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There are hundreds of different ways to save energy. Here are the top tips to save energy with Variable Speed AC Drives. Follow the links to learn more!

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Energy Saving Tips by End-User Industry

Energy Saving Tips by Application

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AC drives from ABB save tens of Millions tons CO₂

ABB AC Drives has ddelivered almost a million frequency converters or AC drives during the last twenty years. We can estimate that all of the units delivered during last ten years are still in use. The savings in all pumps, fans, conveyors, mixers etc. can be added together:
Energy save total 46 billion kWh/year
Reduction in CO₂ emissions 23 billion kg/year
Other benefits:
Improved process controls
Reduced maintenance cost
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

Appliances plant water pump - AC drive instead of throttling

A UK domestic appliances manufacturer invested in AC drives at its factory. Borehole water is pumped directly into the mains by a 30 kW motor. The drive installed on this motor resulted in a 30% saving and the drive installed on the raw water pump produced savings of 88%.
Energy save total 191,000 kWh/year
Reduction in CO₂ emissions 95'500 kg/year
Other benefits:
Payback period of 14 months
Reduced stress to the supply
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

Auditor visit from ABB representative

The energy efficiency of different machines in an industrial plant is not quite easy to see without a closer study and analysing. If the plant has no suitable personnel for doing this work, there is an opportunity to call an ABB representative for auditing. He has been trained to use suitable measuring equipment software tools and analysing methods to find the most profitable targets for upgrading.
Benefits:
Reliable specialist doing the work
Own resources saved for daily work
Possibility to get financial advice from ABB
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[Tips by Application] [Alphabetical Index]

Bakery depanners - AC drives instead of constant speed

In a British bakery two depanners use a vacuum system to remove bread from the baking trays and tins. The vacuum is generated in vacuum chambers by fans driven by standard 15 kW AC motors. AC drives were installed to control the fan motors, and hence the vacuum generated.
Energy save about 135,000 kWh/year
Reduction in CO₂ emissions 67,500 kg/year
Other benefits:
Damage of bread rolls was minimized
Payback period 1.3 years
Reduced maintenance cost
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[Tips by Application] [Alphabetical Index]

Bank's computer centre cooling pumps - AC drives instead of throttling

A British bank has invested in variable speed control. Four frequency converters were installed in the cooling system of the bank's computer centre to control the speed of four pumps (total power 240 kW). The pumps were previously running at constant speed.
Energy save about 1,000,000 kWh/year
Reduction in CO₂ emissions 500,000 kg/year
Other benefits:
Improved cooling control
Payback in less than a year
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

Boiler coal mills - AC drive instead of bypass

In a boiler installation 20 coal mills with a drive output of 710 kW each are used. A speed-controlled drive with a control coupling or with an AC drive is to replace the bypass method. The possible saving with a control coupling is about 11 GWh and with an AC drive 23 GWh as shown below.
Energy save about 23,000,000 kWh/year
Reduction in CO₂ emissions 11,500,000 kg/year
Other benefits:
Better boiler control with fewer losses
Grushing wheels of the mills last longer
Payback period 2.5 years
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[Tips by Application] [Alphabetical Index]

Boiler extract fans - AC drive instead of dampers

A UK power plants extract fans (200 kW + 150 kW) were running at full speed with flow control by dampers, but as the boiler run at low loads for long periods they believed that energy could be saved with variable speed control. With variable speed AC drives:
Energy save about 1,000,000 kWh/year
Reduction in CO₂ emissions 500,000 kg/year
Other benefits:
Faster response to load changes
Noise level reduced from 89 dBa to 77 dBa
Payback period of just 16 months
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[Tips by Application] [Alphabetical Index]

Boiler feed pump - AC Drive instead of fluid coupling

An European power plant was comparing Fluid coupling with AC drive for their feed pump (1450 kW) control. The comparison show that within the speed range needed the AC drive consumed about 150 kW less than the Fluid drive.
Energy save about 1,200,000 kWh/year
Reduction in CO₂ emissions 600,000 kg/year
Other benefits:
Reduced reactive power
Reduced stress to the supply
Reduced need of maintenance
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[Tips by Application] [Alphabetical Index]

Broadcasting studio fans - AC drive instead of on off

A television studio's air conditioning fan motors ran at constant speed and were manually started and stopped. This was unsatisfactory in many reasons and an AC drive was installed for two 7.5 kW motors.
Energy save about 30,000 kWh/year
Reduction in CO₂ emissions 15,000 kg/year
Other benefits:
Stable pressure control
Lower air conditioning noise level
Improved working environment
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[Tips by Application] [Alphabetical Index]

Car painting booth fans - AC drive instead of inlet vanes

Air pressure, inside and outside a car painting booth, has to be balanced. Too high or too low pressure inside the booth causes problems. The booth's inlet air fan ran at constant speed and the air flow was controlled with a guide vane. Air pressure was instable and the fan consumed much energy and an AC drive 45 kW was installed.
Energy save about 56,200 kWh/year
Reduction in CO₂ emissions 28,100 kg/year
Other benefits:
Stable pressure control
Improved painting quality
Improved working environment
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[Tips by Application] [Alphabetical Index]

Cement factory ID fan - AC drive instead of damper

A Greece cement plant controls their ID fans with AC cascade converters 630 kW. In this way large energy savings were achieved compared with the conventional method of regulating the flow rate through dampers. Power consumption was reduced by 163 kW with following benefits:
Energy save about 1,250,000 kWh/year
Reduction in CO₂ emissions 625,000 kg/year
Other benefits:
Reduced reactive power
Payback period 1.8 years
Reduced need of maintenance
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[Tips by Application] [Alphabetical Index]

Centrifuge - regenerative AC drive instead of resistor braking

An European centrifuge manufacturer tested the energy efficiency of an AC drive with regenerative braking compared to mechanical braking. The motoring cycle including filling, accelerating and high speed phase consumed 1,828 kWh but during the deceleration 0,987 kWh was fed back to the network. Energy saving was 0,841 kWh per cycle and:
Energy save about 42,000 kWh/year
Reduction in CO₂ emissions 21,000 kg/year
Other benefits:
Reduced reactive power
Increased capacity
Increased end product quality
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[Tips by Application] [Alphabetical Index]

