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LCC approach for big motor-driven systems savings
24
Feature
WORLD PUMPS
November 2008
Life cycle costs
LCC approach for big motor-driven systems savings ABB’s Jukka Tolvanen, energy efficiency market manager, introduces life cycle cost (LCC) analysis and shows how efficient motors and AC drives can often be used to minimize lifetime costs, especially in high usage pump and fan systems.
F
aced with a number of alternative motor-driven systems, organizations often choose the one that is cheapest to buy and install. This approach can turn out to be very expensive: the initial purchase price is usually only a small portion of the overall lifetime cost, and the option that is cheapest to purchase is often the worst in terms of energy efficiency. Spending a little more to start with can result in huge savings later.
less significant. However, the initial purchase, energy and maintenance costs usually play an important role in the LCC of motor-driven applications.
Initial purchase cost The price tag is the most visible expenditure item and yet, in high usage
What is LCC? The life cycle cost (LCC) of an item of equipment includes all the costs associated with the equipment over its entire lifetime. To determine the LCC of a system, an analytical study is undertaken to first identify all the relevant costs and then quantify them. The main costs typically comprise the initial acquisition, installation and commissioning costs, energy, operation, maintenance and repair costs, environmental costs, and decommissioning and disposal costs. In any given system, some of these costs will be more important and some www.worldpumps.com
Figure 1. A high efficiency motor costs more than a regular product, but the price difference can be recovered in less than two years through energy savings. The efficient motor then continues to save energy ‘for free’ over the rest of its lifetime. The EFF1 motor shown here is an M3BP model from ABB..
0262 1762/08 © 2008 Elsevier Ltd. All rights reserved
WORLD PUMPS
Feature
November 2008
motor-driven systems, the initial purchase cost is often only a small part of the total LCC. One factor which affects the initial cost is the quality of the equipment. Higher quality, energy-efficient motors cost a little more than regular units but their superior efficiency and reliability will compensate for the price differential in a relatively short time. A 90 kW, energyefficient motor can cost €2,000 more to buy than a standard efficiency model, for example, but can save over €1,400 per year over its whole service life. Adding a variable speed AC drive (VSD) to the system to control motor speed will increase the purchase cost but generally reduces energy consumption significantly. In fact, the payback time for a drive is often a matter of months on the basis of energy savings alone. Another factor which will affect the LCC analysis in favor of energy efficient alternatives is that a number of countries have introduced financial incentives to encourage users to select efficient equipment. These incentives can naturally be offset against the purchase cost in the LCC analysis.
Figure 2. Using AC drives to precisely control motor speed can dramatically increase overall system efficiency. Many advanced drives – such as the ABB industrial drives shown here - can also be supplied with application-specific software for enhanced functionality in controlling pumps, fans, and other motor-driven systems.
efficiency motors cost less to buy but their lower efficiency means that they tend to run hotter, which leads to more frequent breakdowns. Using higher quality, more reliable equipment also provides greater scope for maintenance planning. By preparing a
maintenance plan and establishing a preventive maintenance regime, unexpected downtime can be minimized. This is important in constantly running processes like paper machines, where downtime costs are extremely high. In these types of critical applications
Energy costs Energy costs are often the biggest element in life cycle costs, especially for equipment that runs most of the time. Over its lifetime, a high usage electric motor can consume energy costing 100 times the motor’s original purchase price. Using a more efficient motor can therefore produce big energy savings over the years. The use of higher efficiency motors also cuts unnecessary carbon dioxide emissions. Generating the electricity to drive motors produces an estimated 37 million tonnes of CO2 annually. It has been calculated that this figure could be cut by as much as 10–25% if inefficient motors were upgraded. Energy costs in systems where a variable output is needed can usually be cut dramatically if an AC drive is used to run the motor at the required speed, rather than operating it at full speed and then throttling the output.
Maintenance costs Maintenance costs depend to a significant extent on the quality and reliability of the equipment. Lower quality, lower www.worldpumps.com
25
26
Feature
WORLD PUMPS
November 2008
equipment reliability is paramount and efficient, high quality motors are essential. Installing an AC drive to control the motor speed will often result in reduced maintenance costs: the drive regulates the motor speed for an optimum match with the requirements of the process, cutting mechanical wear and tear within the system. In the case of pumping applications, ABB industrial drives can be supplied with software which not only controls the basic operation of the system but also enables the drive itself to perform basic preventive maintenance and therefore reduce overall maintenance costs. Programs available include routines to
Figure 3. €142,850 worth of energy is being saved per year by an ABB motor driven by an ABB industrial drive at Salt Union in Runcorn in the UK.
