Energy efficiency through the optimal interaction of system components

Tuesday, 10 March, 2009

In November 2008, the latest world energy report of the International Energy Agency (IEA) was presented in London. It demonstrates once more that climate change, the growing demand for energy and limited reserves of fossil fuels are the central challenges of our time. Many industrial companies are already taking action, with steps both large and small. Tetra Pak, for example, the world's largest producer of beverage cartons, has set itself the goal of cutting its worldwide CO2 emissions by 10% by 2010 compared with 2005 levels, despite rising production. To that end, the company is trying to achieve a systematic increase in energy efficiency. In the coming years, additional production locations will also be converted to use renewable energy sources like wind, water and solar power. The two production plants in Limburg and Berlin already rely exclusively on such energy sources.

Using energy more productively

The products and technologies that help make more efficient use of energy in companies are already available — whether they be variable-speed pumps, intelligent valves, low-loss drives, low-friction linear guides or flexible control mechanisms. But they must be used in areas which, to date, have not been the centre of interest. Increasing productivity is one of the objectives of every company. The higher energy costs climb, the greater the interest in improving energy productivity becomes. The notion of energy productivity describes the relationship between energy consumption and production. The savings potential in industry is huge, the production of goods and services accounts for about 42% of the energy consumption in Germany. Energy expenditures make up more than half of the life-cycle costs of machines and equipment. A significant reduction in consumption therefore results in a lasting increase in competitiveness.

Optimising ancillary processes

A study of the Fraunhofer Institute for Systems and Innovation Research (ISI) shows where the greatest untapped efficiency reserves are located. According to the study, the core processes of the manufacturing industry consume only about a third of the energy.

The ancillary processes account for two thirds of the energy demand. In these processes, 30% of the energy consumption is due to pumps; 14% is due to fans; and air compressors still account for 10% of the consumption. Frequently, the ancillary processes involve systems that have been in service for many years and operate around the clock, even if the full output is not required at all times.

The potential for increasing efficiency is thus correspondingly high, but tapping into it is not necessarily straightforward: studies show, for instance, that an energy-saving motor by itself generates only part of the possible savings. When a load-dependent drive control is used, even a model with a poor efficiency class reduces the power consumption more than an uncontrolled electric motor with the highest energy-efficiency rating EFF1. Only the combination of an innovative drive and a modern control will provide the maximum gain in efficiency.

High efficiency

According to the German Association for Electrical, Electronic and Information Technologies (VDE), half of the total power consumption in Germany is due to electric motors. Increasing the efficiency of electrical products and systems is therefore probably the most important task for the future.

Companies like Bosch Rexroth have been devoting themselves to this issue for years. On the one hand, the aim is to increase the efficiency of all the components, and the efficiency of the overall system is also expected to contribute to further savings. With the IndraDrive drive family and the frequency converters of the IndraDrive Fc series, Rexroth is supplying modules that help turn ungoverned motors into controlled, energy-efficient drive solutions.

Two aspects contribute to the energy efficiency of the IndraDrive drives: on the one hand, their power supply units are capable of reclaiming the output of the connected motors during braking and feeding it back into the supply line.

On the other hand, the systematically modular design makes it possible for the drive control units to exchange energy amongst themselves in accordance with the load via a shared intermediate circuit. That means an energy surplus at one point is not transformed into wasted heat but instead used at some other point.

Pressure with feeling

Modern pneumatics solutions also contribute to more efficient energy use through the combination of sophisticated individual components and intelligent overall systems.

Depending on the system, energy can be lost at many points during the generation and use of compressed air. Rexroth is thereby approaching the problems from various directions: modern pneumatic components, for example, operate without any losses due to leakage, so the pressure in the line is maintained. Because of its compact dimensions and low space requirements, the valve support system LS04 can be placed in the immediate vicinity of the actuators. The low weight and compact dimensions of the individual valves of the LS04 series even make it possible to mount them directly on moving parts. This concentration of pneumatic functions in a small space prevents pressure losses that can arise as a result of long lines from the control cabinet to the pneumatic drive, and it also shortens the cycle times.

The use of electronic controls also makes it possible to optimise the speed and even the air consumption.

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