Wind Resource: Utilising Hydrogen Buffering

Glasgow Optimisation

Optimisation Process

The optimisation process used in this case study somewhat resembled that of case study 1 but with a few obvious differences. The first of these differences was the fuel cell optimisation. For the first case study this was automatically done by HOMER for the duration of the project lifetime. For case study 2 the fuel cell had a manually constructed fuel cell schedule consisting of times when the fuel cell was forced on and when the fuel cell was forced off. This method of optimising the output meant that the fuel cell output could be manipulated to give the desired output for the three scenarios.

Aside from this the iterative process by which the search space was narrowed to find the optimal component sizes was much the same as case study 1. The HOMER optimisation algorithm ranked system configurations in terms of Net Present Cost and therefore made choosing the most cost effective system that met the required load a simple case of observation. However these models all differed in one fundamental way from the model analysed in case study 1 in that there was no discrete load to meet. The model in case study 1 was sized to meet a load in the form of the town of Stornoway. The models in case study 2 were not constructed in this way because the aim was to supply firm power for fixed amounts of time and not to match supply with demand. The systems were therefore sized by using the wind farm output as the fixed variable and calculating the output possible by the system after efficiency losses from the buffering system. It was calculated that the maximum possible annual energy output from the fuel cell was 28.05 GWh after efficiency losses through the buffering system. The fuel cell output could then be set by making it meet a flat load profile for the required amount of time in each scenario. The magnitude of the load it could meet was then calculated by closely matching the annual energy demand to the annual fuel cell output.