When planning the expansion or replacement of a cooling system in
an existing building, owners should consider energy storage.
Energy storage is a demand-responsive system that can eliminate electrical-system upgrades, electric demand-charge increases, reduce maintenance,
and reduce energy costs. With energy storage, owners can also avoid the significant
expense of installing additional chiller capacity.
Underwriters Laboratories Inc. Headquarters, Northbrook, IL
What is energy storageand how does it work? Energy storage is a proven
system that takes advantage of low-cost, off-peak electric rates
to produce cooling energy for use when electric rates are higher.
CALMAC’s IceBank® thermal energy storage tanks
work in conjunction with a building’s chiller to make ice during
less-expensive off-peak hours at night. The ice is stored in the
tanks and then used the next day to cool the building during more-expensive on-peak hours.
There are at least three energy storage strategies to consider: full storage,
partial storage, or a combination. Full storage shifts a building’s
entire cooling load to off-peak hours. The building’s chiller only
runs at night in order to charge the IceBank tanks. During the discharge
cycle, the stored ice is used to cool 100 percent of the building’s load
the next day. Full storage can be ideal when an existing chiller is
already in place and a building owner wants to reduce energy costs.
With partial energy storage, IceBank energy storage tanks work in tandem with the chiller.
The existing chiller will produce ice at night and continue to run
the following day, cooling a percentage of the building’s load up
to 70 percent, depending upon rates and building usage. The stored
ice in the IceBank tanks cools the remaining percentage of the
building’s load. A partial-storage strategy enables building owners
to meet the increased cooling load of their expanded building without
adding chiller capacity, or to replace the existing cooling system with
smaller chillers, cooling towers, and pumps.
Underwriters Laboratories Inc. (UL) chose hybrid cooling for the energy efficiency and operating flexibility it provided. Since the installation of energy storage in 2001, they have saved $350,000 on their utility bill annually. "Overall, the new system reduced operating cost from $0.14 to $0.066 per tn-hr.", a 52 per cent savings according to Volker Kotscha, UL's Director of Facilities Operation. This air-conditioning system is entirely redundant. "We can cool the entire facility with ice for a minimum of six hours to take advantage of any energy curtailment incentive windows offered by the local utility", said Volker, Kotscha
Click here (PDF, 440 Kb) for more information regarding energy storage.
Additional retrofit benefits
- Energy storage lowers operating costs up to 40 percent depending upon electric rates.
- Energy storage is demand responsive, providing further savings opportunities.
- Energy storage gives owners the ability to expand the size of a building without increasing chiller capacity. It works in conjunction with an existing chiller to meet a building’s increased cooling load while reducing energy costs.
- The payback period is typically two to five years. Some owners have received payback in less than one year.
- Lower operating costs increase a building’s property value.
- The size and cost of air handlers, motors, ducts, and pumps can be reduced by 20 to 40 percent, further increasing cost savings.
- Click here for a complete list of building-owner benefits.
I do not have enough space for the tanks. Very little
space is required for ICEBANK tanks. It is easy
to relate the space needed for partial energy storage to space needed
for a residential water heater. A typical 1700 square-foot home has
a 4 square-foot water heater. The water heater uses (4 square feet/1700 square feet) or 0.23 percent of available floor space. An
ICEBANKenergy storage tank can provide
approximately 20 tons of cooling over 8 hours. With the 500 square foot
per ton rule, a 70 square-foot ICEBANK tank provides enough cooling
for about 10,000 square feet of building space, and uses about 0.70
percent of floor space (full-storage system). Most hybrid cooling systems are
partial storage, where storage accounts for about 30 percent of the
total cooling required reducing the floor space needed to about ¼ of
1 percent of the conditioned space. A 100,000 square-foot building
would require only 2,500 square feet for the ICEBANK tanks.
ICEBANK tanks can be place indoors or outdoors. Outdoors, the
tanks can be placed on the roof or on grade, or they can be partially
or totally buried.
Click here for a partial listing of energy storage projects.
Please click here to contact any of CALMAC’s regional managers for
additional information or questions.