Chilled water is produced during periods of
                                     off-peak electrical demand when rates are
                                     lower, collected in a DYK thermal energy
                                     storage (TES) tank, then withdrawn and dis-
                                     tributed through the facility during peak
                  demand periods. This process lowers energy costs by reducing
                  power consumption, lowering the unit cost of electricity, and
                  minimizing or eliminating utility demand charges.

                                        To stay online 24/7, companies with mission-
                  BACKUP                critical equipment install substantial back up
                  COOLING               electric services to support their facilities.
                  SYSTEMS               Thermal energy storage can provide both
                  day-to-day cooling and reserve cooling capacity for sustaining
                  the facility in the event of power outages or brownouts. Using
                  TES for cooling in place of running chillers substantially reduces
                  the emergency power needed during an outage.

                  COMBUSTION                Cooling of the inlet air to the
                                            compressor of a gas turbine system
                  TURBINE                   raises gas turbine output in hot
                  INLET                     weather – exactly when most peaking
                  COOLING                   power turbines are brought online.
                  Fewer turbines are needed to generate a given capacity, thus
                  minimizing a major portion of capital expenditures for a new
                  installation or delaying upgrades in existing plants. Compared to
                  inlet air temperature of 90°F, cooling turbine inlet air to 50°F
                  increases output capacity by 15% to 40%.

                                     DYK Incorporated designs and builds naturally stratified chilled
 University of Southern California   water thermal energy storage tanks for use as an integral part of
 Los Angeles, California             a facility’s air conditioning system, as well as other applications.
                                     When used in large industrial facilities, on university or corporate
                                     campuses, in district energy projects or in commercial buildings, a
                                     DYK thermal energy storage tank can yield annual savings in the
                                     hundreds of thousands of dollars.

                                     The thermal energy storage concept was first applied and proven
                                     in warm weather climates, where the demand for air condition-
                                     ing and the savings opportunities are at their highest. Today, with
                                     deregulation and real-time pricing, thermal energy storage makes
                                     economic sense in virtually any region. Return on investment is
                                     typically three to five years.
Chilled water (thermal energy) is produced during periods of
off-peak electrical demand, collected in a thermal energy
storage tank, then withdrawn and distributed through the
facility during peak demand hours, providing several ways to
lower energy costs.

LOWER POWER CONSUMPTION With thermal energy storage,
chiller operation is shifted to evening hours when ambient
temperatures are lower. As a result, the chillers operate more
efficiently and consume less energy for a given cooling load.

LOWER USAGE RATES Many utilities have established “time-of-
day” rates as a way of encouraging customers to use more
energy at night (off-peak), thus spreading energy generation
and consumption more evenly over a 24-hour period.
Operating chillers during the evening, when off-peak rates are
in effect, lowers the cost of electricity used for cooling. In a
deregulated market, having a TES installation in your facility
also buys you
more leverage
for negotiating     HOW THERMAL ENERGY STORAGE
a favorable rate
structure with      SAVES MONEY IN AN
your electric
supplier.           AIR CONDITIONING SYSTEM
LOWER DEMAND CHARGES Utilities may also charge customers
a “demand charge”, typically a monthly surcharge based on
the maximum number of kilowatts used by the customer in
any given hour over the previous twelve months. This sur-
charge covers the customer’s share of the expense to the utility
of generating enough power to meet maximum demand
requirements, whether the customer uses the electricity or not.
Operating the chiller plant during the local utility’s off-peak
period, can substantially lower a facility’s on-peak demand
yielding significant annual savings.

SHARED CONSTRUCTION COSTS Because thermal storage helps
postpone or avoid construction of expensive new generating
stations, some electric utilities offer substantial cash incentives
or rebates to companies installing thermal storage systems.
Several electric utilities will also share the cost of an engineer-   Naval Medical Center
ing study to assess the feasibility and profit potential of a         San Diego, California
thermal energy storage installation.

