Energy Survey Workshop
The first step in energy management
Andrew Ibbotson
Joe Flanagan
What is an energy survey?
For a site, dept, or process
• Establishes the energy cost and consumption
• Is a technical investigation of the energy flows
• Aims to identify cost effective energy savings
• Examines both the technical and ‘soft’
management issues.
Why carry out a survey?

Identify savings

Establish the viability of an energy
management programme

Establish a ‘baseline’
The Energy Management Process
Identify where Energy is Used
and Develop an Action Plan
Survey
Senior Management
Commitment
Measure Energy Consumption
and Production
Review Performance
and Action Plan
Develop Targets
Implement Energy
Saving Measures
Produce Reports to Monitor
Energy Use Against Output
DIY or Consultant?
Consultant
DIY

Expertise

No cost

Fresh pair of eyes

No learning curve

Should not be afraid
to poke into any
corner

Projects should be
viable

Opinions may carry
more weight

Job will be completed
Choosing a Consultant

Salesman or consultant?

Ensure he/she is experienced in your
process

Don’t be afraid to take up references

Cost - day rate of fixed price
The Survey Process
1.
Define the scope
2.
Establish energy balances
3.
Identify priority areas
4.
Identify energy saving projects
5.

Low cost (control, housekeeping, awareness)

Medium cost (revenue expenditure <1 year payback)

High cost (capital expenditure <2-3 year payback)
Reporting
How much effort is required?
Depends upon

complexity of the site and scope

Level of detail available (esp. sub-meters)

Size and energy intensity

Rule of thumb

Up to €200,000 – 6 mandays

Up to €1,000,000 – 10-15 mandays
Scope

Electricity, gas, oil, solid fuel etc

?Water, effluent, industrial gases

In general further detailed study will be
required for medium and high cost
opportunities
Energy Balances and Data Analysis

Last 12 months bills

Sub-meter readings

Principal energy users

Production and climatic data

1st Law of Thermodynamics – energy can
neither be created or destroyed
Electricity Bills

Maximum Demand charges (kVA, kW)

Capacity charges (kVA, kW)

