Specialists in Heat Transfer Products and Services Specialists in Heat Transfer Products and Services
1
Ice Storage Systems
Ice Storage Systems
and and
Impact on Electric Demand
Impact on Electric Demand
Georges Hoeterickx Georges Hoeterickx
0 2 4 6 8 10 12 14 16 18 20 22
Time of Day
C
o
o
li
n
g
L
o
a
d
Typical Cooling Load Profile
Conventional System
Chiller
Cooling Load Cooling Load
Ice Storage System
Ice Storage Tank
Chiller
Cooling Load Cooling Load
0 2 4 6 8 10 12 14 16 18 20 22
Time of Day
C o o li n g L o a d
Ice Storage Cycle
Ice Ice Storage Storage Cycle Cycle Ice Ice Storage Storage Cycle Cycle 7
Advantages of Thermal Ice Storage Advantages of Thermal Ice Storage
• Reduced equipment costs
– Only 60% - 90% of chillers and heat rejection equipment and is required
– Associated electrical equipment is reduced
– Reduced thermal energy storage space
• Reduced energy and operating costs
• Reduced GHG emissions
• Increased flexibility to adapt to changing utility structures and requirements
Reduced Equipment Size with Ice Storage
0% 20% 40% 60% 80% 100%
0 3 6 9 12 15 18 21 0
%
P
e
a
k
Load
11
Reduced Equipment Size with Ice Storage
0% 20% 40% 60% 80% 100%
0 3 6 9 12 15 18 21 0
% P e a k Load
Advantages of Thermal Ice Storage Advantages of Thermal Ice Storage
• Reduced thermal energy storage space
• Ice storage requires 1/4 to 1/6 of the space of chilled water storage
– 41.4 kW-Hr/m³ (1 Ton-Hr/3 ft³)
– Ice storage insensitive to system ΔT
Chilled Water Storage
55m D x 16m H
310 mW-Hours (88,000 Ton-Hours)
Advantages of Thermal Ice Storage Advantages of Thermal Ice Storage
• Reduced equipment costs
• Reduced energy and operating costs
• Reduced GHG emissions
• Increased flexibility to adapt to changing utility structures and requirements
Thermal Ice Storage Uses Less Energy Thermal Ice Storage Uses Less Energy
• At night, chillers operate when ambient temperatures are much lower
• During days, chillers operate at higher CHW supply temperatures and greater efficiency when piped upstream of ice storage
• Pump energy can be less by taking full advantage of colder CHW supply
temperatures
1 2 3 4 5
-8 -6 -4 -2 0 2 4 6 8 10
COP
CHW Supply Temperature ( C) Ambient Temperature ( C)
25 30 35 40 45
COP of Chillers with Air-Cooled Radiators
“Normal” Design Point CHW Pre-Cool Final Ice-Build
Chiller Piped in Series with Ice Storage Chiller Piped in Series with Ice Storage
Thermal Ice Storage Uses Less Energy Thermal Ice Storage Uses Less Energy
• At night, chillers operate when ambient temperatures are much lower
• During days, chillers operate at higher CHW supply temperatures and greater efficiency when piped upstream of ice storage
• Pump energy can be less by taking full
advantage of colder CHW supply temperatures
Advantages of Colder Chilled Water Advantages of Colder Chilled Water Supply Water Temperatures
Supply Water Temperatures
• Smaller distribution pumps and piping
• Reduced pumping power
• Allows for economical building isolation (indirect interface) with smaller heat
exchangers
Colder Supply Water Temperatures Colder Supply Water Temperatures
CHW Supply Temp. CHW Flow* Difference
5 C (44.6 F) 8610 m³/h (37900 gpm) Base
4 C (44.6 F) 7530 m³/h (33170 gpm) -13%
3 C (44.6 F) 6700 m³/h (29480 gpm) -22%
2 C (44.6 F) 6030 m³/h (26530 gpm) -30%
1 C (44.6 F) 5480 m³/h (24120 gpm) -36%
*12°C (53.6°F) CHW Return Temp. 70 mW (19,900 TR) Peak Load
Advantages of Thermal Ice Storage Advantages of Thermal Ice Storage
• Reduced equipment costs
• Reduced energy and operating costs
• Reduced GHG emissions
• Increased flexibility to adapt to changing utility structures and requirements
