Some people in the PV industry say that solar modules are commodities. If they’re right, then solar modules are the only commodity in the world that comes with a 25-year warranty.
We’re not talking about toasters or televisions, where consumers don’t really care if the products don’t last longer than a decade. Billions of dollars are staked on solar modules meeting performance expectations for 20 years or more, in any and all environmental conditions. Although photovoltaic technology has generally proven to be extremely reliable — crystalline silicon modules installed in the 1970s are still performing well today — we’ve learned a lot over the last three decades that should inform both manufacturing operations and module purchase decisions.
In 1996, when my boss’s boss’s boss, CEO of Suntech Dr. Zhengrong Shi, was just my colleague, we were both hopeful that crystalline silicon-on-glass (CSG) thin-film modules would be the next big thing in solar. Dr. Shi was then the Deputy Research Director at our small thin-film startup in Sydney, Australia, called Pacific Solar (later renamed CSG Solar), a spin-off from a research lab at the University of New South Wales (UNSW). Although competitive CSG conversion efficiencies were merely a dream — and still are — it was our goal to bring a commercial product to market before the turn of the century. Consequently, we had to think seriously about module degradation and the vulnerabilities of deploying a new silicon substrate less than two microns thick (think human hair).
In the absence of significant field data for CSG module performance — there was no such product in existence, and we couldn’t wait twenty years — all we had to go on was internal product testing data. At the time, the major solar product standards bodies used a similar variety of product durability tests to simulate accelerated module degradation, including damp heat, thermal cycling, and humidity freeze. A common shortfall was that each test was always performed on a fresh module. The standards did not — and still do not — require the same module to undergo a variety of simulated, real-life environmental conditions. As a result, these standards are at best equivalent to three to five years of outdoor exposure and should be viewed as a baseline test protocol (Hoffman & Ross 1978, McMahon et al. 2000).
Consequently, we didn’t have a lot of faith that the standard testing requirements would provide insight into actual long-term module degradation patterns, especially when deployed in extreme climates. That’s a big problem if you’re responsible for a product for longer than you’re legally responsible for your own children. We believed our tests had to go above and beyond the required standards, leaving no doubt that the product would meet or exceed an aggressive 25-year power output warranty.