VSDs boost efficiency of entire drive system Within Europe, choosing an efficient motor (at least for the most commonly used AC motors in the range 1.1 to 90 kW ) has become easier following the introduction of the European efficiency classification scheme. The classifications run from EFF3 (least efficient) to EFF1. EFF1 motors can be up to 6% more efficient than EFF2 models; this difference offsets the higher price of EFF1 models in 18-24 months, after which an EFF1 motor continues to save energy “for free” over the rest of its lifetime. For further information on the scheme, visit www. cemep.org To minimize lifetime energy costs select an EFF1 motor. Confirm that it is a high quality unit with good reliability by requesting guaranteed efficiency data, as well as temperature rise, vibration and noise level data. For efficient operation, motor oversizing and rewinding should generally be avoided. ■ Oversized motors are often specified 'just in case' requirements increase in future, but this results in significant unnecessary energy costs. ■ Rewinding usually results in lower efficiency. Rewinding a motor over 30 kW can reduce its rated efficiency by 1%, while the figure for smaller motors can be 2%. A new motor naturally costs more, but the cost of a high
www.worldpumps.com
efficiency motor can be quickly recouped through energy savings VSDs boost efficiency of entire drive system AC drives are becoming increasingly sophisticated, compact, and less expensive. Energy costs, by contrast, are rising. As drives help to save energy in most applications, this means that the payback times for drives are getting shorter. In industry, 65% of total electricity consumption is used for driving electric motors. Of this, an estimated 20% is wasted in throttling mechanisms. Using AC drives to control motor speed according to demand makes savings up to 70% in energy consumption possible. There is massive potential for energy savings using drives, as 97% of all installed motors under 2.2 kW have no form of speed control at all. Optimal speed control by a drive not only saves energy but also reduces the motor’s maintenance needs. Within a production process, accurate control will also generally improve product quality and increase productivity. Nowadays drives not only handle the basic speed control function, but in many cases can also be supplied with special application software. Drives can perform routine maintenance, and even act as online monitoring units, issuing alerts when predetermined situations occur.
prevent clogging of the pump, avoid the build-up of sediment on tank sides, and keep the pipes clear.
Calculating LCC Once all the relevant purchase, energy, maintenance and other cost components have been quantified, the LCC can be calculated. As the lifetime of a system may be 20 years or more, present or discounted values should be used. This is because ‘a dollar today is worth more than a dollar tomorrow’ – and a lot more than a dollar in 20 years. Other inputs needed for the calculation will include the expected lifetime of the equipment, energy and labor costs, and interest rate. As the calculations are partly based on assumptions and estimates, the results will be approximate – but they will enable different systems to be compared. LCC analysis can be applied to both new and existing systems. When an existing system is analyzed, the analysis should include the ‘do nothing’ case so that the other alternatives can be compared to the option of leaving the existing system unchanged. Analysis of an existing system often reveals that it has been inefficient from the outset, or has become inefficient because the function it performs has changed over the years. A large proportion of the existing motordriven applications worldwide consists of pump and fan systems, and many of these are inefficient. This offers the potential for big energy savings on a global scale through relatively straightforward and inexpensive upgrades.
WORLD PUMPS
Feature
November 2008
Efficient operation Many existing pump and fan systems are based on throttling arrangements: the motor is driven at full speed and then the flow of liquid or gas is regulated by valves, vanes or similar throttling mechanisms. Throttling the output in this way is clearly very wasteful. An AC drive can increase the system’s efficiency by adjusting the motor speed to the correct operation point and eliminating the need for throttling. A small reduction in speed can make a big difference in energy consumption. A pump or fan running at half speed consumes only one quarter as much energy as a unit running at full speed. This is because the power required to run a pump or fan changes with the cube of the volume. Because many pump and fan systems run at less than full capacity for much of the time, variable speed drives can produce huge savings. If a 100 kW fan is throttled by 50%, for example, the investment in a variable speed drive will have a payback time of only six months of continuous operation. A good example of the real savings that can be achieved is provided by a recent upgrade project at Salt Union, a UK salt producer. One of the company’s processes used a fan to suck air through
a damper unit to dry salt. An energy audit revealed that the fan motor was oversized and the damper was in fact 95% closed during normal operation. The damper and oversized motor were then replaced with an appropriately rated unit controlled by an AC drive. This resulted in savings of 1,600 MWh or €142,850 per year. The company stated that the fan had been correctly sized when it was originally installed, but had then become oversized following a change in the nature of the product being processed. LCC analysis is an extremely useful tool. Assuming that it is based on reliable data, it delivers the information needed by management to compare alternative solutions and select the most costeffective. It can produce substantial energy savings and help to cut carbon dioxide emissions.