Advantages of Thermal Ice Storage Advantages of Thermal Ice Storage
• Require less kWh than conventional systems
• Energy line losses at night are 4% to 5% lower than during the daytime
• Utilize efficiently produced power that
produces fewer carbon dioxide emissions Source: Source Energy and Environmental Impacts of Thermal Energy Storage, California Energy Commission - February 1996
TES Meeting Summer System Load in South Florida, USA
23 0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
mW
Hour
Base Nuke Base Coal Combined Cycle TES Adds to CC Steam GT TES Shifts Steam GT
Source: Thermal Energy Storage Time of Day Impact on Power Plant Emissions, John Nix - June, 2008
Specialists in Heat Transfer Products and Services Specialists in Heat Transfer Products and Services
Ice Storage System
Ice Storage System
Design Considerations
Design Considerations
Full Storage vs. Partial Storage Full Storage vs. Partial Storage
0 2 4 6 8 10 12 14 16 18 20 22
Time of Day
C o o li n g L o a d (T o n s )
Batch Cooling or Process Load Profile Batch Cooling or Process Load Profile
0 2 4 6 8 10 12 14 16 18 20 22
Time of Day
C o o li n g L o a d (T o n s )
Full Ice Storage System Example Full Ice Storage System Example
Batch Cooling or Process Application Batch Cooling or Process Application
Ice Charge
0 2 4 6 8 10 12 14 16 18 20 22
Time of Day
C o o li n g L o a d (T o n s )
Air Conditioning Load Profile Air Conditioning Load Profile
0 2 4 6 8 10 12 14 16 18 20 22
Time of Day
C o o li n g L o a d (T o n s )
Full Ice Storage System Example Full Ice Storage System Example Air Conditioning Application
Air Conditioning Application
Ice Charge
Ice Storage System Design Ice Storage System Design Full Ice Storage
Full Ice Storage
Advantages
• Best suited for short, peak demand periods and/or high, peak loads
• Shifts largest electrical demand that provides the lowest operating cost • Provides system standby
capability and operating flexibility
Disadvantages
• Largest storage volume required
• Larger chiller required • Most expensive thermal
storage design
0 2 4 6 8 10 12 14 16 18 20 22
Time of Day
C o o li n g L o a d (T o n s )
Partial Ice Storage System Example Partial Ice Storage System Example Air Conditioning Application
Air Conditioning Application
Ice Charge
Ice Charge Chiller Chiller Ice Discharge Ice Discharge
Partial Ice Storage System Example Partial Ice Storage System Example Air Conditioning Application
Air Conditioning Application
0 2 4 6 8 10 12 14 16 18 20 22
Time of Day
C o o li n g L o a d (T o n s ) Ice Charge
Ice Charge Chiller Chiller
Ice Discharge Ice Discharge
0 2 4 6 8 10 12 14 16 18 20 22
Time of Day
C o o li n g L o a d (T o n s )
Partial Ice Storage System Example Partial Ice Storage System Example Air Conditioning Application
Air Conditioning Application
Ice Charge
Ice Charge Chiller Chiller
Ice Discharge Ice Discharge
0 2 4 6 8 10 12 14 16 18 20 22
Time of Day
C o o li n g L o a d (T o n s ) Base Chiller Base Chiller Ice Charge
Ice Charge Chiller Chiller
Ice Discharge Ice Discharge
Partial Ice Storage System Example Partial Ice Storage System Example Air Conditioning Application
Air Conditioning Application
Ice Storage System Design Ice Storage System Design Partial Ice Storage
Partial Ice Storage
Advantages
• Best suited for long cooling periods
• Lower first cost due to reduced storage
volume and smaller chiller
• Provides system operating flexibility
Disadvantages
• Less standby capability
• Less electrical demand shifted to off-peak
Specialists in Heat Transfer Products and Services Specialists in Heat Transfer Products and Services
35
Ice Storage System
Ice Storage System
