The cost of using 1970 s era design concepts and fear in chilled water systems
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The Cost of Using 1970’s Era Design Concepts and “FEAR”in Chilled Water Systems. Presented By : Hemant Mehta, P.E. WM Group Engineers, P.C. What is the “FEAR”. No change in design as previous design had no complains from client No complain because no bench mark exists

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The Cost of Using 1970’s Era Design Concepts and “FEAR”in Chilled Water Systems

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The cost of using 1970 s era design concepts and fear in chilled water systems

The Cost of Using 1970’s Era

Design Concepts and “FEAR”in

Chilled Water Systems

Presented By: Hemant Mehta, P.E.

WMGroup Engineers, P.C.


What is the fear

What is the “FEAR”

  • No change in design as previous design had no complains from client

    • No complain because no bench mark exists

    • Fear to take the first step to change the concepts to use state of the art technology

    • Consultants sell time. Fear is any new concept will take lots of time and it is not worth the effort


What are1970 s era design concepts

What are1970’s EraDesign Concepts?

  • System Design for Peak load only

  • Primary/Secondary/Tertiary Pumping

  • 5°C (42°F) supply temperature

  • System Balancing

  • Circuit Setters

  • Band Aid solution for any Problem

  • Projected Demand way above reality

  • Oversized chiller, pumps TDH and everything else to cover behind


State of the art plant concepts

State of the Art Plant concepts

  • Plant designed for optimum operation for the year. Peak hours are less than 200 hours a year

  • Variable flow primary pumping system

  • 3.3°C (38°F) or lower supply temperature

  • No System Balancing. Balancing is for a static system.

  • No Delta P valves – No Circuit Setters

  • No Band Aid solution for any Problem

  • Use chilled water system diversity (0.63) to Project Cooling Demand

  • The total Chilled water pumping TDH even for a very large system should not be more 63 meters(than 200 feet)


Selecting equipment to optimize efficiency

Selecting Equipment to Optimize Efficiency

Chiller equipment is often erroneously selected based on peak load efficiency.

Peak load only occurs for a small number of hours of the year, as shown on the load duration curve below:


The design of the human body

The Design of the Human Body

Lungs(Chillers)

Brain

(Building End-Users)

Heart

(Variable Volume Primary Pump)


Basic 1970 s era chiller plant design

Basic 1970’s Era Chiller Plant Design

Decoupler Line

Building Loads

Chiller

Primary Pump

Secondary Pump


Current design used on many large district chilled water systems

Current Design Used on Many Large District Chilled Water Systems

Chiller

Energy

Transfer

Station

Decoupler Line

Building Loads

Primary Pump

Secondary Pump

Building Pump


Modern variable volume primary chiller plant design

Modern Variable Volume Primary Chiller Plant Design

Building Loads

Chiller

Variable Speed Primary Pump


Lost chiller capacity due to poor t

Lost Chiller Capacity Due to Poor ΔT

Ideal Design Conditions

150 L/sec

(2,400 gpm)

150 L/sec

(2,400 gpm)

13°C (55.5°F)

13°C (55.5°F)

No Flow Through Decoupler

5°C (41°F)

5°C (41°F)

150 L/sec

(2,400 gpm)

150 L/sec

(2,400 gpm)

Chiller sees a ΔT of 8°C (14.5°F) at a flow of 150 L/sec (2,400 gpm)

The chiller capacity is therefore 5,000 kW (1,450 tons)


Lost chiller capacity due to poor t1

Lost Chiller Capacity Due to Poor ΔT

Case 1: Mixing Through Decoupler Line

75 L/sec

(1,200 gpm)

150 L/sec

(2,400 gpm)

9°C (48.25°F)

13°C (55.5°F)

75 L/sec

(1,200 gpm)

at

5°C (41°F)

5°C (41°F)

5°C (41°F)

75 L/sec

(1,200 gpm)

150 L/sec

(2,400 gpm)

Chiller sees a ΔT of 4°C (7.25°F) at a flow of 150 L/sec (2,400 gpm)

The chiller capacity is therefore 2,500 kW (725 tons)


Lost chiller capacity due to poor t2

Lost Chiller Capacity Due to Poor ΔT

Case 2: Poor Building Return Temperature

150 L/sec

(2,400 gpm)

150 L/sec

(2,400 gpm)

9°C (48.25°F)

9°C (48.25°F)

No Flow Through Decoupler

5°C (41°F)

5°C (41°F)

150 L/sec

(2,400 gpm)

150 L/sec

(2,400 gpm)

Chiller sees a ΔT of 4°C (7.25°F) at a flow of 150 L/sec (2,400 gpm)

