Photosynthesis is the process of converting light energy to organic compounds such as sugar that acts as a storage for chemical energy. This is the primary process for plants and some bacteria in manufacturing their own food. The process starts when energy from sunlight is absorbed by proteins called "photosynthetic reaction centers" that contain chlorophylls (the green pigment in plants). In plants, these proteins are held inside organelles called chloroplasts, while in bacteria they are embedded in the plasma membrane. Some of the light energy gathered by chlorophylls is stored in the form of adenosine triphosphate (ATP). The rest of the energy is used to remove electrons from a substance such as water.
Photovoltaics (PV) is a method of generating electricity by converting solar radiation (sunlight) into direct current electricity by using semiconductors that exhibit the photovoltaic effect. These semiconductors are also called solar panels and are composed of a group of solar cells containing a photovoltaic material. Materials presently used for photovoltaics include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium gallium selenide/sulfide. Due to the growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years.
Combining the two processes, Cal Tech have produced a photelectrochemical cell that harness sunlight to generate chemical fuel, specifically by splitting water to generate hydrogen.
Video: Creating Hydrogen from Solar Energy
The Lewis Research Group in Cal Tech demonstrated a new technique in the production of hydrogen. Hydrogen is being looked upon as a promising source of alternative fuel. Taking the idea of photovoltaic cells where electricity is produced and the process of photosynthesis where chemical energy is made by plants, the process involves uses silicon to produce hydrogen. Silicon is also used in solar panels to create electricity.
Silicon is coated with platinum catalyst particles to create a photoelectrochemical cell. When energy is applied to the cell such as solar energy, it produces hydrogen in a process similar to the electrolysis of water.
Although the research is still in its early stages, it shows promising results that one day this process may be perfected to collect the produced hydrogen and successfully convert it into a viable fuel source.
Getting More Out of the Sun's Rays: Artificial Photosynthesis
California Institute of Technology
Lewis Research Group
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