Researchers at Stanford University have answered a question that has been on the minds of industry observers and critics. A recent study – ‘Energy Balance of the Global Photovoltaic (PV) Industry – Is the PV Industry a Net Electricity Producer?’ – found that the amount of energy that solar panels produce has likely surpassed the amount of energy needed to manufacture them.
This is welcome news, say the study's authors. ‘I've heard people say the solar industry has not produced any energy since it started because it consumes so much energy to make the solar modules,’ says Sally Benson, director of Stanford's Global Climate & Energy Project (GCEP). ‘We asked if that was true, and we did our own analysis.’
Benson and Michael Dale, a postdoctoral fellow at GCEP, co-authored the study, which was published in the journal Environmental Science & Technology. Dale explains that their study was a meta-analysis, or a review of previous studies from 1990 to 2011. The researchers looked at the six PV varieties: monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, CIGS and ribbon.
‘What we did was we looked at how the energy costs changed over time,’ Dale says. ‘We created a model for predicting energy costs for panels at a certain moment in time. We used historical data for how the industry has grown, and we predicted how much energy the industry is consuming to produce new panels.’
Earlier studies looked at particular devices. The new study's model can track energy costs of manufacturing and installing PV systems, and even balance-of-system components. The model can also forecast electrical energy requirements to scale up the PV industry and determine the electricity balance of the global PV industry to 2020.
Among the study's results: The PV industry was a net consumer of electricity until about 2010, and in 2012, the industry became a net electricity provider. Also according to the research, the industry will ‘pay back’ the electrical energy required for its early growth before 2020, maybe as soon as 2015.
The findings are important because the PV industry has grown quickly over the last few years, creating an increased need for energy – mostly from fossil fuels – for manufacturing.
‘If we can continue to reduce energy input, it will be easy for the solar industry to continue to grow at a rapid rate because it doesn't take much energy to manufacture things,’ Benson says.
The fossil fuels part of the equation is an important detail here, says Dustin Mulvaney, assistant professor of sustainable energy resources at San Jose State University.
‘Manufacturers are using fossil fuels to make solar panels that generate clean energy,’ says Mulvaney, who is also the lead technical advisor for the Silicon Valley Toxics Coalition. ‘If we made all our solar panels in factories that have solar panels on the roof, the energy payback time would be a moot point.’
Several factors have contributed to the reduced use of energy during the manufacturing of PV products. Manufacturers have invested in technological developments that save energy and money. Silicon wafers have become thinner, and there is less waste in the wafering process. On the energy production side, PV panels are more efficient, as thin film panels have especially improved.
Some forms of PV use more energy than others in manufacturing. ‘In general, crystalline silicon is more energy-intensive than thin film,’ Dale says. ‘The least energy-intensive are cadmium telluride and CIGS.’
Dale says the PV industry should feel encouraged by the study's findings. ‘The industry is very aware of the energetic costs of manufacturing, more so than other industries. I think they still need to reduce cost, and that will be a bigger benefit to society,’ he says.
Benson says the feedback from the industry has been positive. ‘People are happy, they think it's interesting, and it creates another performance target in terms of continuing to decrease embodied energy that the community can focus their efforts,’ she says.
Nora Caley is a Denver-based freelance writer.