Design Considerations
Design Considerations
Internal Melt vs. External Melt Internal Melt vs. External Melt
Ice Storage System Types Ice Storage System Types
Direct Contact Cooling Indirect Contact Cooling
Ice Storage System Design Ice Storage System Design Ice on Coil
Ice on Coil -- Internal MeltInternal Melt
• Cold glycol solution is circulated through the
coil to the chilled water (glycol) system
• Warm glycol solution, circulating through the
coil, is cooled indirectly by the melting ice
ICE ICE ON COIL
WARM GLYCOL IN COLD GLYCOL OUT WARM GLYCOL MELTING OCCURS FROM INSIDE Indirect 37
Ice Storage System Design Ice Storage System Design
Internal Melt (Indirect Contact) Internal Melt (Indirect Contact)
Internal Melt Ice Coils Internal Melt Ice Coils
Discharge Temperature Profile Discharge Temperature Profile
0 1 2 3 4 5 6
0 20 40 60 80 100
Ice W ate r Sup pl y T em p. ( °C)
% Ice Depleted
Internal Melt Ice Coils Internal Melt Ice Coils
Discharge Temperature Profile Discharge Temperature Profile
0 1 2 3 4 5 6
0 20 40 60 80 100
Ice W ate r Sup pl y T em p. ( °C)
% Ice Depleted
Internal Melt Ice Coils Internal Melt Ice Coils
Discharge Temperature Profile Discharge Temperature Profile
0 1 2 3 4 5 6
0 20 40 60 80 100
Ice W ate r Sup pl y T em p. ( °C)
% Ice Depleted
41 Note: 6 Hour constant discharge; 25 mm nominal ice thickness
Internal Melt Ice Coils Internal Melt Ice Coils
Discharge Temperature Profile Discharge Temperature Profile
0 1 2 3 4 5 6
0 20 40 60 80 100
Ice W ate r Sup pl y T em p. ( °C)
% Ice Depleted
Without Air Agitation
Internal Melt System Schematic Internal Melt System Schematic
Internal Melt System Schematic Internal Melt System Schematic
Ice Storage System Design Ice Storage System Design Internal Melt
Internal Melt
Advantages
• Simple to design and operate
– simple controls for various operating modes
– closed, pressurized loop
• Stable, cold discharge temperatures
– 36°F to 38°F typical
Ice Storage System Design Ice Storage System Design Internal Melt
Internal Melt
Disadvantages
• Heat exchanger required to eliminate glycol from chilled water loop
• Not able to discharge as quickly as direct contact cooling
Ice Storage System Design Ice Storage System Design Ice on Coil
Ice on Coil -- External MeltExternal Melt
• Ice water is circulated through the ice
storage tank to the chilled water system
• Warm return water, circulating through the
tank, is cooled via direct contact with the ice
WARM WATER
Direct
ICE ICE ON COIL
REFRIGERANT OR GLYCOL MELTING OCCURS FROM OUTSIDE WATER IN WATER OUT AIR AIR 47
Ice Storage System Design Ice Storage System Design
External Melt (Direct Contact) External Melt (Direct Contact)
External Melt Ice Coils External Melt Ice Coils
Discharge Temperature Profile Discharge Temperature Profile
0 1 2 3 4 5 6
0 20 40 60 80 100
Ice W ate r Sup pl y T em p. ( °C)
% Ice Depleted
10 Hour 2 Hour 1 Hour
External Melt System Schematic External Melt System Schematic
External Melt System Schematic External Melt System Schematic
Ice Storage System Design Ice Storage System Design External Melt
External Melt
Advantages
• Lowest chilled water supply temperatures
• Quickest discharge capability
Ice Storage System Design Ice Storage System Design External Melt
External Melt
Disadvantages
• Chiller with lower temperature capability generally used
• Glycol control valves required on multi-coil systems
• Heat exchanger may be required to manage static head of open system
Ice Storage System Design Ice Storage System Design
External Melt vs. Internal Melt External Melt vs. Internal Melt
External Melt
• Project requires a
constant, cold supply water temperature of 1°C or
