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storage system can allow the plant to switch off during peak
electrical tariff periods thereby saving on electrical costs. But the
equipment has to be increased in capacity so that it can deliver
the same capacity in a reduced time and still reduce the peak
heat load.”
Barry Watts, team leader at Johnson Controls highlights,
“any application can find a thermal ice storage system beneficial,
however, its installation is dependent on space and the area a
client has for the tanks.”
HOW A THERMAL STORAGE SYSTEM WORKS
Figure 1
The TSU-C/D is an external melt system that produces and builds ice
(1) around a coil (2) submerged in water (3). A refrigerant or cold
glycol (4) circulates through this, while ice accumulates in the outside.
The ice is melted by circulating warm water (5) from the load over the
coil, which cools the water (6). Low pressure air (7) from an air pump
(8) is distributed below the coil for water agitation.
Figure 2
The Calmac ice tanks are added to the system almost like an
additional chiller as they increase cooling availability through a
three-way valve, which controls the system,” says Muller.
Thermal storage systems can be installed in new construction
and retrofits (replacement and / or expansion of systems or
improvement to existing systems). Some of the applications
include manufacturing / process cooling, office buildings,
retail (for example banks, malls), schools, hospitals, district
cooling plants, stadiums, hotels, emergency cooling, breweries,
meat processing, wet-air pre-cooling for storage of fruits and
vegetables and cooling for mines. “Although this is a design
decision ultimately it is an investment with return on investment
pay back, so the additional cost of the ice system will be directly
compared to the savings to generate years of return. With a
lifespan between 20 and 30 years – with no moving parts and
on most buildings, this is a great investment into running costs
for the company,” says Muller. Andre adds that such a lifespan
is determined by a quality design and well-maintained system.
Additionally, “regular maintenance inspections of coil and casing
conditions and ensuring the water quality is within specification
will add to a preserved system,” says Glenn.
Most installations are unique from client to client, mainly
depending on their needs. Andre states, “depending on the
application a thermal storage design strategy can be a ‘full
storage’ or a ‘partial storage’. Calmac explains this further, “full
storage, fully shifts all of a building’s cooling load to off peak
hours. While initially more expensive to install, full storage
normally offers the greatest savings over time. Partial storage
employs a chiller which is approximately half the size of a
conventional installation. During the night it stores cooling;
during the following day, that stored cooling helps meet a
portion of the building’s load while the downsized chiller handles
the rest. Partial storage is often chosen for many new projects
because it is very cost-effective”.
Christo shares some considerations for opting for such a
system in office air conditioning and process factories. “For office
air conditioning, if you have to handle the peak heat load that
can occur then the plant room equipment and power supply has
to be sized for the peak load that occurs only for around four to
five hours a day. If a thermal storage system is installed, then
the peak heat load is reduced, and the plant room equipment
can be smaller as it works harder for most of the day. In process
factories peak loads occur when either warm product is received
and has to be chilled quickly or if a pasteurisation process needs
maximum cooling to cool the product after it has been warmed
up. If there is no thermal storage system, the plant has to be
designed to handle the peak heat loads which would only occur
at certain times during the day. The thermal storage system
reduces the peak load and ensures that the plant works at a
consistent but reduced level throughout the day. The thermal
The TSU-M is an internal melt system that produces and builds ice
(1) around a coil (2) submerged in water (3), most of which freezes
within the tank. The warm glycol (4) from the load circulates
through the coil and melts the ice from the inside. The newly cooled
glycol (5) is then pumped through the building cooling system or
used to cool a secondary refrigerant that does the same. Internal
melt is ideal for air-conditioning involving cooling at higher
temperatures than external melt.
Source: Baltimore Aircoil Company (BAC)
LOAD SHEDDING AND THERMAL STORAGE
As reports suggests the country will experience load shedding
over the next few months, is thermal storage one way of
ensuring survival during the blackouts? “If the system is designed
correctly to have ice available whenever required, then it is
definitely a viable solution for cooling during load-shedding,”
says Glenn. Andre explains, “The only standby generating
energy needed will be to run some pumps as well as the system
air handling units as opposed to installing full plant energy
requirement for chillers, etc.”
Christo Vermeulen from Intramech says, “An interruption in
indoor climate control can cause HVAC havoc – sweltering offices,
RACA Journal I May 2020
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