Power play
28 Nov 2006
Drives: Few companies have a joined-up strategy when it come to energy saving
While rising energy costs have pushed energy efficiency onto the boardroom agenda, most companies have yet to develop a joined-up strategy in response - even though most engineers within these companies know exactly where the solutions lie.
For many industrial applications, because electric motors on average use over 60% of the electrical energy, engineers clearly see the benefit of investments such as variable speed drives. However, there is often nothing they can do if saving energy is not a priority in the boardroom.
Equipment makers often still find it difficult to find a dedicated person in charge of energy at end-user companies as the issue is deferred to senior management, according to Steve Ruddell, ABB's recently appointed energy spokesperson.
"The guy who buys the motor is not the same one who worries about the energy bill. In most cases, the engineer wants a motor to fill the hole just vacated by one that has given up. If it fits and produces at least the same speed and torque, he is happy," said Ruddell.
Many users are only too well aware of the imperative to reduce energy costs, but are constricted by the even higher priority demands of their day jobs, believes Steve Barker, Siemens Automation & Drives business manager, energy & power quality.
Barker wants more end-users to adopt "a coherent and systematic strategic approach" to saving energy. This, he said, should encompass everything from the initial system analysis through to an ongoing commitment to continually reduce costs and carbon emissions.
"Saving energy is not difficult but it needs a systematic approach. Begin by looking at continuously running equipment. If you do not need it, switch it off," Barker asserted. "Much equipment keeps running 24/7, although there is no real need for it. Then, look at pumps and fans. Are they controlled by variable speed drives? If not, they should be."
Today, though, even when companies do have an energy manager looking at these issues, they are normally more concerned with buying energy more cheaply, improving the efficiency of an existing process or reducing the running hours of that process, said Ruddell.
"It's precisely for these reasons that the majority of motors in industry are oversized. We think industry should look at the whole life cycle, starting when new kit is bought and new plant is designed," the ABB man commented.
According to Ruddell, the water utilities woke up to this a few years ago and started using variable speed drives (VSDs) on a wide scale to improve their processes. He also cited how one leading water company is allowing its engineers spend £5,000 a week on minor purchases without consulting senior management.
Investments in VSDs can, typically, provide 30% energy savings and give a realistic payback within a year. The key to these energy savings is the speed control in the application, rather than the intrinsic efficiency of the products, Barker emphasises. For instance, a 100 kW fan throttled by 50% in continuous operation will give payback in six months if equipped with a variable speed drive. One end user reported savings of over £100,000 a year, and a payback of less than three months, after upgrading a fan with a variable speed drive.
According to Barker, deciding on the optimum size of motors for applications such as pumps, fans and conveyors is one area where major savings can be made — especially in fixed speed applications.
"The efficiency of motors reduces under light load and therefore matching the product selection more closely with the actual load demand would be very helpful," Barker said. "The use of variable speed drives is sometimes to compensate for the initial engineering gaps, but the VSD will increase the overall system efficiency at light loads and will reduce the overall energy consumption."
A widespread culture of overating motors has built-up, agrees Andy Glover of WEG UK. "This involves engineers at various stages of the pump system design process adding 10% or 15% to the motor capacity 'just to be on the safe side.'"
This practice is so widespread that it is estimated that only 20% of the pump drive motors in operation are running at their full rated input, according to Glover.
A motor running at a typical commercial or industrial site for 4,000 hours a year has an annual electricity cost of about 10 times its capital cost, said Glover. "This is serious money, and effectively underlines why pump suppliers and pump users should ensure optimum efficiency from their systems by effectively matching drive motors to pumps. Unfortunately, this is not usually the case."
The implications for the end-user are, firstly, an exagerated capital cost for the motor itself; secondly, a commensurate increase in associated equipment, such as motor starters, drives and cabling; and, finally, gross inefficiencies in the system's operation.
Meanwhile, Barker believes many systems are not commissioned in the optimum way, for example, with motor details often entered incorrectly during VSD parameterisation, or the correct control requirements not introduced into the logic control scheme.
"Even if the initial commissioning is acceptable, the system becomes less optimal as adjustments are made over time," the Siemens manager added. "One large utility estimated that the overall system efficiency could be improved by as much as 8% if the systems were optimised."
