Technical Results
Initial system modelling used an ideal‑gas framework to define parameter ranges for the pump and bladder. A simplified endoreversible model captured key mass and energy transfer processes, enabling interactive tuning of simulation parameters. The model was extended to include dissipative losses such as pressure drops in piping, heat losses in the tank and bladder, and friction in the pump.
Energy storage capacities were quantified for bladder volumes ranging from 50 L to 252 L (Table 1). The corresponding stored energies increase linearly from 271.4 kJ to 1341.0 kJ, demonstrating the scalability of the bladder concept.
- 50 L → 271.4 kJ
- 75 L → 400.0 kJ
- 100 L → 536.1 kJ
- 125 L → 672.2 kJ
- 150 L → 801.1 kJ
- 175 L → 936.6 kJ
- 200 L → 1066.3 kJ
- 225 L → 1200.4 kJ
- 252 L → 1341.0 kJ
Energy requirements for a container lift operation were evaluated for both empty and full loads (Table 2). The release (absetzen) and set (aufsetzen) phases show a clear dependence on load mass, with full loads consuming up to 253.5 kJ during the set phase.
- Release, empty: 6.0 kJ
- Release, full: 73.4 kJ
- Set, empty: 20.7 kJ
- Set, full: 253.5 kJ
Simulations of acceleration and braking cycles revealed that larger bladder volumes yield higher energy savings, while varying pump stroke volumes also influence the recovery efficiency. Comparative studies of multiple smaller bladders versus a single large bladder of equal total capacity showed no significant advantage in recovery potential, suggesting that a single high‑pressure bladder is preferable for system simplicity.
The system’s control logic was designed to interface with the vehicle’s CAN‑bus, enabling real‑time monitoring of pressure, temperature, and flow. GPS integration allows for route‑based load profiling, facilitating predictive control of the recovery system.
Collaboration and Impact
The HySEB‑KA consortium brings together academic and industrial partners: the Technical University of Chemnitz (TUC), GEWES, AMR, WHZ, and others. Joint efforts focused on defining system parameters, validating the simulation model, and conducting field tests on an 18 t truck platform. The demonstration runs provided empirical data on real‑world load cycles, informing further model refinement.
Beyond technical development, the project supports educational objectives by integrating the hydraulic recovery concept into physics and computational science curricula. The resulting publications and dissertation work will serve as training material for students and a foundation for future research on hydraulic hybrid systems.
Industrial collaboration extends to the development of a hydraulic pump optimized for the recovery system, with plans for both new vehicle integration and retrofit applications. The modular architecture—comprising an integrated drive train and an intermediate frame module—minimizes installation time and cost, making the technology attractive for fleet operators seeking fuel‑efficiency gains.