138 The Green and Virtual Data Center
Unlike wind or solar energy generation, which depend on available wind
and clear sunny days, respectively, fuel cells can have a much higher availabil-
ity as a standby or primary energy source. For example, moving forward, a
data center facility can leverage primary utility power when it is readily avail-
able and switch to co-generation or self-generation using fuel cells when
appropriate. Fuel cells, like solar and other alternative energy sources, can
also be used for charging standby batteries for UPS systems, off-loading
energy demand from primary energy sources. Fuel cells are still an evolving
technology, but as they mature and become more affordable they should be
able to provide primary and secondary power ...