Engineers also need training and support, believes Ruddell of ABB. "Most drives that find their way onto end-users' plants are not set correctly for energy savings. Site engineers need to keep in touch with the manufacturer and get appropriate training." In essence, users need to look at the equipment they run and ensure it operates in the most efficient way, while equipment makers need to supply tools that save energy.
Energy management starts when buying new equipment, said Ruddell. OEMs will always try to sell the most competitively priced equipment. For them, it will always be cheaper to put a throttling valve into a pipeline than to use a variable speed drive with a pump.
But what is cheapest for the OEM may end up costing the owners of the equipment dearly. By getting the equipment wrong on the first day of production, the costs will only escalate. If the motors are to be working for more than 4,000 hours a year, for example, high efficiency motors should be specified. It may be more expensive initially, but the long-term savings will be considerable.
According to ABB, the greatest savings tend to be achieved with pumps and fans, which in many applications run with oversized motors that are only available with a certain number of fixed speeds.
"Rather than fitting the next bigger size relative to the requirement and then throttle the output, it is much better to reduce the motor speed with a VSD. For instance, a pump or a fan running at 80% speed only uses 51% of the energy compared to one running at full speed. It also gives more accurate control and less mechanical wear," said Ruddell.
In the water industry, for example, many working drives were installed in the water industry some 15 years ago. A modern drive will cause substantially lower energy losses in a motor than an older unit, so the whole system needs to be considered.
Pumping air to aeration tanks may account for over 70% of the energy consumption on a typical sewage treatment plant, so monitoring dissolved oxygen with appropriate analysis equipment can make a huge difference. The information can then be used to control air feed pumps or the speed of an agitator.
Possibly the biggest potential for energy savings in any water network lies with the drives that control pumping operations. Typically, reducing pump speed from 100% to 80% can cut energy consumption by up to 50%, said Ruddell.
Severn Trent Water was recognised at the Electrical Industry Awards 2006 for "Best Environmental Initiative of the Year", following an installation that reduced energy consumption by over £12,000 per annum at its Wanlip Sewage Treatment Works in Leicestershire.
The savings at the Wanlip site were achieved by Sentridge replacing three 20-year-old 37kW Heenan drives on water process pumps with ABB standard drives of the same rating. This produced an energy saving of more than 65%. Payback was achieved in just six months, and over £150,000 will ultimately be saved over the working life of the drives.
Severn Trent also saved thousands of pounds in energy and maintenance costs by replacing two drives from the 1980s with new models at its Ladywood sewage pumping station in Ironbridge, Shropshire. The combined savings mean the new drives will pay for themselves in well under two years.
As a result of realising what savings are possible, the utility company has set up an Energy Saving Project Group to look at replacing and upgrading existing drives and installing new ones throughout its network of sewage treatment plants. The initiative follows a three-year programme, completed in 2004/2005, to test pumps and replace or refurbish those found to be inefficient.
The company is following this up in 2005/2006 with a review of around 400 of its largest energy-consuming sites. Taken together, such initiatives played a significant part in helping Severn Trent to improve its energy efficiency by nearly 4% during 2004/05, cutting its total energy use from 1.139 million kWh to 1.083 million kWh.
CompanySalt Union, Runcorn
Severn Trent Water, Wanlip
Corus
Llanwern
Crisp Maltings, Portgordon
New Heinz energy centre, WiganOperationSalt production
Water process pumps
Strip steel milll
Drying unit at malting plant
Canned food productionInvestment£50k
N/a
£760k
N/a
N/a
ReplaceFixed speed fan, motor
20-year old Heenan drives
Four 1.4MW fixed speed descaling pump motors
Two 207kW DC motors to drive 2-metre diameter fans
Centre to replace existing steam plantInstall132kW fan/motor, ABB industrial drive
Three 37kW AC drives
from ABB
Four Siemens medium voltage VSD systems
Two WEG 132kW EEF1 high efficiency motors, CFW-09 Vectrue drives
Eight standard ABB 55 kW drives for fans on gas-fired burnersSaving/Payback£250k/year, CO2 emissions down 704t/yr
£150k over lifetime of drives, 65% energy, six months payback
£17,000/week
£40k/year, 48% energy saving per motor, 10-months payback
Energy centre 14% more efficient than existing steam plant.