Contact ABB Oy Jukka Tolvanen Market Manager P.O Box 184 FI-00381 Helsinki Tel: +358 10 222 2897 Fax: +358 10 222 2866 Email: jukka.tolvanen@fi.abb.com www.abb.com/drives
www.worldpumps.com
27
Feature
WORLD PUMPS
November 2008
Life cycle costs
LCC approach for big motor-driven systems savings ABB’s Jukka Tolvanen, energy efficiency market manager, introduces life cycle cost (LCC) analysis and shows how efficient motors and AC drives can often be used to minimize lifetime costs, especially in high usage pump and fan systems.
F
aced with a number of alternative motor-driven systems, organizations often choose the one that is cheapest to buy and install. This approach can turn out to be very expensive: the initial purchase price is usually only a small portion of the overall lifetime cost, and the option that is cheapest to purchase is often the worst in terms of energy efficiency. Spending a little more to start with can result in huge savings later.
less significant. However, the initial purchase, energy and maintenance costs usually play an important role in the LCC of motor-driven applications.
Initial purchase cost The price tag is the most visible expenditure item and yet, in high usage
What is LCC? The life cycle cost (LCC) of an item of equipment includes all the costs associated with the equipment over its entire lifetime. To determine the LCC of a system, an analytical study is undertaken to first identify all the relevant costs and then quantify them. The main costs typically comprise the initial acquisition, installation and commissioning costs, energy, operation, maintenance and repair costs, environmental costs, and decommissioning and disposal costs. In any given system, some of these costs will be more important and some www.worldpumps.com
Figure 1. A high efficiency motor costs more than a regular product, but the price difference can be recovered in less than two years through energy savings. The efficient motor then continues to save energy ‘for free’ over the rest of its lifetime. The EFF1 motor shown here is an M3BP model from ABB..
0262 1762/08 © 2008 Elsevier Ltd. All rights reserved
WORLD PUMPS
Feature
November 2008
motor-driven systems, the initial purchase cost is often only a small part of the total LCC. One factor which affects the initial cost is the quality of the equipment. Higher quality, energy-efficient motors cost a little more than regular units but their superior efficiency and reliability will compensate for the price differential in a relatively short time. A 90 kW, energyefficient motor can cost €2,000 more to buy than a standard efficiency model, for example, but can save over €1,400 per year over its whole service life. Adding a variable speed AC drive (VSD) to the system to control motor speed will increase the purchase cost but generally reduces energy consumption significantly. In fact, the payback time for a drive is often a matter of months on the basis of energy savings alone. Another factor which will affect the LCC analysis in favor of energy efficient alternatives is that a number of countries have introduced financial incentives to encourage users to select efficient equipment. These incentives can naturally be offset against the purchase cost in the LCC analysis.
Figure 2. Using AC drives to precisely control motor speed can dramatically increase overall system efficiency. Many advanced drives – such as the ABB industrial drives shown here - can also be supplied with application-specific software for enhanced functionality in controlling pumps, fans, and other motor-driven systems.
efficiency motors cost less to buy but their lower efficiency means that they tend to run hotter, which leads to more frequent breakdowns. Using higher quality, more reliable equipment also provides greater scope for maintenance planning. By preparing a
maintenance plan and establishing a preventive maintenance regime, unexpected downtime can be minimized. This is important in constantly running processes like paper machines, where downtime costs are extremely high. In these types of critical applications
Energy costs Energy costs are often the biggest element in life cycle costs, especially for equipment that runs most of the time. Over its lifetime, a high usage electric motor can consume energy costing 100 times the motor’s original purchase price. Using a more efficient motor can therefore produce big energy savings over the years. The use of higher efficiency motors also cuts unnecessary carbon dioxide emissions. Generating the electricity to drive motors produces an estimated 37 million tonnes of CO2 annually. It has been calculated that this figure could be cut by as much as 10–25% if inefficient motors were upgraded. Energy costs in systems where a variable output is needed can usually be cut dramatically if an AC drive is used to run the motor at the required speed, rather than operating it at full speed and then throttling the output.
Maintenance costs Maintenance costs depend to a significant extent on the quality and reliability of the equipment. Lower quality, lower www.worldpumps.com
25
26
Feature
WORLD PUMPS
November 2008
equipment reliability is paramount and efficient, high quality motors are essential. Installing an AC drive to control the motor speed will often result in reduced maintenance costs: the drive regulates the motor speed for an optimum match with the requirements of the process, cutting mechanical wear and tear within the system. In the case of pumping applications, ABB industrial drives can be supplied with software which not only controls the basic operation of the system but also enables the drive itself to perform basic preventive maintenance and therefore reduce overall maintenance costs. Programs available include routines to
Figure 3. €142,850 worth of energy is being saved per year by an ABB motor driven by an ABB industrial drive at Salt Union in Runcorn in the UK.
