(277b) Sustainable Chemical Processing Combining Concentrated Sunlight and Natural Gas

 “The sun has a unique role in sustainable energy production, in that it is the undisputed champion of energy; the resource base presented by terrestrial insolation far exceeds that of all other renewable energy sources combined”[Lewis and Nocera, 2006].   Solarthermal chemical processing is ideally suited for driving high temperature chemical reactions where products don’t have to be stored as intermediates for downstream continuous processing.  Major technical challenges revolve around the availability of thermal shock and oxidation resistant high temperature materials for fabricating solar receivers/reactors and the design of scalable reactors having high efficiency.  Heat recuperation/integration is a key issue for achieving high thermal efficiency.  The efficiencies for such processes are typically higher than those of competing solar technologies because the energy from the sun is used to directly drive chemical reactions instead of first being converted to another energy form, e.g. electricity.  According to the U.S. Geological Survey, 1 barrel of oil equivalent is roughly equivalent to 6,000 standard cubic feet (SCF) of natural gas (NG) in terms of energy. Therefore, with oil near $100/barrel and NG near $3/1000 SCF ($3/28.3 SCM), $100 of oil has equivalent energy content as ~$18 worth of NG.  This ~ 5X price differential provides for a solarthermal pathway in which low cost NG can be used as a feedstock or, possibly, as a supplement to solar energy used to heat the chemical process 24/7.  Major economic challenges include the cost of installed heliostats and competition from low cost fossil fuels such as NG.  Three rather near-term opportunities for commercial application include the decarbonization of NG to produce carbon black and hydrogen, the steam-methane reforming of NG for generating peak power, and the gasification of biomass with additive NG.