27 Jul 2012

Keithley donates SourceMeter to Oregon State University’s Solar Vehicle Team

Keithley Instruments has donated a Model 2440 5A SourceMeter instrument to Oregon State University’s Solar Vehicle Team (OSUSVT), for analysis of mono-crystalline silicon solar modules.

These modules are powering the Phoenix, the solar race car in which the team competed in the 2012 American Solar Challenge. The donated instrument has already helped the team boost the power output of this year’s vehicle by 50 percent over last year’s.

The team, made up of students, staff, and faculty members, has developed a soldering, testing, and laminating procedure to produce slightly flexible, lightweight solar modules based on mono-crystalline solar cells.

To maximise vehicle performance, the team requires parametric data on each of the solar modules they construct in order to arrange the sub-arrays on the car in the most efficient manner.

The Keithley Model 2440 SourceMeter instrument, acquired through a donation arranged between OSU’s Kathy Han and Chuck Cimino, one of the company’s marketing directors, is used to characterise each module’s overall power output and maximum power point current using an I-V curve tracing technique.

The Model 2440 allows students to gather accurate data on the performance of each module quickly and simplifies making side-by-side comparisons.

Each solar module is characterised both before and after lamination and the data obtained is used in troubleshooting problems such as shorted cells and cracked cells.

In addition, this data was employed in current matching in the sub-arrays, as well in projecting the output of the vehicle’s entire solar array.

Kathy Han, the OSUSVT manager, notes: "The Model 2440 allows us to obtain accurate I-V curve data on all our solar modules consistently and easily both before and after lamination. The data we obtained on maximum power output, open-current voltage, short-circuit current, maximum voltage, and maximum current let us detect problems like shorted and cracked cells, as well as to determine the best sub-array location for each module to maximise overall power output or to reject a module outright."

"Before we had access to the Model 2440, we had problems with one of our previous solar arrays that used solar cells that had been laser-cut from the front side, which we now know produces some melting of the p/n junction. This caused internal shorts and increased internal resistance in the cells," she added. "The Model 2440 made it possible to detect problems that simply weren’t detectable before and to match solar cells better. Because of Keithley’s generous donation, this year’s vehicle has 50 percent higher power output (900W instead of 600W) than last year’s."

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