If you are designing an HVAC system for new construction or
retrofit office/commercial applications, you should consider
the numerous advantages that a CALMAC energy storage
system can provide.
Moorhead Federal Building Tanks
What is energy storage and how does it work? energy storage is a
proven technology that takes advantage of low-cost, off-peak
electric rates to produce cooling energy for use when electric
rates are higher. A building’s chiller is used to charge
CALMAC’s IceBank® thermal energy
storage tanks with ice during less expensive off-peak hours
at night. The ice is stored in the IceBank tanks and then used
the next day during the discharge cycle to cool the building
during on-peak hours. Click here (PDF, 371 Kb) for system configuration information and a technical review of the energy storage process.
Air-cooled chillers perform most efficiently when the outdoor temperatures are relatively low, as naturally occurs during cooler nighttime hours. Operation at night with 20 degree lower condensing temperatures can improve energy efficiency typically by 2 to 8 percent over non-storage systems operating during the day.
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 storage, IceBank tanks work in tandem with the chiller.
The chiller charges the IceBank tanks at night and continues to run
the following day during the discharge cycle, cooling up to 70 percent
of the building’s load, and the stored ice cools the remaining 30
percent. A energy storage system configuration enables chillers
to operate at or near full load continuously, eliminating the
inefficient cycling and capacity modulation that accompanies part-load
operation and normally causes a chiller to operate at peak efficiency
only 25 percent of the time.
Click here (PDF, 371 KB) for system configuration information and technical review
of the energy storage process.
Additional design engineer benefits
- Thermal energy storage design is similar to a chilled-water system and is not complicated.
- Provides customers with a demand responsive cooling system.
- Provides customers a cooling system with fuel-source flexibility, on-peak or off-peak energy.
- Offers architects a path to ASHRAE 90.1 compliance or improved LEED™ ratings.
- Provides a design with a chiller that is 40 to 50 percent smaller, to minimize inefficient operation of oversized equipment with minimal risk.
- Added design costs, if any, can be easily paid for with life-cycle savings.
- The size of air handlers, motors, ducts, and pumps can be reduced by 20 to 40 percent, which saves design time.
- CALMAC can provide a wealth of information to help engineers efficiently design an energy storage system.
- Click here for a complete list of other benefits.
I understand partial energy storage, but I don’t like the
risk I’m taking with downsizing the chiller. Look at an example
comparison of conventional cooling with two 50-ton chillers for
a 100-ton building and partial storage. The energy storage system for this
example might be two 30-ton chillers and one CALMAC 1320 IceBank energy storage
tank. If only one chiller operates on the conventional system,
50 tons of the 100-ton peak-cooling load can be met. If only one
chiller is available on the partial ice storage system, over
50 tons of the 100-ton peak cooling-load tons can easily be
achieved. Thirty tons come from one chiller and 40 to 50 tons
come from the ice stored in the IceBank tank. The systems have
similar capabilities, should one machine be inoperable. The risk
of a component being down is the same for each system.
Moorhead Federal Building
For example, two 990-ton chillers were originally installed at
the Moorhead Federal Building located in Pittsburgh, Pennsylvania.
The consulting and project engineer decided to replace the 990-ton
chillers with two 600-ton, high-efficiency centrifugal chillers,
along with a CALMAC energy storage system that included 39
IceBank energy storage tanks
rated, at 190 ton-hours each, for a total of 7,410 ton-hours
(or 26,000 kW-hours).
On mild days during the cooling season, the chillers are not run
at all during peak times, and 100 percent of the cooling is
provided from the stored ice.
Click here for complete product and specifications information.
Click here for a partial listing of IceBank energy storage projects..
Please click here to contact any of CALMAC’s regional managers
for additional information or questions.