Chemical industry acid pump - AC drive instead of throttling

A Finnish chemical industry replaced their existing constant speed acid pump control with an AC drive (37 kW). The process is running about 8000 hours a year and the average flow less than 50% of the pump rated flow. The results were:
Energy save about 120,000 kWh/year
Reduction in CO₂ emissions 60,000 kg/year
Other benefits:
Reliable control for a demanding material
Reduced maintenance cost
Payback period about 1.3 years
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[Tips by Application] [Alphabetical Index]

Chemical industry filter - AC drive instead of damper

Filter control is an important application within the chemical sector. A drive is often sized to pull air through a dirty filter, but most of the time the air flow is too great and so a damper is used. This causes losses and the fan speed control is better solution. The case is calculated for a 100 kW fan motor.
Energy save about 262,000 kWh/year
Reduction in CO₂ emissions 131,000 kg/year Other benefits:
Production running stable
Reduced maintenance cost
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

Chemical industry fin fan - AC drive instead of damper

A fin fan cooler is a special type of fan which normally lies in the vertical plane, drawing air from outside and blowing it downwards into a manufacturing process. Variable speed control gives enormous energy savings. The case is calculated for a 100 kW fan motor.
Energy save about 438,000 kWh/year
Reduction in CO₂ emissions 219,000 kg/year Other benefits:
Production running stable
Reduced maintenance cost
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

Chemical industry screw compressor - AC drive instead of on-off

An European biochemical company processes need oxygen with very constant pressure but the oxygen volume is very variable. The system was earlier controlled by switching on and off two compressors of different sizes. Because of problems with high power consumption, noise level and maintenance cost the larger compressor was equipped with an AC drive. The results were:
Energy save about 1,700,000 kWh/year
Reduction in CO₂ emissions 850,000 kg/year Other benefits:
Production running stable
Reduced maintenance cost
One year payback period
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[Tips by Application] [Alphabetical Index]

Chiller compressor - AC drive instead of mechanical control

An European compressor manufacturer developed a new screw compressor drive refrigeration and freezing plant. Stepless control with an AC drive allows the compressor to maintain high total efficiency even at reduced loads. Energy consumption can be reduced by 15 per cent compared with conventional capacity control(100 kW unit/6000 hours/year).
Energy save about 50,000 kWh/year
Reduction in CO₂ emissions 25,000 kg/year
Other benefits:
Versatile solution
Low life cycle cost
Reduced maintenance
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[Tips by Application] [Alphabetical Index]

Clay workshop ID fan - AC drive instead of damper

An Irish china clay workshop replaced the damper control with an AC drive in their 150 kW ID fan. The existing fan and motor were could be used without any alterations. Savings were achieved in both reduced drive power required by the fan and economy in gas consumption. Continuous operation for 51 weeks per year.
Energy (electrical) save about 640,000 kWh/year
Reduction in CO₂ emissions 320,000 kg/year Other benefits:
Reduced gas consumption
Reduced pollution
Payback period eight months
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[Tips by Application] [Alphabetical Index]

Clean water pump - AC drive instead of on-off

A German city waterworks improved their clean water pumping station control by installing an AC drive (185 kW). Estimated energy saving was about 50% with other benefits.
Energy save about 740,000 kWh/year
Reduction in CO₂ emissions 370,000 kg/year
Other benefits:
Constant water pressure
Reduced pressure shocks
Reduced maintenance cost
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[Tips by Application] [Alphabetical Index]

Container crane - regen AC drive instead of resistors

Rapid, precise and efficient control of crane movements reduces stresses on both the system and the operator. In modern container cranes AC drives are used for all three movement directions. The hoisting movement is most demanding and regeneration gives energy savings when braking.
Energy save about 190,000 kWh/year
Reduction in CO₂ emissions 95,000 kg/year
Other benefits:
Improved safety
Faster operation
Reduced maintenance cost
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[Tips by Application] [Alphabetical Index]

Control the engine speed instead of braking

The importance of speed control has been always clear in cars. You could imagine how difficult it is to manage a car keeping your foot on the gas and control your speed with the brakes. It is much easier to change to a lower gear and reduce engine revs. With a medium size (100 kW) car:
Energy save about 25,000 kWh/year
Reduction in CO₂ emissions 12,500 kg/year
Other benefits:
Improved safety
Easier to control
Reduced maintenance cost
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[Tips by Application] [Alphabetical Index]

Dairy air compressor - AC drive instead of relief valve

A US producer of dairy products improved their total heating and cooling processes by using so called pinch technology. There were several changes in the system including a new AC drive to a 11 kW air compressor.
Energy save about 85,600 kWh/year
Reduction in CO₂ emissions 42,800 kg/year
Other benefits:
Reduced maintenance cost
Payback period 2.7 years
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

Dairy boiler feed water pump - AC drive instead of throttling

A US producer of dairy products improved their total heating and cooling processes by using so called pinch technology. There were several changes in the system including a new AC drive to a 7.5 kW boiler feedwater pump.
Energy save about 55,400 kWh/year
Reduction in CO₂ emissions 27,700 kg/year
Other benefits:
Reduced maintenance cost
Payback period 3.6 years
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

Dairy refrigeration compressor - AC drive instead of relief valve

A US producer of dairy products improved their total heating and cooling processes by using so called pinch technology. There were several changes in the system including two new AC drives to a 200 kW and a 250 kW refrigerating compressors.
Energy save about 202,000 kWh/year
Reduction in CO₂ emissions 101,000 kg/year
Other benefits:
Reduced maintenance cost
Payback period 2.5 years
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

Decanter - AC multidrive instead of mechanical control

Decanters are centrifuges used to separate solid particles from liquid or slurry. A typical decanter construction is a rotating bowl with a scroll screw inside to move the solid particles out of the bowl. By using a common dc-bus solution about half of the scroll drive power can be saved:
Energy save about 100,000 kWh/year
Reduction in CO₂ emissions 50,000 kg/year
Other benefits:
Reduced maintenance cost with soft start
Accurate decanter control
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

