As part of the "Low-noise logistics mobility study" (Mobilitätsstudie geräuscharme Logistik), the Fraunhofer Institute for Material Flow and Logistics IML, in cooperation with the experts from Peutz Consult, measured the noise emissions of selected vehicles during driving and maneuvering movements. With its 18-tonne prototype truck with "KEYOU-inside" hydrogen engine, KEYOU was also part of the measurements. The result is both surprising and impressive: at low speeds, the hydrogen combustion engine is perceived as only about half as loud as comparable diesel trucks.
The Fraunhofer Institute's "Mobilitätsstudie geräuscharme Logistik", which is funded by the Ministry for Environment, Environmental Protection and Transport of North Rhine-Westphalia, aims to develop standards for the measurement of noise emissions in connection with driving and manoeuvering movements, among other things, in order to provide an approval basis for urban logistics through the use of trucks with alternative drive systems. With its prototype truck, KEYOU was involved in the study, which is being led by the Fraunhofer IML. The results are surprising in their clarity.
Fraunhofer Institute confirms: KEYOU truck half as loud as a diesel truck
"The measurements for the truck with the hydrogen engine showed a level around 11 dB lower for the constant pass-by at 20 km/h, compared to the typical approach from the literature. In terms of the constant pass-by at 30 km/h, the level measured at 50.8 dB is approx. 10 dB lower, while the difference in level is 7.5 dB for the accelerated pass-by. The KEYOU truck is therefore only about half as loud as a conventional diesel truck", explains Michael Wirtz, project manager for the measurements at Peutz Consult GmbH. In order to better classify the noise development of the truck with "KEYOU-inside" hydrogen engine, Wirtz draws a comparison with conventionally powered passenger cars: "With a sound power level of approx. 49 dB(A)/m at 20 km/h, the hydrogen truck is only 1dB 'louder' than the passenger car with 48 dB(A)/m."
Thomas Korn, CEO and co-founder of KEYOU, is extremely satisfied with the test results: "Our goal at KEYOU has always been to contribute to combating climate change and to offer our customers a competitive CO2-free vehicle. After all, an emission-free alternative will only be accepted by the market if it is cost-effective and also suitable for everyday use. It was clear to us that our trucks could also help to significantly reduce noise emissions in cities and thus further improve the quality of life, but not to this extent."
A surprise: the noise level of hydrogen trucks is comparable to that of eTrucks
In addition to the KEYOU prototype, various other trucks with alternative drive systems were examined. An initial comparison of the results shows: The KEYOU hydrogen truck is also on a par with an electric truck in terms of noise emissions: "Our measurements hardly showed any differences between hydrogen and electric trucks, especially when passing consistently in the lower speed range of up to 30 km/h," explains Wirtz. This is an impressive result given that electric vehicles have significantly less driving noise compared to conventional combustion engines, especially at low speeds of up to 35 km/h.
"Of course, this greatly increases the flexibility and possible applications for our customers - for example, by allowing them to use the trucks for deliveries in residential areas during off-peak hours, if the legal framework for this is created," says Korn.
Study setup and measurement methods
The final study is expected to be published in spring 2024, but the results with the KEYOU measurement data are already available. These were collected during a series of measurements on the test track at the University of the German Armed Forces (Universität der Bundeswehr) in Neubiberg. Experts sent KEYOU's 18-tonne prototype truck onto the track and measured its noise level. Employees of the accredited measuring body Peutz Consult GmbH carried out the measurements on behalf of Fraunhofer IML. They set up calibrated hand-held sound level meters at a distance of 7.5 meters to the right and left of the road.
Various scenarios were simulated on the test track and their noise emissions measured: Firstly, driving at 20 km/h and 30 km/h as well as reversing with the reversing warning system switched on and off. In addition, data was collected for the accelerated starting, braking and parking manoeuvres. Each measurement was repeated at least ten times.
Background and objectives of the study
Considering the requirements for noise and sound insulation in many approval procedures, the necessity of the study becomes clear: "In Germany, there is currently neither a market overview nor standardized data on noise emissions from alternatively powered commercial vehicles in logistics use," explains Daniela Kirsch, project manager at Fraunhofer IML. "That's why we need a solution that companies can use as a guide. One positive example from our European neighbours is the Dutch PIEK certificate, altough it cannot be transferred to Germany in this form." In order to obtain certification, for example for night-time deliveries, trucks and transport equipment in the Netherlands must undergo an acoustic test. They must not exceed the prescribed decibel limits at a distance of 7.5 meters. With the study, the Fraunhofer IML wants to contribute to the development of a standardized regulation: "By creating a manual for the evaluation of noise emissions from trucks with alternative drive systems for urban deliveries, we want to make the work of municipalities and approval authorities easier in the future," says Kirsch.
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