maximum pressure is 750 bars. A control strategy activates some valves and selects the tank to be filled in or emptied. A case study with system simulation The simulation of the system, reproducing a one- year scenario, requires less than 15 minutes using a conventional laptop. After running a simulation, advanced pre- and post-processing tools help to better visualise and analyse the simulation results. Optimisation studies can also be performed. Running the simulation makes, for instance, it possible to analyse the fluctuation of the energy produced by the solar panels, the wind turbines and the wave converter all year long. On a monthly analysis ( Figure 2 ), we can visualise that the system is able to produce much more power during winter than during summer. Moreover, it can be noticed that, in the system, wind energy is the most predominant source, with 71% of the produced energy (22% for the wave converter, 7% for the wind turbines). In these conditions, hydrogen production fluctuates a lot during the year ( Figure 3 ). This reveals that, especially during summertime, it would be necessary to use electric power from the grid when the hydrogen content in the storage system reaches a low threshold. Hydrogen compression to 750 bars also
Its speed is also variable, considering the seasons (up to 8 m/s). The wind turbines can produce up to 350 kW of electrical power. • Solar panels: The system is based on 62,500 cells of 16 cm 2 each. It can deliver 20 kW of electrical power. The solar azimuth and altitude are dependent on localisation and time. They are supposed to be localised in Lyon (France). The impact of clouds is also variable. Add power output. • Wave converter: The wave converter uses a float actuated by the waves to actuate a piston. The piston diameter is 235 mm. Then a hydraulic system combined with a generator is producing electric power. The waves have a variable amplitude (up to 3 m) and frequency (up to 0.07 Hz). What can be noticed here is that a first wave converter detailed model has been initially developed to evaluate the design and performances of this component. Then, to perform annual simulations, the model was used to train and generate a neural network model, reproducing the same simulation results but significantly reduced simulation time. • Electrolyser: The electrolyser is made of 100 cells (300 cm 2 each). With a maximal electric power of 330 kW, it can produce 6 kg/h of hydrogen. • Hydrogen storage: The hydrogen can be stored in three different tanks of 0.785 m 3 each. The
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Figure 3 Hydrogen storage analysis
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