Distillery cooling pump - AC drive with flux optimisation

A Scottish distillery uses Ac drive with flux optimisation for two 30 kW centrifugal cooling pumps. Flux optimisation feature offers energy savings higher than other AC drives. Drive losses can be reduced by 30% when the pump is less than 30% loaded. Comparison against throttling gives:
Energy save about 131,400 kWh/year
Reduction in CO₂ emissions 65,700 kg/year
Other benefits:
Reduced maintenance cost
Accurate flow control
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

District heating pump - AC drive instead of throttling

A small town in Germany had throttling and on-off control for their seven district heating pump stations. In September 1992 AC drives were installed to control the pumps. During 1993, the first full year with the AC drives the energy consumption was reduced by about 60 per cent. Energy save about 330,000 kWh/year
Reduction in CO₂ emissions 165,000 kg/year
Other benefits:
Reduced maintenance cost
Reduced noise
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

District heating emissions reduced by upgrading

The German town upgrading project included not only the pumps control, but also flue gas cleaning and change from brown coal to coal. All this reduced the burning process emissions of dust, CO₂, CO, SO₂ and NO_x.
Heating energy save 38,000,000 kWh/year
Reduction in CO₂ emissions 19,000,000 kg/year
Other benefits:
Reduced maintenance cost
Reduced noise
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

Duty Cycle has to be considered

It is important to consider the duty cycle of the controlled system. The energy saving with a variable speed drive can be compared in Case 1 and Case 2 shown in the chart.
Case 1 with new motor:
Energy save about 84,000 kWh/year
Reduction in CO₂ emissions 42,000 kg/year Case 2 with AC drive:
Energy save about 230,000 kWh/year
Reduction in CO₂ emissions 115,000 kg/year
The rule of thumb:
Install an AC drive if significant flow variations occur
Install a lower speed motor if flow variation is small but motor/pump is too large
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[Tips by Application] [Alphabetical Index]

Efficiency optimised by AC drive

Pump or fan efficiency is usually as highest around the rated flow and head (A = 78%). In case the flow rate is reduced by speed control, the efficiency stays close to the maximum (B = 77%). In case the flow is reduced by throttling the efficiency is much lower (C = 60%). If we look at a 100 kW pump motor and 5000 h/year, we get:
Energy save about 85,000 kWh/year
Reduction in CO₂ emissions 42,500 kg/year
The rule of thumb:
Install an AC drive instead of throttling if significant flow variations occur

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[Tips by Application] [Alphabetical Index]

Electrical power - savings 5 times the useful energy

Use of efficient technology at the customer site can save energy for instance 50 per cent meaning an increase of efficiency from 30 per cent to 60 per cent. Because of the low efficiency (30-40%) at the power plant, the total efficiency with throttling can be so low as 10 percent and 50% saving improves it to 20 per cent.
Total primary energy savings 50%
Savings 5 times the useful energy
Reduced losses through the system

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[Tips by Application] [Alphabetical Index]

Energy taxes can be avoided

Many countries in Europe are introducing some form of energy tax to encourage more efficient use of energy. In the UK, the government estimates that its Climate Change Levy will cut CO₂ emissions by 2,5 Million tonnes a year by 2010. Another initiative to encourage the adoption of energy-saving equipment is a tax incentive - Enhanced Capital Allowances (ECA) - that will allow companies to write off 100% of the cost of certain type of equipment like AC drives.
Estimated energy savings 5 billion kWh/year
Reduction in CO₂ emissions 2,5 billion kg/year
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[Tips by Application] [Alphabetical Index]

Engine test rig - regenerative AC drive instead of mechanical

Load testing of car engines requires some kind of load to simulate the car driving conditions. There are different methods but AC drive has the feature to regenerate and feed the engine power (average 100 kW/2000 h/year) to the electric network.
Total energy savings 200,000 kWh/year
Reduction in CO₂ emissions 100,000 kg/year Other benefits:
Four quadrant operation
Flexible means for programming
Extensive speed range
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[Tips by Application] [Alphabetical Index]

Fabric dyening pump - AC drive instead of throttling

An Australian Dyening company retrofitted their dye circulation pump with an AC drive (30 kW). The energy consumption was monitored before and after the drive installation. The average power was reduced from 14.1 to 2.1 kW. With 6000 operating hours per year the results are:
Total energy savings 72,000 kWh/year
Reduction in CO₂ emissions 36,000 kg/year
Other benefits:
Payback period was 32 months
Mass throughput increased 9.7%
Fabric length throughput increased 10.3%
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[Tips by Application] [Alphabetical Index]

Fan speed control instead of dampers

In the past the control of air flow rates from fans was not concerned with reduced energy consumption. Although there are number of methods to control flow rates, not all are energy efficient. The most basic and inefficient way of controlling the flow rate is the adjustment of a damper in the ventilation duct. Using instead AC drive with 30 kW motor running 5000 hours/year:
Total energy savings 76,500 kWh/year
Reduction in CO₂ emissions 38,250 kg/year
Other benefits:
Soft starting less maintenance
Short payback period
Better flow control
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[Tips by Application] [Alphabetical Index]

Fan speed control instead of inlet vanes

In the past the control of air flow rates from fans was not concerned with reduced energy consumption. Although there are number of methods to control flow rates, not all are energy efficient. Inlet guide vanes are more sophisticated method for flow control, but using AC drive instead in case of 30 kW motor running 5000 hours/year:
Total energy savings 37,500 kWh/year
Reduction in CO₂ emissions 18,750 kg/year
Other benefits:
Soft starting less maintenance
Simpler fan construction
Better flow control
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[Tips by Application] [Alphabetical Index]

Fan speed control instead of on-off

In the past the control of air flow rates from fans was not concerned with reduced energy consumption. Although there are number of methods to control flow rates, not all are energy efficient. A very basic way of controlling the flow rate is to modulate the fans on or off. Using AC drive instead in case of 30 kW motor running 5000 hours/year:
Total energy savings 51,000 kWh/year
Reduction in CO₂ emissions 25,500 kg/year
Other benefits:
Soft starting less maintenance
Much better flow control
Better comfort for people
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[Tips by Application] [Alphabetical Index]

