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8: What About Chillers, Cooling Tower Fans, and All That
Cooling Equipment Usually Ignored by IT? 133

■ Solar energy can be stored at high temperatures using molten salts. Salts
are an effective storage medium because they are low cost, have a high
specific heat capacity, and can deliver heat at temperatures compatible
with conventional power systems.
■ Off-grid photovoltaic systems have traditionally used rechargeable bat-
teries to store excess electricity. With grid-tied systems, excess electricity
can be sent to the transmission grid. Net metering programs give these
systems a credit for the electricity they deliver to the grid. This credit
offsets electricity provided from the grid when the system cannot meet
demand, effectively using the grid as a storage mechanism.
■ Pumped-storage hydroelectricity stores energy in the form of water
pumped when energy is available from a lower elevation reservoir to a
higher elevation one. The energy is recovered when demand is high by
releasing the water to run through a hydroelectric power generator.

The tried-and-true methods of cooling a data center haven’t changed
much over the years. You find a large air conditioner or two and bring in a lot
of electric power to drive the air conditioners. Across the globe, network and ptg
server administrators tend to keep light jackets or sweaters in their cubicles
to provide some warmth when they have to spend time in the server room.
This is because those massive air conditioners placed in the ceiling, the floor,
or along the walls are pumping out 60-degree air and keeping the whole
room frigid. It’s a solution that certainly works but is obviously wasteful.
Why keep the whole room at 68 degrees when the only place you need air
that cold is at the front of the racks?
One solution is the use of new in-row cooling solutions. Rather than sit-
ting on the sidelines and blowing cold air everywhere, they’re placed between
the racks, where they push the cold right where it needs to be: directly into
the servers. By going right to the heat source, in-row solutions reduce waste,
cut the energy bill, and eliminate the need for the data center parka.
These new cooling solutions can save a significant amount of energy.
However, whether it’s data center cooling systems or other data center
energy-savings solutions, we need enhanced measurement systems for all
parts of the data center. Figure 8.1 indicates the scope of power management
at a data center. The data center management required would need to include
the use of stored cooling or direct use of chillers for cooling. Appendix A,
“Green IT Checklist and Recommendations,” describes some of the tools
available for managing data center energy use.