The first step in energy management

1
Energy Survey Workshop

• The first step in energy management
• Andrew Ibbotson
• Joe Flanagan

2
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.

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Why carry out a survey?

• Identify savings
• Establish the viability of an energy management
  programme
• Establish a baseline

4
The Energy Management Process
5
DIY or Consultant?

• Consultant
• Expertise
• Fresh pair of eyes
• Should not be afraid to poke into any corner
• Opinions may carry more weight
• Job will be completed

• DIY
• No cost
• No learning curve
• Projects should be viable

6
Choosing a Consultant

• Salesman or consultant?
• Ensure he/she is experienced in your process
• Dont be afraid to take up references
• Cost - day rate of fixed price

7
The Survey Process

• Define the scope
• Establish energy balances
• Identify priority areas
• Identify energy saving projects
• Low cost (control, housekeeping, awareness)
• Medium cost (revenue expenditure lt1 year payback)
• High cost (capital expenditure lt2-3 year payback)
• Reporting

8
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

9
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

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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

11
Electricity Bills

• Maximum Demand charges (kVA, kW)
• Capacity charges (kVA, kW)
• Day and night rates
• Power factor

12
Power Factor
PF kWh/kVAh cos f
From the electricity bill kWh 17,400 kVArh
8,700 What is the power factor?
13
Power factor

• tan f 8,700/17,400
• 0.5
• f 26.5º
• cos 26.5 0.89
• PF improved by adding capacitors
• Worthy of further investigation below 0.85-0.90

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Gas Bills

• More frequently estimated (in the UK)
• Errors more prevalent
• Very rarely obtain ½ hourly demand
• Can obtain some useful energy management
  information

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Base or process gas load
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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

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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
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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
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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
kW v3V I PF
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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
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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
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Estimating Electricity

• High accuracy is time consuming
• 10 is very good
• Portable data logger useful for large users
• Dont underestimate the large number of small
  users e.g. conveyors, fans, pumps

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Electricity Balance
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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

29
Could CHP be feasible?

• Power demand gt500 kW
• Coincident heat (steam or hot water) demand?
• Heat to power 31
• High operating hours gt 2 shift 5d/week

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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

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Boilers Steam Systems
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Scope
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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

34
Heat Recovery Process
Gas Passes - convection
Burner
Furnace Tube - radiation
35
Boiler Losses
Convection proportional to T Radiation
proportional to T4
36
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

37
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)

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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

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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

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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)

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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

43
Heat Recovery

• economiser (to feedwater)
• recuperator (to wash water)

44
Insulation

• check existing quality
• insulate all hot pipework, flanges (1m pipe),
  valve bodies (5m pipe)
• hotwell cover and insulation

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Key Points for the Boiler House

• Check
• Boiler efficiency
• Blowdown procedure
• Condensate return
• insulation

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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
• Total 2770 100

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System Standing Losses

• Fixed loss from
• Pipework
• Valves
• Fittings etc.
• Losses range from 2 to 5

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System Variable Losses

• Flash and losses with steam at
• condensate ? bar g cond. at 0 bar g
• return 7 5 3 0
• Total loss 26 24 22 15
• 50 cond. return 19 17 15 7

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Management Control

• Automatic isolation systems
• Pressure reduction
• Energy management
• Metering
• Data analysis
• Action

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Fixed Losses

• Insulation
• air ingress
• steam leaks

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Pipework

• Size
• cost trade-off
• Installation
• air removal
• condensate drainage
• weather sealing
• group users

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Pressure Reduction

• More efficient
• Saves fuel
• Cost incurred for
• pressure reduction sets
• larger heat exchangers
• larger traps
• Consider life cycle costs

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Steam Leaks
1000
800
12.5 mm
600
400
10 mm
7.5 mm
200
100
5 mm
80
60
40
3 mm
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Examples Steam Leak 7.5mm diameter Steam
Pressure (barg) ( or pressure difference between
steam and condensate) 6 bar Steam Loss 100
kg/h
10
8
6
4
3
3
4
5
7
10
14
2
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Steam Trapping Air Venting

