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Building Performance and SustainabilitySiemens S.A
Building Technologies
Demand FlowTM Case Study
Efficiency Through Operational Truths
18.as Jornadas de Climatização, October, Portugal
Reabilitação Energética de Edifícios em Cenários de Alterações Climáticas
Siemens S.A
Building Technologies
• Demand Flow Essentials – Introduction 3
• Demand Flow Essentials - Typical Chiller Plant Design 5
• Demand Flow Essentials - So, what is Demand Flow? 6
• Demand Flow Essentials - Refrigeration Cycle – Demand Flow 7
• Demand Flow Essentials - Variable Pressure Curve Logic (VPCL 9
• Demand Flow - Time Line Example 10
• Demand Flow - Financial Analysis 12
• Demand Flow - Global projects 13
• Demand Flow - Siemens Desigo CC Dashboard 14
• Demand Flow - Hospital Case Study 15
Demand Flow
Table of content
Page 2
Siemens S.A
Building Technologies
The open building management platform is designed
to create comfortable, safe and efficient
facilities for today and the future
Visualize and manage all
rooms from one location and
control all disciplines
Check performance, increase
transparency and make system
changes easily, even at field level
Desigo CC – the open building management platform – designed
to meet your needs today and in the future
Page 3
Siemens S.A
Building Technologies
Demand Flow Essentials
Introduction
Page 4
Siemens Demand Flow (DF) is a unique and proven energy and operational cost saving
application for water-cooled centrifugal or screw type chillers.
DF provides typically 20-50% energy savings with a simple payback from 1 to 4 years with a
IRR of 25% but also provides operational savings related to reduce equipment runtime and
increases system deliverable capacity on systems without sacrificing comfort or production for
energy savings.
Demand Flow Solution holistically manages your chiller plant with specialized variable
pressure control algorithms.
These algorithms require the conversion of constant speed condenser pumps, chilled water
pumps, and cooling tower fans to variable speed.
Siemens S.A
Building Technologies
These 5 subsystems are interdependent:
– Energy and deliverable capacity depend on each other
– Often "conservation methods" reduce deliverable system capacity
– 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
Demand Flow Essentials
Introduction
Page 5
The deliverable capacity of a chiller plant is influenced by 5
fundamental subsystems that consumes energy:
1. Chilled Water Pumping
2. Condenser Water Pumping
3. Chillers
4. Cooling Tower Fans
5. Air Side
Siemens understands these technical relationships, delivering a "holistic" approach to Chilled Water Plant operation
Example of a Chiller Plant
Siemens S.A
Building Technologies
Demand Flow Essentials
Typical Chiller Plant Design
Page 6
Typical Design of a chiller plant:
– Constant Volume Primary Loop
– Constant Volume Condenser Water Loop
– Variable Flow Secondary Loop
– Constant System pressure maintained by a physical bypass
sometimes includes modulating valve to maintain system diff.
Pressure
– Many AHU’s have 3W Valves used to control AHU discharge air
temperature. This is another form of bypass
Chillers
Bypass
AHUs
100 m3/h
Pump w/VFD
200 m3/h
Constant Volume
Pump
11 ºC
100m3/h
Thru bypass7ºC9.5 ºC
23ºC 20ºC
300 m3/h
Constant Volume
Pump
Primary Loop
Secondary
Loop
Condenser
Water Loop
Cooling Towers
Every 0.6ºC reduction ≈ 1%
increase in compressor
efficiency
7ºC
Demand Flow:
– All system pumps will be paired with a VFD
– Eliminates all Chilled water bypass thereby reducing pumping energy
and wasted chiller energy
– The entire plant is essentially run and controlled as one Primary loop
– Flow and Head pressure requirements are monitored and controlled
accordingly
Siemens S.A
Building Technologies
Demand Flow Essentials
So, what is Demand Flow?
Page 7
Demand Flow for Chilled Water:
– Provides a method and equipment for highly efficient operation
of chilled water plants. Okay, but how?