The chiller capacity is therefore 2,500 kW (725 tons)


Small loss in t rapidly reduces chiller capacity

Small Loss in ΔT Rapidly ReducesChiller Capacity

Assuming a design ΔT of 8°C (14.4°F):


Technical paper by erwin hanson pioneer in chilled water system design

Technical Paper by Erwin Hanson(Pioneer in Chilled Water System Design)

8°C

9°C

11°C


Billing algorithm for buildings to give incentive to owners to improve t

Billing Algorithm for Buildings to Give Incentive to Owners to Improve ΔT

  • Adjusted Demand Cost

  • Adjusted Consumption Cost

  • Total Cost = Demand + Consumption


The design of the human body1

The Design of the Human Body

Lungs(Chillers)

Brain

(Building End-Users)

Heart

(Variable Volume Primary Pump)


History of variable primary flow projects

History of Variable Primary Flow Projects

  • King Saud University - Riyadh (1977)

  • Louisville Medical Center (1984)

  • Yale University(1988)

  • Harvard University (1990)

  • MIT(1993)

  • Amgen (2001)

  • New York-Presbyterian Hospital (2002)

  • Pennsylvania State Capitol Complex (2005)

  • Duke University (2006)

  • NYU Medical Center (2007)

  • Memorial Sloan-Kettering Cancer Center (2007)


King saud university riyadh 1977

King Saud University – Riyadh (1977)

  • 60,000 ton capacity with 30,000 tons for first phase

  • Six 5,000 ton Carrier DA chillers

  • Seven 10,000 GPM 240 TDH constant speed pumps

  • Major Problem: Too much head on chilled water pumps

  • Lesson Learned: Be realistic in predicting growth


Louisville medical center 1984

Louisville Medical Center (1984)

  • Existing system (1984)

    • Primary/Secondary/Tertiary with 13,000 ton capacity

  • Current System (2007)

    • 120 feet TDH constant speed primary pumps with building booster pumps – 30,000 ton capacity

    • Changed the heads on some of the evaporator shells to change number of passes

    • Primary pumps are turned OFF during winter, Early Spring and Late Fall. Building booster pumps are operated to maintain flow.


Yale university 1988

Yale University (1988)

  • Existing system (1988)

    • Primary/Secondary/Tertiary with 10,500 ton capacity

  • Current System (2007)

    • 180 feet TDH VFD / Steam Turbine driven variable flow primary pumps – 25,000 ton capacity

    • Changed the heads on some of the evaporator shells to change number of passes


Amgen 2001

Amgen (2001)

  • Creation of a computerized hydraulic model of the existing chilled water plant and distribution system

  • Identification of bottlenecks in system flow

  • Evaluation of existing capacity for present and future loads

  • Two plants interconnected: Single plant operation for most of the year, second plant used for peaking

  • Annual Energy Cost Savings: $500,000


Additional variable primary flow projects

Additional Variable Primary Flow Projects

  • Harvard University (1990)

  • MIT(1993)

  • New York-Presbyterian Hospital (2002)

  • Pennsylvania State Capitol Complex (2005)

  • Duke University (2006)

  • NYU Medical Center (2007)

  • Memorial Sloan-Kettering Cancer Center (2007)


Duke university background

Duke University Background

  • CCWP-1 plant was built four years ago

  • CCWP-2 design was 90% complete (Primary/Secondary pumping)

  • We were retained by Duke to peer review the design

  • Peer review was time sensitive

  • Plant design for CCWP-2 was modified to Variable Primary pumping based on our recommendations


Duke ccwp 1 before

Duke CCWP-1 Before


Duke ccwp 1 after

Duke CCWP-1 After

  • Dark blue pipe replaces old primary pumps


Duke ciemas building chw system

Duke CIEMAS Building CHW System

90% closed

Triple duty valves

50% closed


Duke ciemas building ahu 9

Duke CIEMAS Building AHU-9

Balancing valve

50% closed


Nyu medical center 2007

NYU Medical Center (2007)

  • Plant survey and hydraulic model indicated unnecessary pumps

  • 1,300 horsepower of pumps are being removed, including 11 pumps in two brand new chiller plants

  • $300,000 implementation cost

  • $460,000 annual energy savings


Nyu medical center 20071

NYU Medical Center (2007)

  • Plant survey and hydraulic model indicated unnecessary pumps

  • 1,300 horsepower of pumps are being removed, including 11 pumps in two brand new chiller plants

  • $300,000 implementation cost

  • $460,000 annual energy savings

8 Pumps Removed

3 Pumps Removed

7 Pumps Removed

3 Pumps Removed


Memorial sloan kettering before

Memorial Sloan-Kettering - Before


Memorial sloan kettering after

Bypass or removal of pumps

Memorial Sloan-Kettering - After

Bypass or removal of pump

Bypass or removal of pumps


Pump cemetery

Pump Cemetery

To date we have removed several hundred large pumps from our clients’ chilled water systems


Plant capacity analysis detailed system analysis is a necessity

Plant Capacity Analysis -Detailed System Analysis is a Necessity

Modern computer software allows more complex modeling of system loads, which has proven to be very valuable to optimize performance and minimize cost.

