Efficiency Through Operational Truths

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


• 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

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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

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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


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


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

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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

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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



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

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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)

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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


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


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


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

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Demand Flow

Hospital Case Study – Initial condition

Page 16

Secondary Chilled Water Pump

Condenser water pumps and chillers

Cooling Towers

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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


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.

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Demand Flow

Hospital Case Study – Solution Implementation

Page 19

New Differential pressure sensors

VFDs at the Secondary Water Pumps

New high accuracy temperature sensors

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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

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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

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Demand Flow

Hospital Case Study - Results

Page 22

Base line

efficiency

COP of 3.1

Commissioning

efficiency

COP of 5.4

Siemens S.A


Goncalo Neves

Sr. Energy Engineer

Global Energy Project Development Team

Siemens Building Technologies Division

Mobile: +351 91 000-5851

E-mail: [email protected]

Questions?

mailto:[email protected]

Documents

Efficiency Through Operational Truths