Siemens Demand FlowTM
A unique energy and operational cost savings application for watercooled, central chilled water plants
by
Arvind Rotiwar
Siemens LLC
arvind.rotiwar@siemens.com
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HVAC products from Siemens –
a unique portfolio in width, depth, and quality
Building automation systems
Sensors
Standard systems/controllers
Valves and actuators
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Building control
Damper actuators
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Room thermostats
Variable speed drives
Heat /Cool meters
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Desigo –
our offering for building automation and control
ƒ Reduced energy costs – thanks to intelligent energy
management, innovative energy saving and monitoring
functions as well as effective processes
ƒ Long-term investment protection – as a result of
open communication and simple expandability
ƒ Flexible system design – for every building thanks
to a modular product range
ƒ Optimum comfort regarding living, working, and userfriendliness – thanks to easy handling
ƒ Reliability of a proven system – with a wide installed base
ƒ Worldwide support – over the entire life cycle
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The Demand FlowTM Solution
Demand FlowTM is a unique energy optimization application for water-cooled central chiller
plants.
The solution automatically controls and sequences the operation of an entire chilled water
plant. In particular, Demand Flow optimizes temperature set points for chilled water and
condenser water, while controlling pump and fan speeds to maintain the proper energy
balance.
Demand Flow – exclusively offered by Siemens – is a comprehensive energy management
system that reduces the electricity use in the most energy-intensive component of most
facilities.
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Central Chilled Water Plants
Chilled Water Plant Characteristics
ƒ Most chilled water plants have some form of constant flow pumping
ƒ Most plants bypass chilled water flow – excessive pumping energy
ƒ Operate best with wide temperature splits across the chiller – at or near original design intent
(known as "delta-T")
ƒ Usually operate at design intent conditions only 5% of the time
Chilled Water Plant Operational Shortcomings
ƒ Most plants today are plagued with "Low Delta-T Syndrome"
ƒ Inefficiently operated 95% of the time due to design
ƒ The Industry has tried to solve these issues with limited success
ƒ Often plant efficiency is sacrificed for comfort
ƒ Nominal plant capacity is usually never realized – causing perceived need for additional chillers
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Central Chiller Plant Energy Use
5 fundamental subsystems of a chilled water system that consumes energy and
influences deliverable capacity;
ƒ Chilled Water Pumping
ƒ Condenser Water Pumping
ƒ Chillers
ƒ Cooling Tower Fans
ƒ Air Side
These 5 subsystems are interdependent
ƒ Energy and deliverable capacity are interdependent
ƒ Often "conservation methods" reduce deliverable system capacity
ƒ Often what is done in the name of energy conservation results is a "transfer of energy" among these
5 subsystems with no net savings realized, or increase in energy
As the Solutions Provider, Siemens understands these technical relationships,
delivering a "holistic" approach to Chiller Plant Optimization
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The Demand FlowTM Solution
AHUs
What's Different?
Secondary Pumps
ƒ Effectively establishes only One Chilled Water Loop, virtually
no bypass water
ƒ Water Flow Varies thru Chiller Evaporator and Condenser
ƒ VFDs are installed on all CHW & CW Pumps and on all Cooling
Tower Fans
ƒ VFDs are not required on the Chillers
ƒ Optimize Pressure and Temperature set-points on Chilled and
Condenser Water systems based on current system dynamics
Effects
Bypass
Primary Chilled Water Loop
(Constant Volume)
Chillers
Condenser Water Loop
(Constant Volume)
Cooling Towers
Sub Cooling
ƒ Increases system deliverable tonnage
ƒ Manages chiller "lift", effectively eliminates refrigerant flow
issues at low load conditions
ƒ Stable Chiller Refrigerant loop performance at virtually all
tonnage loads
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Sump
Demand FlowTM System Effects
System Energy Shifts
ƒ CHW Pumping Energy is Reduced
ƒ CW Pumping Energy Reduced
ƒ Chiller KW/Ton Reduced
ƒ Airside Fan savings possible (VAV Systems)
ƒ Net Cooling Tower Fan Energy Optimized
ƒ Net Plant Energy Consumption Reduced
ƒ Dramatic energy savings in most cases
System Capacity Shifts
ƒ Increased Chiller Plant Deliverable Cooling Capacity (not nominal & where low Delta T is present)
ƒ All pumping and tower fan subsystems are sub metered through the KW Outputs on the VFDs
ƒ Chillers are sub metered by Digital Energy Monitors (DEM) to measure their performance
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How do we control?