Fan speed control instead of two-speed motor

In the past the control of air flow rates from fans was not concerned with reduced energy consumption. Although there are number of methods to control flow rates, not all are energy efficient. A quite simple way of controlling the flow rate is the use of two-speed motor, but it has two flow rates only. Using AC drive instead in case of 30 kW motor running 5000 hours/year:
Total energy savings 52,500 kWh/year
Reduction in CO₂ emissions 26,250 kg/year
Other benefits:
Soft starting less maintenance
Short payback period
Better flow control
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[Tips by Application] [Alphabetical Index]

FanSave for fan energy calculations

FanSave is a Visual Basic Application for MS Excel to estimate the energy savings available when using an adjustable frequency drive compared to other fan control systems. Calculations are based on typical fan operating characteristics. Results should be used only for estimating purposes. The outputs of the calculations are:
Total energy savings kWh/year
Total energy cost savings Currency unit/year
Direct payback period
Other benefits:
Quick way to make alternative calculations
Simple drive selection is included
Available on the web
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[Tips by Application] [Alphabetical Index]

Flour mill extract fan - AC drive instead of dampers

Dust is extracted from the flour milling process by 75 kW electric motor driven fans. Fan was originally controlled by a star/delta starter but the motors were operating at full speed and airflow was controlled by dampers. An AC drive was installed to control the fan speed.
Energy save about 114,000 kWh/year
Reduction in CO₂ emissions 57,000 kg/year
Other benefits:
Payback period about 2.5 years
Less maintenance
Reduced reactive power
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[Tips by Application] [Alphabetical Index]

Gateroom air conditioning - AC drive instead of full speed

An European airport replaced their gaterooms fixed volume air handling units (AHU) with variable speed AC drives. The two fans (15 kW + 7 kW) of the AHU run earlier continuously with full speed and energy consumption was 192,000 kWh a year. The AC drives reduced the energy consumption with 63.5 per cent:
Energy save about 122,000 kWh/year
Reduction in CO₂ emissions 61,000 kg/year
Other benefits:
Reduced reactive power
Improved quality of air conditioning
Less supply problems and mechanical wear
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[Tips by Application] [Alphabetical Index]

High efficient motors instead of low efficient motors

New efficiency labelling is coming into force for electric motors, ranging from 1.1 to 90 kW, used in Europe. Thus, anyone buying a motor can easily make a choice for energy efficiency. For example 11 kW motors eff1 > 91.0% and eff3 < 88.4%. For using eff1 motor running 8000 h/year:
Energy save about 2,288 kWh/year
Reduction in CO₂ emissions 1,144 kg/year

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[Tips by Application] [Alphabetical Index]

Hospital HVAC control - AC drive instead throttling

A Finnish hospital wanted to reduce the energy wasted with ventilation exhaust air. The hospital's HVAC system vas renewed with the advanced building control system with heat recovery and 60 AC drives (2.2 - 37 kW). As a result the specific heat energy consumption is now lower than in any other hospital in the county.
Energy save about 4,840,000 kWh/year
Reduction in CO₂ emissions 2,420,000 kg/year
Other benefits:
Specific heat consumption reduced by 30%
Improved quality of air conditioning
Estimated payback period 4 years
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[Tips by Application] [Alphabetical Index]

HVAC Air Handling Unit - AC drive instead of vanes - Amex4

A US company in New York City replaced in their Air Handling Unit (AHU) the Variable Inlet Vane control (VIV) to an AC drive control (VSD). With 3800 hours/year the projected savings were 49 per cent:
Energy save about 18,440 kWh/year
Reduction in CO₂ emissions 9,220 kg/year
Other benefits:
Reduced reactive power
Improved quality of air conditioning
Estimated payback period 3.9 years
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[Tips by Application] [Alphabetical Index]

HVAC Air Handling Unit - AC drive instead of vanes - Amex5

A US company in New York City replaced in their Air Handling Unit (AHU) the Variable Inlet Vane control (VIV) to an AC drive control (VSD). With 3700 hours/year the projected savings were 53 per cent:
Energy save about 31,000 kWh/year
Reduction in CO₂ emissions 15,500 kg/year
Other benefits:
Reduced reactive power
Improved quality of air conditioning
Estimated payback period 2.3 years
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[Tips by Application] [Alphabetical Index]

HVAC Air Handling Unit - AC drive instead of vanes - Douglas

A US company in Oregon replaced in their Air Handling Unit (AHU) the Variable Inlet Vane control (VIV) to an AC drive control (VSD). With 2800 hours/year the projected savings were 75 per cent:
Energy save about 26,800 kWh/year
Reduction in CO₂ emissions 13,400 kg/year
Other benefits:
Reduced reactive power
Improved quality of air conditioning
Estimated payback period 2.6 years
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[Tips by Application] [Alphabetical Index]

HVAC Air Handling Unit - AC drive instead of vanes - Hewlett

A US company in New Jersey replaced in their Air Handling Unit (AHU) the Variable Inlet Vane control (VIV) to an AC drive control (VSD). With 2860 hours/year the projected savings were 68 per cent:
Energy save about 35,000 kWh/year
Reduction in CO₂ emissions 17,500 kg/year
Other benefits:
Reduced reactive power
Improved quality of air conditioning
Estimated payback period 1.5 years
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[Tips by Application] [Alphabetical Index]

HVAC Air Handling Unit - AC drive instead of vanes - Mobil

A US company in New Jersey replaced in their Air Handling Unit (AHU) the Variable Inlet Vane control (VIV) to an AC drive control (VSD). With 2860 hours/year the projected savings were 61 per cent:
Energy save about 18,430 kWh/year
Reduction in CO₂ emissions 9,215 kg/year
Other benefits:
Reduced reactive power
Improved quality of air conditioning
Estimated payback period 3.0 years
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[Tips by Application] [Alphabetical Index]

HVAC Chiller water pump - AC drive instead of throttling

In the chiller water distribution system of a big hotel, a conventional throttling control was replaced by 34 pcs 100 kW AC drives. The system is running 4000 hours a year.
Energy save about 4,000,000 kWh/year
Reduction in CO₂ emissions 2,000,000 kg/year
Other benefits:
Reduced reactive power
Better flow control
Less supply problems and mechanical wear
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[Tips by Application] [Alphabetical Index]

