Last semester, through the PLUS program at McCombs, my team and I worked on a business plan for a carbon capture hub sponsored by the DOE. While at their campus in Albequerque presenting, they gave us a detailed tour of their facilities and showed us a wide variety of solar energy experiments. One of these experiments was their ambitious “Sunlight to Petrol” project. The aim of this project is to reverse the combustion cycle using Sunlight and CO2 to create carbon monoxide, a building block of most fuels. This project has brought a lot of positive press to Sandia and is marketed as a future carbon solution that is within 15 -20 years of implementation.
The Sunlight to Petrol process starts with an 88 square meter solar furnace that focuses sunlight onto a solar reactor. They have named this device the Counter-Rotating Ring Receiver Reactor Recuperator. A name obviously coined by Engineers. (We will call it the CR5 for the sake of brevity) This is a heat engine that does chemical work instead of mechanical work, dividing carbon dioxide into carbon monoxide and oxygen. Within the CR5 are rotating rings of cobalt ferrite. The concentrated sunlight heats the rings up to 2600 degrees Fahrenheit causing them to release O2. As the rings rotate the temperate drops down to 2000 degrees, at which point the rings are exposed to CO2. Since the cobalt ferrite is now missing oxygen, it takes some back from the CO2 leaving behind carbon monoxide. The cobalt ferrite has now returned to its original state and rotes around the engine for another cycle.
The point of all this is to take advantage of all the CO2 pouring out of our coal-fired power plants and use it to make gasoline. In the end, when the gasoline is burned, it would still release CO2 into the atmosphere, but the fossil fuels would be used at least twice (once for electricity generation and a 2nd time for engine combustion) before this takes place. This means in the end, less CO2 would reach the atmosphere and we would reduce the amount of fossil fuels we pull out of the ground.
To give you an idea of its possible implementation, imagine a field of solar furnaces attached to CR5s surrounding a power plant. Each unit would reclaim 45lbs of CO2 daily producing enough carbon monoxide to convert into 2.5 gallons of fuel. With the existing fuel infrastructure already in place, the installation of the solar furnaces and CR5’s would be your only significant capital costs.
As with many technological innovations in the energy industry, Sunlight to Petrol is a sexy solution that piques the public’s interest and brings our energy issues onto the front page. However, as with many of these technologies, you have to question whether this is a viable solution or if it is more useful as marketing tool. 45lbs of CO2 and 2.5 gallons of fuel per unit per day do not seem like significant numbers. These solar furnaces take up a large amount of space (88 meters square). Can we install enough of these at a power plant and have enough sunlight for them to function correctly to make a difference? The government is selling this as a solution that is only 15 -20 years down the road. If they really believe in it as an actual solution then why have such a lead-time for implementation?
When our tour guides at Sandia showed us the actual prototype, it surprised me how crude the production was. It seemed to me like the engineers were tinkering with the technology for fun rather than feverishly perfecting a prototype for production. Please understand that this is no criticism of the actual engineers working on the project. They have an entire portfolio of possible solar solutions that they tinker with daily. I just wonder if we had a clear policy and more effective deployment of government sponsored R&D, could we move these technologies into production more quickly and find out if they are actually solutions to the problem or just fancy technologies that are fun to talk about.