Demand Flow Variable Pressure Curve Logic (VPCL)
ƒ A majority of the industry controls to a constant pressure
ƒ A majority of systems have some component of constant speed pumping
ƒ Demand Flow uses variable speed pumping on both chilled and condenser water flow
ƒ Demand Flow resets systems pressure based on load
Calculated “Dynamic” Variable System Pressure Curve
ƒ Siemens Demand Flow Desigo Panel calculates the optimal variable system pressure curve
ƒ Demand Flow resets system pressure as pump speed varies along this variable system pressure
curve
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Constant Speed Pumping
Feet of Head
Pump Curve – Constant Speed
24
22
20
18
16
14
12
10
8
6
4
2
0
Design Point
0 20 40 60 80 100 120 140 160 180 200 © 2011 Siemens Industry, Inc. All rights reserved.
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GPM
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Constant Pressure Pumping
Feet of Head
Variable speed pump curves
24
22
20
18
16
14
12
10
8
6
4
2
0
Constant Pressure*
Operating points
60Hz
50Hz
40Hz
GPM
0 20 40 60 80 100 120 140 160 180 200 *requires VFD on Pump
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Variable Pressure Pumping
Feet of Head
24
22
20
18
16
14
12
10
8
6
4
2
0
Variable speed pump curves
Calculated
Dynamic Variable System Pressure Curve
Operating points
GPM
0 20 40 60 80 100 120 140 160 180 200 © 2011 Siemens Industry, Inc. All rights reserved.
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Energy Management Methodology
The Demand FlowTM process begins with our team of expert engineers evaluating the chiller plant
energy usage over a 12 month period. This allows us to identify the energy trends and key inefficiencies
in the existing system.
After initial identification, our energy engineers conduct a detailed analysis and evaluate the saving
potentials to be realized by Demand Flow. These savings can even be guaranteed if requested by the
customer.
Once the savings are calculated and presented to the client, the implementation process begins. The
energy savings are then verified through a customized measurement and verification plan.
2008-04-01
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Statistical Energy Modeling
Our holistic analysis utilizes 12 months of customer historical chiller logs to develop baseline energy consumption vs. optimized energy consumption via Demand FlowTM
Annual KW Profile
1800
KW
1600
1400
As Built KW
1200
Demand Flow KW
1000
DF & Replacement Chiller KW
800
Poly. (As Built KW)
600
Poly. (Demand Flow KW)
400
Poly. (DF & Replacement
Chiller KW)
200
0
0
30
60
90
120
150
180
210
240
270
300
330
360
Day of Year
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EMC
Energy Monitoring and Reporting Solution
EMC is Web-Based Sub-Metering and
Reporting
ƒ EMC is an M&V application for Demand Flow
ƒ Critical DF Points are sub-metered
ƒ Trended data is viewable via the internet on the
EMC web-based tool
ƒ One way transmission of data to EMC server
ƒ Performance indicators will be measured and
reported electronically on a monthly basis
ƒ Basic reporting is average KW/Ton performance
ƒ Advanced reporting and solutions can be
customized for more in-depth analysis
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Benefits of Demand FlowTM
ƒ
Increases the deliverable tonnage of the chilled water plant
ƒ
Simplifies plant operations without sacrificing comfort
ƒ
Allows plant to more accurately maintain optimal differential system pressure
ƒ
Entire system saves energy
ƒ
Specialized control algorithms
ƒ
No costly variable frequency drives on chiller compressor motors
ƒ
Automatically optimizes all functions
ƒ
Control from anywhere via Internet
ƒ
Chiller agnostic; i.e. not specific to any chiller manufacturer
ƒ