HVAC cooling tower fans - AC drive instead of on-off

Cooling towers typically use banks of fans, each feeding cooling cells. In the cells the fan moves outside air through through a spray of water, allowing heat to dissipate from the water. With variable speed control energy saving can be 60%. In case of 100 kW total motor power and 4000 h/year.
Energy save about 200,000 kWh/year
Reduction in CO₂ emissions 100,000 kg/year Other benefits:
Reduced reactive power
Better HVAC control
Less supply problems and mechanical wear
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[Tips by Application] [Alphabetical Index]

HVAC supply fan - AC drive instead of eddy-current clutch

In the ventilation system of a publishing company in Germany, a conventional damper control was replaced by an eddy-current clutch. Energy saving was 30%. The measurements indicated that there was a further energy-saving potential of around 35% with AC drives. The fan motor is 16 kW and the system is running 4000 hours a year.
Energy save about 18,000 kWh/year
Reduction in CO₂ emissions 9,000 kg/year
Other benefits:
Reduced reactive power
Pay-off period 2 years
Less supply problems and mechanical wear
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[Tips by Application] [Alphabetical Index]

HVAC system comfort cooling with AC drive

An office area of about 1000 square metres requires in summer time during 2000 h/year cooling air 5 m3/s. With an accurate AC drive (about 55 kW) control the energy use can be optimised and 100 kW less cooling power is needed.
Energy save about 200,000 kWh/year
Reduction in CO₂ emissions 100,000 kg/year
Other benefits:
Better comfort for people working
Reduced reactive power
Less supply problems and mechanical wear
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[Tips by Application] [Alphabetical Index]

HVAC system comfort heating with AC drive

A painting plant about 6000 square metres requires in winter season during 2000 hours/year heating air 33 m³/s. With an accurate comfort zone control with AC drives (total 300 kW) the energy use can be optimised and 585 kW less heating power is needed.
Energy save about 1,170,000 kWh/year
Reduction in CO₂ emissions 585,000 kg/year
Other benefits:
Reduced reactive power
Better working environment
Less supply problems and mechanical wear
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Irrigation pumps - AC drive instead of on-off control

A farmer irrigates his fields during periods of dry weather to ensure normal growth. As the irrigators are driven by water flow, a constant pressure is essential for even water distribution over the fields. To keep up the constant pressure a 75 kW AC drive was installed instead of on-off control.
Energy save about 60,000 kWh/year
Reduction in CO₂ emissions 30,000 kg/year
Other benefits:
Reduced maintenance cost
Water pressure peaks eliminated
Farm's profitability increased
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Laboratory glove boxes - AC drive vacuum control

In a research laboratory, toxic materials are handled in closed glove boxes and a good ventilation is required. The laboratory replaced the suction air fan's 75 kW constant speed drive with variable speed AC drive. Estimated running hours are 4000 h/year.
Energy save about 150,000 kWh/year
Reduction in CO₂ emissions 75,000 kg/year
Other benefits:
Reduced reactive power
Safe conrol of vacuum in the boxes
Only one common fan is required
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Lift speed control - AC drive instead of pole-changing motor

A lift with a load capacity of 1000 kg, 17 m travelling height and 5 stops is conventionally driven with a pole-changing 8.8 kW motor. Compared with this conventional solution, a 6.3 kW motor fed via an AC drive with special gear and energy recovery saves up to 81 per cent. With a utilisation of 6 hours per day:
Energy save about 15,000 kWh/year
Reduction in CO₂ emissions 7,500 kg/year
Other benefits:
Reduced reactive power
Payback period about 1.5 years
Less supply problems and mechanical wear
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Malt kiln fan - AC drive instead of inlet vanes

A UK malt producer installed two 400 kW variable speed AC drives for its malt kilning installation with 250 tonne capacity. In other malting installations the fans are controlled by using mechanical inlet guided vanes. With AC drives overall energy consumption has fallen from around 200 kWh/tonne to less than 100 kWh/tonne.
Energy save about 9,000,000 kWh/year
Reduction in CO₂ emissions 4,500,000 kg/year
Other benefits:
Better process control
High reliability
Higher power factor
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Malt kiln fan - new AC drive instead of old drive

A Finnish malt producer had variable speed AC drives for its malt kiln fans since early 1980's. They replaced those old drives with new ones. The average energy needed for one batch of malt went down 10 percent.
Energy save about 114,762 kWh/year
Reduction in CO₂ emissions 57,381 kg/year
Other benefits:
Less equipment space
Less cooling capacity needed
Possibility to limit the peak power
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Metal industry ID fans - AC drive instead of damper
A Norwegian aluminium producer compared their boiler ID fans (8 units 400 kW each) existing damper control against variable speed control. Energy save about 2,738,400 kWh/year Reduction in CO₂ emissions 1,369,200 kg/year Other benefits: Payoff period 1.1 years Improved controllability Reduced reactive power [Top of the page] [Tips by Industry] [Tips by Application] [Alphabetical Index]

Metal industry scrubber pump - AC drive instead of throttling

A Norwegian aluminium producer compared their scrubber circulation pumps (8 units 100 kW each) existing throttling control against variable speed control.
Energy save about 2,240,800 kWh/year
Reduction in CO₂ emissions 1,120,400 kg/year
Other benefits:
Payoff period 0.5 years
Improved controllability
Reduced reactive power
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Milking machine - AC drive instead of relief valve

A US manufacturer replaced the mechanical vacuum controller in their milking machine with a variable speed AC drive (22 kW/5 hours/day). The mechanical controller was replaced with a vacuum transducer giving the pressure signal to the AC drive. Because of the fluctuating milk volume the energy savings were remarkable:
Energy save about 26,800 kWh/year
Reduction in CO₂ emissions 13,400 kg/year
Other benefits:
Reduced noise and heat
More pleasant working environment
Increased life time of mechanical parts
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Mine cooling fan - AC drive instead of damper