– Controls pumping of chilled water and condenser water to:
Reduce or eliminate the Low Delta T Syndrome;
Reduce energy utilization;
Managing the compressor lift;
Allow a chilled water plant to meet cooling demand
Siemens Motor
Siemens Motors and VFDs
Siemens S.A
Building Technologies
Demand Flow Essentials
Refrigeration Cycle
Page 8
Saturated Condenser
Temperature / Pressure E DA
B
Saturated Evaporator
Temperature / Pressure
Mixed
Region
Sub-Cooled
RegionSuper Heat Region
Condenser
Superheat
Useful Refrigerant Effect
Enthalpy
(kJ/kg)
Pressure
(bar)
Lift
C
Heat of
Compression
Chiller Capacity (W):
Q = m (hC-hB)
Refrigerant circulated (kg/s)
m = Q / (hC-hB)
Compressor Energy (W)
W = m (hD − hC)
Chiller Efficiency:
COP = Q / W
Siemens S.A
Building Technologies
Demand Flow Essentials
Refrigeration Cycle – Demand Flow
Page 9
Saturated Condenser
Temperature / Pressure E DA
B
Saturated Evaporator
Temperature / Pressure
Mixed
Region
Sub-Cooled
RegionSuper Heat Region
Condenser
Superheat
Useful Refrigerant Effect
(expanded)
C
Pressure
(bar)
Enthalpy
(kJ/kg)
Chiller Capacity (W):
Q = m (hC - hB)
Refrigerant circulated (kg/s)
m = Q / (hC - hB)
Compressor energy (W)
W = m (hD’ − hC)
Chiller Efficiency:
COP = Q / W
2
2
1
4 3
Reduce water flow to
reduce low delta t
syndrome
5
4
Less Refrigerant
circulated and colder
water to the condenser
less compressor work
Same produced capacity
less compressor work
better efficiency
D’A’
Reducing or eliminating the
Low Delta T Syndrome
Colder water to
the condenser
Lift
(Reduced)
Siemens S.A
Building Technologies
Demand Flow Essentials
Variable Pressure Curve Logic (VPCL)
Page 10
Operating
Points
kpa
179
165
152
138
124
110
97
83
69
55
41
28
14
m³/h0 45 91 136 182 227 273 318 363 409 454
Design
“Constant Pressure”
50Hz
40Hz
30Hz
20H
Variable speed pump curves
Demand Flow
Continuously resets system differential pressure along
calculated curve and takes advantage of:
- The energy savings of flow reduction;
- System head pressure reduction;
By using:
-Control algorithms;
- VFD’s;
- Siemens Automated building control systems.
Calculated Dynamic Variable
System Pressure Curve
Siemens S.A
Building Technologies
Demand Flow
Time Line Example
Month
9
Month
8
Month
7
Month
6
Month
5
Month
4
Month
3
Month
2
Month
1
Phase 2• Site visit
• Obtain copies of
12 month Chiller
Log Data
•"Chalk Talk”
•Annual
Savings Analysis
2 months
Month
11
Month
10
Phase 3Enter into Project Development
Agreement (PDA)
1) Develop Scope and Cost Proposal.
2) Firm up Savings analysis
3 months
Phase 1• Site Visit
• Plant Data Collection
•"Snap Shot”
•Quick Prequalification
Analysis
Month
12
Project Award
-Project Starts
Material
Ordering
2 months
Project
Implementation
3 months
Month
13
Month
14
Month
15
Month
16
2 months
T&C
Month
17
Month
18
M&V
X Years
Page 11
Siemens S.A
Building Technologies
Demand Flow Financial Analysis
What Can You Expect
Page 12
YearDF Savings
(€)
Project
Cost (€)
Incentives
Received (€)
Service
(€)
Annual
Cash Flow (€)
Cumulative
Cash Flow (€)
0
1
2
3
4
5
6
7
8
9
10
Break-even
point
Typical Sell Price: € 300k
Typical Savings: €100k/yr
Service: € 15k/yr
CPI: 2% escalation
-300,000
+100,000 -300,000 -15,000 -215,000
+102,000 - -15,300 +86,700 -128,300
+104,040 - -15,606 +88,434 -39,866
+106,121 - -15,918 +90,203 50,337
108,243 - 16,236 +92,007 142,343
110,408 - 16,561 +93,847 236,190
112,616 - 16,892 +95,638 331,914
114,869 - 17,230 +97,638 429,552
117,166 - 17,575 +99,591
119,509 - 17,926 +101,583
529,143
630,726
Total Cost: € 300,000
IRR: 27.2%
Total Benefit: € 630,726
ROI: 210.2%
3.4 Year
Payback
0 +85,000
Important Note:
This example is
based in a turnkey
solution of Demand
Flow project, i.e. this
sell price of €300k
includes the entire
tasks of Demand Flow
scope of work.