Can be implemented without voiding equipment warranties
ƒ
Integration of all commercially available controls and building management systems
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Demand Flow
Case Studies – Financial Performance
Project
Financial Impact
1
Beau Rivage
Casino
ƒ Average annual energy savings of $300,000
ƒ One year return on capital investment
2
L’auberge du lac
Casino
ƒ Average annual energy savings in excess of $300,000
ƒ Completed 160,000 SF expansion without any additions to central plant
3
Ochsner Main
Hospital
ƒ Annual savings of $1,033,000
ƒ Reduction of 20,000,000 pounds of CO2/year
ƒ 36% reduction in annual electricity usage
4
Ochsner Baptist
Hospital
ƒ 50% reduction in annual energy consumption
ƒ Annual savings of $
5
VA Gulf Coast
Veterans HCS
ƒ Annual energy savings of $135,000
ƒ Chiller efficiency improved from 1.2 kW/ton to 0.71 kW/ton
6
VA Museum of
Fine Arts
ƒ $250,000 annual energy cost reduction
ƒ Meets VA governor’s executive order of 20% reduction in enrgy usage
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Demand Flow
Case Studies – Financial Performance
Project
Financial Impact
7
Aquarium of the
Pacific
ƒ Electricity usage reduced by 51% (2.1 million kWh to 1.0 million kWh)
ƒ First year savings of $168,000
ƒ $114,000 additional rebate from the local utility
8
Point Loma
Nazarene Univ.
ƒ Chilled water plant electricity consumption reduced by 42%
ƒ Chiller plant efficiency improved from 1.4 kW/ton to .47 kW per ton
ƒ Energy costs reduced by $97,000 per year
9
IBM Research
Triangle Park
ƒ Annual savings of $250,000
ƒ $230,000 additional rebate from local utility
ƒ 27% reduction in annual electricity usage
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Demand FlowTM Implementation
Process
Site Visit / Plant
Data Collection
PDA Process
"Snap Shot" – Quick
Prequalification Analysis
No Savings
Customer
Meeting
1) Develop Scope and Cost Proposal.
2) Firm up Savings analysis
If appreciable
energy savings
Present Turn Key Proposal with
Payback Analysis
Site visit / obtain copies of 12
month Chiller Log Data
End
"Chalk Talk" – Annual
Savings Analysis
No Savings
End
© 2011 Siemens Industry, Inc. All rights reserved.
Customer
Meeting
Enter into
Construction Agreement
If appreciable
annual savings
Project Implementation and System
Commissioning
Enter into Project
Development
Agreement (PDA)
Begin Savings M&V Reporting
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New Construction vs. Retrofit
What is Different?
Retrofit
New Construction
•
Can show energy savings against
current operating baseline
•
Can calculate annual average efficiency
target from design information
•
Limited by existing mechanical system
•
Opportunity to possibly influence
Direct sale to owner
– Benefits from energy savings
– Simplicity of operation
•
•
Demand Flow brings accountability to plant
performance before it’s built
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mechanical design to complement DF
Dual benefits to owner and consulting
engineer
– Energy savings
– Colder water
– Less first costs
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24
Demand Flow in New Construction
Siemens Chalk Talk Energy Model
ƒ Load Calculations
ƒ Equipment Selections
ƒ Calculate energy efficiency target (Average Annual KW/Ton)
ƒ Compare Chalk Talk target to consultants model (Trane Trace, Equest, etc.)
Demand Flow Benefits for New Construction
ƒ Colder water year-round (X < 40°)
ƒ Stipulated or guaranteed Annual Average Efficiency
ƒ Possible lower first costs of construction
ƒ Proven offering
ƒ Simplicity of Operation
Demand Flow Differentiates the Design
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25
Questions?
Demand FlowTM
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