The clean energy revolution is finally taking shape. Over the past 10 years the amount of clean electricity produced in the U.S. has almost doubled, from about 8% of total demand to about 15%; at the same time, the share of coal-produced-electricity used in America fell from about 50% to 30%. The trend is only projected to continue into the 21st century, with more and more of our power coming from wind, solar, and hydro. But there’s a problem with renewables that has many energy experts worried: how to keep the lights on when the sun isn’t shining or wind isn’t blowing. As dirty as fossil fuels are, they’re incredibly reliable—as long as we have fuels, we can burn them up and create the electricity we need. On the other hand, renewable energy can’t run 100% of the time, and it’s proven difficult to store energy during productive periods for later use.
So, how to overcome this storage problem?
Batteries can certainly help but are unlikely to solve the problem. Existing technologies can serve for short term demand (think charging cell phones or electric cars) but aren’t nearly strong enough to power a passenger plane across an ocean, or heat a home during wintertime (let alone an entire city). Here’s how Bill Gates, who’s often known as a technology optimist, put it in an interview in M.I.T.’s Technology Review: “I’m in five battery companies, and five out of five are having a tough time…When people think about energy solutions, you can’t assume there will be a storage miracle.”
But now, research coming out of the Edward Sargent Lab at the University of Toronto might have an answer to this storage problem. In a paper released today in Cell Press, a team of researchers from the University of Toronto outlined a method of converting renewable energy into chemical form by using captured carbon dioxide; the resulting renewable energy fuel would be stable, transportable, and potentially provide a solution for energy storage.
“Nature does a really good job of this already: plants take carbon dioxide, water and sunlight, and make sugars and other foods for itself to grow,” explained Phil De Luna, PhD candidate in materials science at the University of Toronto. “All we’re trying to do is what nature does, but more efficiently and faster.”
De Luna went on to explain that rather than looking at CO2 as a waste product from fossil fuel, the team at the Edward Sargent Lab view it as a useful material. “We’re trying to look at it as an energy carrier, or as a potential to move renewable energy,” he said. “What we’re trying to do is close the carbon loop; CO2 would be captured, converted into fuel, and then it could be stored, burned in the winter time as fuel, and captured again.”
The first phase in the process that De Luna is describing is the capture of carbon before it escapes into the atmosphere—CO2 would be contained from smokestacks, and transported via pipelines (either in gas or liquid form) to a secure location. This process, known as carbon capture and sequestration, is already fairly advanced, with the largest prohibitive factor being that it’s expensive to build all of the needed infrastructure (more on that later).
The next thing that needs to happen is that the captured carbon is converted into small building block molecules. Just like carbon capture, the technology behind the conversion process is already well on its way. And again, the biggest prohibitive factor here is cost, as the conversion process is fairly energy intensive. Still, De Luna is hopeful that as “renewable energy gets cheaper and cheaper, and the grid greener and greener, we’ll be able to work with the energy, and these capture and conversion technologies will be more and more feasible.”
One of the applications that De Luna and his team are most excited about is converting captured carbon into carbon monoxide, which is then used to create syngas (a fuel gas mixture).
Another application is transforming CO2 into ethylene (a hydrocarbon), which is the precursor to major consumable plastics. This could both allow for the creation of greener plastics, and also facilitate the recycle of plastic products (by burning plastics in a contained environment, capturing the CO2 that’s being emitted, transforming it back into ethylene and ultimately back into plastic).
All of this might sound like magic. Or some nutty circle of life edict. But the truth is that it’s just physics and chemistry.
It’s worth mentioning that while carbon capture and conversion could help fill the intermittency gap in renewable energy and provide a use for waste CO2, these technologies won’t be able to transform our massive fossil fuel energy economy into a clean energy system. Carbon capture is simply too expensive to be applied on a national, let alone global, scale. An article from MIT does a good job of illustrating the massive size of the infrastructure needed to make fossil fuels clean: “If we were to [capture] just one-fifth of the global carbon dioxide emissions, we would need to build an industry capable of handling twice the volume of stuff as the entire oil industry, an industry that took 100 years to develop, driven by a large and mostly expanding market.”
The fact that carbon capture is prohibitively expensive has made many environmentalists skeptical of whether the technology can play a pivotal role in the battle against climate change. And yet the carbon capture and conversion methods that are being proposed by the Edward Sargent Lab could play an important role in the renewable energy revolution, by providing keys to renewable energy storage, a critical element in the success of a green economy.
“Ideally in the future, 100 years from now, all of the world’s energy infrastructure would be renewable,” said De Luna, “carbon capture and conversion, by offering a solution to the storage problem, could help get us there.”