PhD Thesis - Energy Systems Research Unit - University of Strathclyde

Again, the rate of use of the feedstock from seasonal supplies may be slower
than the production rate to allow fuel production beyond the harvest periods.
For seasonal supplies, if there is excess feedstock left over in the store at the end
of the simulation period, and this is more than the minimum required for the fuel
production process, the entire simulation period is analysed again, and the
results from this second simulation period are used.
6.4.2 Continuous Process Characteristics
As the continuous process cannot be easily started and stopped, it must run
continuously throughout the day, and not between set times. The following
process information is required to create the temporal fuel production and
energy use profiles.
• The maximum and minimum feedstock feed rates (kg/hr).
• Any other inputs (e.g. yeast, water, malt), type, amount and units per
hour.
• The ethanol production rate (litres/hr).
• The wet and dry animal feed production rates (kg/hr).
• Any other outputs (e.g. carbon dioxide), type, amount and units per hour.
• The electricity and heat demands (kW).
For each timestep, if more feedstock than necessary (feedstock feed rate /
timesteps per hour) is available for that timestep, the process outputs, inputs and
energy use are as input. If the amount of available feedstock is between the
maximum and minimum feedstock required for that timestep, a partial
production factor is calculated using Equation 6.6, and is applied to all inputs
and outputs. The partial production factor is also applied to the heat demand, as
this would vary with the amount of feedstock. It is not applied to the electricity
demand, as this would not vary with the amount of feedstock. If there is not
enough feedstock available, the process does not run. Feedstock is subtracted
from the stored volume as it is used.
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