Efficiency is a matterof perspective

Energy efficiency

Energy intensive production processes such as those found in the plastics industry hold an especially large potential for savings. Companies would be remiss not to take full advantage of this potential, not only because it is a matter of adhering to legal regulations, but also because they stand to benefit from considerable competitive advantages. When it comes to improving energy efficiency, the first step is to analyze where, when and how much energy is actually being consumed – however, not all analytical tools are created equal.

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Where resources are limited, efficiency is a key topic. As govern-ments around the world set energy targets, manufacturing and processing companies are constantly confronted with new direc-tives, standards and regulations. Yet efficiency is more than just a necessary evil – it holds great potential for developing a com-petitive edge.

Those quickest to adapt stand to gain the most, and their newly gained know-how will help improve the company’s overall perfor-mance. As one of the most energy-intensive types of processing, plastics technology is at the front line of efforts to optimize en-ergy consumption.

“Get more efficient.” – Ok, but how? The call for improved efficiency raises the question of a point of reference: “Where are we today and what will be the basis on which we measure our efficiency?” Over the years, the specific energy consumption, or SEC, has established itself as the stan-dard for measuring energy efficiency. This value is a ratio that tells us how much energy is consumed to produce a certain quantity of output. Before the SEC can be calculated, it is first necessary to clearly define the boundaries within which the con-sumption and output will be measured.

Let us look at a company that processes 40 tons of material per year and uses 100 MWh of energy to do so. The ratio of these two values gives us what is called the S-SEC, or site-specific energy consumption. This is the specific energy consumption for a plant, with the physical units kWh/kg. For this example, the value would be 100,000 kWh/40.000 kg, or 2.5 kWh/kg.

Energy efficiency

Author: Dr. Otto UrbanekBusiness consultant with a focus on machine manufacturing and plastics processing

After graduating from The University of Vienna with a degree in mechanical engineering, Otto Urbanek spent around thirty years in leadership positions at some of the top manufacturers of plastics machinery. In 2009 he founded his own consulting company, with a focus on machine manufacturing and plastics processing. On the behalf of the European association for plastics and rubber machinery manufacturers (EUROMAP), Urbanek conducted a Europe-wide study in 2011 to establish a comprehensive evaluation of the potential for increased energy efficiency in the fieldof plastics and rubber processing.

Comparing the efficiency of machinesIn a similar way, we could also measure the M-SEC, or machine-specific energy consumption, to determine the consumption of a particular processing machine. This value tells us how efficiently the machine is able to produce a given product.

When a machine is to be replaced, comparing the M-SEC values for representative products can help a company make a well-informed decision. Some machine manufacturers offer energy analysis tools in their controllers that provide data regarding overall energy con-sumption and the consumption of individual processing stages.

Increasing productivity increases efficiencyAlthough energy efficiency hasn’t always been a priority during development, machines have continuously grown more efficient over the years. The demand for higher productivity has spurred new machine designs and new technologies, which are intrinsi-cally more energy efficient. The current state-of-the-art tech-nologies, particularly in the area of motion control, promise to continue improving efficiency for years to come. This positive development is especially prominent when it comes to cyclic pro-cesses such as injection molding and blow molding.

Cyclic processes are notorious energy guzzlers and hold consid-erable potential for savings through the use of servo technology. As more and more machines are replaced with this technology, the benefits will continue to roll in.

It is relatively simple for a company to get a picture of how the overall efficiency of a plant develops over time. By collecting total

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A graph of the machine-specific energy consumption (M-SEC) over time for injection molding machines. The benefits of current developments will con-tinue to provide improved energy efficiency in the European machine popu-lation in the years to come.

A comparison between the consumption of machines and plants with re-spect to the various processing methods quickly illuminates the differences between the M-SEC and S-SEC values of the most prominent plastics pro-cessing technologies, as well as the weighted average values according to the European plastics consumption data from 2008.

energy consumption data over the course of several years and setting it in relation to the output quantities, the company can track changes in the S-SEC value. However, the amount of energy consumed by individual machines and different processing tech-nologies can vary enormously.

Product-specific energy data provides clarityIndependently of the type of technology used, energy consump-tion can generally be estimated using the ratio 9:3:1.

The value 1 represents the thermal energy that must be applied to the material in order to perform the molding process.

The energy required for the machine as a whole, including the thermal energy, is approximately 3 times higher than this value.