A Mexican iron mining company installed AC drive instead of the existing constant speed 1250 kW cooling fan motor. Energy savings of 23% was achieved.
Energy save about 2,300,000 kWh/year
Reduction in CO₂ emissions 1,150,000 kg/year
Other benefits:
Better process controllability
lower motor noise and vibration
Reduced maintenance cost
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Mine ore conveyor - AC cage motor and drive instead of slip-ring motor

A South American copper mine had problems with its 5 km long ore conveyor belt. Conveyor capacity was limited and had high maintenance cost. The old drive with slip-ring motors was replaced with cage motors (2*630 kW) and AC drive. This caused the capacity increase of 30 per cent and:
Energy save about 1,200,000 kWh/year
Reduction in CO₂ emissions 600,000 kg/year
Other benefits:
Improved production capacity
Reduced reactive power
Reduced maintenance cost
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Mine submersible pump - AC drive instead of throttling

A Finnish chrome mine compared control methods for a submersible pump 37 kW. Power saving with an AC drive was 16 kW in average. Pump is running about 8000 h/year.
Energy save about 128,000 kWh/year
Reduction in CO₂ emissions 64,000 kg/year
Other benefits:
Better flow control
Reduced reactive power
Reduced maintenance cost
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New AC drive and motor instead of old ones

Efficiency Tool is a Visual Basic Application for MS Excel to estimate the energy savings when replacing an old AC drive, motor or both drive and motor with new equipment. This example is calculated for the Malt kiln case above assuming that both motor and drive were replaced.
Energy save about 144,300 kWh/year
Reduction in CO₂ emissions 72,150 kg/year
Other benefits:
Less equipment space
Less cooling capacity needed
Possibility to limit the peak power
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New AC motor instead of old motor

Efficiency Tool is a Visual Basic Application for MS Excel to estimate the energy savings when replacing an old AC drive, motor or both drive and motor with new equipment. This example is calculated for the Malt kiln case above assuming that only the motor is replaced.
Energy save about 11,520 kWh/year
Reduction in CO₂ emissions 5,760 kg/year
Other benefits:
Less equipment space
Less cooling capacity needed
Possibility to limit the peak power
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Oil terminal pumps - AC drives instead of throttling

An oil terminal in United Arab Emirates was looking for new solutions to control the oil pumping between tanks, from tank to ship an from ship to tank. This was a green field project with 20 centrifugal pumps (350 kW each) and a Multidrive with 2 supply units was chosen.
Energy save about 580,000 kWh/year
Reduction in CO₂ emissions 290,000 kg/year
Other benefits:
Ultimate flexibility in choosing pumps
Less moving parts and less maintenance
Simple and effective solution - user friendly
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Paper machine - AC drive instead of DC drive

A US paper mill compared their paper machine (4000 kW total power)drive losses with AC drive and DC drive. The losses with AC drive were about 4.5% less than with DC drive:
Energy save about 1,600,000 kWh/year
Reduction in CO₂ emissions 800,000 kg/year Other benefits:
Robust motors
Less maintenance
Less reactive power
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Paper mill pulper - AC drive instead of full speed

A german paper mill improved their pulper control because there was often quite long waiting before the ready pulp can be delivered further in the process. By reducing the pulper speed (from 50 hz to 35) by an AC drive the power consumption was reduced from 400 kW to 164 kW. With 7500 h/year:
Energy save about 442,500 kWh/year
Reduction in CO₂ emissions 220,000 kg/year Other benefits:
No sedimentation with continuous running
Less maintenance by soft starting
Shorter pulper cycle time possible
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Power plant booster fan - AC drive instead of inlet guide vanes

A US university power plant installed a 1000 hp AC drive for their scrubber booster fan. Energy efficiency improved by 25% against the that of inlet vanes.
Energy save about 1,460,000 kWh/year
Reduction in CO₂ emissions 730,000 kg/year Other benefits:
Better process controllability
Less maintenance by soft starting
No more start-up problems
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Power plant FD fan - AC drive instead of inlet guide vanes

A power plant compared inlet guide vanes to AC drives (110 kW each) for their FD (Forced Draft) fan. The power plant is running continuously and the fresh air flow varies from 50% to 90% of the maximum capacity. With AC drive is:
Energy save about 482,000 kWh/year
Reduction in CO₂ emissions 241,000 kg/year Other benefits:
Better pressure control with varying loads
Less maintenance by soft starting
Efficient combustion
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Power plant fans - AC drive instead of inlet guide vanes

A peat power plant replaced inlet guide vanes to AC drives (total 300 kW) for their Primary air, Secondary air an Induced Draft fans. The electric power required to produce 1 MWh heat was reduced by 33% from 30 kWh to 20 kWh.
Energy save about 43,600 kWh/year
Reduction in CO₂ emissions 21,800 kg/year
Other benefits:
Better pressure control with varying loads
Less maintenance by soft starting
Efficient combustion of peat
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Power plant ID fan - AC drive instead of fluid coupling

A finnish pulp mill compared hydraulic coupling to AC drive (1370 kW) for their power plant ID (Induced Draft) fan. The power plant is running continuously and the flue gas flow varies from 50% to 90% of the maximum capacity. With AC drive is:
Energy save about 376,000 kWh/year
Reduction in CO₂ emissions 188,000 kg/year
Other benefits:
Better pressure control
Less maintenance by soft starting
Fan critical speeds can be avoided
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Pulp mill debarking drum - AC drive instead of constant speed

A pulp mill's debarking drum did not debark logs satisfactorily because the drum speed could not be adjusted for the different quality of the logs. The mill bought three AC drives (400 kW each) to control the speed of the drum motors.
Energy save about 1,200,000 kWh/year
Reduction in CO₂ emissions 600,000 kg/year
Other benefits:
Logs can be equally debarked
Less maintenance by soft starting
Reduced reactive power
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Pulp mill pumps - AC drive instead of throttling

A Swedish pulp mill discovered that at 850 kWh per pulp ton, its energy consumption was far too high. Variable speed control of pumps, changing too large pump motors with more suitable and making changes in pipe layouts were the actions causing a reduction to 635 kWh per pulp ton. With variable speed AC drives:
Energy save about 134,400,000 kWh/year
Reduction in CO₂ emissions 67,200,000 kg/year
Other benefits:
Improved pulp process control
Less maintenance by soft starting
Return on hardware investment about 12 months.
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Pulp pumping - AC drive instead of smaller impeller

