterns, including shading.

Thermal imagery can identify soiled or shaded individual cells within the systems as hotter areas of resistance. In a photovoltaic installation, efficiency is a function, in part, of temperature; cooler panels run more efficiently. As individual cells fail, they can begin to heat up, rather than collect energy, and this heat increase is easy to see with a thermal imaging device.

If a cell shows up hot in the thermal image but is not shaded or soiled, Begley can zoom in for a closer look to pinpoint the problem. Common defects in PV cells such as shunt or series resistance, or crystalline nonuniformities can reduce efficiency – even shut down an installation.

Begley uses other industry-standard measures to confirm the potential problems identified by the thermal imager, including current testing, voltage readings and IV curve tracing. If the cell is found to be defective, Halcyon can replace the solar module before it actually fails.

Halcyon’s camera includes both a thermal imager and a daylight camera, with the onboard camera ability to fuse both types of images into a single composite image that clearly shows customers where and what the problem is.

Advanced in-camera algorithms and preset temperature triggers can quickly detect low and high temperatures as well as offer differential, or Delta-T, readings. All temperature data, object parameters, voice and text comments are stored with the infrared image, enabling advanced postprocessing and report writing.

Begley is particularly pleased with the data collection and reporting functionality software analysis tools that complement and extend the use of his thermal camera, including easy image organization tools and report templates. “I can quickly and easily generate a complete report with images to show a client that clearly identifies potential issues.”

Solar is a clean source of renewable energy, with essentially free energy input and, as such, has tremendous environmental and political benefits. However, to become a truly viable alternative, solar installations must achieve the absolute maximum in production and performance. And as larger, more complex and more numerous installations become more common, thermal imaging can help the technology to reach its full potential.

Meet the author

Lisa Bell is a writer at Flir Commercial Systems Inc. in Wilsonville, Ore.; e-mail: lisa.bell@flir.com.



GLOSSARY
algorithm
A precisely defined series of steps that describes how a computer performs a task.
shading
1. The sorting of lenses by their color. 2. In an optical system, an irradiance or brightness gradient in the image that is not present at the object.
video
Referring to the bandwidth and spectrum location of the signal produced by television or radar scanning.
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