Day and night rates

Power factor
Power Factor
kWh
PF = kWh/kVAh
φ
= cos φ
kVArh
kVAh
From the electricity bill
kWh
= 17,400
kVArh = 8,700
What is the power factor?
Power factor
tan φ
= 8,700/17,400
= 0.5
φ = 26.5º
cos 26.5 = 0.89
PF improved by adding capacitors
Worthy of further investigation below 0.85-0.90
Date
01-Jan-02
02-Jan-02
03-Jan-02
04-Jan-02
05-Jan-02
06-Jan-02
07-Jan-02
08-Jan-02
09-Jan-02
10-Jan-02
11-Jan-02
12-Jan-02
13-Jan-02
14-Jan-02
15-Jan-02
16-Jan-02
17-Jan-02
18-Jan-02
19-Jan-02
20-Jan-02
21-Jan-02
22-Jan-02
23-Jan-02
24-Jan-02
25-Jan-02
26-Jan-02
27-Jan-02
Tue
Wed
Thu
Fri
Sat
Sun
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Mon
Tue
Wed
Thu
Fri
Sat
Sun
00:30
01:00
01:30
02:00
02:30
03:00
03:30
04:00
04:30
05:00
05:30
144
148
146
146
148
146
148
148
148
152
146
586
576
570
558
572
558
560
568
562
564
560
570
580
550
568
564
568
556
576
574
546
568
544
570
572
566
566
574
568
562
566
582
568
544
560
516
506
452
408
400
412
416
408
374
494
512
504
504
514
506
516
524
526
510
528
594
574
570
562
554
542
534
544
538
550
518
584
574
570
564
566
566
562
564
572
566
568
576
550
556
568
570
560
568
566
552
560
568
568
556
564
556
548
526
538
544
550
536
524
576
568
578
568
572
566
564
570
538
564
576
458
446
422
406
360
294
290
272
228
190
174
502
502
492
486
472
506
508
512
508
478
508
590
572
566
564
552
544
548
572
584
536
534
602
582
568
580
562
562
560
572
590
580
572
562
560
562
524
544
546
558
542
540
538
544
570
566
572
546
562
542
554
554
522
542
564
586
588
572
566
576
568
570
574
556
580
576
344
292
282
230
196
194
194
194
198
204
204
496
504
506
502
504
506
492
516
518
508
526
586
574
524
560
560
560
564
556
560
560
540
582
572
576
544
546
566
566
572
558
544
562
564
572
536
552
552
550
544
558
532
564
566
566
570
564
538
544
546
522
566
560
562
566
570
572
572
550
562
556
542
532
572
560
570
408
398
354
336
288
234
226
210
206
210
210
512
510
490
502
468
442
444
452
454
446
458
Average Electricity Half Hourly Data Lock Street (Year to 30/9/02)
700
Monday
Tuesday
Wednesday
Thursday
600
Friday
Saturday
Sunday
400
300
200
100
23
:0
0
22
:0
0
21
:0
0
20
:0
0
19
:0
0
18
:0
0
17
:0
0
16
:0
0
15
:0
0
14
:0
0
13
:0
0
12
:0
0
11
:0
0
10
:0
0
09
:0
0
08
:0
0
07
:0
0
06
:0
0
05
:0
0
04
:0
0
03
:0
0
02
:0
0
01
:0
0
0
00
:0
0
kWh per 1/2 hour
500
Gas Bills
• More frequently estimated (in the UK)
• Errors more prevalent
• Very rarely obtain ½ hourly demand
• Can obtain some useful energy
management information
Figure 2: Monthly Gas Consumption
500,000
450,000
‘Base’ or
process gas
load
400,000
350,000
kWh/month
300,000
250,000
200,000
150,000
100,000
50,000
0
Jan-99
Feb-99
Mar-99
Apr-99
May-99
Jun-99
Jul-99
Aug-99
Sep-99
Oct-99
Nov-99
Dec-99
Electrical Balance
• Sub-meters help – but rarely provide all the
required information
• Need to list major electrical consumers
(pumps, fans, compressors, chillers,
lighting, process heating etc)
• Need rating and running hours
Estimating Electricity
Load
Design
kW
Actual
kW
Load
factor
Hours
per year
kWh
Grinder
150
120
0.7
4000
336,000
Pump
55
55
1
6000
330,000
Compressor
150
140
0.5
6000
420,000
Lights
25
25
1
3000
75,000
Total
1,161,000
Estimating Electricity
Load
Design
kW
Actual
kW
Load
factor
Hours
per year
kWh
Grinder
150
120
0.7
4000
336,000
Pump
55
55
1
6000
330,000
Compressor
Design kW
150
140= rating
0.5 on equipment
6000
Lights
25 e.g. plate
25 rating
1 of a motor;
3000
Total
wattage of a bulb
420,000
75,000
1,161,000
Estimating Electricity
Load
Design
kW
Actual
kW
Load
factor
Hours
per year
kWh
Grinder
150
120
0.7
4000
336,000
Pump
55
55
1
6000
330,000
Actual
kW = best
Compressor
150
140 estimate
0.5 of actual
6000 power 420,000
reading
or
design data 75,000
Lights e.g. based
25 on ammeter
25
1
3000
Total
1,161,000
kW = √3*V * I * PF
Estimating Electricity
Load
Design
kW
Actual
kW
Load
factor
Hours
per year
kWh
Grinder
150
120
0.7
4000
336,000
Pump
55
55
1
6000
330,000
allows for
Compressor Load
150 factor140
0.5 variable
6000load
Lights
Total
e.g.25air compressor
on
/ off load
25
1 load 3000
420,000
75,000
1,161,000
Estimating Electricity
Load
Grinder
Pump
Design
kW
150
55
Compressor
150
Lights
25
Total
Actual
kW
120
Load
factor
0.7
Hours
per year
kWh
4000
336,000
Total should = metered total
55
1
6000
330,000
either for whole site or for a sub-meter
140
0.5
6000
420,000
25
1
3000
75,000
1,161,000
Estimating Electricity
• High accuracy is time consuming
• ±10% is very good
• Portable data logger useful for large users
• Don’t underestimate the large number of
small users e.g. conveyors, fans, pumps
Electricity Balance
Figure 1: Electricity Balance
Lehr Heating
2%
Batch Plant
2%
Lehr Fans
3%
Bath bottom cooling fans
4%
Other
10%
Furnace Cooling Fans
14%
Lighting
17%
Bath Heating
6%
Furnace Water Pumps
7%
K Line EP
11%
Fin Fan Coolers
11%
Compressors
13%
Fuel Balances
• Process vs. space heating from a year of
monthly or weekly data
• Difficult to estimate the distribution among
process users if there is no metering
• Most gas process plant will operate well
below MCR – manufacturers specification
• No portable gas metering
Could CHP be feasible?
• Power demand >500 kW
• Coincident heat (steam or hot water)
demand?
• Heat to power 3:1
• High operating hours > 2 shift 5d/week
Benchmarking
• Comparison to a published benchmark often seen
as method for estimating savings
• Treat with caution
> ‘best practice’ often refers to ‘state of the art’
> Utilisation has a large influence
• Generally confirms what you already know
• Greatest validity for ‘basic’ industry – metals,
ceramics, glass etc..
• Lots of information at www.actionenergy.org.uk
Boilers & Steam Systems
Scope
Basic Combustion Process
Natural gas
8N2 + CH4 + 2O2  CO2 + 2H2O + 8N2
Plus the release of ~10 kWh/m3 of CH4
10 volumes of air required for 1 volume of
methane
