how chilled water optimization makes cogeneration - nehes

October, 2013

Presentation to:

How Chilled Water Optimization makes

Cogeneration More Effective with a

Better Payback

By

Hemant Mehta, P.E.

WM Group Engineers, P.C.

Post Sandy

Challenge our industry

Resiliency

Answer

Micro Grid - CHP

Island mode operation

CHP Implementation

Challenge from the bean counters

Payback

Answer

Improve coincident factor by

reducing peak power demand and

annual operating costs

OTHER

LOSSES

4.8%

INP

UT

10

0%

LOSSES

25.8%

EXHAUST

LOSSES

21%

THERMAL

OUTPUT

44.5%

ELECTRICAL

OUTPUT

29.7% USEFUL ENERGY

74.2%

CHP Limitation

• High electric to thermal demand during summer

limits CHP operation.

• Decreasing the summer electric demand allows

best operational scenario for CHP.

Every Manufacturer has different energy

profile

CHP Selection

• Reduction in power consumption in summer

allows the selection of smaller CHP units with

low minimum thermal output optimal in summer

• It allows the better unit selection with more

operating hours and more energy savings

resulting in good payback.

• Chilled Water Optimization is a necessary step

for CHP operation.

Opportunity - Chilled Water System optimization

1. Power requirements for Chilled

water system establish peak

summer demand

2. I have yet to see an efficient

chilled water system

• Design inconsistency of chilled water plant, distribution system and building systems by consulting Engineers

• Poor Delta T

• High Chilled water pump TDH

• System hydraulics

• Inefficient Condenser water system

• Band Aid Solutions

The reasons of poor design and/or operation or system inefficiencies are:

Signs of inefficient systems

• If your fall and Spring Chilled water Delta T is

lower than summer peak delta t

• If your pumping system is primary/secondary or

primary/secondary/tertiary

• If you have division of responsibility between

plant and buildings

• If your control logic is same as 1970 design

Chilled Water Optimization Pyramid:

Software

Operators Training

Re-engineering

The Big Picture – Why reengineer to

primary system?

Heart (Variable Volume Primary Pump)

Lungs (Chillers)

Brain (Building End-Users)

Chilled water system optimization

• I realized the power of system optimization in

1984 while working on a project for the Louisville

medical Center

• Let’s review some of the case history on how the

analysis and reengineering of the existing

system reduced electric peak demand,

consumptions and saved millions of dollars to the

client

Case study – Louisville Medical Center

• 12,000 ton plant could not meet the Cooling requirements

• Local consultant recommended Installing 3,000 tons of

additional capacity

• We were called in for peer review

• Our review indicated that the cooling load was only 8,800 tons

• Reengineering the plant we regain the capacity and reduced

PEAK Power

Case study – Memorial Sloan Kettering Cancer Center New York

• World famous cancer treatment hospital campus

• Four individual chiller plants operating

individually

• Major issues:

– Not enough chiller capacity. Client planned to spend

millions to add chiller capacity

– Too much pumping

– Inefficient operation

Summary of Reengineered system

• Interconnected four plants to operate as one system

– Interconnections eliminated need for a stand by

chillers. Old stand by chillers are now available for

campus expansion.

– No need to add additional chillers for a while saving

millions of dollars

• Removed 32 pumps, reduced power by over a

megawatt and saved over a million dollars a year in

annual cost

Power Reduction – MSKCC

19,000 tons CHW production

capacity interconnected

32 pumps bypassed

23 pumps demolished

$1 million in projected annual

energy savings

$662,000 NYSERDA funding

Pump Cemetery reduced

power by over One MW

Case study – Purdue University

• System comprised of two chiller plants with a

combined capacity of 36,800

• Major issues:

– Operating capacity was limited to 28,800 tons. Loss

of 8,000 tons equates to loss of 16 million dollars

– Almost 40 percent more chilled water demand than

average due to simultaneous heating and cooling

– Too much pumping

• Oversized pumps is causing operators to run cars with

brakes on.

– Design pump dynamic head 310 feet.

