Solar Power's Elephant in the Living Room

By Matthew Holzmann

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Solar power generation is one of the fastest growing industries in the world. This year, shipments of solar modules globally will exceed 7.8 gigawatts. Taking an average output of 200 W/module, this represents 39,000,000 modules per year. A growth rate of 30% per year is expected over the next several years. One reason for that growth rate is that Germany and Japan recently announced plans to exit nuclear power generation, and photovoltaic (PV) installations are one of the most attractive solutions for filling the generation gap.

Life Expectancy Doubts

But there is a problem. Solar power users expect modules to last between 25 and 30 years, but there is little data to support this expectation, and there are no recognized test standards in place to validate these assumptions. The current standards do not come close to the 25-year benchmark.

Companies have internal test methodologies, but there are no generally recognized standards. Warranties for manufacturing defects are typically 5 to 10 years, while efficiency warranties are between 10 and 25 years. Almost all of these warranties are based upon internal testing, which is held as "company secret" for competitive advantage.

In addition, there is little traceability. So what happens in 5 or 15 years if a module goes bad? Solar installations are multigenerational. Some of the companies manufacturing and installing solar power now might not be around in 25 years. What then?

Most solar modules generate DC electricity, which is fed through a junction box to an inverter, where that electricity is converted to AC and then fed into a home or business or directly to the grid. A typical home array is feeding approximately 2.5 kW constantly while the sun is shining. There is no way to turn it off except to cover the array. In the wide range of applications for solar power globally, solar modules can be exposed to temperatures exceeding 65C (149F) and down to as low as -60C (-76F). In addition, humidity has been identified as a significant contributor to module failures in tropical climates. Additional failure mechanisms based upon the location of an installation include atmospheric salt exposure, corrosion from pollution, extreme weather conditions, and exposure to ammonia in rural installations where livestock is kept.

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