Charles Dickens once wrote, “It was the best of times; it was the worst of times.” According to the annual Greenhouse Gas Bulletin issued by the U.N. World Meteorological Organization, the atmospheric concentrations of CO2 reached 403.3 ppm in 2016, setting an 800,000-year record. A multidisciplinary team of engineers at Cornell University in Ithaca, N.Y., are working to convert waste carbon emissions into fuels and feedstocks that power the economy and fit into a planetary carbon cycle through the HI-Light reactor being developed at the school.

HI-Light is a solar thermal chemical reactor technology for converting CO2 to fuels. Creating high-value products from CO2 by using energy from all parts of the solar spectrum to photocatalytically produce renewable fuels will make CO2 capture and conversion economical. Similar to fiber optics in telecommunications, the wave-guide technology will enable the light to be distributed evenly within the reactor so as to increase reaction rate, decrease capital cost and increase operation outcomes. The claim of the reactor design derives from the concurrent optimization of light-coupling and catalyst availability.

How it works

By using built-in waveguides inside a scalable reactor, the Cornell team is developing a new approach to turning CO2 into useful products and fuels. The HI-Light reactor is trying to do what nature has already done with photosynthesis systems but with materials and technologies nature has not had access to. The basic chemistry and idea is the same: to convert CO2 and energy as input into something energetically more useful. In nature plants absorb CO2, water and sunlight and then convert those things into the food that helps the plant grow. HI-Light is a photothermalcatalytic reactor that acts likes a leaf. With this technology CO2 is converted into fuels and feedstocks that could serve as the building blocks for products that humans use every day.

This process begins with a massive source of carbon waste; for example, the exhaust system of an electric power plant. The idea is to channel that waste CO2 gas into a large reactor. Within the reactor there are a bundle of rods coated with a photocatalyst. The rods will guide the light to the inside of the reactor, and CO2 gas will react with the catalyst to form different products, depending on how the catalyst is designed.

(Source: Cornell University)


Impacting climate change

The HI-Light reactor deals with carbon emissions. The vast majority of industrial processes emit CO2 as a waste product, and nature has a built-in system for handling these emissions. The carbon gas released by burning goes into the atmosphere and is then taken back up by plants that recycle the energy. But the cycle has gotten completely out of whack. There is more carbon being released into the atmosphere than the world’s plants can handle, and the excess is playing havoc with the Earth’s climate.

Capturing CO2 to keep it out of the atmosphere is a promising strategy to fight climate change. To combat this problem, the Cornell team hopes to use this ultracompact reactor that is powered by the sun and converts CO2 to higher value fuels. This easily scalable technology is a three-way win: It runs on solar, captures CO2 and yields a valuable solar fuel. The Cornell team also is partnering with Dimensional Energy to develop green solar fuels for commercialization.

Next steps

The team started from building a laboratory scale reactor, for which it was testing different catalysts and trying to optimize the reaction parameters to achieve the maximum conversion rate. After showing proof of concept by the small reactor, the team is working to scale up the reactor. The most difficult problems are related to guiding the light and heat more evenly in the reactor and fi guring out the photocatalyst with the best performance for specifi c photoreactions.

The next steps include further increasing the conversion rate and scaling up this technology eventually to the industrial scale. The potential is to transform the CO2 into different sorts of chemicals depending on how the catalyst is designed. Currently, the team is concentrating on things that could replace natural gas as a fuel source.

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