• Actual requirement 180 feet

– Operating constant speed pumps together with

variable speed pumps • Cause – Variable speed pump can not generate any flow

• I observed major valves partially closed all over

• Balancing is a crime for any dynamic hydraulic system

• Partially closed valves eats up pump energy for no reason

Purdue pumping system issues

Purdue pumping system issues

• Use of Building Pumping Unnecessary, Removed 130

pumps from the buildings. Power reduction 1.1 megawatt

• Removed 130 pumps from the buildings

Distribution Observations

Pressure Wasted by Closing

valve

Pressure Increased

by pump

Summary of optimization at Purdue

• Within six weeks of the project, at zero cost

reduced peak power by 1.1 Megawatt

• Removed 130 tertiary pumps

• Anticipate to reduce annual operating cost by

over 3 millions a year

• Interconnect 3 existing chilled water systems serving 4 buildings (6100 Tons)

• Freed up 1,500 tons from stand by capacity

• No need to purchase chilled water from NY Presbyterian. Saving of over

$500,000 per year

Columbia University Medical Center

Case study – US Capitol

• Original plant of 28,000 tons designed by my

company in 1979

• Plant expanded by 15,000 tons by another

engineer in 2003

• Major issues:

– “ Cut and Paste” signature design by other engineer

– Operating capacity loss of thousands of tons

– Inefficient operation

DE

CO

UP

LE

R

PP

CH-5

CH-6

CH-7

CH-1 CH-2

CH-3 CH-4

MIN

BY

PA

SS

FM FM

PRIMARY PUMPS

SECONDARY

PUMPS

PRIMARY PUMPS

DISTRIBUTION

VFDVFDVFDVFDVFD

Primary-Constant Speed Primary/Secondary Variable

Poor Design – Incompatible Addition

Poor Design

• Oversized Pumps causing valves to throttle at 60%.

• Flow above 4000 GPM through the de-coupler.

Generation Utilization

Division of Responsibility cause of inefficiency

Division of Responsibility

CHILLERS

Variable

Primary

Pumping

Farthest

Building

Both

Pumps

remain

OFF

Valve

OPEN

Valve

CLOSED

User Buildings

Building connections: Chilled water pressure being utilized improperly at

buildings.

Building connections: Chilled water pressure being utilized improperly

at buildings.

Division of Responsibility

Pressure drop:10psi

Head Loss: 23 ft

At peak load flow of 46,000

GPM, additional power required

for Pumps at Chiller Plant is

46000*23/(3960*.8)

= 335 HP or 250.2 kW

Chilled water flowing through

non-operating pump.

With equivalent 4000 full load hours, annual energy loss is 1,000,883 kWh

At $0.0912/kWh, annual loss is $91,281

Equivalent peak demand savings: 250 kW

Summary of optimization at US Capitol

• Provided training to the operators on how to

operate plant at optimum efficiency within the

given constraints of poor plant design

• Reduced annual operating costs by $430,000

without spending any money to fix the plant

• Peak Power Reduction of over 250 KW

Duke CIEMAS Building CHW System

90% closed Triple duty valves 50% closed

Balancing valve 50% closed

Duke CIEMAS Building AHU-9

Duke Levine Science Research Center

CHW System

Before

After

Case study - Benefit of Peer Review

Duke University Project

• Plant #1 built in 2000

• Final bid docs for Plant #2 were

being prepared for construction

• Our client from Yale asked that we

review the Duke project

• Our peer review reduced

significant power consumption

and cost by over $2 million.

• As money was already funded, used

to redesign Plant #1.

Dark blue pipes replaced

old primary pumps

NYU Medical Center (2007)

• Four separate chilled water plants

• Primary/Secondary pumping

• Needed more chiller capacity

NYU Medical Center (2007)

• Interconnected Four plant as One Virtual variable flow primary System.

• Freed up 3600 tons of stand by capacity

• 1,300 horsepower of pumps are being removed, including 11 pumps in two

brand new chiller plants

• $300,000 implementation cost and $460,000 annual energy savings

3 Pumps Removed

7 Pumps Removed

8 Pumps Removed

3 Pumps Removed

Central CHW Plant & River Water Systems Design

• Design of 12,500 ton central chiller plant and site CHW

distribution system serving multiple buildings.

