Thermal Energy Storage - Airlines Reduce Operating
Costs with Ice Balls
Repeat Installations Keep Design Costs Down and Reflect
|You are sitting in a wide-body
aircraft on a hot, humid afternoon at Miami International Airport. You are
shoulder to shoulder with a couple hundred people and the doors of the plane
are open as the ground crew loads up the soft drinks and peanuts for the
flight. Even though the plane is on time, you know it may be a while.
Fortunately, that little nozzle above your head is blasting out cold air.
How do they do that? How can they afford to keep so many people cool in a
confined space with the doors open? The answers can be found in PCA
(preconditioned air) and TES (thermal energy storage).
In the past, an airplane's auxiliary power unit (APU) was
called upon to supply cooling. The APU is a small jet engine designed to
provide cooling, electrical power and, in some cases, power to start the
main engines. These engines consume between 35 and 120 gallons of jet fuel
per hour. In addition to high fuel costs, the APU is subject to costly FAA
approved maintenance based on hours of operation.
The economic and practical necessities of shifting air
conditioning loads away from costly APU engines led to development of the
PCA system. The economics of electrical power to run PCA chillers led to the
addition of thermal energy storage.
As compared to typical air conditioning systems, these
installations are designed for the most extreme demands. The most obvious
extremes are those associated with high, short-term loads imposed on the
system while the aircraft is parked followed by no-load conditions when the
plane departs. In addition to the "peaky" intermittent demands for cooling,
PCA systems normally use 100% outside air for cooling and ventilation. Of
course, this means high temperature air (and often very humid air) must be
cooled without the benefit of recirculation - remember, the doors are open.
PCA ducting under jetway
To accomplish the task of managing such extremes in an
economical manner, water-cooled industrial grade chillers are combined with
thermal energy storage in a low temperature glycol loop. The system supplies
aircraft with a large volume of relatively high-pressure air (22 inches of
water) at the low temperature of approximately 30°F. In order to meet such
unusual conditions, cold fluid from the glycol based system is delivered at
about 20°F. Thermal storage not only flattens the peak loads inherent with
such an application but also allows the use of lower cost off-peak
electricity to charge the system at night.
Cryogel Ice Ball Thermal Storage Tank
|Exact details of
the low temperature process are proprietary and the key system components
and Cryogel Ice BallTM thermal storage media are protected by
|Since 1995, ten
PCA systems using Cryogel Ice Balls have been installed for major airlines
at the international airports in Atlanta, Miami, San Francisco, Los Angeles,
Chicago, Phoenix and Dallas/Ft. Worth. The simple fact that the same
airlines continue to install system after system is the strongest single
indicator of the economical operation and reliability of the combined PCA/TES