Reducing industrial electricity costs—an automative case study

Reducing Industrial Electricity Costs-an Automo6ve Case Study Alan Price is Principal Engineer for Ford Mofor Company in ifs plant engineering office. He has a Bachelor of Science degreefiom,Case Institute of Technology and has done graduate

work in mathematics,

electrical

engineering, and computer science. Marc Ross is professor of physics at the University of Michigan and senior scientist in the Energy and Environmental Systems Division, Argonne National Laboratory. He holds a Ph.D. in physics from the University of Wisconsin. With Robert H. Williams he has written a book on energy policy, Our Energy: Regaining Control. Recently he has worked on energy issues under the aegis of Congress’ Office of Technology Assessment and the American Council for an Energy Efficient Economy. The authors wish to thank the many individuals who contributed to this effort, especially George Sherkus of the Ford Motor assembly plant in Edison, NJ., whose comments inspired this effort, and Charles Millar of the Michigan Public Service Commission for his comments and counsel.

40

Energy savings of 30% and capacity savings of 20% are achievable in automotive manufacturing and like industrial facilities, by the authors’ observations. Utilities and regulators can help gain this improved efficiency by providing customers solid rate and planning information. Alan C. Price and Marc H. Ross

I. ABSTRACT

T

he automotive industry and similarly situated industries

automative manufacturing and similarly situated industries. These conclusions are based on

purchase about 13% of all electric

the writers’ observations at more

utility sales in the United States.

than 40 facilities in North Amer-

This article explores the potential

ica and Europe.

for reduction in electricity purchases by automotive manufactur-

II. INTRODUCTION

ing facilities through qanded use me asures currently of conservation

The authors of this paper met as participants in a study commis-

employed in some plants.

sioned by Michigan Governor

Existing, cost effective conserva-

Blanchard to assess the states’s fu-

tion installations observed by the

ture electricity requirements and

authors have the potential to re-

estimate the costs and potential ca-

duce electrical energy use by 20 to

pacity contributions from both

40% and peak demand by 15 to

supply side (new generation) and

30% for existing applications in

demand side (conservation).

The

The Electricity Journal

authors’ work on the demand

than 1% to total cost of production

motor controls.

side portion of the study included

and is perceived in an historical link

visits to several auto assembly

between increased labor productiv-

and stamping plants in Michigan.

ity and increased electricity use.

A few of the conclusions in this

Labor cost is about 25% of the pmd-

paper replicate those published in

uct cost in the automotive industry

the Michigan study,’ but many

and actions that might increase

are based on observations from in-

labor cost have been looked on with

III. MONITORING

AND

CONTROL A. Information on Electricity Use A key to identifying opportunities to reduce the cost of electricity

dustrial facilities not included in

disfavor. Recent attitudes have

is measuring how much is used,

that study, including a large num-

changed in response to the rise in

when, and where. Even without

ber from other states and coun-

the price of electricity the publicity

systematic information at the

ties,

given to potential further increases

point of use, a great deal can be

pplication of conservation

and the demonstrated success of

learned from a load curve for an

techniques has been slow in

pilot installations of conservation

entire plant showing the power

devices and techniques.

use over the day or better still,

A

industries like automotive manufacturing because many of the tech-

Electricity consumption in auto-

several days.

S

ample load curves for three au-

niques involve relatively new hard-

motive manufacturing is shown

ware, such as semiconductors and

broken down by principal end

computers, that requires trial pilot

use in Table 1. These are esti-

shown in Figure 1. Half-hour inte

tomotive assembly plants are

installations. No rational manager

mates because few auto plants

grated electrical demand data were

wants to risk production outages

measure electricity use by func-

obtained for the 1987 Memorial

because an untested device that has

tion. However, it is generally ac-

Day weekend (May 23 through 25).

been added to the machinery

cepted that approximately three-

These. plants assemble different ve

needed to meet production sched-

fourths of the electricity used in

hi&s but all have essentially the

ules failed. The applications de

auto plants is for motor operation.

same process, so a comparison of

scribed in this paper am the known

Thus, many of the conservation

the load on Saturday evening with

survivors of the trial period. Conservation techniques dis-

applications described in this

the Friday peak indicates the “tight-

paper will involve motors and

ness” of shutdown. Data were nor-

cussed in this paper are applicable to a much broader slice of industry than the automotive plants

Table 1: Electricity Consumption in Auto Manufacturing,

where they were observed. Instal-

(Percentages as of Early 1980s)

lations involving several of the techniques are known to exist in plastic molding, metal stamping, electrical equipment and white good (major appliance) factories. In 1985 automobile manufacturers and parts suppliers spent over $1 billion, or $120 per vehicle, for electricity? This corresponds to

lectricity

Assembly Space conditioning, (mostly fans)

17

Paint systems (mostly fans)

