Efficient cooling – Plastics specialist Rehau saves huge amounts of electricity

Dusseldorf For many industrial companies, the energy-intensive part of their production involves heat. They have to generate so-called process heat, for example in order to be able to melt and dry. But in many cases, and often in addition, process cooling is also required – cooling that dries paint or hardens plastics.

According to the German Energy Agency (Dena), five to ten percent of the total energy consumption in the plastics processing industry is required for process cooling. Measured against the total energy consumption in Germany, that is 2.3 percent or 53 terawatt hours per year. Not only the energy prices, which have risen sharply as a result of the Ukraine war, represent an incentive to save.

The Rehau family company provides an example of how much can be achieved with a strategic approach. He has managed to save more than 80 percent of the energy previously required for cooling his painting systems – also with the help of the weather conditions. An innovation that recently received an award from Dena.

Frank Stegemann heads energy management at Rehau. It is clear, he explains, that such high savings potential cannot simply be spontaneously exploited. There have already been 500 energy saving projects in the past 14 years: “We would consume 140 gigawatt hours more energy a year if we hadn’t implemented energy efficiency measures, based on the year 2009.” Four gigawatt hours have already been saved in this year alone.

The innovation in the cooling of a paint shop, which Dena awarded, is that not only is the energy consumption of the cooling reduced all year round through better processes, but the lower outside temperatures of the winter months are used to cool less.

Order boom also due to the heat pump

This alone reduces Rehau’s energy requirements by 40 percent. If the outside temperature falls below six degrees, the outside air alone can be used for cooling. The so-called free cooling from the outside supports the water-driven cooling on the inside between six and twelve degrees.

And only when the outside temperature is above twelve degrees does the cooling system have to work at full capacity. Overall, 82 percent less energy was used, which corresponds to an absolute energy saving of 692 megawatt hours per year and an annual CO2 saving of 372 tons.

This already benefits the family business, because: people are eager to produce. Rehau manufactures window profiles, underfloor heating pipes, drinking water and waste water pipes, which are currently in demand due to the heat pump boom, as well as side rails for kitchen worktops and other furniture. There are also bumpers and spoilers for the automotive industry. Rehau has a turnover of more than four billion euros and employs more than 20,000 people in 43 plants at 170 locations worldwide.

Stegemann was able to trace the company’s energy efficiency efforts back to the founding year of 1948, he says. During his research, he came across notebooks from 1949 that document exactly that. “The owner family has always been committed to sustainability,” explains the energy manager. Veit Wagner, son of company founder Helmut Wagner, now heads the board of directors. Deputy is Veit’s brother Jobst.

>> Read the first part of the series “So Germany saves”: How high investments in energy efficiency saved the Westerkamp wood mill

The success of the company, which was founded in Rehau, Franconia, is closely linked to that of the automotive industry. The first growth driver was the VW Beetle, for which Rehau supplied running boards and straps. Because the car manufacturers are now positioning themselves more sustainably, the suppliers must also make their contribution. Rehaus savings are therefore also a competitive advantage.

In the beginning there was the ISO standard

Overall, the family business has saved around 20 percent in energy consumption and more than 43 percent in CO2 emissions over the past five years. Rehau mainly uses electricity and only a little gas. Each plant has its own key figure: the kilowatt hours used in relation to the output production volume per year. At the administrative locations, the company is even increasingly using its own photovoltaic systems. Two parks are currently being built at the headquarters, which will supply up to seven megawatts of solar power.

In the beginning, Stegemann’s narrative suggests, there was the norm. The ISO standard 5001 is something like the international guidelines for introducing an energy management system. Stegemann speaks of the “heart of saving energy”, from where you simply approach everything else systematically.

The introduction of the energy management software, the sensors and the metering devices for electricity, heat and gas were an important milestone, remembers Stegemann. “As a result, we suddenly became able to see.” Now, with the help of the software, Stegemann and his team were able to determine that, for example, two identical chillers consume different amounts of energy. Or that the most energy-efficient filter wasn’t the most expensive at all.

The sensors were installed specifically, after manual measurements of the consumption. The mobile measuring devices for this cost almost as much as a small car. “You need a full year of data to get reliable data. Stegemann and his team train the local energy management officer in each plant.

The shortage of skilled workers is also slowing down energy saving

Dietmar Grünig from the German Energy Agency judges: “The example clearly shows how important it is to proceed step by step. By systematically recording the energy consumption of systems, great potential for increasing energy efficiency can be identified and made visible.”

The effort, on the other hand, is quite high, and it takes a long time before you have enough data and facts: “Measure yourself is the maxim, you can even optimize a brand new plant, and we do that too.” Because: The companies carrying out the construction cannot set the optimal working point of the machine, which is required during operation. By adjusting the machines, we were able to reduce the water pressure from six to three bar.

But even at Rehau there is a limiting factor when it comes to saving energy. Stegemann regrets that only 23 of the 43 plants are certified due to a lack of manpower. Electrical engineers, process engineers and engineers from the heating and air conditioning industry work in his energy management team. And they are currently sought after and rare. Stegemann has no illusions that this will change soon: “If I find someone in a year or two, it would be great…”

In the series “So saves Germany” the Handelsblatt presents how companies reduce their energy consumption – and what can be learned from them.

More: The FDP asked these questions about the heating law – and this is how Habeck answered

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