A device that pulls carbon out of the air on the cheap, with renewable energy, creating fresh fuel in the process, would help us put a harness on our planet’s runaway temperatures. Xiangkun (Elvis) Cao, now a Schmidt Science Fellow at MIT , created just such a device, the HI-Light Solar Thermal Chemical Reactor, while pursuing his Ph.D. with David Erickson at Cornell. It won the team SAE’s Create the Future Design Contest award in 2017.
The idea was inspired by the Erickson Lab’s prior work on biofuel production from algae. “For algae cultivation, only the top layer will get access to light,” said Cao. “So, our lab previously engineered waveguides for uniform light distribution within the whole reactor for better algae production.” They decided to apply a similar system with non-living materials.
Cao set out to create a scalable reactor for photothermal catalytic CO2 conversion. In short, incoming light irradiation into the reactor is transmitted by glass rod waveguides with specially designed scattering surfaces to enable uniform irradiation. The surface of those rods is coated with a catalyst that breaks apart CO2 and other reactants, producing renewable solar fuels.
Things have come a long way since 2017, both for Cao and for the solar reactor technology. “For me, I feel like the Create the Future award was the starting point for my professional career,” he said. The industrial partner for the HI-Light effort, Dimensional Energy, was a finalist for the $20 Million Carbon XPrize . In 2019, Forbes featured Cao as one of their “30 Under 30” in Energy for North America . The reactor has progressed in terms of efficiency, scalability, and how it’s manufactured — just how remains proprietary.
And the reactor may have abilities beyond producing fuel. The same system can be used for other solar-driven catalytic processes. And people on this planet may not be the only ones to benefit from the technology. “It could potentially do a very good job on Mars,” added Cao. “There’s far more CO2 there than on Earth, and there’s evidence of subglacial liquid water on Mars . When you feed CO2 and H2O into the reactor, you could produce methanol to power a spacecraft and oxygen for the first Martians.”
Closer to home, Cao is working on pathways to integrate various carbon capture and utilization processes. “For example, taking pure CO2 out of the air — whatever the method — can be costly. But if, instead, we created concentrations of carbon at 1,000 parts per million (compared to air’s 420), the result could be used in greenhouses at little cost. “1,000 is not good for human health, but tomatoes really like it,” said Cao. “There are many existing carbon capture and carbon utilization processes out there. If we think can outside of the box to bridge carbon capture and utilization, we can create new exciting economic opportunities while working to mitigate global climate change.”
He’s also turned his mind to policy issues and believes the world needs to work together to create a roadmap for carbon capture that’s implemented immediately. “The United States just banned the EPA from banning emissions from power plants — that doesn’t make sense at all,” he says. “Right now we need a global system. We don’t have a global carbon tax yet.”
“The problem is that we have really limited time to deal with the massive CO2 emissions,” said Cao. “I’m thinking about the whole field: with the technologies that are out there already, what can we do right now, not 20 years later.”
2017 Grand Prize Winner:
INNOVATORS: Xiangkun (Elvis) Cao (left) and David Erickson
INNOVATION: A solar thermal device mimics photosynthesis to convert carbon dioxide emissions into a clean energy resource.
IMPACT: The HI-Light reactor transforms CO2 and water into methanol and other high-value hydrocarbons, which could help reduce carbon emissions and make carbon dioxide capture and conversion more economical.
Learn more about the 20th Anniversary Contest at www.createthefuturecontest.com .