27

-

Lighting

15

10

14

25

8

6

2

32

10

6

4

4

100%

100%

70%

80%

Compressed Materials

air

handling,

E

Miscellaneous

torically been assigned a low

power tools

Metal forming, shearing, Welding & soldering

priority in fabrication and assembly

ventilation

Stamping

20

about 2240 kWh per vehicle.3

conservation has his-

by Function

machining

TOTAL Share of above use attributable

to motors

activities because it contributes less

July 1989

41

and ventilating units. The com-

tion of off-peak energy at Plants 2

load for Friday as the 100% value,

pmssedairsysteminPlant1is

and 3.

and plotted for the &hour period

equipped with satellite compressors

commencing at oO:OO hours on Fri-

and section valves enabling shut-

departmental level is a powerful

day, May 22. The Memorial Day

down of the main system during

conservation technique. Sub-me-

malized using the peak electrical

Sub-metering electricity at the

weekend was chosen for this com-

non-production hours, thus largely

tering has been observed by visi-

parisonbecause, with the exception

eliminating compressed air leakage.

tors at most Japanese auto plants,

of the maintenance crew working

Plants 2 and 3 lack these facilities.

where data are used to establish

for eight hours on Saturday at Plant

T

1, the weekend shutdown was es-

he installation of equipment at

department budgets and evaluate

Plant 1 to facilitate tight shut-

worker and supervisor perfor-

sentially complete at all three plants.

downs was started in response to

mance. Departmental sub-meter-

The Saturday evening load at

electricity rate increases driven by

ing is used at some automotive

Plant 1 was approximately one-

high oil prices in the 1970s. The util-

plants in North America with fa-

sixth the Friday peak (shutdown

ity serving Plant 1 had oil as the

vorable results; and while the

ratio of 6:l). The shutdown ratios

marginal fuel at nearly all hours,

practice has not yet gained wide acceptance, its use is growing.

at Plants 2 and 3 were approxi-

thus the rate increases in the 1970s

mately 3:l and 2.5:1, respectively.

were heavily weighted toward the

Differences in tightness of shut-

energy side. This resulted in a high

down are attributable more to dif-

off-peak energy charge that jrzstified

ferences in control equipment

installing facilities to reduce off-

tervals with a weekly summary pro-

than to the presence of an army of

peak (non-production) energy use.

vided to departmental supervisors.

equipment “shutter-offers ” at

The utility serving Plants 2 and 3

After metering by department had

t A

one Canadian auto plant,

electricity use by each depatt-

ment is measured in 15-minute in-

Plant 1 and the absence of this

had, and still has, coal as the mar-

been in place for three years, bud-

army at Plants 2 and 3. A look at

ginal fuel at nearly all hours and

geting by department was insti-

the control facility differences be-

thus (properly) has a lower off-peak

tuted and a reduction of over 5% in

tween Plant 1 and its two sister

energy charge and a higher de

annual electric enery use resulted.

plants reveals substantial differ-

mand charge than the utility serv-

This reduction was achieved largely

ences.

ing Plant 1. Thus, Plant 1 was pre

in non-production hours and in

sented with a strong incentive to

shifts with very low rates of produc-

conserve off-peak energy while less

tion.

lant 1 has Energy Management I?

System (EMS) control of most

Systematic departmental sub-

incentive produced less conserva-

of the lighting and major heating

Figure 1: Shutdown Load Curves for Three Assembly Plants (Demand Friday, May 22-Saturday,

Plant

1 operated

only

and had a maintenance shift

42

on Saturday.

one shift

on Friday

crew in for one

Plant

2 had some departments

two shifts There

and others

were

one shift

no operations

May 23)

operating

Plant

on Friday.

and none on Saturday.

3 operated

two full

shifts

on Friday

on Saturday.

The Electricity Journal

metering usually is very costly to

As an example, if 10 million

the rising popularity of “mini

install as a retrofit to an existing

kWh were used in a month, with

mills” that process steel scrap

plant. However, where the distri-

3.0 million kWh in the on-peak pe-

“mined” from local salvage yards

bution bus system is designed

riod, and the peak demand was

into products such as reinforcing

with metering in mind, as was the

20,000 kW, the charge for the

bars and light structural steel

case at the Canadian plant, the

month would be:

shapes. The connected electric

sub-metering costs very little. At this plant electricity costs are one of several monitored components in the overall cost-reduction goal for each department.

This 5% re-

20,OOOkW x $13.14/kW $262,800 (demand

= charge)

3,000,OOOkWh x $O.O40/kWh = $120,000 (on-peak energy charge)

duction was achieved in spite of

7,000,OOOkWh x $O.O33/kWh = $231,000 (off-peak energy charge)

low off-peak electricity prices be-

Total = $613,800

furnace load is between 5% and 15% of system peak load on many utilities. Utility rates which incorporate higher demand charges and lower energy charges and generous interruptible-service

de-

mand discounts can effect substantial reductions in the contribu-

cause measured achievements by individual departments were rec-

or an average cost of 6.1 cents per

tion of electric furnace shops to

ognized.

kilowatt hour. Note that nearly

system peak demand.

