Chemical fuels from carbon neutral sources are another important component in need of development if we are to achieve a sustainable energy future. Chemical fuels are especially important to the transportation sector as roughly one third of our energy goes into transportation—and currently over 40% of global transportation cannot be electrified, such as ships, aircraft, and trucks.
The Sun produces enough energy in one hour to power all human activity on Earth for a full year, and yet storage of this energy in the form of convenient, inexpensive fuels has remained technically elusive. Addressing this challenge at Caltech is the Joint Center for Artificial Photosynthesis (JCAP) and CCI Solar, which are two organizations dedicated to the production of solar fuels. Both JCAP and CCI solar aim to find a cost-effective method to produce fuels using only sunlight, water, and carbon dioxide as inputs.
Researchers including Professors Nate Lewis, Harry Gray, Jonas Peters and Mike Hoffmann are focused on this effort. They are looking at the photocatalytic splitting of water to produce molecular hydrogen, and via the photocatalytic reduction of CO2 to produce useful products such as syngas, methane, and other hydrocarbons. They’re developing enhanced light absorbers, optimized catalyst materials and their integration into functional assemblies.
Professor Sossina Haile is using a thermochemical approach to solar fuel production. This method relies on the oxygen uptake and release capacity of oxides such as ceria. Because the process uses sunlight in the form of heat, it has the potential to utilize the entire solar spectrum with high efficiency. Her group has demonstrated production of a range of fuels from water and carbon dioxide. The two-step process is inherently simple to implement, and the Haile group is collaborating with colleagues at the University of Minnesota to construct operational reactors which achieve the high efficiencies required for commercial adoption.
Professor Frances Arnold uses directed evolution, a method she invented, to engineer enzymes that help convert plant material into fuels and commodity chemicals. Arnold believes that cellulosic biofuels could sustainably replace more than half of US oil imports. Former Resnick Fellow Matt Smith developed a computational tool for protein engineering that identified structural regions of protein that could be swapped in order to construct a more productive cellulase, which is the enzyme that breaks down plant material into its constituent sugars—that are then fermented by microbes to make fuels and chemicals.