Saving Energy with Tailored Drive Solutions
30 May 2012
The reality of global climate change means that production and manufacturing techniques must become more modern and sustainable. The EU has already set the 20-20-20 goal as part of its Europe2020 strategy, with the objective of reducing carbon emissions by 20 per cent, lowering energy consumption by 20 per cent, and increasing the proportion of renewable energies by 20 per cent, all in order to curb climate change. From the manufacturing perspective, the term ‘sustainable production’ includes technologies able to make products with no greenhouse gas emissions, no non-renewable or toxic materials, and no waste – all while optimising profits and supply chain integrity.
The manufacturing industry is responsible for 33% of total energy consumption. A reduction of just 1% would be equivalent to saving about 55 million barrels of oil a year – avalue of about a billion dollars.
For a manufacturing company, saving energy brings significant advantages. Lower energy consumption translates to lower production and operating costs and makes the company more competitive. In addition, it helps companies cope more easily with energy price rises. And last but not least, a company that actively saves energy scores points in the area of environmental commitment.
Companies wanting to save energy can analyse a whole production or manufacturing process, or start by looking at individual applications. There are various online tools available, like the Rockwell Automation Energy Evaluator,that give a manufacturer a complete analysis of its current water, air, gas, electric and steam (WAGES) management performance. These tools also deliver a clear understanding of how its operating strategies compare with its peers in the same industry and in other sectors. The tool provides a 20-minute online assessment to generate a real-time report outlining a facility’s competitive WAGES management baseline. The results allow employees at all levels of the business to identify and implement strategic changes and to set improvement goals – both for individual facilities and across their entire organisation.
When companies look at specific applications, the electric drive system is a focal point due to its energy consumption. The ZVEI, the German electrical and electronic engineering industry association, reports that two thirds of all electrical energy consumed in the industrial environment is used for driving machines with motors (published in Motoren und geregelte Antriebe,April 2010).
Pump and fan control applications are to be found in manufacturing companies and make up about 55 per cent of motor applications. This is where significant energy savings can be made, especially if production processes do not need a pressure or flow rate of 100 per cent, which is the case with most pump and fan control applications. Many are still direct-drive applications – in other words, their motors are running at the maximum power levels. However, most of these applications are characterised by variable or regulated speeds that are often controlled by valves and dampers. This mechanical regulation offers a lot of potential for saving energy. A car is a good example of this, as no driver would slow the car down using only the brakes if the engine was still running at full speed.
Regulating pump and fan control applications can easily be performed with the addition of an AC drive. Unlike valves and dampers, the pressure or flow is changed by regulating the motor speed, and this in turn has a considerable effect on the power consumption of the motor. Energy savings are equivalent to the reduction in speed cubed (n3), resulting in significantly lower energy consumption. For example, reducing the speed of an application with variable torque by just 20 per cent would achieve energy savings of up to 50 per cent!
Many pump applications are suitable for this type of regulation, including main pumps for factory water as well as dosing, circulation, booster, cooling water, cooling tower and process pumps. In addition, as the motor is started and stopped by the AC drive, there is less mechanical stress on the motor, pump or fan, valves, tubes etc. This extends their lifecycle and allows for more efficient operation, providing further possible savings on maintenance and operating costs.
The following calculation is an example of possible cost savings that could be made by replacing mechanical with electrical regulation.
A factory is using an older 250kW motor to drive a pump. The flow is regulated using a damper. Let us assume it is operating under the following conditions: three-shift operation, six days a week, with energy costs at €0.15/kWh including taxes.
With the cubic formula mentioned above, an average speed reduction of 20% for this pump application would lower power consumption by almost 50%. Without taking flow conditions or other parameters into account, this reduction would enable the factory to save approximately €135,000 per year.
The Energy Saving Calculator is available to companies wanting an overview of potential energy savings in their facilities. This convenient new tool from Rockwell Automation (http://www.rockwellenergycalc.com) allows manufacturers to use mobile devices or computers to calculate potential savings derived from variable frequency drives for power pumps and fans. Manufacturers can use the energy savings calculator online or download the free mobile application to their iPad, iPhone, BlackBerry or Android device. With this new tool, users can compare conventional methods, such as valves for pump control and dampers for fan control, to the effect of variable frequency drives and see the estimated cost savings they could obtain by installing an Allen-Bradley PowerFlex drive.
The new Allen-Bradley® PowerFlex AC Series 750 drives from Rockwell Automation are well suited to pump and fan control applications. They provide multiple control, communications, safety and hardware options. With the new PowerFlex 750 series, Rockwell Automation now covers a power range of up to 1500 KW in the400/480Vand 600/690Vareas. From frame size 8 and 250KW upwards, the PowerFlex 755includes a cabinet concept based on Centerline 2500 MCC, making it a suitable solution for flexible applications.
ThePowerFlex755 AC drive can be rolled out of the cabinet for convenience, making it easier to connect the large power cables to the power tracks. The movable L-brackets help make this job even easier. The flexible design allows the power wiring to be inserted from the top or the bottom. The drive only needs to be wired once, as each drive unit can be taken out without cutting the power wiring.
The drives are based on a common platform with the same supply and control structure, extending their power range and providing a consistent user experience. If more power is needed, the appropriate drives can be added.
The PowerFlex 755 also offers seamless integration into the Logix environment, facilitating and improving application development and diagnostics. Add-on profiles and embedded motion commands help to reduce development time and the associated costs, while optimising the configuration, control and collection of data. An additional function contributing to increased productivity is the automatic device configuration. The Logix controller automatically detects a replaced PowerFlex 755 and downloads all configuration parameters onto it.
As with the other models in the PowerFlex 750 series, the high-definition LCD display provides six lines of text for more meaningful explanations of parameters and events. Drive data can be configured, controlled and collected with the standard embedded Ethernet port. Five slots are available to support additional options for I/O, feedback, safety, communications and auxiliary power supply. As a result, the AC drive can be adapted to the exact requirements of the application and is suitable for use as a drive solution in practically all industry sectors.
About the author
Michael Müller (48) is Business Manager for the drive, safety technology and switchgear areas at Rockwell Automation in Germany. He started his career as a telecommunications specialist, then completed a degree in electrical engineering with a specialisation in energy technologies. Müller then joined Rockwell Automation as a sales engineer, moving up to sales manager level in 2004 and to his current Business Manager position in 2009.
For further information please contact:
Rockwell Automation Ltd, Pitfield, Kiln Farm, MILTON KEYNES, MK11 3DR Tel 0870 242 5004 www.rockwellautomation.co.uk