Optimisation of biomass compression.

The compression of biomass is essential for facilitating transport and storage. Biomass, like wood, landscape refuse, straw and hay, is mostly compressed with a press moulding machine because of continuous operation which results in high capacities.

The working principle of press moulding machines is based on friction of the material with the compression chamber. Higher friction means more compression but also results in high energy consumption for pushing the material out of the chamber. Studies show that the actual compression energy is less than 50% of the total required energy of the compression process. This low energy efficiency is inherent to the current design of press moulding machines in agriculture and allows for optimizing the process.

High forces are needed for the compression and the transportation of the biomaterial and thus the metal work has to be very solid. A tractor driving mobile press moulding machines then requires a lot of energy for off-road transportation.

This research will found the development of new balers with higher energy efficiency and a lighter construction and will consist of two parts. The first and biggest part will model the interaction between the baler and the biomaterial in the compression chamber. This will result in a three dimensional dynamic finite element model that correlates the applied forces with the density of the biomass. The (time dependent) inputs of the compression process consist of machine and crop parameters together with the settings of the machine. Literature, lab research and fieldwork will explore the dependency of the model to the crops. The model validation will be done on the baler that is currently present at the lab.

The second part of this research will show the advantages of a model-based optimization and will show the power of in-silico design optimization. This part will combine insights and expertise from experienced drivers with the modelling to eventually determine new machine parameters. The optimization will aim to minimize the work for transportation of the compressed biomaterial in the compression chamber while compressing till 200 kg/m³. Mechanical adaptations and suggestions for alternative control algorithms will be validated in the field with a large square baler to evaluate the optimal, theoretical efficiency in practice.