While everyone looks to solar power as a form of clean energy, itdoes have some dirty secrets. Among them are the materials used in somesolar panels, like cadmium, which is used in cadmium tellurium(CdTe)-based photovoltaics.
“There are potential negative environmental and health impacts fromPV modules throughout their life cycles, ranging from raw-materialsextraction and procurement impacts, toxic and hazardous materials use in manufacturing, and the disposal and recycling of modules at the end oftheir useful lives,” according to the Silicon Valley Toxics Coalition’s“Solar Scorecard 2011.”
The scorecard rates solar module manufacturers for theirenvironmental safety of their modules. Still, some CdTe manufacturers,like First Solar and Abound Solar, are considered among the safest solar manufacturers out there.
Abound Solar and First Solar have strong module recycling programs in place to reclaim all the cadmium used in their modules. Both scored 87in the scorecard tied with Renewable Energy Corp. (REC), surpassed onlyby Trina Solar, which received an 89.
Cadmium is a carcinogenic element used in many industrial processesand is present in many batteries. It may cause cancer of the prostate,kidney, or bladder, according to the National Institutes of health.
“Breathing high levels of cadmium can severely damage the lungs andmay cause death. Eating food or drinking water with very high levels ofcadmium can severely irritate the stomach, leading to vomiting anddiarrhea, and sometimes even death,” the institute said.
The amount of cadmium in CdTe modules is minute, but even at thatlevel it can be hazardous. The main risk stems from when a CdTe moduleis crushed and exposed to water.
“Any broken CdTe panel exposed to water will leak cadmium,” saidTrond Westgaard, vice president of technology for REC, a manufacturer of silicon-based photovoltaics.
The most hazardous material in silicon photovoltaics, by comparison, is lead.
“Leaching potential test results show that such panels have aleaching potential of approximately 4 grams of lead per kilowattinstalled, compared to approximately 23 grams of cadmium per kilowattinstalled for CdTe panels. This has to be weighed against that cadmiumis considered approximately 10 times more hazardous than lead,”Westgaard said.
Some CdTe panels are frameless and can break or be damaged duringinstallation, under adverse weather conditions, by de-lamination orduring uninstallation and disposal, according to Westgaard.
“The major concern is about de-installation due to the lack ofcash-back incentives in the recycling schemes and lack of propermarking. Other industries whose products are not subject to incentivized recycling struggle to have more than half of the waste recycled. SinceCdTe panels are not marked as dangerous to the environment, they havethe risk of being mixed with ‘harmless’ waste,” he said.
But manufacturers of CdTe photovoltaics, like Abound Solar, say they have programs in place to manage the risks of cadmium.
“We use cadmium in our process, but it’s in a compound, so its CdTe,It’s in a compound our vendors supply, so it’s already stable. Thatcompound is stable up to 1,041 degrees,” said Abound Solar SalesAssociate II Emily Weinstein during a recent tour of their manufacturing facility in Colorado.
“In addition, we have a commitment to recycle every module at the end of the product’s life. Every module gets recycled. At the time of thesale, there is a portion of that sale price that goes into an escrowfund and is kept safe for the life of the module, up to 40 years,”Weinstein said.
Indeed, large-scale solar farms are not likely to pose much threat.
“It is likely that CdTe photovoltaics installed in large scale solarfarms operated by utilities will be properly monitored during operation, and it is also likely that they will be decommissioned in aprofessional way, including recycling,” Westgaard said.
However, REC is concerned about small and mid-size installations, that may be owned privately or by financial investors.
“This is the market where photovoltaics has its main strength indistributed power generation, and CdTe panels represent an environmental risk in this market. REC believes that a technology neutral regulationof heavy metals (cadmium, mercury, and lead) in products used in thesemarkets is an appropriate measure,” Westgaard said.