Using Solar Power to Make New Fuels

When we think of renewable energy, it’s mainly as a primary source of energy that we can use for heating, powering vehicles etc. However, there are also a growing number of applications that use renewable energy to create other energy sources. For example, green hydrogen is hydrogen manufactured by separating water using renewable energy. It is a very handy trick for renewable energy, as it doesn’t have a constant, regular way of generating power. If it is a calm day, wind generators will not generate electricity, and if the wind is strong, it will generate a lot of energy, there is not usually a happy medium. Being able to use the excess energy to create a new source of power that can be easily stored for later use goes a long way to negate one of the biggest downsides of renewable energy.

Another example of renewable energy being used to create another energy source has recently been demonstrated by researchers who captured carbon dioxide from industrial processes and transformed it into clean sustainable fuels using solar power. The researchers, from the University of Cambridge, have designed a solar-powered reactor that converts captured CO2 and plastic waste into sustainable fuels and other valuable chemical products. The CO2 was converted into syngas, a key building block for sustainable liquid fuels, and the plastic waste was converted into glycolic acid, which is widely used in the cosmetics industry.

This test was a refinement of the process that the team originally demonstrated, with the change being that the CO2 used came from real world sources. Previously the solar-driven experiments had used concentrated CO2 from a cylinder. In this test, the researchers captured and concentrated the CO2 from the atmosphere and converted it into sustainable fuel. Professor Erwin Reisner’s research group, based in the Yusuf Hamied Department of Chemistry at the University of Cambridge, has already been developing sustainable, net-zero carbon fuels inspired by photosynthesis using artificial leaves. These artificial leaves convert CO2 and water into fuels using solar power.

The researchers took their inspiration from carbon capture and storage (CCS). This is a process where CO2 is captured and pumped and stored underground. They then adapted their solar-driven technology to work with flue gas or directly from the air, converting CO2 and plastics into fuel and chemicals. CO2 selectively gets trapped bubbling air through the system containing an alkaline solution, and the other gases present in air, such as nitrogen and oxygen, bubble out. The bubbling process allows the researchers to concentrate CO2 from air in solution, making it easier to work with. The integrated system contains a photocathode and an anode. The system has two compartments: on one side is captured CO2 solution that gets converted into syngas, a simple fuel. On the other plastics are converted into useful chemicals.

The scientists are currently working on a bench-top demonstrator device with improved efficiency and practicality to highlight the benefits of coupling direct air capture with CO2 utilisation as a path to a zero-carbon future.