A

nEMScanbeusedbothfor

40% of the cost of electricity is as-

submetering and as a sophisti-

sociated with the demand charge.

prior to production start-up and turns them off immediately after the workday ends. The mom so phisticated EMS schemes can also be used to control peak demand. B. Reducing the Demand

ome utilities offer special rates to customers that can reduce

loads at the utility dispatcher’s di-

cated time clock that turns on the lights and equipment immediately

S

Substantial savings can result from departmental metering and energy budget&g.

rection to lessen system peaks. !3everal manufacturers in Georgia, including one auto assembly plant, have installed on-site generation that is operated for this purpose at the direction of the utility C. Thermal Storage and Peak Shaving

Charge

Most auto plants don’t have

Typically large customers are

large electric loads that can be dis-

charged for both maximum lants with major loads that can

placed in time to meet utility

hours and for total energy use

P

(kWh). For example, the present

such as metal melting can substan-

tant and growing exceptions are

Detroit Edison Company (DECO)

tially reduce their demand charge.

process-related cooling loads and

rate includes a monthly on-peak

Electric melt shops in the steel and

air conditioning of manufacturing

demand charge of

casting industries normally use de

facilities. Factory cooling loads

$13.14/kW/mo, and energy charges of 4.0 cents/kWh on-

mand control to minimizthede mand charge. Metal melting fur-

have grown with the use of computers and “clean rooms“ in pro-

peak, and 3.3 cents/kWh off-

naces are sometimes operated

duction. Cold storage facilities

peak, including fuel and other ad-

entirely off-peak to eliminate the de-

have been used in warm climates

justments.

mand charge. Metal melting shops

to reduce peak electric loads for

energy charges vary slightly with

ate usually the largest customers

several years, but only recently

the delivery voltage; the values

taking interruptible service from

have facilities of this type been in-

cited are medians.) DECO’S de-

those utilities that offer low cost in-

stalled in the cooler climates. Two

mand charge is based on on-peak

terruptible service rates.

facilities recently completed in

power use (kW) during specified

(Both demand and

periods, which are the weekday hours from 11 a.m. to 7 p.m.

July1989

be shifted to off-peak hours,

The electric furnace load on most utility systems grew with

needs for interruptibility.

Impor-

Michigan with year-round cooling requirements, a hospital and a

43

corporate headquarters that includes a computer center, incorpo-

IV. MOTOR

SYSTEMS

The following discussion is or-

important opportunity, VSCs, are presented. Pump and fan systems tradi-

rated thermal storage facilities

ganized around the equipment,

with favorable results.4

starting with motor controls; but

tionally were designed with over-

it is important to examine the en-

size constant-speed motors to fa-

thermal storage facility at a on-automotive manufacturAn ing plant in Kentucky incorporates

tire system and to consider the

cilitate control and assure

load and its role in the production

adequate flow in extreme condi-

a three-million gallon storage tank,

process.

tions. Although VSC installations

which has been in operation for two

A. Motor Controls

are relatively costly, with the

years and is credited with reducing

Motor applications where ac-

equipment costing about three

the plant’s electrical demand by ap

tual load requirements of the pro-

times the motor cost,7 the reduc-

proximately 5%.5 This application

cess are highly variable are often

tion in electricity use is large

was a retrofit to an existing system,

cost&f ective applications for

enough to provide a good return

but the greatest economies are ob

solid state motor controls. The

on investment.

tained when cold storage is part of

last few years have seen signifi-

lations are cost effective with dis-

Many VSC instal-

the original design. Athermal stor-

cant reductions in the first cost of

placed electricity values of 4 cents

age application at a new auto as

electronic controls that can be ap-

per kWh.

sembly plant in Kentucky is cred-

plied to motors of up to several

ited with cutting the electrical

hundred horsepower. There are

Th ant provides a good example.

charges for plant cooling by

two broad groups of electronic

Rxisting constant-speed systems

roughly half.6 The contribution of

controls: Variable Speed Controls

have high piessums designed in, to

process-related cooling and air con-

(VSCs) applicable principally to

provide plenty of flow with all ma-

ditioning loads to electrical system

pumps, fans and compressors

chines in production &Iistorically/

peakscouldbeminimizedwith

that have variable flow require-

more was better, so the flow rates

proper incentives to install thermal

ments, and Variable Voltage Con-

and pressures were almost always

storage. This would in turn lessen

trols (VVCs) that are applicable to

overdesigned.)

the need for new construction by

variable loads requiring constant

A VSC offers two major advan-

the affected utility systems, with a

speed such as stamping presses

potential benefit to all ratepayers.

and metal cutting machine spin-

tages: (1) precise pressure and adequate flow can be maintained at

dles. Two examples of the more

levels substantially below those

e pumping of machining cool-

Many industrial processes can yield significant energy savings.