FEWER EQUIPMENT PURCHASES In both new construction and
facility expansion projects, it is often possible to substitute a
thermal storage tank for some or all of the chiller plant equip-
ment that would otherwise need to be purchased. Current
capital outlays and future operating costs are both reduced,
yielding significant energy cost savings for years to come.
AN EFFICIENT,                                   At the heart of a chilled water thermal energy storage
                                                system is a water storage tank with an integral diffuser
RELIABLE                                        system connected to the inlet and outlet pipes leading to
                                                and from the chiller plant.
STORAGE                                         To take full advantage of the energy cost savings
TANK                                            opportunities, the tank must be superior in several
                                                important areas:
                                                     • thermal efficiency;
                                                     • laminar flow qualities of the diffuser;
                                                     • long-term reliability of the tank;
                                                     • tank maintenance requirements;
                                                     • size and siting options.
  DYK thermal energy storage prestressed concrete tanks offer significant customer benefits in all five
  areas of consideration.
  THERMAL EFFICIENCY The natural insulating characteristics of concrete are greater than the
  other material option – steel. In an above grade or a partially-buried installation, a concrete tank will
  require less insulation. Moreover, unlike steel tanks, prestressed concrete tanks can be totally buried,
  thus using the earth itself as an insulator to limit or eliminate the need for additional insulation.
  LAMINAR FLOW A thermal energy storage tank depends on a sharply defined, stable
  thermocline to separate chilled water from warm water within the tank. DYK’s unique diffuser
  system is designed to eliminate turbulence as the water enters and exits the tank.
  LONG-TERM RELIABILITY DYK Incorporated has over 40 years of tank building experience. We
  routinely build water storage tanks that remain in continuous, day-to-day service for several decades.
  All of our tanks conform to AWWA (American Water Works Association) Standard D110, a
  design/build standard proven in thousands of tanks across the country.
  NO MAINTENANCE DYK prestressed concrete tanks never rust and never require repainting.
  That means you never need to remove and replace costly insulation, as would be necessary with a
  steel tank. And it means your DYK tank stays in continuous service every day, every year. Steel tanks,
  on the other hand, are usually serviced or repainted in summer months, when the need for uninter-
  rupted thermal energy storage is most critical. DYK TES internal diffuser systems are made of high
  strength, non-corrosive PVC piping with all stainless steel, PVC or fiberglass supports and fasteners.
  SIZE AND SITING ADVANTAGES A DYK TES tank can be built in capacities from 1,000
  ton/hours to 200,000 ton/hours, and can be sited above grade, partially buried, or totally buried,
  allowing multiple use of valuable real estate. Many prestressed concrete storage tanks have been
  installed under parks, parking lots, tennis courts, heliports, etc.

                             Texas Instruments’ corporate headquarters
                                                           Dallas, Texas
CUSTOM DESIGNED                     University of California –
FOR EACH INSTALLATION                               Riverside
                                        Riverside, California
DYK thermal energy tanks
are built using prestressed
concrete to assure water-
tightness and years of
trouble-free performance.
They are specifically designed
to meet the topographic,
hydraulic, and thermal
requirements of each
installation. DYK tanks may
be built above grade, partial-
ly-buried, or totally buried.
                                       A second tank at the
Roofs are concrete and may
                                    University of California –
be either a free-standing                           Riverside
dome or column-supported                Riverside, California
flat slab.

Thermal efficiency is the net
cooling available for distribu-
tion after chilled water has
been stored in the thermal
energy storage tank. DYK
thermal energy systems pre-
stressed concrete TES tanks
are conservatively rated to                   University of
                                        Southern California
produce a minimum thermal            Los Angeles, California
efficiency of 92.7%. In prac-
tice, they produce 95% effi-
ciency and more. No other
thermal energy storage tank
is capable of greater thermal

It takes just a few months to
build a DYK thermal energy                    University of
storage tank, and just a few            Southern California
                                     Los Angeles, California
years – typically three to five –
to realize 100% return on
Here’s what the Facility Engineer for a major manufacturer in the
Southwest had to say about his 24,500 ton/hour thermal energy
system utilizing a prestressed concrete tank to store chilled water.
“It was installed as a retrofit project in just 10-1/2 months at a total
cost of $68 per ton/hour (62¢ per gallon). Since start-up it’s perform-
ance has exceeded our expectations. In particular, we’ve enjoyed
100% reliability, 92.7% cycle thermal efficiency, 34% greater savings
than projected, and 13% greater capacity than designed.
“In addition to reducing our on-peak electric demand by 2,900 kW,
we have reduced electric usage by an average of 175,000 kWh per
month, or 3.7%.
“Annual savings are now about $340,000 per year.”

Signal Hill, California
Warm and chilled water enters and exits a thermal energy storage tank through upper and lower
diffuser systems. Just as in a lake, the chilled water (between 39.2°F and 42°F) is naturally heavier
and stabilizes in the bottom of the tank, while the lighter warmer water (50°F to 65°F) rises to the
top. Separation between the two is maintained by creating a stable, sharply defined transition layer
or “thermocline”. This process by which warm water and cold water in the same vessel naturally
separate, is known as “natural stratification”.
The illustration shows a buried DYK TES tank as it would appear early in the daily distribution phase.
Chilled water (blue) exits the tank through the bottom diffuser and is replaced by warm water (red)
entering through the top diffuser. When the distribution phase is complete, the tank will contain
mostly warm water, and be ready for the start of another recharge or “cooling” phase.
In the recharge phase, warm water is withdrawn through the top diffuser, circulated through the
cooling plant, and returned to the tank through the bottom diffuser. When that process is ended, one
thermal energy storage cycle is complete, and the tank again appears as it is shown in the illustration.
       DYK Incorporated has been designing and building wrapped
       prestressed concrete tanks for over forty years. In that time,
       we have installed tanks for hundreds of communities across
       the country interested in preserving and managing one of
       their most precious assets – their municipal water supply.
       Our record of experience includes over 800 tanks and over
       three billion gallons of storage capacity.

       DYK tanks are known for their long-term reliability, durability
       and cost-effectiveness. And DYK Incorporated is known for
       integrity, honesty and commitment to customer satisfaction.

                                                                                                               Printed in U.S.A. 3/05

Prestressed. Maximum Efficiency. Minimal Maintenance.
351 Cypress Lane • P.O. Box 696 • El Cajon, CA 92022-0696
Toll-Free: 800.227.8181 • Phone: 619.440.8181 • Fax: 619.440.8919 • Email: • Web:

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