Example: Avg
6,300 kW Plant
Capacity
A Demand Flow project have a
typical observed* Payback less
than 4 years
*Observed in more than 450 Demand Flow Projects
Siemens S.A
Building Technologies
Demand Flow
Global projects
Page 13
Siemens S.A
Building TechnologiesPage 14
Demand Flow
Siemens Desigo CC Engineer Dashboard
Siemens S.A
Building TechnologiesPage 15
Demand Flow
Siemens Desigo CC Operators Dashboard
Siemens S.A
Building Technologies
Demand Flow
Hospital Case Study – Initial condition
Page 16
Secondary Chilled Water Pump
Condenser water pumps and chillers
Cooling Towers
Siemens S.A
Building Technologies
Demand Flow
Hospital Case Study – Scope of Work
Page 17
Task ID Task Description
1 Close system bypass(s)
2 Install VFD’S on all chilled water pumps, all condenser water pumps and all cooling tower fans
3 Install kW monitoring devices
4 Install one flow meter in the CHWR or CHWS line at the best location
5 Install in the chilled water, condenser water and bypass line high accuracy temperature sensors
6 Install in the chilled water, condenser water barrels (evap and cond) high accuracy DP sensors
7 Install a high accuracy OSA temperature/humidity sensor (close to the cooling towers)
8 Check all air side coils / AHU’S and clean if necessary
9 Install a chiller interface
10 Demand Flow (CHW) Sequence of Operation to control the plant
Siemens S.A
Building Technologies
Demand Flow
Sensor Standards
Page 182/3
In some key measuring location DF uses
high accuracy sensors.
• For temperature, Sitrans TS500 (Display for
the chiller sensors, 0.025% of spam);
• For DP, Sitrans P410 with Manifold (0.065% of
spam.
Siemens S.A
Building Technologies
Demand Flow
Hospital Case Study – Solution Implementation
Page 19
New Differential pressure sensors
VFDs at the Secondary Water Pumps
New high accuracy temperature sensors
Siemens S.A
Building Technologies
Demand Flow
Hospital Case Study – Commissioning
Demand Flow – Startup:
• Industry standard Logic statements develop locally;
• System Specialist develops Xworks locally;
• Pre Commissioning Checklist by branch team:
− All points are installed and tested end to end;
− Loops are tuned (AHU) and proven by dynamic trend viewer;
− DF Graphics are in place;
CoE Commissioning:
− Live commissioning, usually no shut down necessary;
− By subsystem; SCHWP, CHWP, CH, CWP, CT;
− Full plant test; shut down and restart if possible.
Page 20
Demand Flow site Commissioning
21/21
Siemens S.A
Building Technologies
Demand Flow
Hospital Case Study - Results
Page 21
1 kW/ton = 3.516/COP
Chiller Plant Efficiency
5.37 COP
Chiller Efficiency
6.35 COP
Siemens S.A
Building Technologies
Demand Flow
Hospital Case Study - Results
Page 22
Base line
efficiency
COP of 3.1
Commissioning
efficiency
COP of 5.4
Siemens S.A
Building Technologies
Goncalo Neves
Sr. Energy Engineer
Global Energy Project Development Team
Siemens Building Technologies Division
Mobile: +351 91 000-5851
E-mail: [email protected]
Questions?