New Solar Technology Pays Back Energy Investment Faster in a Matter of Months

In the solar power research community, a new class of materials called perovskites is causing quite a buzz, as scientists search for technology that has a better “energy payback time” than the silicon-based solar panels currently dominating the market.

Now, a new study by scientists at Northwestern University and the U.S. Department of Energy’s Argonne National Laboratory reports that perovskite modules are better than any commercially available solar technology when products are compared on the basis of energy payback time.

Solar panels are an investment — not only in terms of money, but also energy. It takes energy to mine, process and purify raw materials, and then to manufacture and install the final product. Energy payback time considers the energy that went into creating the product and is a more comprehensive way to compare solar technology than conversion efficiency.

The research team reports the energy payback time for solar panel technology made with perovskites could be as quick as two to three months, easily beating silicon-based panels, which typically need about two years to return the energy investment.

“People see 11 percent efficiency and assume it’s a better product than something that’s 9 percent efficient,” said Fengqi You, corresponding author on the study and assistant professor of chemical and biological engineering at Northwestern’s McCormick School of Engineering and Applied Science. “But that’s not necessarily true. One needs to take a broad perspective when evaluating solar technology.”

In what’s called a cradle-to-grave life cycle assessment, You and his colleagues traced a product from the mining of its raw materials until its retirement in a landfill. They determined the ecological impacts of making a solar panel and calculated how long it would take to recover the energy invested.

Perovskite technology has yet to be commercialized, but researchers everywhere are excited about the materials. Most projects, however, have been narrowly focused on conversion efficiency — how effectively the technology transforms sunlight into useable energy.

The paper, titled “Perovskite Photovoltaics: Life-Cycle Assessment of Energy and Environmental Impacts,” was published in the journal Energy & Environmental Science and featured on the back cover of the journal’s July issue.

This study looked at the energy inputs and outputs of two perovskite modules. A solar panel consists of many parts, and the module is the piece directly involved in converting energy from one form into another — sunlight into electricity.

Perovskites lag behind silicon in conversion efficiency, but they require much less energy to be made into a solar module. So perovskite modules pull ahead with a substantially shorter energy payback time — the shortest, in fact, among existing options for solar power.

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