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Water-cooled, Central Chilled Water Plants
Save energy & operational cost – Payback 1 to 4 years – Performance Guaranteed
Demand Flow® Concept
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Agenda
• Building Life Cycle
• Market Driving Factors
• Overview of Chilled Water System Optimization
• Overview of Demand Flow Concept
• Statistical Model
• Case Studies
• Discussion
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Buildings are a key factor for the environment,
climate and energy worldwide ...
28%Mobility
31%Industry
59%other
Buildings account for 41%
of the global energy demand.
41%Buildings
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• Energy typically one of the highest operating costs
• Rising prices can have tremendous impact on bottom line
• Impacts core business as budget/investments are prioritized
Building Lifecycle Costs
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Market Driving Factors –
Chilled Water System Optimization
• Volatile energy prices and rising demand
• Legislative landscape that requires action
• Concerns for occupant comfort and safety
• Growing interest in sustainability issues
Global Factors
• Pressure to lower operating costs
• Reducing hot calls and improve comfort
• Increased system reliability
• Staffing pressures
• Need for simpler system operation
Internal Factors
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Overview: Why Chiller Plant Optimization?
Source: "All Variable Speed Chiller Plants", ASHRAE Journal, September 2001
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3
Standard Code Based
Chiller Plants
New Technology,
All-Available Speed
Chiller Plants
High-Efficiency,
Optimized
Chiller Plants
Older
Chiller
Plants
Chiller Plants with Repairable Design or Operational Problems
Excellent Good Fair Needs Improvement
Pre-Optimization(Annual Average typically
> 0.8 kW/Ton)
Post-Optimization(Annual Average can range from 0.5 – 0.75
kW/Ton)
kW/ton *
(Annual Average)
* Includes Chiller, Pumps and
CT Fans Combined
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Pre
1000T peak chiller
plant at 1.1
kW/Ton
Source: "All Variable Speed Chiller Plants", ASHRAE Journal, September 2001
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3
Standard Code Based
Chiller Plants
New Technology,
All-Available Speed
Chiller Plants
High-Efficiency,
Optimized
Chiller Plants
Older
Chiller
Plants
Chiller Plants with Repairable Design or Operational
Problems
Excellent Good Fair Needs Improvement
Pre-Optimization(Annual Average typically
> 0.8 kW/Ton)
Post-Optimization(Annual Average can range from 0.5 – 0.75
kW/Ton)
kW/ton *
(Annual Average)
* Includes Chiller, Pumps
and CT Fans Combined
Pre
3300T peak chiller
plant at 0.96 kW/Ton
Post
3300T peak chiller plant
optimized to 0.7 kW/Ton
Estimated Savings**
~ AED1,000,000/yr**Assumptions: AED 0.45/kWh, Dubai Conditions
Overview: Why Chiller Plant Optimization?
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80ºF 90ºF
Cooling Towers
Sump
Condenser Water Loop(Constant Volume)Condenser
Water Pumps17,678 GPM
67ºF73ºF
ΔT=6ºF
ΔT=10ºF
Chillers
Primary Chilled Water Loop(Constant Volume)Primary Pumps
10,608 GPM
43ºF58ºF
ΔT=8ºF
44ºF ΔT=14ºF51ºF
Bypass
Secondary Chilled Water Loop(Variable Volume) Secondary Pumps
9,000 GPM
AHUs
Every 1ºF reduction ≈ 1% increase incompressor efficiency
58ºF 44ºF Fundamental energy consuming sub-systems that influence
deliverable capacity:
1. Chillers
2. Chilled Water Pumping
3. Condenser Water Pumping
4. Cooling Tower Fans
5. Air Side
These 5 subsystems are interdependent
• Energy and deliverable capacity are interdependent
• Often "conservation methods" reduce deliverable capacity
• Often energy conservation methods result in a "transfer of energy"
among the 5 subsystems
• Most chilled water systems are plagued with "Low Delta-T Syndrome“
• Comfort is often sacrificed to obtain efficiency.