Quite often are industrial pumping systems oversized for the real average need. If the maximum capacity is never needed, there is an opportunity to reduce the pump impeller size. This case was with an original pump impeller of 410 mm.
Energy save about 461,000 kWh/year
Reduction in CO₂ emissions 230,500 kg/year Other benefits:
Improved pulp process control
Less maintenance by soft starting
Reduced reactive power
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Pump speed control instead of recirculation

Centrifugal pumps can be controlled by methods similar to those for controlling fans. In practice, the most common method is throttling by means of a control valve. Recirculation is also used, but it is most inefficient in energy point of view. Using AC drive instead in case of 30 kW motor running 5000 hours/year:
Total energy savings 100,500 kWh/year
Reduction in CO₂ emissions 50,250 kg/year
Other benefits:
Soft starting less maintenance
Short payback period
Better flow control
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Pump speed control instead of throttling

Centrifugal pumps can be controlled by methods similar to those for controlling fans. In practice, the most common method is throttling by means of a control valve. Throttling causes quite a lot of losses both in the pump and in the valve itself. Using AC drive instead in case of 30 kW motor running 5000 hours/year:
Total energy savings 58,500 kWh/year
Reduction in CO₂ emissions 29,250 kg/year
Other benefits:
Soft starting less maintenance
Short payback period
Better flow control
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Pump flow control - PFC instead of fixed speed

An European water utility compared the energy consumption a fresh water pump with existing On-off control against proposed variable speed AC drive with PFC (one pump with variable and 3 pumps with fixed speed. 55 kW each). With 7000 h/year were results:
Energy save about 195,000 kWh/year
Reduction in CO₂ emissions 97,500 kg/year
Other benefits:
Payback period only 3 months
Better water pressure control
Less reactive power
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PumpSave for pump energy calculations

PumpSave is a Visual Basic Application for MS Excel to estimate the energy savings available when using an adjustable frequency drive compared to other pump control systems. Calculations are based on typical pump operating characteristics. Results should be used only for estimating purposes. The outputs of the calculations are:
Total energy savings kWh/year
Total energy cost savings Currency unit/year
Direct payback period
Other benefits:
Quick way to make alternative calculations
Simple drive selection is included
Available on the web
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River water axial pump control - AC drive instead of throttling

In a river-water pumping station, an axial pump with a rated output of 1500 kW is used. Considering the energy efficiency for partial load the axial pump at constant speed and with throttling as flow-rate control is extremely inefficient. In contrast to this, the pump output can be matched to the output of the installation with low losses if electronic speed control is used.
Total energy savings 2,386,000 kWh/year
Reduction in CO₂ emissions 1,193,000 kg/year
Other benefits:
Soft starting less maintenance
Payback period one year
Energy saving 32 per cent
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Rubber mixer - AC drive instead of hydraulic drive

A Finnish tyre manufacturer installed AC drives (1500 kW) to their new rubber mixer instead of the traditional hydraulic drive. Estimated energy saving was 20%.
Energy save about 1,200,000 kWh/year
Reduction in CO₂ emissions 600,000 kg/year
Other benefits:
Better quality of the end product
Reduced noise level
Less reactive power
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Saw mill conveyor - AC drive instead of two-speed motor

Most of sawmills today use AC drives to control the speed of sawmill line conveyor according to the timber diameter. In this example the average line speed can be increased 13 per cent if compared to two-speed motor. The energy saving can be estimated to be 13 per cent as well. The power of line motors is about 100 kW and the running hours about 5000 hours a year.
Energy save about 65,000 kWh/year
Reduction in CO₂ emissions 32,000 kg/year
Other benefits:
Better quality of the end product
Protection against too high load
Less reactive power
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Ship podded propulsion - AC Drive instead of pitch control

A recent innovation for enhanced maneuverability and reduced fuel consumption is Azipod, a podded propulsion unit azimuthing through 360 degrees. It incorporates an electric motor which is controlled by a frequency converter. On a recently launched cruise liner reduction in fuel consumption was 8 per cent equivalent to 40 tons of heavy fuel oil per week. Energy save about 10,000,000 kWh/year
Reduction in CO₂ emissions 5,000,000 kg/year
Other benefits:
Improved maneuverability
Reduced stress to the supply
Reduced reactive power
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Ship sea water pump - AC drive instead of throttling

The sea water of a freight ship was dimensioned according to the engine cooling demand in tropical waters of 30 degrees C. Most of the time it is sailing in waters which are much cooler, the average only 15 degrees C. With variable speed AC drives the 45 kW pump motor power goes down to 5 kW. With 5000 hours running time:
Energy save about 200,000 kWh/year
Reduction in CO₂ emissions 100,000 kg/year Other benefits:
Less corrosion
Less mechanical stress
Less reactive power
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Sewage aeration control - AC drive instead of throttling

A Swedish sewage treatment plant succeeded to reduce the nitrogen release more than 50% with speed control of the aeration fan motor (55 kW). An efficient control is needed because incoming flow varies dramatically during the year. This application is double eco-efficient because in addition to reduction of nitrogen releases and:
Energy save about 200,000 kWh/year
Reduction in CO₂ emissions 100,000 kg/year
Other benefits:
Payback time 16 months
Accurate control of treatment process
Less reactive power
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Sewage pump - AC drive instead of throttling

For an outdoor pumping station, the following data are available: Maximum flow of waste water is 750 m³/h and the average flow is 400 m³/h.The pump is operated for 8,000 hours per year. Motor output is 70 kW. Average power input with three control methods were compared: Throttling: 44.4 kW, On-off Control: 32.4 kW and AC drive: 23.0 kW. AC drive compared to throttling gives:
Energy save about 172,000 kWh/year
Reduction in CO₂ emissions 86,000 kg/year
Other benefits:
Payback period only 6 months
Accurate control of treatment process
Less reactive power required
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Sewage pumps - AC drive instead of on-off control