Heat Recovery Process
Gas Passes convection
Burner
Furnace Tube - radiation
Boiler Losses
Exhaust
(~20% on gas, ~16% on oil)
Air & Fuel
Blowdown
(<5%)
Convection proportional to T
Radiation proportional to T4
Convection &
Radiation
(1% to 1.5% @
max continuous
rating (mcr))
Combustion Losses
• heat loss in flue gases
• Latent heat of water vapour in flue gases
• incomplete carbon combustion
• ‘Excess’ air must be kept to a minimum
• Generally at least 10% excess is required to
ensure good combustion
• Combustion losses depend upon volume and
temperature of flue gases
Excess Air
• measured by inference from O2 in exhaust or
level of CO2 in exhaust
• Portable instrument (measures O2, temp and CO
• Permanent zirconia probe in stack linked to
air/gas valves (oxygen trim)
Best Boiler Efficiency
• optimised fuel / air ratio well insulated (shiny
surface)
• clean burner nozzles
• clean boiler surfaces
• minimum steam pressure / temperature
• reasonable load (~80%)
• optimised TDS controlling blowdown
Combustion
• 1% efficiency increase, 79% to 80% savers 1- 0.8 =
1.25% fuel
> reduction of 02 by ~2%
> reduction of exhaust temperature by ~20ºC
• oxygen trim control; 1% to 1.5% on well adjusted boiler
• Air preheat (duct from air compressors or boilerhouse)
saving 0.5% to 1%
Blowdown
• maintaining recommended TDS levels ensures
clean heat transfer surfaces
• operating low TDS waste energy, water,
chemicals and increases effluent costs
• heat recovery (for large boilers payback 2-3
years)
Other
• check optimum load on boilers
• rank multiple boilers to operate the group with
minimum loss
• Shutdown Loss Minimisation
> gas side isolation with dampers
> water/steam side isolation with crown valve
Heat Recovery
• economiser (to feedwater)
• recuperator (to wash water)
Insulation
• check existing quality
• insulate all hot pipework, flanges (1m pipe),
valve bodies (5m pipe)
• hotwell cover and insulation
Key Points for the Boiler House
Check
• Boiler efficiency
• Blowdown procedure
• Condensate return
• insulation
The Nature of Steam
Breakdown of heat content of 7 bar g saturated steam
Item
Heat Content
KJ/kg
Latent at 7 bar g
%
2050
74
Flash at Atmospheric from 7 bar g
300
11
Condensate at Atmospheric
420
15
2770
100
Total
System Standing Losses
Fixed loss from:
• Pipework
• Valves
• Fittings etc.
Losses range from 2% to 5%
System Variable Losses
Flash and
condensate
return
% losses with steam at
? bar g & cond. at 0 bar g
7
5
3
0
Total loss
26
24
22
15
50% cond. return
19
17
15
7
Management Control
• Automatic isolation systems
• Pressure reduction
• Energy management:
> Metering
> Data analysis
> Action
Fixed Losses
• Insulation
• air ingress
• steam leaks
Pipework
• Size:
> cost trade-off
• Installation:
> air removal
> condensate drainage
> weather sealing
> group users
Pressure Reduction
• More efficient
• Saves fuel
• Cost incurred for:
> pressure reduction sets
> larger heat exchangers
> larger traps
• Consider life cycle costs
Steam Leaks
1000
800
600
12.5
mm
10 mm
400
7.5 mm
200
100
80
60
5 mm
40
3 mm
20
10
8
6
4
3
2
3 4 5 7 10 14
Examples:
Steam Leak = 7.5mm diameter
Steam Pressure (barg) ( or pressure difference
between steam and condensate) = 6 bar
Steam Loss = 100 kg/h
Steam Trapping & Air Venting
• Steam trapping
>
>
>
>
function
testing
group trapping
sizing traps
• Air venting
• Scale and dirt removal
Condensate Recovery
Saves costs for:
• Water
• Treatment chemicals
• Fuel
• Effluent
Produces rapid payback
Flash Steam Recovery
By:
• Indirect method
• Direct method
Potential sinks:
• BFW
• Wash water
• Process fluid
• Space heating
Key Points for Steam Systems
• Pipe insulation
• Leaks
• Isolation of redundant plant/off line plant
• Steam traps
• Condensate return
Lighting
Lighting
• Overview of main industrial lighting types
• Their efficiency
• Common savings
Lighting
• Typically 10-50% of electricity use
• Good lighting is critical to all manufacturing
operations
• Survey is relatively easy to carry out
Estimate of Load
• Rating of lamp
• Number
• Operating hours
• Add 10% for control gear
Common Industrial Lighting Types
• Fluorescent
> Offices, general manufacturing
> Good colour rendering
> Instant instantaneous on and off
• Metal Halide (HPI, MBI)
> Good colour rendering
• High Pressure Sodium (SON)
> Poor colour rendering
• Low Pressure Sodium (SOX)
> Very poor colour (orange yellow)
> Very efficient
Comparison of Lamp Types
Lamp Type
Lumens/watt
GLS
12
Standard Life hrs
(50% survival)
1,000
CFL
70
8,000
T8
70-100
6,000-15,000
T12
Metal halide
70
60-80
5,000-10,000
6,000-13,000
SON
108
15,000-30,000
SOX
138
12,000-23,000
Induction
70
60,000 (80%)
Typical Illuminance Levels
Lux
Activity
50
Cable tunnels, walkways
100
Corridors, bulk stores
150
Loading bays. Plant rooms
300
Offices (300/500), assembly
500
Engine assembly, painting spraying
750
Ceramic decoration, meat inspection
1000 Electronic assembly, toolrooms
1500 Precision assembly
Savings with Fluorescents
• Change T12 for T8
• Control (PIR, zoning, daylight)
• New systems
> High frequency ballasts
> High efficiency reflectors/diffusers
> Payback 2-4 years
Length
T8 (ø26mm)
T12 (ø38mm)
600mm 2’
18W
20W
1200mm 4’
36W
40W
1500mm 5’
58W
65W
1800mm 6’
70W
75/85W
2400mm 8’
100W
125W
Savings with Metal Halides
• Convert to SON (beware of colour issues)
• Payback ~1 year if replace 400W MBF to
250W SON (8760h/y). Cost of SON €100
• Convert to fluorescent if switching off is
possible
Top Tips for Lighting
• Lux measurement is worthwhile
• Switch off
• Need high lighting hours (2 shift) to justify
replacement
• Plenty of suppliers will carry out free
surveys
Compressed Air
Compressed Air
• Background to Compressed Air
• Reducing loads and pressure
• Improving distribution
• Improving generation
Compressed Air
• very expensive form of energy