• Steam trapping
• function
• testing
• group trapping
• sizing traps
• Air venting
• Scale and dirt removal

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Condensate Recovery

• Saves costs for
• Water
• Treatment chemicals
• Fuel
• Effluent
• Produces rapid payback

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Flash Steam Recovery

• By
• Indirect method
• Direct method
• Potential sinks
• BFW
• Wash water
• Process fluid
• Space heating

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Key Points for Steam Systems

• Pipe insulation
• Leaks
• Isolation of redundant plant/off line plant
• Steam traps
• Condensate return

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Lighting

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Lighting

• Overview of main industrial lighting types
• Their efficiency
• Common savings

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Lighting

• Typically 10-50 of electricity use
• Good lighting is critical to all manufacturing
  operations
• Survey is relatively easy to carry out

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Estimate of Load

• Rating of lamp
• Number
• Operating hours
• Add 10 for control gear

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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

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Comparison of Lamp Types
Lamp Type Lumens/watt Standard Life hrs (50 survival)
GLS 12 1,000
CFL 70 8,000
T8 70-100 6,000-15,000
T12 70 5,000-10,000
Metal halide 60-80 6,000-13,000
SON 108 15,000-30,000
SOX 138 12,000-23,000
Induction 70 60,000 (80)
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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
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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
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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

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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

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Compressed Air

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Compressed Air

• Background to Compressed Air
• Reducing loads and pressure
• Improving distribution
• Improving generation

70
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

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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)

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Compressed Air System Components
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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?

74
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

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Distribution

• Three main issues
• pressure drops
• water
• leaks

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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

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Distribution Lines The Effect of Water

• Problems with water
• Causes corrosion
• Product quality
• Increases pressure drops
• Is drying adequate? Additional automatic drain
  points

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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

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Leak reduction
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Leakage Losses
Hole diameter Hole diameter Leakage at 7 bar/100 psi 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
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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

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Life Cycle Costs of Compressor
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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?

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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

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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)

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Guidelines for Drying

• Generally design to dry air to 6ºC below ambient
  temperature
• Dont run pipework outside if possible
• Only dry as much air as is necessary (i.e. have a
  separate wet and dry system)

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Compressor Efficiencies
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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

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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

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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

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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

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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

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Modulating and Variable Speed Control
Modulating
100
Power
Variable Speed
Output
100
50
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Heat Recovery
Into air or water for

• Compressed Air Treatment
• Dryers
• Boiler Pre-heating
• Feed Water
• Combustion Air

• Process
• Drying
• Heating
• Building Services
• Space Heating
• Water Heating

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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.

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Heat Recovery Potential
97
Intake Air Temperature
For every 4?C that the intake air temperature
falls The energy required for compression
falls by 1
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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

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Summary

• compressed air is very expensive
• often equivalent to gt50p/kWh
• only use when really necessary
• minimise system pressure
• minimise leaks
• simplify distribution
• isolate unused sections
• optimise generation efficiency

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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

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Energy Management
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Refrigeration
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General comments

• Refrigeration systems are often complex
• Maintenance often sub-contracted
• Poor energy efficiency not obvious
• Savings potential is good 20

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The Refrigeration Process (1)
High pressure liquid
High pressure vapour
Expansion valve
Compressor
High P
Low P
Low pressure vapour
Low pressure liquid/vapour
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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

111
System Efficiency

• Coefficient of Performance (COP) useful
  cooling/system power
• Theoretical efficiency (Carnot efficiency)
  Te/(Tc Te) (T is degK)
• Useful approximation COP0.6Te/(Tc Te)

Chillers often specified in tons (US) 1 ton 200
BTU/min (3.52kW)
112
Measurement of Tc Te

• Often chillers only equipped with pressure gauges
  
• Pressure can be converted temp. if refrigerant is
  known

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Typical Compressor COPs

• COP
• Air Conditioning 15C 5
• Chilling 3C 4
• Freezing -30C 2

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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

