The turning point in drive technologies can be viewed in a rather inconspicuous building in Stuttgart. Up until a good two years ago, conventional combustion engines were being tested there, but now the focus is primarily on future technologies. In addition to petrol and diesel engines, hydrogen-powered drive concepts in particular are tested on the test benches of the Mahle technology group.
The company set up the test bench on 1,400 square meters and invested two million euros in the new facility, which was built during the first phase of the pandemic. More than 100 employees now work here and test components for fuel cell and hydrogen drives.
The core competences of the group include the areas of air management, engine components, thermal management as well as power electronics and mechatronics, which will also have to prove themselves in the new drive world in the future. “We test here,” says Peter von Kietzell, head of the drive component test facility, “our components that will be used in fuel cell drives in the future.” The 120 kW fuel cell that is currently being used comes from the Canadian specialist Ballard. Mahle sees this drive as an area of application for heavy trucks, among other things, because “a purely battery-electric drive results in excessive payload losses. However, battery-electric trucks can make sense for short-distance distribution traffic,” von Kietzell looks to the future.
In addition to use in heavy trucks, Kietzell believes that the fuel cell will also play an important role in other areas such as buses or SUVs. The engineer does not yet see a future for this drive in the passenger car sector due to the lower driving performance and sufficient battery technology. However, the few fuel cell series models already contain components from Mahle.
Japan is the global pioneer in the passenger car sector. The political framework conditions there provide the hydrogen drive with the necessary security for investments. In addition, the infrastructure for the energy source is already being expanded. According to a report in the “Neue Zürcher Zeitung”, Japan wants to build a global supply chain by 2030 and create a large market for hydrogen. The plans envisage 800,000 fuel cell cars and 5.3 million fuel cells for homes.
For the observer, the test stand at Mahle appears as an inscrutable labyrinth of hoses and lines that the visitor must not get too close to. After all, high-voltage conditions prevail here. “We can simulate the different driving conditions here in order to check our components intensively,” von Kietzell describes the arrangement. In addition to the filters, this also includes the thermal management and other components. Mahle can draw on many years of experience, as the company has been supplying components for fuel cell vehicles for ten years. The hydrogen comes from a tank in front of the building, which is reduced from the original 200 bar to the required pressure of around eight bar for the test runs so that it can be used in the fuel cell.
In order for the fuel cell to work, it needs particularly clean and humid air in order to be able to develop its performance over the longest possible service life. That is why the Mahle filters and humidifiers, among other things, are extensively tested on the test bench in all load conditions. The other components also have to prove themselves in this environment. “The electricity generated by the fuel cell is fed back into the plant’s internal network,” says von Kietzell, describing a welcome side effect of the system. Deionized water is used to cool the fuel cell stack.
A complex concept with a large number of sensors and detectors has been developed and installed to ensure the safety of employees and the system. Even the smallest hydrogen concentrations or hydrogen flames that are barely visible to the eye can be detected using a special flame detector. Even if safe operation in the vehicle or in stationary use is not a problem according to the vehicle manufacturer, a test bench must also carry out tests in which the individual components are specifically stressed beyond their limits.
In addition to the fuel cell drive, Mahle is also testing hydrogen-powered combustion engines in the building. “The technological leap to the hydrogen internal combustion engine is short, and the manufacturers have the appropriate production facilities. In addition, combustion engines can also convert impure hydrogen in a climate-neutral manner and reduce CO2 emissions by almost 100 percent,” explains Peter von Klietzell.
Six pistons from a truck engine that has just run 200 hours on the test stand are lying on a support. In order to convert the drive from self-igniting diesel to hydrogen, the specialists at Mahle redesigned the cylinder head, among other things, and also integrated their own components. In addition, the steel pistons were replaced with aluminum ones. “The performance was just below the diesel level, and in terms of emissions, the engine was well below that of a diesel engine in all areas,” von Kietzell sums up. (Walther Wuttke/cen)
