According to David Fassbender, clever and efficient mobile hydraulic concepts have been introduced already decades ago, but we are still stuck with the same type of valve-controlled hydraulic systems that have average efficiencies of only 20 percent.
“The motivation for efficiency improvements has been low in the past because with diesel engines, which consume fuel even if they are idling, it is hard to achieve significant consumption reductions by increasing the efficiency of the powertrain. Furthermore, diesel prices have been low and did not motivate for investing in more efficient concepts,” he explains.
Recently, the energy prices have been rising in the face of crises, and even heavy-duty mobile machines start to run on electric batteries instead of diesel. Now the efficiency really matters, and the more efficient concepts have become relevant.
”More efficient machines can run with batteries that are smaller and less expensive. Furthermore, they can operate longer without recharging, and the electricity bill will look better as well. Those advantages can also justify installing more expensive components if they increase the efficiency. However, this effect might not be enough,” Fassbender says.
Many proposed concepts are based on using multiple electric machines, a ton of additional valves with new challenging requirements and a lot of electronics. In the end, they might achieve an extraordinarily high efficiency with such an approach, but the costs. can be extraordinary as well or the concept is simply not feasible because the added components are too heavy, bulky, or simply not commercially available yet. By explaining this, Fassbender justifies his approach of looking not necessarily for the most efficient concepts, but for the concepts that are quite efficient while being cost effective and feasible at the same time.
Developing a new concept to fit a heterogenous group of heavy-duty mobile machines
As if finding a more efficient, cost effective and feasible hydraulic concept for one machine would not be difficult enough, it becomes more challenging when you consider that different types of heavy-duty mobile machines can have very different characteristics from each other. An excavator for example, looks very different than a forklift and operates in another manner.
“To really reach cost effectiveness, a concept should fit as many of those different machine types as possible. This is why I put a special focus on those differences and their analysis in my dissertation,” Fassbender says.
Moreover, Fassbender did not stop at analyzing the issue and proposing a method for obtaining new concepts. He proposed two concepts himself, which are characterized by their modularity.
“By combining two concepts, one for low-cost but less efficient and one for more costly but also more efficient actuation, a balance between energy and cost savings can be obtained as well as the flexibility to match different machine types,” he concludes.
With his work, David Fassbender hopes to point out possibilities to other researchers and to industry as well as to contribute to the green transition that is needed in the face of global warming.
Public defence on Friday 25 August
The doctoral dissertation of Dipl.-Ing. David Fassbender in the field of mobile hydraulics and electrification titled Towards Energy-Efficient Electrified Mobile Hydraulics – Considering Varying Application Conditions will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University at 12 o’clock on Friday 25.08.2023 at Hervanta campus, Konetalo building, auditorium K1702 (Korkeakoulunkatu 6, 33720 Tampere). The Opponents will be Docent Liselott Ericson from Linköping University and Associate Professor Lasse Schmidt from Aalborg University. The Custos will be Associate Professor Tatiana Minav from University of Tampere.
The doctoral dissertation is available online.
The public defence can be followed via remote connection.
Photo: Hannah Lenhard