The Solar Energy Research Center (SERC) is one of three Helios projects in which researchers from Lawrence Berkeley National Laboratory (LBNL) are working to develop fuels from sunlight.
The other two complementary projects, which focus exclusively on biofuels, are the Energy Biosciences Institute (EBI), centered at the University of California at Berkeley and funded by the oil company BP, and the Joint Bioenergy Institute (JBEI) in Emeryville, California. JBEI, a partnership between LBNL, Lawrence Livermore, and Sandia National Laboratories, and several universities, is one of three Bioenergy Research Centers established by the U.S. Department of Energy.
While these two projects research crops and enzymes associated with conversion of cellulose to fuels, SERC sidesteps plant biology completely. In this process, solar cells (photovoltaics, or PVs) collect sunlight and supply electrical currents that are used to drive fuel-forming chemical reactions. As envisioned, the chemical reactors convert water and carbon dioxide into a high-energy-density fuel that can be stored, transported, and used for transportation or other applications. The entire process can take place in a single reactor (termed a photoelectrochemical, or PEC, cell) that collects sunlight and is the site of the reactions involving water and ambient carbon dioxide.
The photosynthetic reactions that occur in plant leaves undergo a somewhat similar process, absorbing sunlight and producing sugars from water and carbon dioxide. For this reason, the process under development in SERC is often termed “artificial photosynthesis.” In bypassing the production of complex plant material, prototype PEC cells have been shown to be much more efficient than cellulosic routes to biofuels. These prototype PEC cells can transform in excess of 10 percent of the solar energy they absorb into fuel energy.
The disadvantage of the designs of the current prototypes is that, to obtain high efficiency, they employ metals that are not in abundant supply. To overcome this limitation, and so that PECs can be used on a scale that would enhance the United States’ fuel supply, SERC researchers are developing new complex materials and catalytic molecules made of abundant elements.
It will take innovation and scientific discovery to develop a significant new carbon-neutral fuel source that satisfies the twin imperatives of efficiency and scalability. This challenge is recognized as one of the most exciting problems in physical sciences today, and a new generation of physical and chemical scientists is galvanized to resolve the problem.