The Electricity Journal

required with a fixed-speed sys-

viously possible. The average elec-

creased use of high-efficiency mo-

tem; and (2) flow can be turned

tricity savings depend on boiler

tors in industry is 1 to 2% of the industrial load.

off for workpiece change at one

load, but will exceed 60% in a typi-

machining station without affect-

cal year. Coal use has, of course,

ing the flow and pressure at other

alsobeen reduced and the reduced

stations. In one application at an

steam loss has reduced water treat-

engine plant, pressure at the

ment cost?

pumps was reduced from a typical 64 psi to 45 psi, average flow

M

C. Motor Drive and End-Use Efficiency Improvements Improving the mechanical efficiency of the transmission or end-

otor control applications con-

use also reduces energy use in

tinue to be discovered by

electrical motor systems. Gener-

cut in half, and power usage re-

plant engineers. Demonstrations of

ally this type of efficiency im-

duced by over 50% with no ad-

control applications for specific situ-

provement is made by the equip-

verse effect on part quality or tool

ations in a great variety of plants are

ment manufacturer to ensure satisfactory service (e.g., ineffi-

life.8

cient gear boxes tend to overheat

An ancillary benefit of the reduced fluid pressure and flow is a

and fail prematurely).

In any

reduction in “misting” of the cool-

event, field retrofits of major me-

ant. Reducing the coolant-system

chanical components on a ma-

pressure and flow reduces the ve-

chine are usually so expensive

locity of the stream directed at the

that replacing the entire machine

workpiece, thus reducing the ten-

is more economical.

One retrofit

dency of the coolant to “atomize”

item that is economically practical

into an aerosol mist. Coolant mist

is the replacement of standard vee

is objectionable because it in-

belts with cog belts. Before-and-

creases ventilation requirements,

after tests run by user personnel

cleaning costs, etc.

on actual field installations have shown motor load reductions of 2

Energy used to control air flow from fans can often be reduced by

to 10% after installation of cog

replacing damper control with a

belts. Belt drives make up a vari-

VSC. Damper control of flow

able, but significant, portion of

from draft fans on coal-fired boil-

the total motor drive population in most plants. A reduction in

ers is a typical example. In one application, control of combus-

needed before wide adoption will

total industrial plant load of

tion and air pollution as mea-

occur. Few plants have made sys-

about 1% as a result of vee belt to

sured by opacity was inadequate

tematic surveys of motor control op-

cog belt conversions appears a

at low load. For this reason, boil-

portunities.

reasonable expectation.

ers had to be operated above re-

B. Replacing Inefficient

Motors

quired levels during low steam

The efficiency difference of

load periods, with part of the

about 5% between standard and

steam being vented.

high-efficiency motors,10 is usu-

v. COMPRESSED

AIR SYS-

TEMS Central compressed air systems

ally enough to justify use of high-

are a feature of many modern in-

contmlling the fans with VSCs

efficiency motors in new applica-

dustrial plants, representing 10 to

reduced electricity usage in two ways: (1) power to the motors was

tions and when a standard motor

30% of the total plant electrical

is being retired. ** It is not enough

load in the automobile industry

reduced during low steam flow pe

of a difference to warrant replac-

riods, and (2) lower steam flows

ing a working standard motor.

Uses for compressed air range from hand-held rotary tools for

were achieved than were pre

Total savings anticipated from in-

tightening nuts and bolts to huge

E

liminating

July 2989

the dampers and

45

duction hours. For plants with more production than down hours, leak reduction programs are essen-

Table 2: Demonstrated Application of Systems to Reduce Air Compression Loads in Non-production Hours Base

Segmented

Case

System

tial to control compressed air use.

Satellite System

B. Leak Reduction Compressed air leak reduction programs have been instituted at

Production Compressed

air (cfm)

8000

8000

8000

many plants with varying suc-

Compressor

motors (hp)

1600

1600

1600

cess. Correcting the accessible, ap parent (audible) leaks at valve

Non-Production Compressed

air (cfm)

Motors inc. auxiliaries (hp) Power (as % of production)

2500

1500

300

900

600

150*

45

35

5

packings, quick disconnect fittings, hoses and pipe fittings can reduce compressed air usage by 10 to 25% if pursued to completion. The results of a one-year

*Duty factor of 50%

leak reduction campaign at one plant were effective for at least pneumatic cushions for the sta-

arate production-line sections of

two years after the program was

tionary dies in stamping presses. Air-driven hand tools have a

the compressed air network from

completed and the crew reas-

the main supply. They reduced

signed to other tasks. However,

higher power-to-weight ratio than

the off-shift use of compressed air

an ongoing program in the form

electric tools and have the further

from 2500 cfm to 1500 cfm, or by

of a permanently assigned leak re-

advantage of no shock hazard.

