There actually is an extremely powerful and efficient technology for capturing carbon dioxide and storing the energy from sunlight—it’s called photosynthesis. But the “engineering” built into plants by billions of years of evolution includes both complex chemical reactions and detailed structures that can be hard to reproduce in a way that works when, where, and how it’s needed by Planet Earth’s biggest energy consumers. That’s why an article in the current issue of the Proceedings of the National Academy of Sciences, reporting the work of French researchers, while preliminary, appears quite exciting.
Their experiments demonstrate a system that buckles a photo-electric solar cell to the mineral perovskite in a “photo-voltaic minimodule” to convert carbon dioxide into the energy-rich fuels ethylene and ethane. At just 2.3% overall efficiency in converting sunlight into power, the results of the test may not seem all that fantastic. After all even consumer-grade photo-electric solar cells can run close to 20% efficiency in turning sunlight directly into electricity.
But those efficiency numbers aren’t the end of the story. For one thing, the system built by the French team uses only “inexpensive all–earth-abundant” materials. There are no rare elements, or items restricted to just one part of the globe. Perovskites are a class of minerals that are based around crystals of calcium and titanium oxide. They are not only found in many areas, including Russia, Europe, and the United States, and they can also be manufactured in the lab. The photo-cell used was one that doesn’t require rare elements or high end components. And the metal used for the anode and cathode of the microcells was plain old copper rather than the much more expensive alternatives used in some systems. All of that means that the microcells should be able to be built cheaply, and not depend on materials that are hard to obtain, no matter where they are being made.
What this system seems to offer is a low cost, common element model that doesn’t just solve the issue of turning sunlight into power, it also addresses the critical issue of energy storage by turning that sunlight into a form that’s easily stored, easily transported, and easily used. While the full cycle may be carbon neutral, the storage part of the cycle is carbon negative. And it could potentially create fuels that could drive most vehicles already on the world’s roads.
As with almost every experiment when it comes to energy technology—whether that’s photovoltaics, batteries, or alternative storage—this paper represents very early days. But it’s an encouraging outcome that suggests that sunlight might not just power homes, but vehicles and other detached systems.
Other systems have been build that top the 2.3% value obtained in this study. But those systems utilized elements like gallium, germanium, and iridium to achieve success. This system of “artificial photosynthesis” convert CO2 to hydrocarbons at a rate that doesn’t seem astounding … except that it appears to be possible to make at low cost and large scale. They leave room for that efficiency to be greatly increased by looking at all stages of the process for ways in which catalysts and electrolyzers could be tweaked.
But the possibility of solar-powered systems that don’t just create electricity, they also create fuels that could be used to generate power during times when sunlight isn’t available (i.e night) or utilized in non-electric vehicles is certainly intriguing.
