Process Heat

Analysis of energy flows in the manufacture of aluminium parts by extrusion

An energy analysis showed that electricity consumption can be lowered if waste heat from the compressor is used to heat the baths in the purifying units. 



The aluminium processing company alutec manufactures aluminium parts for the automotive industry at its factory in Sternenfels. The parts are mainly produced by extrusion in combination with machining and/or forming.


Project objectives

  • To obtain an overview of where electricity consumption is currently at its highest
  • To identify potential for energy savings and the corresponding measures, particularly through the use of waste heat. One of the main focuses of the project was to examine the feasibility of using the compressors as a source of heat for the process and rinsing baths in the purifying unit
  • To identify the additional potential to save offered by optimised processes and methods
  • Consumption data collected from the compressors and purifying units was used to develop a concept for the use of waste heat from the compressors to heat the baths in both purifying units. This use is conditional upon lower temperatures in the process baths, the feasibility of which was assessed in a series of tests.



  • A constant input of 50kW is necessary to heat the baths in a purifying unit. The temperature of the baths lies between 65 and 79°C. If the heat transfer is to be efficient, the temperature of the heating medium should be about 10°C above that of the bath to be heated.
  • Approx. 100 kW can be decoupled from the compressors with heat exchangers for use elsewhere. This process can take place at temperatures of 70 to 80°C, but higher temperatures may destroy the seals. The heat needed for decoupling is thus available, but not the temperatures needed for an efficient transfer of heat.
  • Attempts were therefore made to lower the temperature of the active baths to approx. 60°C and that of the rinsing baths to around 45°C. The trials were successful, enabling the baths in the purifying unit to be heated exclusively with waste heat from the compressors. The lower bath temperatures in the LPW 610 unit would already save the company EUR 520 per month even before the heat is exploited.


Savings potential:

  • The heat decoupled from the compressors can be released to the purifying unit via an interim storage facility. This measure enables the baths in the purifying units to be run mainly without outside energy, bringing cost savings of around EUR 2,500 per month. This results in reductions of greenhouse gas emissions of 215t of CO2 equivalents each year.
  • In addition, a separate connection for the dryers brings savings of EUR 340 to EUR 680 per month. This results in a reduction in greenhouse gases of 30 to 60t of CO2 equivalents each year.
  • The above measures would enable the company to reduce its overall electricity consumption by around 9%.

Promoting Institutions

Promoting Institutions

Landesanstalt für Umwelt Baden-Württemberg

Promotional program

Programme BEST (2003 - 2010)

More Project Informations

Project period: 2005 - 2007

Project region: Germany (Baden-Württemberg)

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Source: Landesanstalt für Umwelt Baden-Württemberg