**5. The potential of applying the measures for energy efficiency increase**

Measures for increasing energy efficiency of compressed air systems are related to different phases of the life cycle of a compressed air system:


168 Energy Efficiency – The Innovative Ways for Smart Energy, the Future Towards Modern Utilities

pneumatic devices (Mališa et al., 2011).

adjusting the parameters related to compressed air.

**Figure 8.** Complex robotic cell

Having in mind the fact that compressed air is widely used in robot applications, it could be naturally that there are many possibilities for savings and its efficient usage. In that manner we can describe an example of a robotic cell (Fig. 8) optimisation with installed electric and

The key step is to define the parameters within a robotic cell that affect electricity and/or compressed air consumption, e.g. robot's velocity, device activity, movement trajectories, position of the robot relatively to working area; pressure of compressed air; suction capacity (in the case of vacuum); length of the supply tubes, etc. As various factors are present there are three different ways for optimisation of such complex robotic cell. First approach is the most common case when two independent experts (usually robotic expert and pneumatic expert) optimise the parameters in their domain in parallel. Second approach encompasses firstly the optimisation of the parameters that influence the compressed air consumption, and than parameters that influence the electricity consumption. The third method includes optimisation of the parameters influencing the electricity consumption, and after that,

Doing the experiments that would have confirmed one of the mentioned approaches, it was realised that, electric and compressed air parameters could not be observed separately, because most of them influence each other. For instance the adoption of the lowest robot velocity, as the lowest electricity consuming, would disregard the most important principle of a production system: productivity. On the other hand, the highest robot velocity would ensure the highest productivity of the robotic cell, but it would induce the problems with


The greatest potential for achieving the savings exists in times of conceiving a new system because at that moment a great spectrum of energy saving measures, described in the table below, is available. This kind of situation is relatively rare, because new factories are not continuously built so even the best opportunity for systematic design becomes rarely available (first column in table 4). Table 4 gives approximate indications of phases in which each of described measures can be applied.

Much frequently encountered is the case of replacing the main components of the existing system. In this kind of situation, it is possible to implement many measures, some of which are faced with greater difficulty especially the ones that are related to system design: compressed air distribution network, systems with multiple pressure levels, selection of the type of end consumer, etc. It is estimated that the possibility for savings in the existing systems, in the time of replacement of main components, amounts to 2/3 of the efficiency increase that could be realized in a new system that would be designed with initially having energy efficiency in mind (Radgen and Blaustein, 2001).



Increasing the Energy Efficiency in Compressed Air Systems 171

Compressed air systems represent a significant segment of production and service systems. Therefore, it is necessary to pay attention to their energy efficient operation. The application of the measures for an energy efficiency increase in compressed air systems enables prolongation of the component's life cycle and the reduction of total operation costs that in turn increases the economic quality of working process. The procedure that was presented and explained in detail, containing cost effective activities illustrated with appropriate

Aspragathos, NA. & Foussias, S. (2002). Optimal Location of a Robot Path when Considering Velocity Performance. *Robotica*, Vol.20, No.2, pp.139-147, ISSN 0263-5747 Barth, J., Zhang, J. & Goldfarb, M. (2003). Control Design for Relative Stability in a PWM-Controlled Pneumatic System. *ASME Journal of Dynamic Systems, Measurement, and* 

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Dissanayake, M. & Gal, J. (1994). Workstation Planning for Redundant Manipulators. *International Journal of Production Research*, Vol.32, No.5, pp. 1105-1018, ISSN 0020-7543 Dudić, S., Ignjatovic, I., Šešlija, D., Blagojević, V. & Stojiljković, M. (2012). Leakage Quantification of Compressed Air Using Ultrasound and Infrared Thermography.

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Actuator, *Elektronika Ir Elektrotechnika*, (Article in press), ISSN 1392 – 1215

examples, can significantly increase the energy efficiency of compressed air systems.

**6. Conclusion** 

**Author details** 

**7. References** 

Retrieved from

driven-systems.pdf>

Dragan Šešlija, Ivana Ignjatović and Slobodan Dudić

*Faculty of Technical Sciences, University of Novi Sad, Republic of Serbia* 

*Control*, Vol.125, No.3, pp. 504-508, ISSN: 0022-0434

No.2, , pp. 170-176, ISSN (Online) 0975-1084

*Measurement*, (Article in Press), ISSN 0263-2241

EPS-Electric Power Industry of Serbia (2009b). *Prices*

**Table 4.** The applicability of energy saving measures in specified phases of a compressed air system life cycle (Radgen and Blaustein, 2001).

Some measures for energy savings can be implemented into the existing systems in any moment. These are, for example, implementation of sophisticated control systems or waste heat regeneration. The procedures related to maintenance and system operation, especially the frequency of filter replacement, represents one of the main sources for energy savings. These measures can also be implemented at any time during a life cycle of compressed air system components. Table 5 gives the estimate of applicability of these measures based on opinion of the larger number of experts (USDOE, 2001). Only the estimates of the average savings in relation to most significant measures for increasing energy efficiency are given, given that the return of investment time is less than 3 years.


**Table 5.** The experts estimate of the average energy savings for compressed air systems in relation to most significant measures (USDOE, 2001).

#### **6. Conclusion**

170 Energy Efficiency – The Innovative Ways for Smart Energy, the Future Towards Modern Utilities

Optimal choice of compressor ++ + Sophisticated control system ++ ++ Recuperating waste heat ++ ++

Overall system design ++ + Optimising end use devices ++ + Reducing frictional losses ++ + +

given that the return of investment time is less than 3 years.

cycle (Radgen and Blaustein, 2001).

Reduction of overall

Match compressor and

compressor components

most significant measures (USDOE, 2001).

Improvements of

Improvement of

Operation and

**System design acquisition** 

Improvement of drives ++ ++ +

Improvement in air treatment ++ ++ ++

Reducing air leaks + + + ++ Measuring system performance ++ + ++

**Table 4.** The applicability of energy saving measures in specified phases of a compressed air system life

Some measures for energy savings can be implemented into the existing systems in any moment. These are, for example, implementation of sophisticated control systems or waste heat regeneration. The procedures related to maintenance and system operation, especially the frequency of filter replacement, represents one of the main sources for energy savings. These measures can also be implemented at any time during a life cycle of compressed air system components. Table 5 gives the estimate of applicability of these measures based on opinion of the larger number of experts (USDOE, 2001). Only the estimates of the average savings in relation to most significant measures for increasing energy efficiency are given,

**Energy saving measures Applicability % Gain % Potential** 

system requirements 20 - 40 30 20 6.0

load 5 – 15 10 3 0.3

compressor control 15 – 40 25 10 2.5

maintenance 50 – 85 75 10 7.5 Total savings 17.1 **Table 5.** The experts estimate of the average energy savings for compressed air systems in relation to

From – to Average **contribution** 

5 - 20 15 5 0.8

**Installatio n** 

**Component replacement**

**Maintenanc e** 

Compressed air systems represent a significant segment of production and service systems. Therefore, it is necessary to pay attention to their energy efficient operation. The application of the measures for an energy efficiency increase in compressed air systems enables prolongation of the component's life cycle and the reduction of total operation costs that in turn increases the economic quality of working process. The procedure that was presented and explained in detail, containing cost effective activities illustrated with appropriate examples, can significantly increase the energy efficiency of compressed air systems.
