System Integration and Modelling
Obviously, the more fossil primary energy is used, the higher the level of emissions. Computer modelling is the key to evaluating the characteristics of hydrogen systems in these respects.
A minimum level of renewable energy will be necessary to achieve any environmental advantage relative to a standard (diesel) system. This level is determined by the “break even point“. At this point, diesel and fuel cell vehicle produce the same level of global emissions. For the case of CO2-equivalents and a fuel cell bus supplied by a EUHYFIS filling station, the break even point lies in the range of 65%. In other words, a minimum of two thirds of the energy consumed for generating the hydrogen need to come from renewable sources in order to surpass a conventional diesel supply in emission quality.
The figure below shows a typical dimensioning problem. When employing
fluctuating power (wind energy in this case), storage will improve the
share of “green“ hydrogen available. The relationship is non-linear. Main
parameters are the type of renewable energy source, meteorological site
characteristics, the daily load pattern etc.