• Design of river water system and river water pump

house restoration.

• System connected to six different buildings

• Memorial plant machine room only one floor above the

plant

• Memorial building Engineers installed secondary pumps

event though plant pumps were design to pump water

to a mile away

• Convincing the engineer to install by-pass reduced peak

demand

Case Study - Signature “cut and

paste” design-World Trade Center

Chilled Water System Master Plan & Plant Expansion • Master Plan

– Evaluation of system operations

– Design of Central Plant cooling tower replacement

• Plant Expansion

– Installation of two 5000 ton steam turbine driven chillers, pumps, cooling towers and auxiliaries

MITCHILLER PLANT ENERGY USE

7

8

9

10

11

12

13

14

CHW PLANT STEAM

Syska & HennessyModif ications

Off-line System Optimization Package

Modifications

Case Study - MIT

Chilled Water Plant Upgrade • $12 million upgrade program to

increase existing plant cooling capacity.

• Performed comprehensive hydraulic analysis and identified flow restrictions and pump deficiencies, enabling further capacity increase by 2000 tons.

• REDUCED DEMAND AND CONSUMPTION AND ENERGY COST BY 20%

Case study – IBM Corporation

Uptown Facilities

• Chilled water systems optimization

• Saved over $500,000 per year

• Now peak cooling day demand is met by 4 chillers compared to six prior to modification

• 650 kW demand savings

New York Presbyterian Hospital

(Tuesday, July 30, 2002)

10,000

10,250

10,500

10,750

11,000

11,250

11,500

11,750

8 9 10 11 12 13 14 15 16 17 18 19 20

Time of Day

Dem

an

d (

KW

)

Operational

Modification

(~ 650 KW

Savings)

Case Study – NY Presbyterian Hospital

Identification of Bottlenecks

• Two close valves created the blocked area which increases the

increased in pump head.

• Identification and elimination of bottlenecks reduced thousands

of dollars in operating cost.

• Reduction in Power Demand and Consumption

• Annual Energy Cost Savings: $ 500,000

Case study – Amgen Inc.

• Variable Primary Conversion

• 42 pumps removed

• Control system overhauled

• DT Improvement

Case Study – Bristol Myers Squibb

• Gained over 2,000 tons of additional capacity

• Peak Demand reduction by One Megawatt

• $400,000 operational energy cost savings per

year

How does delta T affect Power?

• Compressor Energy (Ce):

PmCe D ΔP

REm

200

• RE: Refrigerant effect increases as ΔT increases.

• Mass flow rate decreases with increase in ΔT

• Hence compressor power decreases with increase in ΔT.

• Low ΔT reduces chiller capacity and more chillers need to

be operated.

• Refrigerant mass flow:

How do you improve delta T?

• Controlling the chilled water flow through the

chillers

• Use of new control technology at AHUs.

Case Study – PA State Capitol Complex

• Increased the delta T, reducing the flow requirement thereby

reducing power consumption and demand.

• Site survey

• Collect trended data from historian

• Determine health of system

• Analytics

• Implement no-cost measures.

• Quantify savings.

• Analyze and prioritize energy conservation measures

System Evaluation Process

Site Survey

• Thorough documentation of complete chilled water

system schematic

• Gather all equipment data

• Record operating parameters, flows, pressures,

temperatures

• Review previous reports

• Interview Operators


• Analytics


• Analytics Example: Pump Mapping


• Analytics Example: Chiller Mapping (Determine Sweet Spots)


• Analytics Example: Cooling Tower Mapping

• Determine actual tower minimum flow rate


• Analytics Example: Water Quality


March 2013

August

2012

December

2012 February

2013

• Analytics Example: Bottleneck (Orifice Plate)


• (5.1.1) Series Configuration for Chillers 9-10

• Upstream Chiller sees lower “lift” (150 Ton Improved Chiller Capacity)

• Lower CHWST during peak conditions (500 Ton Improved Dist. Capacity)

• $34,700 Annual Savings

(ECM 5.1) Wade Plant Re-Engineering

• 8760 Hour Analysis of Measures

MonthCooling

Load (Tons)