> typically costs 1€/kWh
• often used unnecessarily or inappropriately
> Cooling, cleaning etc
• similar philosophy to steam / refrigeration
> minimise loads and pressures
> minimise distribution system losses
> maximise generation efficiency
Potential Savings
• Compressed air can account for up to 20%
electricity use.
• Enviros study identified minimum
potential savings of 27%
> generation (7%)
> distribution (11%)
> end usage (3%)
> new technology (6%)
Compressed Air System
Components
What to look out for - use
• Leaks
• Main uses of air such as tools, painting, instrumentation or
process
• Misuses such as open ended lances, full pressure blow
guns, product ejection and vacuum venturis
• End of line pressure
• Ring or spur mains?
Check Each Load
• why is air being used
> a key requirement or ‘habit’?
• can a load be eliminated or reduced
> replace pneumatic valves with electric
> ‘amplifier’ nozzles
• pressure and air quality requirements
> is it as low as possible
> how does it compare with other loads
Distribution
Three main issues:
• pressure drops
• water
• leaks
The Distribution System
• examine the pressure drop across the system
(velocity 6-9 m/s)
• pipework is rarely upgraded when system extended
• small bore pipe, elbows and short bends increase
pressure drop
• internal corrosion increases friction losses
• A 1 bar pressure drop increases energy cost by
10%
Distribution Lines – The Effect of Water
• Problems with water
> Causes corrosion
> Product quality
> Increases pressure drops
• Is drying adequate? Additional automatic
drain points
Leakage Losses
• typically 25 - 50% of full load usage!
• regular maintenance required to identify
and repair leaks especially where flexible
connections are used
• identify and tag leaks at the weekend
when production areas are quiet
Leak reduction
Leakage Losses
Hole diameter
Leakage at
7 bar/100 psi
Equiv.
Power
mm
Inches
l/s
scfm
kW
0.4
1/64
0.2
0.4
0.1
1.6
1/16
3.1
6.5
1.0
3.0
1/8
11.0
23.2
3.5
Some Ways of Reducing Losses
• Isolate air supplies outside working hours
> to the machines
> Interlock air supply with machinery
> to areas of the factory with different working hours
• Use the lowest possible operating pressure
> reduce pressure locally if possible
• If some consumers use low pressure air install a
separate system
Life Cycle Costs of Compressor
75%
Energy Cost
10%
Maintenance
15%
Capital
What to look out for in the
Compressor Room
•
Type, make, capacity, hours run and control of each compressor
•
Type make and configuration of treatment package
•
Room ventilation, inlets in or outside?
•
Is waste heat recovered?
•
What is the generation pressure?
•
Is there a group controller?
•
What is the estimated demand?
•
Are the feeding mains OK are there any other bottlenecks?
•
Do they have electronic zero loss condensate traps?
Filtration
• Filters cause pressure drops.
> To save energy meet the minimum requirement
> Undersizing raises pressure drop
> Every 25mbar pressure drop increases
compressor power consumption by 2%
Drying
• Ambient air at 15oC contains about 12.5g
water per cubic metre
• Most condenses in the aftercooler
> An after cooler might remove 68% of the water in the air
if cooled to 35oC
• Further drying is usually necessary
> Deliquescent - energy efficient, cheap
> Refrigerated - popular, 3-5% energy cost (dew point 3ºC)
> Desiccant – air regenerated can consume 15-20% of air
produced (dew point -60ºC)
Guidelines for Drying
• Generally design to dry air to 6ºC below
ambient temperature
• Don’t run pipework outside if possible
• Only dry as much air as is necessary (i.e.
have a separate wet and dry system)
Compressor Efficiencies
Configuration
Lubricated Piston
Oil Free Piston
Lubricated Screw/Vane
Oil Free Screw
Centrifugal
Capacity Nm3/h
2-25
25-250
250-1,000
2-25
25-250
250-1,000
2-25
25-250
250-1,000
25-250
250-1,000
1,000-2,000
250-1,000
1,000-2,000
Above 2,000
Specific Power
kWh/Nm 3
14.2
11.8
10.0
15.3
13.0
11.2
14.2
12.4
11.2
11.9
10.6
10.6
12.4
10.6
10.0
Control
Good with step unloading and low
off load power
Good with step unloading and low
off load power
High power on part load
Two step with good part load power
Good over modulation range
Reciprocating Compressors
• Single or multi stage
• Idling losses normally around 25% of full
load current
• Relatively efficient on part load
• Valve deterioration reduces efficiency
• Noisy
• High maintenance
Rotary Screw Compressors
• Normally provide cleaner air
• Most popular unit
• Packaged units available with integral heat
recovery
• Very efficient if run with variable speed
control
• Unloaded power greater than reciprocating
machines
Centrifugal Compressors
• High capacity base load machines
• Large machines have very good efficiency
on full load
• Part load operation achieved by inlet
throttling modulation
• Modulation should only be used around full
load conditions, very poor efficiency at low
loads
Rotary Sliding Vane
• Normally used for less demanding duties
• Generally low capital cost machines
• Used for single shift operations
• No integral heat recovery
• Part load operation very inefficient
Control - General Rules
• On/off control (where possible) is better
than variable speed, which is better than
modulating control
• Modern control systems can select the
optimum combination of compressors
• For multiple compressors check hours run
and loaded meters
Modulating and Variable Speed
Control
Modulating
100%
Power
Variable Speed
50%
100%
Output
Heat Recovery
Into air or water for:
• Process
> Drying
> Heating
• Compressed Air
Treatment
> Dryers
• Building Services • Boiler Pre-heating
> Space Heating
> Feed Water
> Water Heating
> Combustion Air
Heat Recovery Example
• A 20kW compressor would satisfy the
combustion air requirements of a 1 MW
boiler
• For each 20oC rise in combustion air