For many industrial applications, because electric motors on average use over 60% of the electrical energy, engineers clearly see the benefit of investments such as variable speed drives. However, there is often nothing they can do if saving energy is not a priority in the boardroom.
Equipment makers often still find it difficult to find a dedicated person in charge of energy at end-user companies as the issue is deferred to senior management, according to Steve Ruddell, ABB's recently appointed energy spokesperson.
"The guy who buys the motor is not the same one who worries about the energy bill. In most cases, the engineer wants a motor to fill the hole just vacated by one that has given up. If it fits and produces at least the same speed and torque, he is happy," said Ruddell.
Many users are only too well aware of the imperative to reduce energy costs, but are constricted by the even higher priority demands of their day jobs, believes Steve Barker, Siemens Automation & Drives business manager, energy & power quality.
Barker wants more end-users to adopt "a coherent and systematic strategic approach" to saving energy. This, he said, should encompass everything from the initial system analysis through to an ongoing commitment to continually reduce costs and carbon emissions.
"Saving energy is not difficult but it needs a systematic approach. Begin by looking at continuously running equipment. If you do not need it, switch it off," Barker asserted. "Much equipment keeps running 24/7, although there is no real need for it. Then, look at pumps and fans. Are they controlled by variable speed drives? If not, they should be."
Today, though, even when companies do have an energy manager looking at these issues, they are normally more concerned with buying energy more cheaply, improving the efficiency of an existing process or reducing the running hours of that process, said Ruddell.
"It's precisely for these reasons that the majority of motors in industry are oversized. We think industry should look at the whole life cycle, starting when new kit is bought and new plant is designed," the ABB man commented.
According to Ruddell, the water utilities woke up to this a few years ago and started using variable speed drives (VSDs) on a wide scale to improve their processes. He also cited how one leading water company is allowing its engineers spend £5,000 a week on minor purchases without consulting senior management.
Investments in VSDs can, typically, provide 30% energy savings and give a realistic payback within a year. The key to these energy savings is the speed control in the application, rather than the intrinsic efficiency of the products, Barker emphasises. For instance, a 100 kW fan throttled by 50% in continuous operation will give payback in six months if equipped with a variable speed drive. One end user reported savings of over £100,000 a year, and a payback of less than three months, after upgrading a fan with a variable speed drive.
According to Barker, deciding on the optimum size of motors for applications such as pumps, fans and conveyors is one area where major savings can be made — especially in fixed speed applications.
"The efficiency of motors reduces under light load and therefore matching the product selection more closely with the actual load demand would be very helpful," Barker said. "The use of variable speed drives is sometimes to compensate for the initial engineering gaps, but the VSD will increase the overall system efficiency at light loads and will reduce the overall energy consumption."
A widespread culture of overating motors has built-up, agrees Andy Glover of WEG UK. "This involves engineers at various stages of the pump system design process adding 10% or 15% to the motor capacity 'just to be on the safe side.'"
This practice is so widespread that it is estimated that only 20% of the pump drive motors in operation are running at their full rated input, according to Glover.
A motor running at a typical commercial or industrial site for 4,000 hours a year has an annual electricity cost of about 10 times its capital cost, said Glover. "This is serious money, and effectively underlines why pump suppliers and pump users should ensure optimum efficiency from their systems by effectively matching drive motors to pumps. Unfortunately, this is not usually the case."
The implications for the end-user are, firstly, an exagerated capital cost for the motor itself; secondly, a commensurate increase in associated equipment, such as motor starters, drives and cabling; and, finally, gross inefficiencies in the system's operation.
Meanwhile, Barker believes many systems are not commissioned in the optimum way, for example, with motor details often entered incorrectly during VSD parameterisation, or the correct control requirements not introduced into the logic control scheme.
"Even if the initial commissioning is acceptable, the system becomes less optimal as adjustments are made over time," the Siemens manager added. "One large utility estimated that the overall system efficiency could be improved by as much as 8% if the systems were optimised."