• Continuous full speed operation of some plant equipment resulting in
decreased equipment life
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Out-dated Methods of Optimization
• Reset chilled water temperature up
• Chillers sequenced via a database of load profiles
• Attempts to find a “sweet spot”
• Only focuses on optimizing the chiller
Demand Flow Holistic Optimization Solution
• Widens “sweet spot” = increased efficiency throughout the entire
tonnage range
• Increased deliverable tonnage leads to more redundancy
• Fewer start/stops = less wear & tear
• Building load defines system pressure set points
• Focus on optimizing the Whole System
% Load
KW/T
on
Sweet Spot = Lowest kW/Ton
Traditional Optimization method vs. Demand Flow Strategies
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Effects of Chilled Water Reset on Total System Energy - Raising Chiller Water Temp
Cooling Towers
kW
Chillers
CHW Pump
CW Pump
AHU Fan
Total System
KW
Up to 10%
increase
in total
system
energy
use
Typical Results:
Warmer CHW increases CHW Pumping Energy and AHU Fan Energy in
VAV systems
Compromised occupant comfort
Decreased humidity control
Typical "Non-Demand Flow" Chiller Plant optimization Project
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Demand Flow Optimization Project
kW Total System
kW
Up to 50%
Reduction
Up to 10%
Increase
Cooling Towers
Chillers
CHW Pump
CW Pump
AHU Fan
Net Energy Effect of Demand Flow
Reduced energy consumption and greater performance
(Up to 50% reduction of total kW)
Extended equipment life
Simplified system operation
Improved indoor environmental quality
1-4 year Simple Paybacks, 25%+ IRR
Primary Benefits
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The Demand Flow® Concept - What’s Different
• VFDs installed on all Chilled Water and Condenser Water Pumps and
Cooling Tower Fans
• Water Flow Varies thru Chiller Evaporator and Condenser
• Virtually no Chilled Water/Condenser Water bypass
• Optimize Pressure and Temperature set-points based on system dynamics
• VFDs are not required on the Chillers
• Pre and Post Measurement and Verification
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The Demand Flow® Concept - System Effects
• Increases system deliverable tonnage (where low Delta-T is present)
• Manages chiller "Lift", effectively eliminates refrigerant flow issues at low
load conditions
• Stable Chiller Refrigerant loop performance at virtually all tonnage loads.
• Typically up to 50% total Chilled Water System energy savings with 1-4
year simple payback.
• Reduced run-time = less maintenance
• Improved indoor environmental quality - Occupant comfort is not sacrificed
to provide energy savings
Demand Flow results in significant energy savings and improved comfort
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Statistical Energy Modeling
Typical base-line energy consumption vs. optimized energy consumption
As Built KW
Demand Flow KW
DF and Replacement Chiller KW
Poly. (As Built KW)
Poly. (Demand Flow KW)
Poly. (DF and Replacement
Chiller KW)
Annual KW Profile
0
200
400
600
800
1000
1200
1400
1600
1800
0 30 60 90 120 150 180 210 240 270 300 330 360
Day of Year
KW
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Page 15
Case Studies in Dubai
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DAFZ Main Plant performance
• The project includes 12 office buildings, HQ
Building and Chiller Yard
• Plant Size – 11,000TR (6 nos. Water Cooled
Chillers)
• Average annual plant efficiency before Demand Flow implementation was
1.06 KW/Ton
• Average Plant efficiency for period June 14 - Mar 16 was 0.721 KW/Ton
• This has resulted in more than 30.0% savings for the period
• The actual project payback period was less than 1 year
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WAFI DCCP 1 Plant performance
• The project includes a Shopping Mall, Residences ,
5 Star Hotel, Souq and Health/Leisure facilities
• Plant Size – 6075TR (3 nos. Water Cooled Chillers)
• Average annual plant efficiency before Demand Flow implementation was
1.055 KW/Ton
• Average Plant efficiency for period July 14 - July 16 was 0.63 KW/Ton
• This has resulted in more than 40.0% savings for the period
• The actual project payback period was less than 1 year
Thank you for your
attention!
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