115
Improving COP

• From Carnot Te/(Tc Te) theoretical efficiency
  increases as
• Tc Te approach 0
• Te increases for the same temperature lift (Tc
  Te)

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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 ?T
  between refrigerant and process liquid lt5ºC
• Two stage cooling
• Increase Te 1ºC increases efficiency by 3

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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

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Compressor Performance
of full load COP
100
Centrifugal and screw
50
Reciprocating
0
100
of full duty
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Modular Design, 3 water chillers
120
Case Study (a) poor part load control of 3
modular water chillers

• Load Power kW
• Compressor 1 33 90
• 2 33 90
• 3 33 90
• Chilled water pumps 1 100 25
• 2 100 25
• 3 100 25
• Condenser pumps 1 100 20
• 2 100 20
• 3 100 20
• Total Power Absorbed - 405

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Case Study (b) good control

• Load Power kW
• Compressor 1 100 150
• 2 0 0
• 3 0 0
• Chilled water pumps 1 100 25
• 2 0 0
• 3 0 0
• Condenser pumps 1 100 20
• 2 0 0
• 3 0 0
• Total Power Absorbed - 195

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What can be easily assessed?

• If possible calculate COP
• Minimise cooling loads
• Free cooling in HVAC systems
• Two stage
• Cold store housekeeping
• Check ?Ts
• Condition of heat exchangers

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Using Variable Speed Drives and Efficient Motors

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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

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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. SoThe capital
  investment is insignificant compared to running
  costs.

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Motor Operation Costs
132kW motor, cost 3600, efficiency 93 22kW
motor, cost 660, efficiency 90 Electricity cost
4p/kWh, both motors fully loaded
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Typical Motor Efficiency (simplified)
128
Nominal Motor Efficiency v. Rating
Motor Efficiency
Motor Rating (kW)
129
The European EfficiencyLabeling Scheme
Efficiency
kW
1.1
90
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High Efficiency Motors

• reduced Iron (Steel) Losses
• reduced copper Losses
• stray losses minimised
• more efficient motor generates less heat

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High Efficiency Versus Standard Motors Payback
Period
New Motor - 7.5 kW
Hours of Electricity Additional
Payback Usage p.a. Cost Savings Costs
Years p.a.
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.
134
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

135
Switch it off!

• dont 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

136
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

137
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!

138
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

139
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

140
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

141
Electro-Mechanical Drives

• Mechanical (V-belts gears)
• Hydraulic Couplings (Slippage between discs)
• Eddy Current Couplings

142
Variable Speed Motors

• Two speed AC Motors
• AC 3-phase Commutator Motors
• AC Switched Reluctance Motors
• DC Motor Drive Systems

143
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

144
Getting the savings wrong

• Some consultants, salesmen and suppliers assume
  that the cube law always applies
• IT DOESNT 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)

145
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

146
Achieving the maximum saving
Fan feeding large ductwork system
147
Achieving the maximum saving
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)
148
Achieving the maximum saving
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
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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
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Case Study - Variable Speed DriveTownsend 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

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Case Study - Variable Speed DriveTownsend 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

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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

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Top Tips

• Look for large motors with long running hours
• Big motors gt20 kW
• Variable flow (fans and pumps)
• Inventory listing
• HEM policy

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Insulation

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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

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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)

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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

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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

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Process Integration

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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

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Heat sinks
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Heat sources
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Headline Numbers Update
Total Energy Cost Year to May 2003 5.2 million
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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

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Priority Areas

• Compressed air
• Chillers
• RTO
• Colour Line

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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

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1400/day
700/day
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Air Compressors Hourly Electricity Use
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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

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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

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Chillers Daily Elec. Use and Average Temperature
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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_at_50 days potential savings 60,000
  kWh/year (5,400)
• VFD for glycol pumps
• Small chiller for winter

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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

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Hourly Gas Use
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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

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Colour Line

• Is comprehensively metered
• Total gas cost is 400,000/year
• Total electricity is 600,000/year
• Is well controlled

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Colour Line Hourly Gas Use
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Colour Line Hourly Electricity Use
kW
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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

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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
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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

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