The energy required for the entire plant is approximately 9 times higher than the thermal energy input.

For example, if it would theoretically take 1 kWh to mold a plastic item based on physics alone, then a company would actually expect to use – and pay for – a total of 9 kWh (European average for 2011, weighted according to processing technology). Since total energy consumption is not itemized, companies today have no way of knowing exactly what costs are associated with any specific product.

In order to fill the huge gap between the consumption of a plant and that of an individual machine, data must be collected and analyzed for specific products and processes (product/process-specific energy consumption, or P-SEC). The P-SEC provides ex-tremely valuable information regarding product-specific energy consumption, which is necessary in order to optimize costs. It allows the analysis to focus on process-related consumption and exclude energy consumed by building infrastructure such as lighting, ventilation and air conditioning.

Knowing where the money is goingThe first step in an analysis is to determine how resources are being used and where money is being spent. The goal here is to understand the interrelationships and identify sources of waste. Only then can effective measures be developed to make processes more efficient and economical. There are two main approaches:

Solution 1: Selective approach A one-off analysis is performed to obtain a snapshot of the current situation. Energy flow is visualized, and opportunities to improve efficiency are identified. Based on this analysis, a list of measures

Specific energy consumption of injection molding machines

Reference: Market analysis for Europe, UIC 2011

M-SEC [kW

h/kg]

1,4

1,2

1

0,8

0,6

0,4

0,2

0

1990 1995 2000 2005 2010 2015 2020

Years

0,47

0,758

0,93 (Population)

0,19 (Enthalpie)

2,5

2

1,5

1

0,5

0

injection molding extrusion blow molding thermo molding average

S-SECM-SEC

Reference: Market analysis for Europe, UIC 2011

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Energy efficiency

is developed. Once these measures have been implemented, the results are evaluated. This approach is a good first step toward greater efficiency. It also creates increased awareness of ener-gy-related issues. It does not, however, involve any tool that can initiate and maintain ongoing improvements.

Solution 2: Continuous approachStarting with the production machine, the entire production envi-ronment is evaluated, including central functions accessed by the production system. To make the flow of energy more trans-parent, sensors are installed for measuring temperature, pres-sure and flow volume and switching times are recorded. A detailed understanding of individual costs and interrelationships fuels a process of continuous improvement and process optimization.

A successful monitoring solution must include: Expert structural analysis of the production environment, in-cluding preparatory planning

A scalable system solution that is easy to install and use A configurable software tool for custom evaluation of data

Improved efficiency and greater successthrough energy managementThe potential for energy savings in the plastics industry is gener-ally quite high. Companies that succeed in tapping into this potential stand to gain a sustainable economical advantage. The key to doing so is to analyze the production system in its entirety. Continuously monitoring the flow of energy and other resources provides the transparency needed to manage them effectively.

The introduction of ISO 50001 will likely force some companies to finally face the issue of energy management. With the consider-able economic potential involved, however, it would surely pay off to take a more proactive approach and enjoy the competitive benefits of leading the way.

9 : 3 : 1

8,0 TWh

22,8 TWh

S-SEC P-SEC M-SEC Enthalpie

?

66,5 TWh

Reference: Market analysis for Europe, UIC 2011

The large gap between machine-specific and site-specific consumption values is the basis for analyzing the product-specific or process-specific energy consumption. The total energy consumed by a plant is many times higher than the thermal energy required for the forming process.

Clear definitions of specific energy consumption (SEC) have been established and provide a reliable basis for measuring energy consumption S-SEC: Site-specific energy consumption: any energy-related activity of a production site P-SEC: .Product-specific energy consumption (all products): total energy required to pro-duce a particular finished goodM-SEC: Machine-specific energy consumption (plastic machines): Heat input in terms of material, machine movements (screw, clamp, ejector, ect.)Enthalpy..Includes heat of fusion for the molding process (normally cannot be influenced)

APROL

The APROL EnMon system from B&R provides continuous energy monitoring, either as a stand-alone unit or integrated in a process control system. APROL EnMon is a scalable out-of-the-box solution that is easy to integrate. It provides users compre-hensive and intuitive support in the pursuit of optimizing energy consumption. In the face of rising energy prices it is still possible to reduce unit costs while conserving valuable resources. B&R’s solution can be implemented just as easily and effectively on the smallest stand-alone machine or at the most expansive processing plant.

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Energy efficiency