temperature there is an approximate 1% rise
in boiler efficiency.
• If this air is at 60oC, an efficiency increase of
3% may result.
Heat Recovery Potential
Heat available from compressors at full load
Capacity
cfm
Motor Power
KW
Warm air flow
L/s
Heat available
Gas equivalent
£
80
15
450
44000
1249
120
22
810
72000
2076
300
55
1600
182000
5263
600
110
3700
365000
10535
900
160
5600
535000
15424
1200
200
7500
671000
19349
1500
250
9000
840000
24228
Intake Air Temperature
For every 4C that the intake air
temperature falls:
The energy required for
compression falls by 1%
Intake Air Temperature - Example
• A compressor draws air from a plant room
that is typically at 25oC, and consumes
75kW
• The average UK/Ireland outside air
temperature is 10oC
• Taking the air from outside means that the
average temperature is 15oC lower
• Saving 3.75%, 2.8kW, £1000/yr
Summary
• compressed air is very expensive
> often equivalent to >50p/kWh
• only use when really necessary
• minimise system pressure
• minimise leaks
> simplify distribution
> isolate unused sections
• optimise generation efficiency
Top Tips
• Check compressor instrumentation (hrs run,
on-load etc.)
• Simple ‘rotameters’ for (temporary) flow
measurement are very cheap
• Install automatic drain traps
• Look carefully what happens at meal
breaks, shift changes and weekends
Energy Management
Level
Energy Policy
Organising
Motivation
Information
Systems
Marketing
Investment
4
Energy policy,
action plan and
regular review
have
commitment of
top management
as part of an
environmental
strategy
Energy
management
fully integrated
into
management
structure. Clear
delegation of
responsibility for
energy
consumption.
Formal and
informal
channels of
communication
regularly
exploited by
energy manager
and energy staff
at all levels.
Comprehensive
system sets
targets, monitors
consumption,
identifies faults,
quantifies
savings and
provides budget
tracking.
Marketing the
value of energy
efficiency and
the performance
of energy
management
both within the
organisation and
outside it.
Positive
discrimination in
favour of ‘green’
schemes with
detailed
investment
appraisal of all
new-build and
refurbishment
opportunities.
3
Formal energy
policy, but no
active
commitment
from top
management.
Energy manager
accountable to
energy
committee
representing all
users, chaired
by a member of
the managing
board.
Energy
committee used
as main channel
together with
direct contact
with major
users.
M&T reports for
individual
premises based
on sub-metering,
but savings not
reported
effectively to
users.
Programme of
staff awareness
and regular
publicity
campaigns.
Same pay back
criteria
employed as for
all other
investment.
2
Un-adopted
energy policy set
by energy
manager or
senior
departmental
manager.
Energy manager
in post, reporting
to ad-hoc
committee, but
line
management
and authority are
unclear.
Contact with
major users
through ad-hoc
committee
chaired by
senior
departmental
manager.
Monitoring and
targeting reports
based on supply
meter data.
Energy unit has
ad-hoc
involvement in
budget setting.
Some ad-hoc
staff awareness
training.
Investment
using short-term
payback criteria
only.
1
An unwritten set
of guidelines
Energy
management is
the part-time
responsibility of
someone with
limited authority
or influence
Informal
contacts
between
engineer and a
few users.
Cost reporting
based on invoice
data. Engineer
compiles reports
for internal use
within technical
department.
Informal
contacts used to
promote energy
efficiency.
Only low cost
measures taken.
0
No explicit policy
No energy
management or
any formal
delegation of
responsibility for
energy
consumption
No contact with
users.
No information
system. No
accounting for
energy
consumption.
No promotion of
energy
efficiency.
No investment in
increasing
energy efficiency
in premises.
Shape Description
Diagnosis
1 High
Balanced
Score 3 or more on
all columns
Excellent
performance; the
challenge is to
maintain this high
standard
2 Low
Balanced
Balanced score of
less than 3 on all
columns
Is this balance a
symptom or orderly
progress or
stagnation
3 U-shaped
The two outside
columns are
significantly higher
Expectations have
been raised
Shape
Description
Diagnosis
4 N-shaped
The two outside
columns are
significantly lower
Achievement in the
centre is likely to be
wasted
5 Trough
A single column is
significantly lower
than the rest
Underachievement
in this column may
well hold back
success elsewhere
6 Peak
A single column is
significant higher
than the rest
Effort in this area
could be wasted by
lack of progress
elsewhere
7 Unbalanced
Two or more
columns are 2
points above or
below average
The more imbalance
the harder it is to
perform well
Refrigeration
General comments
• Refrigeration systems are often complex
• Maintenance often sub-contracted
• Poor energy efficiency not obvious
• Savings potential is good ~20%
The Refrigeration Process (1)
High pressure
liquid
High pressure
vapour
Condenser
Ambient Cooling Stream
High P
Expansion
valve
Compressor
Low P
Substance Being Cooled
Low pressure
liquid/vapour
Evaporator
Low pressure
vapour
Refrigerants - A Few Examples
• Ammonia
R717
• CFCs
R11, R12, R502
• HCFC
R22
• Pure HFCs
R134a, R32
• HCFC blends
R403B, R408A
• HFC blends
R404A, R507
• Hydrocarbons
R290
System Efficiency
Coefficient of Performance (COP)
= useful cooling/system power
Theoretical efficiency (Carnot efficiency)
= Te/(Tc – Te) (T is degK)
Useful approximation COP
=0.6Te/(Tc – Te)
Chillers often specified in tons (US) 1 ton = 200 BTU/min (3.52kW)
Measurement of Tc & Te
• Often chillers only equipped with pressure
gauges
• Pressure can be converted temp. if
refrigerant is known
Typical Compressor COPs
COP
Air Conditioning
15°C
5
Chilling
3°C
4
Freezing
-30°C
2
Calculation of COP
• Need to know
• Compressor power