VSDs boost efficiency of entire drive system Within Europe, choosing an efficient motor (at least for the most commonly used AC motors in the range 1.1 to 90 kW ) has become easier following the introduction of the European efficiency classification scheme. The classifications run from EFF3 (least efficient) to EFF1. EFF1 motors can be up to 6% more efficient than EFF2 models; this difference offsets the higher price of EFF1 models in 18-24 months, after which an EFF1 motor continues to save energy “for free” over the rest of its lifetime. For further information on the scheme, visit www. cemep.org To minimize lifetime energy costs select an EFF1 motor. Confirm that it is a high quality unit with good reliability by requesting guaranteed efficiency data, as well as temperature rise, vibration and noise level data. For efficient operation, motor oversizing and rewinding should generally be avoided. ■ Oversized motors are often specified 'just in case' requirements increase in future, but this results in significant unnecessary energy costs. ■ Rewinding usually results in lower efficiency. Rewinding a motor over 30 kW can reduce its rated efficiency by 1%, while the figure for smaller motors can be 2%. A new motor naturally costs more, but the cost of a high
www.worldpumps.com
efficiency motor can be quickly recouped through energy savings VSDs boost efficiency of entire drive system AC drives are becoming increasingly sophisticated, compact, and less expensive. Energy costs, by contrast, are rising. As drives help to save energy in most applications, this means that the payback times for drives are getting shorter. In industry, 65% of total electricity consumption is used for driving electric motors. Of this, an estimated 20% is wasted in throttling mechanisms. Using AC drives to control motor speed according to demand makes savings up to 70% in energy consumption possible. There is massive potential for energy savings using drives, as 97% of all installed motors under 2.2 kW have no form of speed control at all. Optimal speed control by a drive not only saves energy but also reduces the motor’s maintenance needs. Within a production process, accurate control will also generally improve product quality and increase productivity. Nowadays drives not only handle the basic speed control function, but in many cases can also be supplied with special application software. Drives can perform routine maintenance, and even act as online monitoring units, issuing alerts when predetermined situations occur.
prevent clogging of the pump, avoid the build-up of sediment on tank sides, and keep the pipes clear.
Calculating LCC Once all the relevant purchase, energy, maintenance and other cost components have been quantified, the LCC can be calculated. As the lifetime of a system may be 20 years or more, present or discounted values should be used. This is because ‘a dollar today is worth more than a dollar tomorrow’ – and a lot more than a dollar in 20 years. Other inputs needed for the calculation will include the expected lifetime of the equipment, energy and labor costs, and interest rate. As the calculations are partly based on assumptions and estimates, the results will be approximate – but they will enable different systems to be compared. LCC analysis can be applied to both new and existing systems. When an existing system is analyzed, the analysis should include the ‘do nothing’ case so that the other alternatives can be compared to the option of leaving the existing system unchanged. Analysis of an existing system often reveals that it has been inefficient from the outset, or has become inefficient because the function it performs has changed over the years. A large proportion of the existing motordriven applications worldwide consists of pump and fan systems, and many of these are inefficient. This offers the potential for big energy savings on a global scale through relatively straightforward and inexpensive upgrades.
WORLD PUMPS
Feature
November 2008
Efficient operation Many existing pump and fan systems are based on throttling arrangements: the motor is driven at full speed and then the flow of liquid or gas is regulated by valves, vanes or similar throttling mechanisms. Throttling the output in this way is clearly very wasteful. An AC drive can increase the system’s efficiency by adjusting the motor speed to the correct operation point and eliminating the need for throttling. A small reduction in speed can make a big difference in energy consumption. A pump or fan running at half speed consumes only one quarter as much energy as a unit running at full speed. This is because the power required to run a pump or fan changes with the cube of the volume. Because many pump and fan systems run at less than full capacity for much of the time, variable speed drives can produce huge savings. If a 100 kW fan is throttled by 50%, for example, the investment in a variable speed drive will have a payback time of only six months of continuous operation. A good example of the real savings that can be achieved is provided by a recent upgrade project at Salt Union, a UK salt producer. One of the company’s processes used a fan to suck air through
a damper unit to dry salt. An energy audit revealed that the fan motor was oversized and the damper was in fact 95% closed during normal operation. The damper and oversized motor were then replaced with an appropriately rated unit controlled by an AC drive. This resulted in savings of 1,600 MWh or €142,850 per year. The company stated that the fan had been correctly sized when it was originally installed, but had then become oversized following a change in the nature of the product being processed. LCC analysis is an extremely useful tool. Assuming that it is based on reliable data, it delivers the information needed by management to compare alternative solutions and select the most costeffective. It can produce substantial energy savings and help to cut carbon dioxide emissions.
Contact ABB Oy Jukka Tolvanen Market Manager P.O Box 184 FI-00381 Helsinki Tel: +358 10 222 2897 Fax: +358 10 222 2866 Email: jukka.tolvanen@fi.abb.com www.abb.com/drives
www.worldpumps.com
27