A Dutch city has a sewage system in which both waste water and storm water from paved areas is collected. A pumping station transports the water to the next station, or to the treatment plant. In 15 stations the pumps are driven by AC drives. Energy savings are achieved under dry weather conditions. AC drive compared to on-off control gives:
Energy save about 150,000 kWh/year
Reduction in CO₂ emissions 75,000 kg/year
Other benefits:
Less maintenance
Better control of treatment process
Less reactive power required
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Ski lift - AC drive instead of constant speed

A ski resort manager had realised problems with constant speed ski-lifts which were for some skiers too fast and for some others too slow. After looking at several options the resort chose an AC drive (132 kW) as a replacement drive for the ski lift. Among the other benefits clear energy saving was also experienced.
Energy save about 26,400 kWh/year
Reduction in CO₂ emissions 13,200 kg/year
Other benefits:
Safe and reliable lift and happy customers
Soft start increases comfort
Less reactive power required
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Steel mill roller table - AC drive instead of fixed speed

In a steel mill roller tables transport steel profiles between workstations. A common regenerative AC drive is used for efficient braking every 18 seconds the 82 pcs of 3 kW motors. As compared to the mechanical braking considerable savings are achieved:
Energy save about 504,000 kWh/year
Reduction in CO₂ emissions 252,000 kg/year Other benefits:
Payback period 2.3 years
Better for environment
Less reactive power required
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Steel melting plant fan - AC drive instead of damper

A British steel melting plant converted two of their four 1200 kW extraction fans from inlet vane control to variable speed AC drives. An energy saving of approximately 37% when using a combination of obscuration meter and AC drive has been demonstrated:
Energy save about 4,680,000 kWh/year
Reduction in CO₂ emissions 2,340,000 kg/year
Other benefits:
Payback period 2.3 years
Better for environment
Less reactive power required
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Sugar centrifuge - AC multidrive instead of two-speed

A sugar mill replaced their two-speed motor control of their six centrifuges 200 kW each by an AC multidrive with PLC control. The benefit with a multidrive the common dc-bus transferring electrical energy from the decelerating centrifuges to accelerating ones causing remarkable energy savings.
Energy save about 2,880,000 kWh/year
Reduction in CO₂ emissions 1,440,000 kg/year
Other benefits:
Optimum speed for the process
Smooth starting - less wear
Less reactive power required
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Sugar mill boiler ID fan - AC drive instead of vanes

A Finnish sugarmill replaced their existing ID fan guide vane control by a variable speed AC drive (132 kW). Operation period for a six months campaign was 4320 hours and measured power reduction 75 kW. AC drive compared to guide vanes gives:
Energy save about 324,000 kWh/year
Reduction in CO₂ emissions 162,000 kg/year
Other benefits:
Payback period 2.6 years
Accurate control of boiler process
Less reactive power required
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Timber drying - AC drive instead of throttling

A Swedish company in woodworking business and the timber drying process is one of the most energy-consuming parts of the process. Timber is dried in kilns each having eight fans mantaining continuous air circulation. Previously the fans were operated continuously at full speed. Company invested in a total of eight AC drives two each installed in four kilns. Fan motors are 7.5 kW each.
Energy save about 900,000 kWh/year
Reduction in CO₂ emissions 450,000 kg/year Other benefits:
Payback of investment in 12 months
Better drying process
Better end-product
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Water booster pump - AC drive instead of throttling

A UK water utility designed a booster pump station to maintain a minimum suction head and to output a maximum of 17 million litres per day. Two variable speed pumps (total 680 kW) were needed instead of four fixed speed pumps. Energy saving are approximately 34%.
Energy save about 990,000 kWh/year
Reduction in CO₂ emissions 495,000 kg/year Other benefits:
Lower construction cost
Better water pressure control
Less reactive power
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Wastewater pumping - AC drive instead of on-off control

The efficiency of a Scottish wastewater pumping station has more than doubled since two AC drives were installed. This arrangement replaces simple on/off control of the motors, with the level monitored with a mechanical float.
Energy save about 130,000 kWh/year
Reduction in CO₂ emissions 65,000 kg/year
Other benefits:
Pumping index up from 14 m³/kWh to 30 m³/kWh
Maintenance cost reduced
Risk of overflowing is minimised
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Water treatment pump - AC drive instead of on-off

An European water utility compared the energy consumption a fresh water pump with existing On-off control against proposed variable speed AC drive. The power demand at full volume (1000 m³/h) every half an hour was 85 kW but at the average volume (500 m³/h) with AC drive speed control only 21 kW. With 8000 h/year were results:
Energy save about 512,000 kWh/year
Reduction in CO₂ emissions 256,000 kg/year Other benefits:
Less maintenance with soft starting
Better water pressure control
Less reactive power
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Wind power generator - AC drive instead of blades only

Conventionally, the wind generator is coupled directly to the electricity grid. The speed of the generator is limited by the network frequency thus limiting the speed range which can be exploited. By using AC drive it is estimated the energy output can be increased by 20%. If the generator power is 1000 kW and it is running 4000 h/year, we get:
Energy save about 800,000 kWh/year
Reduction in CO₂ emissions 400,000 kg/year Other benefits:
Less mechanical stress
Better controllability
Reactive power can be controlled
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Winders and unwinders - AC drive with common DC bus

Winders and unwinders of various sizes are used in industries like paper, metal and plastics. AC drive with common DC bus is the most efficient in these applications because the braking energy from unwinders can be recycled in the winder part. This example is for 100 kW power running 8000 hours per year.
Energy save about 720,000 kWh/year
Reduction in CO₂ emissions 360,000 kg/year Other benefits:
Low power from the supply
Low maintenance cost
Reactive power minimised
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Wood-processing extract fan - AC drive instead of throttling

A fan with a rated power requirement of 7.5 kW which is used in the air-extraction system of a wood-processing plant. The energy saving which results if the flow rate is is not mechanically throttled but adapted to the rate actually needed by means of a three-phase motor controlled by an AC drive is compared.
Energy save about 8,400 kWh/year
Reduction in CO₂ emissions 4,200 kg/year Other benefits:
Payback of investment in 12 months
Better controllability
Reduced reactive power
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