Engineers also need training and support, believes Ruddell of ABB. "Most drives that find their way onto end-users' plants are not set correctly for energy savings. Site engineers need to keep in touch with the manufacturer and get appropriate training." In essence, users need to look at the equipment they run and ensure it operates in the most efficient way, while equipment makers need to supply tools that save energy.
Energy management starts when buying new equipment, said Ruddell. OEMs will always try to sell the most competitively priced equipment. For them, it will always be cheaper to put a throttling valve into a pipeline than to use a variable speed drive with a pump.
But what is cheapest for the OEM may end up costing the owners of the equipment dearly. By getting the equipment wrong on the first day of production, the costs will only escalate. If the motors are to be working for more than 4,000 hours a year, for example, high efficiency motors should be specified. It may be more expensive initially, but the long-term savings will be considerable.
According to ABB, the greatest savings tend to be achieved with pumps and fans, which in many applications run with oversized motors that are only available with a certain number of fixed speeds.
"Rather than fitting the next bigger size relative to the requirement and then throttle the output, it is much better to reduce the motor speed with a VSD. For instance, a pump or a fan running at 80% speed only uses 51% of the energy compared to one running at full speed. It also gives more accurate control and less mechanical wear," said Ruddell.
In the water industry, for example, many working drives were installed in the water industry some 15 years ago. A modern drive will cause substantially lower energy losses in a motor than an older unit, so the whole system needs to be considered.
Pumping air to aeration tanks may account for over 70% of the energy consumption on a typical sewage treatment plant, so monitoring dissolved oxygen with appropriate analysis equipment can make a huge difference. The information can then be used to control air feed pumps or the speed of an agitator.
Possibly the biggest potential for energy savings in any water network lies with the drives that control pumping operations. Typically, reducing pump speed from 100% to 80% can cut energy consumption by up to 50%, said Ruddell.
Severn Trent Water was recognised at the Electrical Industry Awards 2006 for "Best Environmental Initiative of the Year", following an installation that reduced energy consumption by over £12,000 per annum at its Wanlip Sewage Treatment Works in Leicestershire.
The savings at the Wanlip site were achieved by Sentridge replacing three 20-year-old 37kW Heenan drives on water process pumps with ABB standard drives of the same rating. This produced an energy saving of more than 65%. Payback was achieved in just six months, and over £150,000 will ultimately be saved over the working life of the drives.
Severn Trent also saved thousands of pounds in energy and maintenance costs by replacing two drives from the 1980s with new models at its Ladywood sewage pumping station in Ironbridge, Shropshire. The combined savings mean the new drives will pay for themselves in well under two years.
As a result of realising what savings are possible, the utility company has set up an Energy Saving Project Group to look at replacing and upgrading existing drives and installing new ones throughout its network of sewage treatment plants. The initiative follows a three-year programme, completed in 2004/2005, to test pumps and replace or refurbish those found to be inefficient.
The company is following this up in 2005/2006 with a review of around 400 of its largest energy-consuming sites. Taken together, such initiatives played a significant part in helping Severn Trent to improve its energy efficiency by nearly 4% during 2004/05, cutting its total energy use from 1.139 million kWh to 1.083 million kWh.
CompanySalt Union, Runcorn
Severn Trent Water, Wanlip
Corus
Llanwern
Crisp Maltings, Portgordon
New Heinz energy centre, WiganOperationSalt production
Water process pumps
Strip steel milll
Drying unit at malting plant
Canned food productionInvestment£50k
N/a
£760k
N/a
N/a
ReplaceFixed speed fan, motor
20-year old Heenan drives
Four 1.4MW fixed speed descaling pump motors
Two 207kW DC motors to drive 2-metre diameter fans
Centre to replace existing steam plantInstall132kW fan/motor, ABB industrial drive
Three 37kW AC drives
from ABB
Four Siemens medium voltage VSD systems
Two WEG 132kW EEF1 high efficiency motors, CFW-09 Vectrue drives
Eight standard ABB 55 kW drives for fans on gas-fired burnersSaving/Payback£250k/year, CO2 emissions down 704t/yr
£150k over lifetime of drives, 65% energy, six months payback
£17,000/week
£40k/year, 48% energy saving per motor, 10-months payback
Energy centre 14% more efficient than existing steam plant.