Return on investment to the client for detailed analysis is typically very high.


New york presbyterian hospital

~ 20F T

New York Presbyterian Hospital

  • Applied revolutionary control logic

Log Data


Bristol myers squibb

Bristol-Myers Squibb

  • Biochemistry research building

    • 140,000 square feet

    • AHU-1 (applied new control logic)

      • 100,000CFM

    • AHU-2 (existing control logic remained)

      • 100,000 CFM


Bristol myers squibb1

Bristol-Myers Squibb

  • Applied revolutionary control logic


Pa state capitol complex chw t

PA State Capitol Complex – CHW ΔT


South nassau hospital chw t

South Nassau Hospital – CHW ΔT


Good engineers always ask why

Good Engineers Always Ask “Why?”

  • Why does the industry keep installing Primary/Secondary systems?

  • Why don’t we get the desired system ΔT?

  • Why does the industry allow mixing of supply and return water?


Good engineers always ask why1

Good Engineers Always Ask “Why?”

  • Why does the industry keep installing Primary/Secondary systems?

  • Why don’t we get the desired system ΔT?

  • Why does the industry allow mixing of supply and return water?

    Answer: To keep consultants like us busy!

    Why change?


Reasons to change

Reasons to Change

  • The technology has changed

  • Chiller manufacturing industry supports the concepts of Variable Primary Flow

  • Evaporator flow can vary over a large range

  • Precise controls provides high Delta T


Change is starting around the world

Change is Starting Around the World

  • Most of the large district cooling plants in Dubai currently use Primary/Secondary pumping

  • By educating the client we were able to convince them that this is not necessary

  • We are now currently designing three 40,000 ton chiller plants in Abu Dhabi using Variable Primary Flow as part of a $6.9 billion development project


Summary

1985: $ 0.171/ton-hr

2002: $0.096/ton-hr

Summary

  • There are many chilled water plants with significant opportunities for improvement

  • WM Group has a proven record of providing smart solutions that work

  • We will be happy to review your plant logs with no obligation


The cost of using 1970 s era design concepts and fear in chilled water systems

Thank You

Hemant Mehta, P.E.

President

WMGroup Engineers, P.C.

(646) 827-6400

[email protected]


The cost of using 1970 s era design concepts and fear in chilled water systems

The New Royal Project

Central Energy Plant Study

By

September 16, 2008


Project objective

Project Objective

Determine the Optimum Central Energy Plant Configuration and Cogeneration Feasibility


The new royal project

The New Royal Project

  • A new tertiary hospital for the region

  • 95,000 m2 initial area (basis of analysis)

  • Disaster Recovery Consideration

    • N+1

    • Onsite Power Generation (+/- 70% of peak demand)

    • Two separate central plants


Project site

Project Site


Typical utility tunnel

Typical Utility Tunnel


Study approach

Study Approach

  • Developing load profiles for Heating, Cooling and Power

  • Developing and screening of Options

  • Creating a computer model for energy cost estimate

  • Performing Lifecycle Cost Analysis

  • Performing Sensitivity Analysis

  • Conclusions


Load profiles

Load Profiles

  • Cooling/Heating – Daily peaks provided by Bassett

    • Cooling:7,400 kWt (2,100 RT)

    • Heating:8,000 kWt

  • Power – Daily peaks provided by Bassett

    • Peak demand: 4,500 kWe

    • Min. demand:1,400 kWe


Cooling loads

Cooling Loads


Daily cooling load profile

Daily Cooling Load Profile


3 d cooling load profile

3-D Cooling Load Profile


Cooling load duration curve

Cooling Load Duration Curve

607 Equivalent Full-Load Hours


Heating loads

Heating Loads


Daily heating load profile

Daily Heating Load Profile


3 d heating load profile

3-D Heating Load Profile


Heating load duration curve

Heating Load Duration Curve

1,742 Equivalent Full-Load Hours


Electric loads

Electric Loads


Daily electrical load profile

Daily Electrical Load Profile


3 d electrical load profile

3-D Electrical Load Profile


Utility rates

Utility Rates

  • Natural Gas:$9.00 / GJ

  • Electricity (taken from hospital bill):

