**1. Introduction**

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

algorithm presented above without major implications.

**Author details** 

Bjørn R. Sørensen

**7. References** 

*Narvik University College, Norway* 

Most commercial controllers allow for programming and are thus able to incorporate the

**Figure 12.** Fan static pressure difference control system (supply side only). The CO2 concentrations of the zones (or exhaust) are used to determine the degree of set point variation (represented by Kpath).

Daly, B. B. (1988). *Woods Practical Guide to Fan Engineering.* Woods of Colchester Limited. Eck, B. (1973). *Fans: Design and Operation of Centrifugal, Axial-flow and Cross-flow Fans*. 1st

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Sørensen, B. R. (2010). A Model Library for VAV Systems, *Proceedings of the 10th REHVA* 

Sørensen, B. R., Riise, R. (2010). Rotary heat exchanger model for control and energy

Sørensen, B. R. (2008). Rotary heat exchangers and VAV systems. *Proceedings of the 11th international conference on indoor air quality - Indoor Air 2008*, Copenhagen, Denmark. Sørensen, B. R. (2006) Demand Controlled Ventilation - A detailed study of energy usage by

Sørensen, B. R. (2006) Modelling and simulation of solar and atmospheric irradiation of

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*Mechanical Engineering (IEME)*, Xianning, China.

The increase of energy efficiency is a general trend in a worldwide relation. According to the Kyoto Protocol from 1997, the EU has to reduce greenhouse gas emission by 8% below the level from 1990 by the 2008 - 2012 period. To achieve these reductions, substantial efforts have to be undertaken in all branches of human enterprise.

One of the important industry utilities that has to be encompassed by this energy policy are compressed air systems (CASs). The application of compressed air has had a growing trend due to its easy and safe generation, manipulation, and usage. In previous years, the research efforts in this domain were concentrated on the CASs development and application aimed at boosting the productivity regardless of the energy consumption. With increased awareness of the energy costs as well as the effects of greenhouse gas emission, the attention has been recently placed on the energy efficient use of compressed air.

The experience gained in numerous CAS optimisation projects, as well as the opinions of the experts in the field, indicated that many industrial systems are missing the chance to improve energy savings with the relatively low costs of projects for increasing energy efficiency. Energy saving measures in CASs that have been identified in the course of energy audits in the small and medium industrial enterprises may yield an average energy saving of nearly 15%, with a payback of two years, the energy saving potential in some of them amounting from 30% up to even 60% (USDOE, 2001). The basis for all decisions concerning energy efficiency of the existing CASs is the understanding of the way of their functioning and existence of appropriate data. In that sense, it would be necessary to make measurements of consumed electricity of compressors, airflow, system leakage and pressure drop in the system.

Besides energy savings, increasing energy efficiency of CASs may ensure other significant benefits for the enterprise. Energy saving measures imply a high monitoring level of CASs and

© 2012 Šešlija et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

appropriate maintenance. That leads to decreased breakdowns of production equipment, avoiding the loss of raw materials or other inputs, longer life cycle of pneumatic devices and higher reliability of CASs. Reduction in energy consumption will also lower the emissions of dangerous and polluting substances, which will lessen the influence on the environment. Often, these benefits are more valuable than the energy savings.

Increasing the Energy Efficiency in Compressed Air Systems 153

2000, of the overall 2,574 billion kWh, 951 billion kWh were used in the industry. Of this, 614 billion kWh, or 65%, was consumed by motor-driven systems. It was estimated that the potential saving could be 181 billion kWh, (29%), or seven percent of the overall electricity

According to the study "Compressed Air Systems in European Union" (Radgen and Blaustein, 2001), the EU-15 was spending 10% of the total electricity consumed in the industry for the production of compressed air. The most important potential energy savings are related to the system installation and renewal (the overall system design, improvement of drives, use of sophisticated control systems, recovering heat waste, improved cooling, drying and filtering, reducing frictional pressure losses, etc.) and system operation and maintenance (reducing air leaks, more frequent filter replacement, etc.). The percentages of potential saving varied from country to country. For instance, Germany spent seven percent, United Kingdom 10%, Italy, France and the rest of EU 11% (Radgen and Blaustein, 2001). Details on potential energy savings can be found in the corresponding references: for Germany in (Radgen, 2003; Radgen, 2004), for Switzerland in (Gloor, 2000), for Sweden in

The electricity consumption of CASs in Chinese enterprises goes from 10% up to 40% (Li et al., 2008) of the total industrial electricity consumed. According to (Li et al., 2008), the most widely used compressors in China are reciprocating compressors, often several decades old. To meet increased compressed air demands, many enterprises have undertaken retrofits of their CASs, yielding increased compressor capacity, improved system piping, etc. The most frequently implemented energy saving measures are: purchasing rotary screw compressors, application of variable speed drives and changes to the piping system to allow centralized

Based on data of the Electric Power Industry of Serbia (EPS, 2009a), the amount of electricity consumed in Serbia in 2008 was 27,639 GWh. Industrial CASs installed in Serbia consume about 8% of the electricity used by industry (Šešlija et al., 2011). Although this percentage is low compared to the values reported for some other countries (Radgen and Blaustein, 2001; Radgen, 2003; Radgen, 2004), this does not mean that the CASs in Serbia are more efficient. This low consumption percentage is a consequence of the inefficient electricity utilization in the industry, the value of energy intensity being three times higher than in the developed European countries (USEIA, 2006). Besides, the price of electricity in Serbia is relatively low,

There is a high potential for increasing energy efficiency of CASs in Serbia. One of possible ways of increasing the energy efficiency of CASs is the replacement of the reciprocating single-acting compressors with rotary screw compressors, which would reduce the CAS

(Henning, 2005), and for Austria in (Kulterer and Weberstorfer, 2007).

and it does not exist appropriate attention to its economic utilization.

consumption (De Keulenaer et al., 2004).

**2.3. State of energy efficiency in China** 

production of compressed air, etc.

**2.4. State of energy efficiency in Serbia** 

This paper is concerned with the identification of the current state of energy efficiency in the production and usage of compressed air and possibilities for improvements that would yield the corresponding energy saving.
