Efficient forklift trucks

The handling capacity of terminals like the one in Hörsching is likely to grow in the future. According to a prediction by the German Academy of Engineering Sciences, freight traffic in Germany will increase by 34 percent on the road and 55 percent on rail by 2020. To cope with this mountain of packages and to keep CO2 emissions as low as possible, logistics companies are now increasingly relying on efficient, environmentally friendly forklift truck fleets.

E-mobility boom in freight transport

Unlike in freight transport on public roads, electric drive technology is booming for the movement of goods on factory premises. Since 2009, more electric forklifts have been sold in Europe than models with internal combustion engines. These electric trucks offer tangible advantages, not only in enclosed spaces but also in the open air on industrial parks or at airports. They are quiet, exhaust-free, and because they have their own charging infrastructure they do not rely on an extensive network of public charging stations.

However, purely battery-powered forklift trucks also have weaknesses. Most of them use lead-acid batteries, including a majority of the forklifts in Hörsching. Every six to eight hours, the battery needs to be changed and recharged. “A battery can weigh as much as 250 kilograms. It takes two drivers to push them – in high summer and deep winter alike. Even with the help of lifting and rolling devices, this is exhausting work”, Ziegler explained. Exchanging a battery takes around a quarter of an hour, during which time the truck is out of action. In conditions of extreme heat or cold or when the battery is almost empty, performance drops: the forklift drives more slowly and productivity decreases.

The logistics industry is therefore researching alternative drive concepts. Since 2013, ten Linde low-lift trucks have been in operation at the Hörsching terminal. Instead of conventional lead-acid batteries, these vehicles use a fuel cell hybrid system. The field test is part of the E-LOG-Biofleet research project. Battery charging specialist Fronius and warehouse truck manufacturer Linde Material Handling aim to prove that forklifts with hydrogen in the tank are more efficient and environmentally friendly. The two project partners have developed a fuel cell hybrid system to replace lead batteries in electric forklift trucks and warehouse equipment. The system is “fueled” with hydrogen, which is converted into electric energy by a fuel cell. A high-performance battery delivers additional thrust if required. To test the drive system under operational conditions, the two companies brought DB Schenker and other project partners onboard.

Juice for the whole working life of the forklift

After four years of trials, Thomas Ziegler is enthusiastic about the fuel cell forklifts: “No more battery changes, refueling takes only two to three minutes and there is no decrease in performance. Every forklift that is available and can be used under full load makes our work easier.” Another adantage is that the fuel cell lasts for the full working life of a forklift truck: around 15,000 operating hours. In contrast, lead-acid batteries reach the end of their working life after around 4,000 hours. The batteries then need to be disposed of and reprocessed, which involves a high expenditure of energy.

The bottom line is that CO2 emissions from the fuel cell forklifts are almost two-thirds lower than for vehicles powered by lead-acid batteries and electricity from the Austrian energy mix. For DB Schenker, this is an important consideration. By 2020, the logistics company aims to reduce its CO2 emissions by 20 percent.

DB Schenker produces the hydrogen locally from environmentally friendly biogas in a plant on the site. Europe’s first indoor fuel station for hydrogen was built for refueling the forklift. “For the authorities, this was new territory. It was extremely difficult to obtain approval”, Ziegler recalled. 14 times lighter than air, hydrogen can escape upwards in the event of a leakage in the open air, to be diluted into a harmless mixture. Indoor this dilution is not guaranteed. For this reason, the forklift truck is located under a hood during refueling, which sucks up the ambient air. In the event of a fault, escaping gas is immediately dissipated.

Another challenge was the integration of the energy package: the cell, tank and auxiliary battery were installed inside a Linde low-lift truck. “All components needed to fit within the dimensions of a standard battery compartment”, explained Project Manager Dr. Ewald Wahlmüller of Fronius. The engineers reduced the size of the hydrogen tank by one-fifth, but increased the output of the energy unit by a whopping 62 percent compared to the predecessor version. The prototype was tested in Fronius’ own factory for the first time. This engineering feat was achieved mainly by an extremely compact arrangement of the components, which were merged together in injection-molded parts.

Fabric transport with carbon fibers

To get more power out of the fuel cell, the gas diffusion layer (GDL) also played an important role. The gas-permeable layer of carbon fibers directs the reaction gases oxygen and hydrogen to the electrodes, where the electrochemical reaction takes place. “The GDL needs to distribute the reactants as optimally as possible to the electrodes so that the reaction can be used more homogeneously and the product of the reaction, water, can be discharged in a correspondingly safe manner. This means that the GDL has a major impact on the fuel cell’s power density”, explained Dr. Volker Banhardt, Sales Director Fuel Cell Products from Freudenberg Performance Materials. Thanks to its excellent transport characteristics, the Freudenberg GDL improves the drive performance of the forklifts. In addition, the material is easy to handle and extremely stable (see info box).

DB Schenker wants to convert the entire forklift fleet in Hörsching to hydrogen by the end of 2018. According to Thomas Ziegler, the new technology has been well received by the drivers: “To begin with, they were a bit reluctant, but they are now rushing to grab one of the new forklifts. Some even come on shift earlier to make sure they get one.”