• Flow/return temps of primary/secondary refrigerant
• Flow rate of primary/secondary refrigerant
• Thermodynamic properties/specific heat of
primary/secondary refrigerant
• Only possible on large systems
Improving COP
• From Carnot = Te/(Tc – Te) theoretical efficiency
increases as:
• Tc – Te approach 0
• Te increases for the same temperature lift (Tc –
Te)
Increasing Te
• Efficient heat transfer in evaporator
> Clean heat exchange surfaces (e.g. ice on evaporator)
• Avoid overcooling of product
> e.g. product stored at -20ºC, but freezer cools to -30ºC
• Temperature set point unnecessarily; low ΔT between
refrigerant and process liquid <5ºC
> Two stage cooling
• Increase Te 1ºC increases efficiency by ~3%
Condensers
• Water cooled shell and tube (with CT)
> Water approach temp 5ºC
> Water temp rise ~ 5ºC
> Condensing temp 15 ºC greater than wet bulb
• Air cooled
> Condensing temp 15 ºC greater than air
• Evaporative condensers
> Similar to shell and tube
• Decrease Tc 1ºC increases efficiency by ~3%
Compressor Performance
% of full load COP
100
Centrifugal
and screw
50
Reciprocating
0%
% of full duty
100%
Modular Design, 3 water chillers
Case Study (a) poor part load control
of 3 modular water chillers
Load %
Power kW
Compressor
1
2
3
33
33
33
90
90
90
Chilled water pumps
1
2
3
100
100
100
25
25
25
Condenser pumps
1
2
3
100
100
100
20
20
20
Total Power Absorbed
-
405
Case Study (b) good control
Load %
Power kW
Compressor
1
2
3
100
0
0
150
0
0
Chilled water pumps
1
2
3
100
0
0
25
0
0
Condenser pumps
1
2
3
100
0
0
20
0
0
Total Power Absorbed
-
195
What can be easily assessed?
• If possible calculate COP
• Minimise cooling loads
> Free cooling in HVAC systems
> Two stage
> Cold store housekeeping
• Check ΔTs
> Condition of heat exchangers
Using Variable Speed Drives
and Efficient Motors
Content
• Background to Motors and Drives
• Using High Efficiency Motors
• Using soft starts for better control
• Using voltage controllers for partly loaded
motors
• Using variable speed drives
Motor and Drives
• constitute over half of industrial electrical
demand
• overall saving potential - 10% across
Industrial & Commercial sectors
• A motor will consume its capital cost in just
a month of continuous operation. So
The capital investment is insignificant
compared to running costs.
Motor Operation Costs
5000
132kW motor, cost £3600, efficiency 93%
22kW motor, cost £660, efficiency 90%
Electricity cost 4p/kWh, both motors fully loaded
4500
4000
3500
£
3000
132kW motor
2500
132kW running cost
2000
22kW motor
1500
22kW running costs
1000
500
0
0
100
200
300
400
500
Hours in use
600
700
800
900
Typical Motor Efficiency
(simplified)
100
% efficiency
75
50
25
0
0
25
50
% load
75
100
125
Motor
Efficiency %
Nominal Motor Efficiency v. Rating
Motor Rating (kW)
% Efficiency
The European Efficiency
Labeling Scheme
kW
1.1
90
12
Full
Load 9
Power
Loss
(%) 6
Total Loss
I 2R
(copper)
loss
stray loss
iron loss
3
friction and windage
0
0
40
80
120
Load (%)
High Efficiency Motors
• reduced Iron (Steel) Losses
• reduced copper Losses
• stray losses minimised
• more efficient motor generates less heat
High Efficiency Versus Standard
Motors Payback Period
New Motor - 7.5 kW
Hours of
Electricity
Usage p.a. Cost Savings
£ p.a.
Additional
Costs
£
Payback
Years
2000
36
83
2.3
4000
72
83
1.2
6000
108
83
0.8
At 4p/kWh for electricity, the
incremental cost payback occurs after about
5000 hours.
High Efficiency Motors Conclusions
• most suitable for highly loaded motors
• justified on new or replacement motors
> rewinds introduce extra losses – buy HEM
instead of rewinding
• on 4,000 hrs or more operation, marginal
payback just over a year
Switch it off!
• don’t leave motors running needlessly
• fit automatic controls to avoid motors being
left on
> e.g. timers or load sensors on conveyors
• look for fixed loads
> e.g. tank mixers – why not switch motor off for 1
minute every 5 with a saving of 20%
Soft start equipment
• can enable switch off strategies to work
• gives a more controlled motor start
> by ramping up motor voltage
> replaces DOL or star-delta starters
• reduces power surge
• reduces mechanical wear on motor, drive
and connected equipment
• makes it possible to stop and start motors
more frequently
Motor Voltage Controllers
• improve efficiency at loads below 50%
> regulate the voltage at the motor terminals
> iron losses are reduced
> efficiency and power factor are improved
• suitable for variable load motors that operate under
50% load for long periods
• do not use on highly loaded motors
> reduce efficiency at high load!
Variable Speed Drives
• excellent “new” technology to help reduce
electricity consumption
• for pumps / fans savings can be dramatic
> cubic relationship between power and flow
> reduce flow to 80%, reduce power to 50%
• not applicable to all motors
> e.g. difficult for refrigeration compressors
Advantages of VSD
• many loads run at fixed speed, but user requirement
is varying
> e.g. pumps and fans
• system often designed for worst case
> then designer adds a safety margin
• under average conditions flow too high
• at fixed speed control is inefficient
> e.g. dampers, flow bypass etc.
• VSD can provide excellent savings
> e.g. 80% flow at 50% power
Ways to vary the speed
• Electro-mechanical
variable speed
systems
• Electronic Variable
Speed Drives
(Inverters or VSDs)
• Variable Speed Motors
• Some savings, but losses
in transmission systems
• Good savings, efficiency
maintained reasonably
well
• Better than an inverter,
but a special motor
Electro-Mechanical Drives
• Mechanical (V-belts & gears)
• Hydraulic Couplings (Slippage between
discs)
• Eddy Current Couplings
Variable Speed Motors
• Two speed AC Motors
• AC 3-phase Commutator Motors
• AC Switched Reluctance Motors
• DC Motor & Drive Systems
Inverter VSDs
