Lifecycle study names thin-film greenest solar option

Thin-film solar technology has the lowest environmental impact during production, according to a new report from Brookhaven National Laboratory.

The study, Emissions from Photovoltaic Life Cycles, examined four types of commercial photovoltaic systems: multicrystalline silicon, monocrystalline silicon, ribbon silicon, and thin-film cadmium telluride.

Using a "cradle to gate" analysis to assess the energy used and harmful smelting emissons produced during the production of the solar modules, it found that the thin-film cadmium-based process created the fewest harmful air emissions.

"It's really important that this report highlights the use of lifecycle analysis as a metric to compare the environmental attributes of competing technologies," said Lisa Krueger, vice president of sustainable development for cadmium telluride manufacturer First Solar, which targets utility-scale solar projects in Europe with its products. "That [issue] hasn't been that prevalent in the US [as yet]. It's more prevalent in Europe than here."

Lifecycle analysis helps to highlight the differences between the environmental impacts of photovoltaic technologies and fossil fuel-based energy, she added. The report omitted end-of-life disposal and recycling, although First Solar puts aside funds for the recovery and recycling of its modules when sold.

The report also pointed out that although there were small differences in carbon emissions between different photovoltaic technologies, there were all much smaller than those produced by the conventional energy technologies that they could displace.

Thin-film solar technology uses a fraction of the material to be found in conventional photovoltaic systems, and a growing number of companies such as First Solar and PrimeStar Solar plan to use the cadmium telluride process to reduce the cost of manufacturing.

PrimeStar chief executive Brian Murphy believes that the process can deliver a return on investment in roughly half the time of conventional crystalline silicon processes. "The lower the cost of the module, the more likely I am to purchase it, and put it into a solar field or a rooftop," he explained. "It brings me closer to grid parity."