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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
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):

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 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 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
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
slide44
Thank You

Hemant Mehta, P.E.

President

WMGroup Engineers, P.C.

(646) 827-6400

[email protected]

slide45

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
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 load duration curve
Cooling Load Duration Curve

607 Equivalent Full-Load Hours

heating load duration curve
Heating Load Duration Curve

1,742 Equivalent Full-Load Hours

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
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

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
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

energy model
Energy Model
  • Simulation of plant operation
  • Calculation of total energy use (power and fuel) and cost
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
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

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%
sensitivity analysis
Sensitivity Analysis
  • Varying electric demand charge
  • Varying gas cost
  • Change economic parameters
  • Carbon emission tax
  • Use of geothermal energy
slide93
Thank You

Hemant Mehta, P.E.

President

WMGroup Engineers, P.C.

(646) 827-6400

[email protected]

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