WIND ENERGY SYSTEMS - Cd3wd

Chapter 7—Asynchronous Loads 7–45
Figure 17: Plot showing the effect of temperature on electrolysis cell characteristics at 3000
psi.
keeping the acid concentration constant within the electrolyte. On the oxygen side, two water
molecules are decomposed into one neutral oxygen gas molecule, four electrons which move
off to the right within the metal screen, and four positive hydrogen ions which move through
the solid electrolyte. These four ions receive four electrons coming from the left and become
two molecules of hydrogen gas on the hydrogen side of the solid electrolyte.
The two faces of the SPE sheet are coated with a very thin film of catalyst to help the
reaction occur. Platinum black works well but other catalysts are being developed for reasons
of cost and availability.
The spaces for the water and gas next to the SPE sheet are formed by a multi-layer
expanded metal screen package. The open spaces between the screen strands provide a low
resistance flow path for the water and gases. The screen provides physical support for the
SPE sheet to help it withstand high differential pressures and acts as an electrical current
conductor. The fluid cavities are sealed around the edges by a silicon rubber gasket. This
gasket also provides electrical insulation so current flows only where desired. Adjacent cells
are separated by a metal sheet which provides mechanical separation of gases but does not
contribute directly to gas production.
Early problems with the silicon rubber gasket have led to the testing of other separators.
One version replaced the silicon rubber gasket and metal sheet with a sheet of molded carbon
Wind Energy Systems by Dr. Gary L. Johnson November 21, 2001