8 Ways to Save Money in Data Centers
HOW SMART SPACE PLANNING AND BETTER MANAGEMENT CAN REDUCE
YOUR DATA CENTER’S ENERGY BUDGET
temperatures allow the CRAC unit to operate
more efficiently, closer to ARI ratings. By confirming the CRAC unit performance based on
return air temperatures, you can see that the
same CRAC unit has more capacity at higher
return air temperatures. This greater cooling
capacity can allow you to potentially turn off
some of your CRAC units.
Other options for containment include
clear horizontal ceilings at the cabinet level
that block the cascade effect, overhead ducted systems and drop-down curtains, which
resist cascading but drop down during emergencies so they don't block the sprinklers.
2) Free Cooling
Any amount of cooling you can get at
no charge will conserve energy and money,
especially in high-energy applications like
data centers. Whether you opt for a chilled
water system, glycol/DX or total refrigerant
based system, anything you can do to rely
less on the mechanical system will be useful.
Depending on your cooling equipment,
you may be able to configure your system so
that the cold water or refrigerant cooled by
outdoor air is bypassing the compressor and
going to the evaporator coil, which means
the CRAC fan won’t have to work harder in
free cooling mode. Some units or systems will
require an additional free cooling evaporator
coil, which will add static pressure and cause
the CRAC unit fan to work harder.
The designs can include partial free cool-
ing or mechanically assisted free cooling. In
this condition, the free cooling mode brings
in chilled water or refrigerant or condenser
water that is not cold enough for 100% free
cooling and then the compressors do the
rest of the cooling. This is typical when it’s
cold outside but not cold enough for 100%
free cooling. If the temperature outside is low
enough, you may not need the chiller or com-
pressor for mechanical cooling at all.
3) Directed Air
Cooling a data center efficiently is all
about chasing the cold spots. Don’t bring in
more cubic feet per minute than you have
to and don’t overflow the data center with
air. You don’t want to feel cold air when you
walk in because that means that cold air isn’t
going to the front of the cabinets and to the
servers, where it belongs.
Make sure you target cooling by balancing
airflows, putting variable frequency drives on
fans and doing a CFD analysis to make sure
the air is going to the right locations. You can
save fan power if you can reduce your airflow
by being more selective about where you’re
directing the air or via a slight drop in your
supply air temperature. A 2-degree change in
supply air temperature with the same room
or return air temperature lets you reduce fan
airflows by about 10%. This also works with
a 2-degree increase in room or return air
temperature. A 10% reduction in airflow will
reduce the fan horsepower by 40%.
Be careful when you’re using perforated
floor tiles to direct air. Don’t put dampers
on all of them because that will increase the
pressure drop through the perforated floor
tiles, even when the dampers are 100% open.
Instead, strategically locate the floor tiles
with dampers or use floor tiles with different
free area and airflow characteristics.
4) Increasing Supply
Air Temperatures
ASHRAE has broadened the allowable
zone for temperature and relative humidity
conditions in data centers. However, the warranties on your servers may not allow you
to increase the supply air temperature, or
you may have service level agreements that
require specific conditions. Check the manufacturers’ documentation and tenant agreements to see what your options are. Raising
the supply air temperature also increases
free cooling hours.
5) Lowering Humidity
Setpoints
Data center optimization allows you to
drop your humidity setpoints, using less
water and energy. We have a client who
turns off the humidification system completely in their 5 MW data center, which has
a power usage effectiveness of 1.2. They
also deployed a water-cooled chiller system
with water side economizer functions. The
two main ways to humidify a room are by
Optimizing data centers doesn’t always require new equipment and a huge upfront investment. Just implementing better management strategies can
conserve energy and money. Try these strategies to optimize equipment and operations
without the cost of a complete remodel.
1) Containment
The goal is to make sure that the cold air
gets to the servers and equipment that needs
cooling. Containment simply means separating hot and cold air streams. Keeping them
from mixing means you won’t be wasting
cooling air to cool the hot airstream, which
should be pulled out of the data center.
Containment also prevents the hot air
from cascading back into the top third of the
cabinet. Cascading is why the servers and
switches in the top third of the cabinets tend
to have the highest failure rates. Ideally, cold
and hot air are restricted to their own aisles
by placing cabinets front-to-front and back-to-back rather than front-to-back, but if your
data center has a front-to-back layout, you
can still implement a chimney.
Chimneys can be deployed in almost any
data center. The solid metal chimneys mount
on top of cabinets and funnel hot air into the
return air ceiling so that it can go through
the computer room air conditioner (CRAC)
units to be cooled rather than cascading
down and affecting equipment. Make sure
that the opening on top of the cabinet is
large enough to accommodate the chimney and the equipment loads to move the
required airflow out of the cabinet and into
the ceiling cavity.
If you’re about to do a refresh on your data
center, think about changing the layout to
maximize containment. Properly designed,
containment will allow you to duct hotter air
to the CRAC units and the hotter return air