40% (Table 2). The 1000 cfm re-

pair crew is often necessary to

Unfortunately

duction, equivalent to about 200

achieve a lasting result.

kW, saves more than $300 during

S

leaks waste up to

50% of the energy input to the

ome major air leaks are not ac-

compressed air system in many

a single weekend shutdown even

plants.

at the off-peak electricity rate of

the uninitiated. An example is the

$O.O3/kWh.

die cushion on large stamping

ven

A. Off-Shift Operations

E

well-maintained com-

pressed air systems require 20

2. Satellite System. A more radical approach was also tried at the

cessible nor are they obvious to

pressesusedtosupportinsertsin the lower die. As the press de-

to 30% as much power during non-

same plant: provision of com-

scends, the sheet metal is clamped

production hours as they do during

pressed air only where it is regu-

by the frames of the upper and

full operation. In automotive as-

larly needed under non-produc-

lower dies; then it is drawn as the

sembly plants there is some non-

tion conditions. Eight small

insert is pushed down under the de-

production-hour air use for paint

sections of the network were iso-

scending insert of the upper die.

agitation, pneumatic instruments

lated with check valves and pro-

The quality of the stamping de-

and maintenance activities; but

vided with small local compres-

pends on a smooth and constant TP

most compressed air use at those

sors in the 15 - 25 hp range. (See

sponse from the cushion. Histori-

times goes to leakage. Two &rate

Table 2.) This configuration re-

cally, standard die cushions have

gies were tried at the automotive as-

duced electricity usage by 80%

been cylinders pressurized with air

sembly plant identified as Plant 1

from full production to the week-

from the plant system. These units

(in Part III above): segmented sys-

end shutdown cited earlier.

leak little in new or recently rebuilt

tems and satellite systems (see Table

S

hutdown techniques are, how-

presses, but as little as three

ever, most effective in plants

months use on a moderate sized

that operate only one shift and thus

stamping press will often produce

have more “down” hours than pro

leaks of 100 cfm. In a large stamp

2).

1. Segmented System. Automatic valves were installed to sep-

46

7’heElectricity Journal

ing plant with 200 presses this trans-

pistons used as counter-balance

lates into 20,ooOcfm of compressed

cylinders in a stamping press. In

cal, metal halide lamps may be in-

air which in turn equates to about 4

all, a reduction of about 25% in

stalled with an energy saving of

MW of electric load.

compressed air requirements has

about 50% compared to mercury

ie cushions are particularly

been achieved at a stamping plant

vapor or fluorescent lamps. If

tnkrblesomebecause repair re

D

tions where color rendition is criti-

in Michigan from this technology

color rendition is not critical, high

quims taking the press out of ser-

after converting one-half of the

pressure sodium lamps offer en-

vice for several weeks (a luxury

presses. I3 The complete program

ergy savings of 5060% compared

most stamping plants cannot af-

will probably achieve a lo-15% re-

to mercury vapor.

ford) otherwise the leak must be fed

duction in plant electricity use.

with air constantly becauseif the

(There is some uncertainty be-

cushion ” bottoms” it may be diffi-

cause applications have not yet

S

fluorescent tubes. More efficient

ome local or “tasY lighting already involves high-efficiency

cult to raise. Recently press owners

been made with all types of

high-frequency ballasts and specu-

and rebuilder-s have begun replac-

presses.) As the technology gains

lar reflectors can be installed with

ing the pistons with air actuators

wider acceptance it should have a

savings of 50 to 60%. With half as

(heavy-walled rubber air bags sup

major impact on compressed air

many bulbs, this combination will

porting a metal plate) with ex-

usage in the stamping industry,

deliver about 90% as much light as

tremely favorable results. Some of

where 25-35% of the electricity

at present. The performan~ of the

these installations have been in ser-

load is for air compressor drives.

reflectors after use in various manu-

vice for over five years with little or no perceptible air leakage.” This technology has two major

facturing conditions is being evalu-

VI. LIGHTING The typical goal for plant light-

ated. A major office building in Michi-

benefits aside from reduced elec-

ing is to provide adequate area

gan provides an example of sav-

tricity costs: more consistent prod-

lighting using highly efficient

ings possible from reworking

uct and greatly reduced mainte-

lamps with reasonable color, such

lighting systems in administrative

nance (with reported cost savings

as the high-pressure sodium

facilities. High-efficiency fluores-

in maintenance and replacement

lamp, and to provide more in-

cent ballasts and improved reflec-

comparable to those in electricity). The technology has other applications, for example replacing air

tense higher-quality light on pro-

tors are improving lighting levels

duction activities, using efficient

and simultaneously reducing elec-

fluorescent lighting. For situa-

tricity use for lighting from 3.7 to 1.8 Watts/ft2 in office areas. When completed, this lighting system renovation will reduce lighting load by about 50% and the total building electrical load by nearly 10%. Similar results have been obtained in a manufacturing facility of 1950s vintage where fluorescent fixtures using 2W /ft2 have been replaced by metal halide lamps consuming 1W /ft2 and providing improved lighting levels. ssuming that lighting conA

Finding areas where savings are possible can seem like reinventing the wheel.