Total Chiller

Power

(kWH)

Total CHPW

Power

(kWh)

CW Pump

Power

(kWH)

CT Fan Power

(kWH)Cost ($)

Jan 73,253 42,481 5,583 16,023 4,522 $3,430

Feb 434,587 242,603 30,942 83,880 11,545 $18,449

Mar 2,366,054 1,170,524 136,124 259,735 54,696 $81,054

Apr 2,035,622 1,006,826 114,011 225,773 83,751 $71,518

May 3,439,051 1,703,912 207,288 333,584 157,903 $120,134

Jun 4,078,799 2,006,957 228,190 350,618 224,666 $140,522

Jul 5,617,310 2,807,070 315,648 440,303 291,414 $192,722

Aug 4,075,679 2,097,100 227,470 361,732 245,651 $146,598

Sep 3,999,653 1,963,882 231,896 354,066 193,669 $137,176

Oct 2,134,784 1,071,904 108,340 222,158 76,515 $73,946

Nov 1,401,126 732,718 66,521 173,286 49,594 $51,106

Dec 1,529,842 785,992 85,692 200,029 5,886 $53,880

Total 31,185,761 15,631,968 1,757,704 3,021,188 1,399,813 $1,090,534

MonthCooling

Load (Tons)

Total Chiller

Power

(kWH)

Total CHPW

Power

(kWh)

CW Pump

Power

(kWH)

CT Fan Power

(kWH)Cost ($)

Jan 73,253 42,481 5,583 11,572 4,522 $3,208

Feb 434,587 242,603 30,942 60,580 11,545 $17,284

Mar 2,366,054 1,170,524 136,124 187,587 54,696 $77,447

Apr 2,035,622 1,006,826 114,011 163,058 83,751 $68,382

May 3,439,051 1,703,912 207,288 240,922 157,903 $115,501

Jun 4,078,799 2,006,957 228,190 253,224 224,666 $135,652

Jul 5,617,310 2,807,070 315,648 317,997 291,414 $186,606

Aug 4,075,679 2,097,100 227,470 261,251 245,651 $141,574

Sep 3,999,653 1,963,882 231,896 255,714 193,669 $132,258

Oct 2,134,784 1,071,904 108,340 160,447 76,515 $70,860

Nov 1,401,126 732,718 66,521 125,151 49,594 $48,699

Dec 1,529,842 785,992 85,692 144,465 5,886 $51,102

Total 31,185,761 15,631,968 1,757,704 2,181,969 1,399,813 $1,048,573

Base Case

ECM - CWP VFD or Impeller Change


• Hydraulic Modeling


Summary: How to get power reduction and get

your system in shape

1. Keep operating logs; have logs reviewed by an

expert

2. Don’t be afraid of change; use state-of-the-art

technology

3. Interchange operating personal between plant and

buildings, or “cross training”

4. Provide System training to operators

5. Convert HVAC controls to process controls

OAT: 45

Temp Set: 56

Actual

Temp: 58

Cooling Valve: 42%

open to cool air to

set temp.

Valve leak, Pre

heat temp: 59

Mixed Air

Temp: 54

Overheating of air

Case study - Lack of Training - Simultaneous

Heating & Cooling

Operators Training

• Training the operators for systems operation

yields maximum plant savings.

• Systems knowledge eliminates the “fear” of

operation thus eliminating redundant

system/product operations.

• Empowers operators to take knowledgeable

decisions during plant operation.

How can We help you

• Check the health of your central utility

infrastructure

– Email me the following

• Plant operating logs

• equipment design data

• Copies of fuel and power bills for one year

• We will review documents and provide a report

on the health of your system and opportunities

for system optimization at NO COST to you

IDEA Lifetime

Membership Award: Feb.

2013

IDEA Person of Year

Award: June 2013

Association of Energy Engineers

(AEE) Region I Energy Engineer

of the Year: Oct. 2011

Achievements

Thank You

Hemant Mehta, P.E.

President

WM Group Engineers, P.C.

(646) 827-6400

[email protected]

www.wmgroupeng.com

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