Courtesy Stellar.
This 193,000 ton-hr chilled-water TES tank in Riyadh, Saudi Arabia, provides turbine inlet cooling for an
electric power plant while saving capital and slashing on-peak parasitic power by 30 MW.
the margin” during on-peak daytime
periods versus off-peak nighttime
periods.
• A 24-hour flattening of the cooling
and electric power demands of the
district energy plant, improving the
operating characteristics and costs
associated with the new CHP system.
University of Nebraska-
Lincoln
A 16,326 ton-hr, 2. 9 million-gal
chilled-water TES tank was constructed
during 2011 to serve the University of
Nebraska-Lincoln (UNL) East Campus
district cooling network. The tank will be
commissioned by spring 2012. Designed
to operate initially as conventional stratified chilled-water TES, with operating
supply and return temperatures of
42 F and 52 F, the tank is predesigned
for potential future conversion to LTF
TES, for operation at 32 F and 52 F,
achieving an increase in TES capacity of
more than 97 percent to 32,260 ton-hr.
The TES tank is designed to discharge at
flow rates of up to 9,600 gpm or 4,000
tons at the initial (conservative) chilled-water delta T of 10 F, enough to fully
discharge the TES in under 4. 1 hours.
This TES system offers the following benefits:
• Very nearly a capital cost neutrality
versus an equivalent conventional
(non-TES) chiller plant capacity addition, with the small premium capital
investment representing a simple
payback of under one year.
• Millions of dollars in net present value
from reduced annual operating energy
costs (with more than $250,000 in
projected annual savings).
• Remote siting of the TES tank, along
the district cooling network but away
from the central chiller plant, thus
having the tank perform during discharge as if it were a satellite chiller
plant, with resultant enhancement in
the peak capacity of the district cooling piping system.
• Dual use of the tank as TES and as
an emergency fire protection water
reservoir.
serves the combustion inlet air-cooling
needs of 10 simple-cycle gas turbines
(each 75 MW nominal output), in an
environment with a design dry-bulb
ambient air temperature of 122 F in the
shade (though there is no shade). The
tank stores conventional stratified
chilled water, with operating supply
and return temperatures of 45. 5 F and
86.1 F. The TES is designed to discharge
at flow rates of up to 18,780 gpm or
31,773 tons at the chilled-water delta T
of 40. 6 F, enough to fully discharge the
TES in 6 hours.
TES is used during six peak hours
per day to meet 100 percent of the turbine inlet cooling load, with no chillers
operating during that time, achieving a
30 percent net increase in power plant
output compared to an uncooled design
day output. The chillers operate 17 hours
per night to recharge the TES.
The benefits of implementing this
TES installation include the following:
• A reduction in the necessary installed
chiller plant capacity from 31,773
tons to only 11,188 tons.
• Production of an extra 30 MW of net
on-peak power plant output, by
avoiding the consumption of 31,773
tons of chiller plant parasitic power
during that time.
• An immediate net capital cost saving
of well over $10 million versus an
equivalent conventional (non-TES)
chiller plant installation.
• Thus, improvements in both lowering
capital cost and raising net power
output enhancement, to yield an
attractive dollar per kilowatt for the
overall turbine inlet cooling project –
actually less than half of that for
adding equivalent conventional (
non-turbine inlet cooling) simple-cycle
gas turbines.
Electric Utility Power Plant,
Riyadh
At an electric utility power plant in
Riyadh, Saudi Arabia, a 193,000 ton-hr,
7. 9 million-gal chilled-water TES tank
was commissioned in 2005. The tank
McCormick Place Energy
Plant, Chicago
At the McCormick Place energy
plant in Chicago, Ill., a 123,000 ton-hr, 8. 5 million-gal LTF TES tank was
commissioned in spring 1994, serving
an urban district cooling network
comprising a convention district and
surrounding public and private building
customers. The tank stores a stratified