July 1989

sumes an average 10% of total

manufacturing electricity use and

47

thatlessthan25%ofthatuseisnow

plant electricity usage by about

useful thermal energy and met cer-

in high-efficiency features, we esti-

5%. Exact measurements of the re-

tain efficiency standards.

mate that 3 to 4% of total electricity

duction are not available because

use in manufacturing will be saved

major process changes were in

through the above lighting im-

progress during the period that

provements.

VII. HEATING AND VENTI-

systems in U.S. industry reflect

of Electricity

One approach is to cogenerate

the new H&V system was in-

two multiple-purpose

stalled.

able forms of energy at a site re-

transport-

mote from the point of use, usu-

LATING SYSTEMS Heating and Ventilating (H&V)

A. Cogeneration and Steam

VIII. COGENERATION

ally a power house. Three kinds

The advantage of simulta-

of prime movers are in wide use

the fact that many if not most,

neously generating shaft power

for this purpose: steam turbines,

U.S. manufacturing plants are

and heat is that in converting heat

combustion turbines and recipro-

over 30 years old. While nearly

into shaft power all engines must,

cating engines.

all these facilities have seen major

according to the second law of

process changes, few have had a

thermodynamics,

discharge a sub-

team turbine cogeneration is S

typically employed for large

complete overhaul of their H&V

(X25 MWe) applications with a high

systems. As these systems are re-

steam demand (>250,fXX1lbs./hr)

placed, significant reductions in

and is not common in the automo

electricity use can result.

tive industry because it lacks large

r example, a 30 year-old plant

year-round steam loads. Common

I? in Ohio had a mixture of steam

users of steam turbine cogenemtion

coil and both direct and indirect gas

include the petroleum refining and

fired heating units. ln all there were

pulp and paper industries, where

% H&V units with a total installed

process steam loads are substantial

motor load of over 2000 horse

and process by-products are a

power including fans on the coal

major boiler fuel source. Combustion or gas turbines pro-

fired boilers and steam condensate pumps. The H&V “system” lacked

vide a medium power output

coordination, with the result that

(one to 100 MW) with a lower ratio of thermal output to electric-

some areas were excessively drafty stantial part, typically one-half or

ity than is the case with steam tur-

more, of the input heat energy in

bine cogeneration.

the form of lower-temperature

mon type of combustion turbine

computer control of 16 new direct

heat. So, providing power and

installation (or simple cycle

fired gas H&V units with an in-

moderate-to-low

stalled motor load of 800 horse-

heat from one facility is more effi-

power of a combustion turbine to

power. The exhaust, fresh air and

cient than from two separate facili-

drive a generator and the exhaust

recirculation capabilities of the

ties. In many cases it is also more

new gas-fired units are fully con-

economical.

heat to raise steam for process heating in a specially designed

while others were under-ventilated. In 1987 the system was replaced. The new system features

trolled, using a standard IBM PC

temperature

ongress and the Carter Admin-

The most com-

cogeneration) uses the shaft

boiler. lf the steam and electricity

istration thought this practice C was worth special consideration.

can be used at the plant year-

The Public Utility Regulatory Poli-

systems are economical (i.e., the

cies Act of 1978 granted special

steam and electricity together are

terms of correcting the ventilation

legal status to facilities that simulta-

cheaper than providing them sep-

problems and has reduced total

neously produced shaft power and

arately by a boiler and by the elec-

equipped with special software to analyze information from temperature, pressure and haze sensors. The installation is a success in

48

round, then such cogeneration

The Electricity Journal

tric utility).

This is true even

when the cogeneration system is fired with natural gas. Such a system was installed at a Michigan plant in 1985. The 3.8 MW natural gas fired combustion turbine unit produces over 20,000 lbs./hr of 115 psi steam from the turbine exhaust.14

A

vailability for service of cogeneration units is compara-

ble to or better than that of utility central station generating plants. The unit mentioned above was on line for 98% of the planned operat-

Automobile assembly [email protected] many opportunities for efficiency.

ing hours in 1987. A group of 24 similar units in the Netherlands

out going through the intermedi-

time. We have not addressed the

with over 480,000 total operating

ary medium of electricity. An ap-

issue of possible increases in elec-

hours reported a lifetime average

plication of this concept that has

tricity use for new applications.

availability of 95% on the same

reached the funded project stage

The anticipated impact on electric-

basis.