quick discharge periods
• Trained operating staff
available
• Large savings in
distribution piping system
• Highest energy efficiency
Internal Melt
• Project does not require
coldest possible supply temperature
• Simpler design and
operation
• Individual buildings
• Energy efficiency is less
critical (extra heat transfer step required)
Ice Storage System Design Ice Storage System Design
External Melt vs. Internal Melt External Melt vs. Internal Melt
• Most air conditioning applications use internal melt
• Most process and district cooling systems use external melt
Specialists in Heat Transfer Products and Services Specialists in Heat Transfer Products and Services
Ice Storage System
Ice Storage System
Coil Design
Coil Design
Ice Storage Coil Design Ice Storage Coil Design
• Countercurrent flow in adjacent circuits
– Less wasted space
– Better ice packing factor (IPF)
Ice Storage Coil Design Ice Storage Coil Design
Counterflow Headers and Circuits Counterflow Headers and Circuits
Ice Storage Coil Design Ice Storage Coil Design
3.65”
0.85 1.4”
1.4”
3.85”
0.85 1.5”
1.5”
Others Evapco
3.85”
1.4”
Extra
Extra--Pak® Ice Coils Pak® Ice Coils –– Elliptical TubesElliptical Tubes
Less Wasted Space
Others Evapco
Ice Storage Coil Design Ice Storage Coil Design
• Discharge method (internal or external)
• Ice thickness
– Ice build performance
– Ice melt performance
• Quantity of circuits and rows (passes)
• Length of coil/circuit
Ice Storage Coil Design Ice Storage Coil Design
Internal Melt External Melt
Ice Storage Coil Design Ice Storage Coil Design
Custom Ice Coil Configurations Custom Ice Coil Configurations
Glycol Temperature vs. Build Time Glycol Temperature vs. Build Time
-10 -9 -8 -7 -6 -5 -4 -3 -2
0 2 4 6 8 10 12
Time (Hours) G ly co l Su p p ly T em p er atu re (° F )
“Thin” Design for Centrifugal Chillers
“Thick” Design for Screw Chillers
Specialists in Heat Transfer Products and Services Specialists in Heat Transfer Products and Services
Ice Storage
Ice Storage
Products and Installations
Products and Installations
Ice Storage Product Offering Ice Storage Product Offering
– Ice coils internal or external melt
– Ice inventory controls
– Ice thickness controls
– Air blowers
Ice Storage Applications Ice Storage Applications
• Commercial A/C and industrial
• District cooling
– Colleges and universities
– Corporate campuses
– Hospitals
– Convention centers
– Sports arenas
Key Evapco Ice Coil Installations Key Evapco Ice Coil Installations
Project Location Ton-Hours
King Abdul Aziz University, Phase 1&2 Jeddah, Saudi Arabia 84,600 Entergy New Orleans District Cooling New Orleans, Lousiana, USA 52,800 Entergy Houston District Cooling, Phase 2 Houston, Texas, USA 44,000 NATO Command and Control Center Naples, Italy 34,120 Solaris Dutamas, Phases 1 & 2 Kuala Lumpur, Malaysia 34,000 New Pearl River District Cooling, Phase 1 Guangzhou, China 28,728 Hainan Sanya Ice District Cooling Hainan, China 25,536 Moab Khotsong Gold Mine Vaal Reefs, South Africa 24,136 Mponeng Gold Mine Carletonville, South Africa 19,800 Singapore Disrict Cooling DCP1, Phase 2 Singapore 18,326 Leipzig Exhibition Centre Leipzig, Germany 15,350
Specialists in Heat Transfer Products and Services Specialists in Heat Transfer Products and Services
• Plant constructed in 1998
• Expanded in 2008
• 88,000 kWr peak capacity
• 310,000 kWr-Hr ice storage
• Four (4) tanks
• 1.1°C chilled water supply
Entergy Solutions
Entergy Solutions – Houston
Entergy Houston 2008 Capacity Upgrade
Entergy Houston 2008 Capacity Upgrade
Specialists in Heat Transfer Products and Services Specialists in Heat Transfer Products and Services
