Power Generation - Hydrogen and Fuel Cells: Advances in Transportation and Power - page 198

ing integrated PV systems have been installed on the roofs and facades
of houses, factories, offices, schools, public buildings and stadiums. The
power produced can be on site, stored or fed to the grid. Most systems,
except for the very smallest, are connected to local supply networks, and
with suitable connections and metering, many owners can sell their sur-
plus current to the utility.
SOLAR FUEL CELL GENERATORS
DBK has their own brand of 1.2-60-kW solar fuel cell generators.
The fuel for a solar based fuel cell generator is sunlight and water. The
core technology for their product line of Regenerative Fuel Cell (RFC)
systems is the Proton Exchange Membrane, or PEM, fuel cell. This tech-
nology uses a solid polymer membrane as the system electrolyte. This
material works like battery acid but is inert and safe to touch. It func-
tions to transport hydrogen ions or protons to set up either electrolysis
or fuel cell reactions.
In the charge, or electrolysis mode, the process splits water into hy-
drogen and oxygen and can produce hydrogen directly without mechani-
cal compression. Water enters the cell and is split at the surface of the
membrane to form protons, electrons and gaseous oxygen.
The gaseous oxygen leaves the cell while the protons move through
the membrane under the influence of the applied electric field and elec-
trons move through the external circuit. The protons and electrons com-
bine at the opposite surface to form pure gaseous hydrogen.
A fuel cell uses the reverse process. Hydrogen along with oxygen
from the air are applied to the cell. The hydrogen splits to release its elec-
trons to the external circuit and provide power to the load. The protons
move across the membrane, attracted by the oxygen potential, and com-
bine with the oxygen to form water at the opposite electrode surface.
A regenerative fuel cell system combines both of these processes
using a hydrogen storage vessel to store energy. PEM regenerative fuel
cells were developed in the early 1980s by NASA for applications in space
based energy storage. Since that time, others have advanced the concept
using both PEM and alkaline fuel cell technology.
An RFC can provide seasonal energy storage and there is near-zero
self discharge. It provides high levels of storage at a reasonable cost and
has the ability to store energy from multiple energy sources.