• can be applied to most existing 3 phase
motors
• AC current is rectified into DC and then
“inverted” back to AC at any desired
frequency
• motor speed proportional to frequency
> speed can go from ~10% to ~120%
> speed range depends on motor design and load
requirements
Getting the savings wrong
• Some consultants, salesmen and suppliers
assume that the cube law always applies
• IT DOESN’T apply, if
> the variable speed is set to maintain a constant
pressure at the pump or fan discharge
> if a liquid is being pumped up to a tank at higher
level (called “static head”)
Estimating VSD savings properly
• See Good Practice Guide 249, Appendix 3
• You will need
> An understanding of the static head of your system
> A good picture of the flow requirements of your system
> The fan/pump curves from the manufacturer
> The motor and VSD efficiency curves from the manufacturer
Achieving the maximum saving
Control point
A
Control point
B
Fan feeding large
ductwork system
Achieving the maximum saving
Control point
A
Control point
B
At control point A, the pressure cannot change, so the
new power will be in simple proportion to the flow:
Reduced power = old power x (new flow/old flow)
Achieving the maximum saving
Control point
A
Control point
B
At control point B, the pressure through most of the
system can change as friction reduces, so the new power
will follow the cube law:
Reduced power = old power x (new flow/old flow)3
Typical invertor costs
Motor (kW)
Cost €
Typical Payback
11
2,500
1.5-2 years
37
4,500
1 -1.5 years
75
8,000
1 year
132
15,000
1 year
Case Study - Variable Speed Drive
Townsend Hook - Paper
• Fan Drives
• 3x45kW fan motors
> damper controlled and drawing 30kW
• £15,750 to install inverters on 3 motors
• Savings 20kW/motor or £13,500/annum
• Simple payback 14 months
Case Study - Variable Speed Drive
Townsend Hook - Paper
• Pump Drives
• Two pump motors, 1x75kW and 1x37.5kW
• £12,500 to install inverters on both motors
• Savings 74kW or £16,650/annum
• Simple payback 9 months
Summary
• most electricity consumed via electric
motors
• HEMs should always be selected
• motor rewinds can introduce losses
• motor switch off strategies should be
adopted where possible
• VSDs can improve control significantly
Top Tips
• Look for large motors with long running
hours
• Big motors >20 kW
• Variable flow (fans and pumps)
• Inventory listing
• HEM policy
Insulation
Where to Insulate
• Generally any hot surface above 60 ºC and any
cold surface less than 5 ºC
• Types of insulation
> Mineral fibres (bonded or loose)
> Polyurethane
> polystyrene
Estimating Heat Losses (Qr)
Radiation Qr = CE(T4s –T4a) W/m2
C= 5.67x10-8
E = emissivity (0.1 – 0.9)
T = K (ºC +273)
Estimating Heat Losses (Qc)
Radiation Qc = C(T1 –T2)1.25 W/m2
C= 2.56 upward horizontal hot or down horizontal cold
= 1.97 flat vertical surfaces at least 0.5 m high
= 1.32 downward facing hot
= 2.3 horizontal cylinders greater than 150mm diam
Use a factor of V0.8 to allow for forced convection
Heat loss from open tanks
• Can be very large at high temperatures
• Typical areas – metal treatment vats, hot
wells
• Losses can be reduced by ~80% with lids
and insulation balls
Process Integration
Process Integration
• Commonly used technique in the chemical
industry to optimise heat recovery between
hot and cold streams
• Complex process but worthwhile
quantifying fluid heating and cooling
streams
Heat sinks
Ref
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Description
Flow Rate Tin
Tout
Cp
hin
hout
Power Hours/yr Energy
(kg/hr)
(C)
(C) (kJ/kgK) (kJ/kg) (kJ/kg)
(kW)
(MWh)
Boiler feed water preheat
12700
10 105
46
439
1,386
8760 12,145
Thermal converter feed water preheat
5700
10
62
151
439
344
8500
2,925
Deaerator Steam (CHP)
7500
2798
897
3,960
8760 34,693
Thermal Converter deaerator
Chlorine vaporisation & superheating
110
1,200
8760 10,512
XXXX to distillation
69100
65 120
0.826
872
8760
7,639
XXXX to oxidation
59500
15
80
0.826
887
8760
7,773
O2 to oxidation
900
Wash water
Water used in treatment plants
Spray drier supply air No 1
29800
10 700
1.004
5,735
8760 50,234
Spray drier supply air No 2
29800
10 700
1.004
5,735
8760 50,234
Spray drier supply air No 3A
8600
10 700
1.004
1,655
8760 14,497
Spray drier supply air No 3B
11800
10 700
1.004
2,271
8760 19,891
Filter water
Air to ROC drier
16810
10 450
1.004
2,063
8760 18,070
Value
(£ pa)
68,012
23,402
194,282
84,096
61,110
62,187
281,312
281,312
81,184
111,392
101,191
Heat sources
Ref
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Description
Reactor shell
XXXX quench coolers
1st Stage
2nd Stage
Condensor
Liquid XXXX cooling
XXXX cooler
Filter wash water to drain
Spray Drier XX exhaust
Spray Drier XXX exhaust
exhaust 1
exhaust 2
exhaust 3
XXX drier exhaust
Condensate from purification
Condensate from drains etc
Flow Rate Latent Tin
(kg/hr) (kJ/kg) (C)
2748000
28650
23275
59500
59500
72,100
59600
20400
19623
7093
184
70
60
22
136
136
1500
70
105
105
140
140
140
125
141
Tout h in h out
Cp
Power Hours/ Energy
Value Current Heat Sink
(C) (kJ/kg) (kJ/kg) (kJ/kgK) (kW)
(MWh)
(£
pa)
yr
2,634
8760 23,074 184,591 Cooling Tower (water heated to 60C)
40
0.827 18,938 8760 165,900 1,327,196 Cooling Tower (water heated to 38C)
22
0.827
3,790 8760 33,200 265,603 Cooling Tower (water heated to 30C)
-15
0.827
2,998 8760 26,263 210,104 Brine refrigeration system.
136
3,041 8760 26,640 213,121 Cooling Tower (water heated to 36C)
50
0.827
1,175 8760 10,297
82,378 Cooling Tower (water heated to 36C)
Evaporation from flue pond and cooling
200 Rapid cooling essential 20,319 8760 177,994 1,423,956 tower (water heated to 38C). Pond water
10
5,022 8760 43,993 351,942 Drain. NB Heated by heat recovery
30
1.004
1,247 8760 10,921
87,364 Ambient air
30
1.004
427 8760
3,738
29,903 Ambient air
30 2737
84
20,807 8760 182,269 1,458,155 Wash & tower water