    • Demand Charge: $0.265641 per kVA per day

      • Based on contracted annual demand

      • About $10.00 per kW per month

    • Energy Charge:

      • $0.14618 / kWh (on-peak, 7 am to 10 pm)

      • $0.05322 / kWh (off-peak, 10 pm to 7 am and weekends)

    • Fixed Charges: $27.7155 per day

      • About $830 per month


Base option considerations

Base Option Considerations

  • Minimum first cost

  • Two locations

  • Conventional equipment

    • Electric chillers

    • Gas-fired boilers

    • Diesel emergency generators

    • No cogeneration or thermal storage

  • Operational efficiency and reliability


Central energy plant base option

Central Energy Plant – Base Option


Alternative plant considerations

Alternative Plant Considerations

  • Non-Electric Chillers

    • Absorption Chillers (with or without heaters)

    • Steam Turbine Driven Chillers

    • Gas Engine Driven Chillers

  • Thermal Storage

    • Ice Storage

    • Chilled Water Storage

  • Cogeneration

  • Geothermal


Electric vs non electric chillers

Electric vs. Non-Electric Chillers

Sample taken from another project


Hybrid plant option 1a

Hybrid Plant – Option 1A


Ice storage vs chilled water storage

Ice Storage vs. Chilled Water Storage

  • Advantages of ice storage

    • Ice storage requires less space

    • Suitable for low temperature operation

  • Disadvantages of ice storage

    • Ice generation requires more energy

    • Ice storage system has a higher first cost

  • Ice storage is not considered for this project


Thermal storage option 2

Thermal Storage – Option 2


Cogeneration alternatives

Cogeneration Alternatives


Engine generator topping cycle

Engine Generator Topping Cycle


Option 3 cogen w gas engines

Option 3 – Cogen w/ Gas Engines

* Diesel generators not required if onsite LNG storage is provided


Option 4 cogen thermal storage

Option 4 – Cogen & Thermal Storage

* Diesel generators not required if onsite LNG storage is provided


Summary of options

Summary of Options


Energy model

Energy Model

  • Simulation of plant operation

  • Calculation of total energy use (power and fuel) and cost


Hourly computer model

Hourly Computer Model


Detailed equipment data

Detailed Equipment Data


Monthly energy cost summary

Monthly Energy Cost Summary


Monthly energy cost graphs

Monthly Energy Cost Graphs


Comparison of annual energy costs

Comparison of Annual Energy Costs

$4.3 M

$4.3 M

$4.2 M

$3.0 M

$3.0 M


Thermal storage economics

Thermal Storage Economics

  • Installed Cost (Opt. 1A):$1,700,000

  • Annual Energy Savings: $98,000

  • Simple Payback: 17 years

    Low cooling load reduces benefits of thermal storage


25 year lifecycle cost analysis

25-Year Lifecycle Cost Analysis

  • Capital Cost

  • Energy Cost (gas and electric)

  • Maintenance and Consumables Cost

  • Staffing Cost

  • Economic Rates

  • Discount Rate


Construction cost estimates

Construction Cost Estimates


Project cost factors

Project Cost Factors

Based on typical healthcare development projects

  • Preliminaries and Margin:23%

  • Project Contingency:15%

  • Cost Escalation to Start Date:15%

  • Consultant Fees:10%

    Total multiplier is approximately 1.8


Comparison of initial costs

Comparison of Initial Costs


Maintenance and staffing costs

Maintenance and Staffing Costs

  • Options 3 and 4 also require a $240,000 engine overhaul every 5 years (included in analysis)

  • Staffing cost based on $65,000 per year for each full-time staff employee


Economic parameters

Economic Parameters

Based on estimated government rates

  • Discount Rate:8.00%

  • Gas Cost Escalation Rate:4.30%

  • Electric Cost Escalation Rate:3.40%

  • Maintenance Escalation Rate:4.00%

  • Consumables Escalation Rate:4.00%


25 year lifecycle cost analysis1

25-Year Lifecycle Cost Analysis


Cost summary

Cost Summary


Results of lifecycle cost analysis

Results of Lifecycle Cost Analysis


Sensitivity analysis

Sensitivity Analysis

  • Varying electric demand charge

  • Varying gas cost

  • Change economic parameters

  • Carbon emission tax

  • Use of geothermal energy


The cost of using 1970 s era design concepts and fear in chilled water systems

Thank You

Hemant Mehta, P.E.

President

WMGroup Engineers, P.C.

(646) 827-6400

[email protected]


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