is using a combustion turbine for

ity consumption of increased use

The same basic equipment, a

directly driving an air compressor

of robotics is slight in our view, in

combustion turbine and a heat re-

for a stamping plant. About 14%

part because the reduced need for

covery boiler, can also be adapted

in losses are avoided by directly

worker comfort conditioning

for injection of some or all of the

driving the load: 1.5% at the tur-

often offsets the energy consump-

steam into the turbine at the com-

bine-generator gearbox, 5% or

tion of the robot. Even air condi-

bustion chamber (steam injected

more at the generator, 2% at the

tioning of entire manufacturing

gas turbine). This provides for

switchgear and transformers, and

operations has had relatively little

much higher electricity output

5% at the motor. Other applica-

impact on electricity use in facili-

and reduced net steam output,

tions involve using natural gas-

ties which incorporated thermal

thus enabling economic operation

fueled reciprocating engine drives

storage in the air conditioning sys-

with variable steam demand over

for air compressors and mechani-

tem design. However, the values

the year.i5 This configuration is

cal refrigeration equipment.

in Table 3 should not be taken to

relatively new, with several appli-

tential reciprocating engine appli-

mean that there will be no new

cations in California. A unit was

cations have been identified in

uses for electricity,

recently installed in an automo-

assembly plants where the ex-

G

tive plant in Michigani

and an-

Po-

haust heat would be used for heat-

ranting the uncertainty of our

estimate, the potential conser-

other installation is planned for a

ing hot water for the metal pre-

vation opportunity is quite large.

major office building in Detroit.

treatment baths,

The reduction in electricity purchases associated with cogeneration

B. Displacement of Electric Motor Drives with Engine

IX. CONCLUSIONS

is less certain than for other conser-

Drives

Table 3 shows our estimate of

vation measures because more variables am involved. The savings

used in the same immediate vicin-

the probable energy and capacity savings associated with various

ity, then substantial savings may

conservation measures being im-

ior, with existing technology cost

be achieved by cogeneration with-

plemented by industry at this

forecasts, and financial criteria. In

If shaft power and heat can be

July 1989

shown am based on current behav-

49

other words, Table 3 is based on

dustry, since earnings are the

should track utility costs as much as

projects which have already been

major source of capital for imple-

possible. Cost of service should be

successfully implemented in some

menting conservation.

the guiding principle in allocating

plants. In terms of 1989 conditions

years earnings have been rela-

charges to different groups of users

this is a business-as-usual estimate

tively good and projects requiring

and in setting the relationshipbe

of savings. We have not assumed

capital are thus more likely to be

tween energy and demand charges.

complete implementation of pro

implemented.

The industrial sector can and will re

jects where that seems unlikely ese results, while based on a

In recent

Manufacturers have many

spond to high demand charges

proven electricity conservation op

with a combination of peak-shaving

Th study of the automotive indus-

portunities, and most have access

facihties and conservation, and to

try, are applicable in general terms

to the money required to imple-

high energy charges with a combi-

to most fabrication and assembly ac-

ment them. What they do about

nation of cogeneration and conser-

tivities17because their processes ate

them, however, will depend on

vation, including reductions at off-

broadly similar and the ratio of elec-

the stimuli, in the form of rates

peakhours.

tricity cost to value of shipments is

and other financial incentives cre-

about 1 .O%or less. While nationally

ated by utilities and regulators.

the auto industry pumhases just

Perceived future rates are at least as important as current rates

The key factor that drives indus-

in framing decisions to invest in

over 1% of all electrical energy sold

trial users to install conservation

conservation and on-site genera-

by utilities, the assembly and fabri-

and on-site generating equipment

tion. The anticipated savings in

cation industries consume about

is, as it should be, the price of elec-

the second to fifth year beyond

13%.

tricity.

The speed with which these savings will be achieved by industry

the present usually have the great-

n view of that fact, we offer a few

est impact on decision making on

parting observations on the issue

such projects. Even where manag-

I

depends on several factors: elec-

of price which we hope will be use

ers do not rely on formal price

tricity price, management percep

ful to those in utilities and regula-

forecasts, they depend on their

tions of future price escalation,

tory

capital availability and improve-

policy The first point is that rates

bodies who determine prim

judgment about future prices. Thus, planning concerning rates

ments in conservation hardware (including reductions in installed cost).

Table 3: Estimate of Electricity Use Reduction Anticipated in the

Motivations for carrying out

Automotive Industryab

electricity-saving projects other

Energy

Demand

than price include: (1) interest of

(kWh)

(kW)

4-8

-

5-10

5-10

3-5

2-4

Lighting

3-4

3-4

Heating and ventilating

1-5

l-5

3-12

2-10

19-44

13-33

the senior management of the

Shutdown controlsC

firm, and (2) the ancillary benefits

Motor systems

of the projects. If a project will in-

Compressed

crease the reliability of production, improve working conditions and/or reduce maintenance requirements, as well as save energy, it will be done much more quickly. As we have indicated, many energy conservation projects have such ancillary benefits. The pace of saving also depends on earnings within the in-

50

Cogeneration

air systemsd

& electric

motor displacement TOTAL a The savings shown are characteristic

of present behavior

and an average electricity

price of

about 6 cents/kWh. b Percent of total electricity use at the plant. ~Includes EMS and compressed air controls discussed in text. Control of compressed air in non-production hours not included here.