30
20,807 8760 182,269 1,458,155 Wash & tower water
30
19,793 8760 173,387 1,387,093 Wash & tower water
534
2,911 8760 25,498 203,985 Ambient air
605
1,192 8760 10,442
83,537 Drain.
Identify where Energy is Used
and Develop an Action Plan
Survey
Senior Management
Commitment
Measure Energy Consumption
and Production
Review Performance
and Action Plan
Develop Targets
Implement Energy
Saving Measures
Produce Reports to Monitor
Energy Use Against Output
Headline Numbers Update
Energy Use/Part Shipped
12 Months to
Electricity
Gas (m³)
(kWh)
$
Jul-01
15.60
2.95
2.24
Apr-03
17.12
3.25
2.90
Total Energy Cost Year to May 2003 $5.2 million
Electricity Cost By Department
$194,298
$332,951
Colour Line
$339,292
$1,789,556
$359,454
Compressors
$392,723
Chillers
Site Utilities
South Warehouse
$1,413,034
RTO Unit
$1,444,140
Test Laboratory
Prime Line
$1,427,079
North Warehouse
Total Cost from 13/01/2003 to 08/05/2003
Utility Management
• In 2001, utility consumption data was very
poor
• Metering is now excellent
• The only significant gap is the RTO
• Environmental drivers are more powerful
• Montage, Powerlogic and ORCI all provide
excellent data
Priority Areas
• Compressed air
• Chillers
• RTO
• Colour Line
Air compressors
• Well metered
• Annual energy consumption is 5.3 million
kWh/year ($480,000)
• Centacs now meet all demand
• One machine is shutdown at weekends
• Manual control
$1400/day
$700/day
Air Compressors Hourly Electricity Use
800
E Broomwade
E Centac Units
700
$1400/day
E XLE-1
E XLE-2
600
Total
$970/day
400
300
200
100
03
13
.0
5.
03
12
.0
5.
03
11
.0
5.
03
10
.0
5.
03
09
.0
5.
03
08
.0
5.
03
07
.0
5.
03
06
.0
5.
03
05
.0
5.
03
04
.0
5.
03
03
.0
5.
03
5.
02
.0
5.
03
0
01
.0
kW
500
Scope for Savings
• Run a Centac and the Broomwade estimated saving $150,000/year
• Just run the Broomwade at night and
weekends estimated saving $30,000
• When Prime Line restarts investigate a heat
regenerated drier
Chillers
• Chillers, pumps and CTs consume 6 million
kWh/year ($550,000)
• 1 chiller in the winter and 2 in the summer
• System is oversized and inflexible
• In the winter cooling load from ASH is 74kW
(+90kW from old compressors) actual
cooling is 750kW and compressor power is
350kW i.e. effective COP of 0.4
19-Oct-02
12-Oct-02
05-Oct-02
28-Sep-02
21-Sep-02
14-Sep-02
35
Mean Temp
20
25000
15
20000
15000
10
10000
5
5000
0
0
kWh/day
30
07-Sep-02
31-Aug-02
24-Aug-02
17-Aug-02
10-Aug-02
03-Aug-02
27-Jul-02
20-Jul-02
13-Jul-02
06-Jul-02
29-Jun-02
22-Jun-02
15-Jun-02
08-Jun-02
01-Jun-02
Average Temp degC
Chillers – Daily Elec. Use and Average Temperature
45000
Chiller kWh
40000
35000
25
30000
6 Pumps
5 Pumps
4 Pumps
3 Pumps
2 Pumps
Chillers Potential Savings
• In the summer one chiller is switched off at weekend
• Corresponding pumps are not always switched off –
potential saving 60,000 kWh/year ($5,400)
• Can a chiller be switched off at night in the summer
3hrs@50 days – potential savings 60,000 kWh/year
($5,400)
• VFD for glycol pumps
• Small chiller for winter
RTO
• Meter has not yet been configured
• Estimated gas use $1.4 million/year
• Electricity use of RTO fan 1.6 million
kWh/year ($140,000)
• Control of flow and LEL to the RTO is
essentially manual
-50
02/05
/2003
1:00
01/05
/2003
1:00
300
30/04
/2003
1:00
29/04
/2003
1:00
28/04
/2003
1:00
27/04
/2003
1:00
26/04
/2003
1:00
25/04
/2003
1:00
24/04
/2003
1:00
23/04
/2003
1:00
CCF/Hour
Hourly Gas Use
350
Total Sub Meters
?RTO
250
200
150
100
50
0
RTO Savings Potential
• Weekend setting for night non productive
time estimated saving 280,000 m³/year
($90,000) for gas and 50,000 kWh/year
($4,500) for electricity
• Optimization of LEL set points (and air flows)
Saving ?$100,000/year
Colour Line
• Is comprehensively metered
• Total gas cost is $400,000/year
• Total electricity is $600,000/year
• Is well controlled
37
95
6
1/ 37 .79
13 95 16
/0
7
6
1/ 3 3 .95
13
:0 83
1/ /03 0:0 4
13
0
7
/0 :00 AM
3
1/
1 :0
13 1:0 0 A
M
/0
0
1/ 3 3 :01
13
:0
A
1/ /03 0:0 M
13
1
7
/0 :00 PM
3
1/
1 :0
14 1:0 1 P
M
/0
0
1/ 3 3 :00
14
:0
P
1/ /03 0:0 M
14
1
7
/0 :00 AM
3
1/
1 :0
14 1:0 0 A
M
0
/0
1/ 3 3 :00
14
:0
A
1/ /03 0:0 M
14
1
7
/0 :00 PM
3
:
0
1/
1
15 1:0 1 P
M
/0
0
1/ 3 3 :01
15
:0
P
1/ /03 0:0 M
15
0
7
/0 :00 AM
3
1/
1 :0
15 1:0 1 A
M
/0
0
1/ 3 3 :01
15
:0
A
1/ /03 0:0 M
15
0
7
/0 :00 PM
3
1/
1 :0
16 1:0 0 P
M
/0
0
1/ 3 3 :01
16
:0
P
1/ /03 0:0 M
16
0
7
/0 :00 AM
3
1/
1 :0
16 1:0 1 A
M
/0
0
1/ 3 3 :00
16
:0
A
1/ /03 0:0 M
16
1
7
/0 :00 PM
3
:
0
1/
1
17 1:0 1 P
M
/0
0
1/ 3 3 :01
17
:0
P
1/ /03 0:0 M
17
0
7
/0 :00 AM
3
1 :0
1/
17 1:0 1 A
0: M
/0
0
3
3: 0 A
00
M
:0
1
PM
CCF/hour
Colour Line Hourly Gas Use
25
20
G Colour Dryoff
G Colour Radiant Zone 2
G Colour Oven Zone 3
G Colour Oven Zone 4
G Colour Radiant Zone 2
G Colour Radiant Zone 1
G Colour Wash Stg1 - B#1
G Colour Wash Stg1 - B#1
15
10
5
0
01
/0
5/
20
03
2:
00
Sat
2:
00
2:
00
Fri
12
/0
5/
20
03
2:
00
Thurs
11
/0
5/
20
03
2:
00
Weds
10
/0
5/
20
03
2:
00
Tues
09
/0
5/
20
03
2:
00
Mon
08
/0
5/
20
03
2:
00
Sun
07
/0
5/
20
03
2:
00
Sat
06
/0
5/
20
03
500
05
/0
5/
20
03
Fri
2:
00
2:
00
Thurs
04
/0
5/
20
03
03
/0
5/
20
03
2:
00
-50
02
/0
5/
20
03
kW
Colour Line Hourly Electricity Use
E Colour Clear Ash
450
E Colour Washline
400
350
300
250
Sun
200
150
100
50
0
Mon
Colour Line Gas Savings Potential
• Appears well controlled
• Improving shut down and start up procedure
would save $3-4000/year for gas and $6,000
for electricity
Potential Savings
Colour Shutdown
$10,000
Compressed air
$180,000
Glycol Pumps
$5,400
Chiller switch off
$5,400
RTO
$190,000
Total
$391,000
Other significant areas are lighting and space heating
Conclusions
• Level of data is very impressive
• Major gaps are:
> RTO
>Main site gas meter
>Correlate chiller performance to ambient
conditions and/or COP
• Next step is to analyse and act upon the data