The Electricity Journal

logne, West Germany

(Oct. 5-7, 1987).

9. R. Futryk and J.A. Kaman, Variable Speed Control of Lorain Assembly Plant Boiler Fans, Presented Ford International Cologne,

at 1987

Energy Conference,

West Germany

(Oct. 5-7,

1987). 10. W. J. McDonald

and H. N. Hickok,

Energy Losses in Electrical Power Systems, IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS,

The end result: a smooth ride

forutilities,

and planning for investments in utility plant which customers will be expected to pay for should be disseminated to the industrial

industry, consumers, and the environment.

TURES 1985, STATISTICS FOR INDUSTRY GROUPS AND INDUSTRIES

high-efficiency

(1985) (including

large or very small motors.

electric energy use

and costs).

opportunity onsider, for example, “incen-

3. This is the electricity

tive,” “economic develop

ment,” or other discounted rates. Such rates are used, as a means of stimulating growth, at many utilities with temporary surplus capacity. But such rates also serve as a disincentive to conservation and cogeneration. While it is proper that conservation and cogeneration

tion and assembly roughly comparable

used in fabrica-

of motor vehicles. A amount of elec-

tricity is used to produce the materials of which the vehicle is made: primarily iron and steel, followed by plastics, aluminum, rubber, glass, copper, lead and zinc. The 2240 kWh figure includes the energy required to melt metal to make castings, such as engine blocks. 4. I? Wright, U-M Hospital Looks to Save Millions with VAV, Thermal Storage Systems, ENGINEERED

needed, it is equally important that

SYSTEMS

(Mar.-

5. J. A. Koehler, Stratified

needed.

Water Thermal Storage System”, 1986 Energy Technology Conference, Wash-

to reduce anticipated costs through conservation and cogeneration in ways that reduce costs for the entire customer community.

n

Footnotes: 1. MICHIGAN DEPARTMENT OF COMMERCE, ELECTRICITY OPTIONS FOR THE STATE OF MICHIGAN: RESULTS FROM THE MEOS PROJECT

July 1989

(1987).

Chilled

The economics with

Establishing

Man-

Control with Flexible Actu-

ator Die Cushions, Presented at 1987 Ford International Energy Conference, Cologne, West Germany

(Oct. 5-7,

1987). 13. K. E. Robbins, Adapting tors to Stamping

Air Actua-

Presses at Grand

Blanc Stamping Plant, Presented at 1987 Ford International Energy Conference, Cologne,

West Germany

(Oct. 5-

14. R. Luke, A New Approach to a Turn-of-the-Century Technology, Presented at 1987 Ford International Germany

ington, D.C. Facility,

PLANT ENGINEERING, March 10, 1988; Toyota Grafts an Assembly Transplant to the U.S., BUILDING & DESIGN CONSTRUCTION, Sept. 1988, at 48-53.

En-

Cologne, West

(Oct. 5-7,1987).

15. R. H. Williams and E. D. Larson, Steam-Injected Gas Turbines and Electric Utility Planning,

6. Designing a State-of-the-Art

7. ELECTRIC

ufacturing

ergy Conference,

they be encouraged when they are

enable industrial customers to act

motor.

less favorable

7, 19871.

Apr. 1986).

on utility planning and rates will

are somewhat

12. K. L. Smedburg,

be discouraged when they are not

Reliable and timely information

11.For lo-150 hp motors, duty over 1000-1500 hours/year yields a 2-3 year simple payback for replacement of a motor at time of retirement by a

2. U.S. BUREAU OF THE CENSUS, ANNUAL SURVEY OF MANUFAC-

community at the earliest possible

C

May-June

1985, at 803-819.

AND SOCIETY

IEEE TECHNOLOGY Mar. 1986 at 29-38;

and E. D. Larson & R. H. Williams, Steam-injected Gas Turbines, ASME J. OF ENG. FOR GAS TURBINE & POWER, Jan. 1987 at 55-63. 16. R. K. Rose and F. S. Ralbovsky,

POWER RESEARCH

IN-

STITUTE, ADJUSTABLE SPEED DRIVES: DIRECTORY, MANUFACTURERS AND APPLICATIONS (2d Ed. 1987). 8. R. E. Strohs, Application of Variable Speed Drive Pumping Systems for Energy Savings, Presented at 1987 Ford International Energy Conference, Co-

New Options and Design Approaches Gas Turbine Cogeneration Plants, TURBOMACHINERY

for

(Mar.-Apr.

1987). 17. Including all sectors of manufacturing, except some textile plants, pulp and paper mills, and industrial

chemi-

cal, petroleum refining, glass and cement, and primary metals facilities.

51