PhD Thesis - Energy Systems Research Unit - University of Strathclyde

Feedstock per day (kg/day) = Land x Yield (6.3)
Days
Where Land = Available land (ha)
Yield = Crop Yield (kg/ha)
Days = Number of days in harvest period
This feedstock is put into a store on the last timestep of each day it is available,
to allow for harvesting and feedstock processing, and, again, a degradation rate
is applied, where appropriate, to any feedstock remaining in store before this
new amount is added. The electricity required for feedstock pre-processing is
calculated as before, and it is assumed that feedstock is processed, where
necessary, as it is harvested, as this makes it easier to store, and often greatly
reduces any possible degradation. If this is not the case, any required electricity
demand can be added to the process requirements discussed in section 6.1.2.
The algorithm dealing with the feedstock availability is shown in Figure 6.1.
This is followed for each timestep in turn.
Although the fuel is only available to put into storage during the harvest period,
it can be used from this store at a much slower rate, if desired, allowing fuel
production beyond the harvest period. 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, in the same manner, but starting with the excess stored amount of
feedstock available for processing. Using the results from this second
simulation period allows the inclusion of fuel derived from feedstock remaining
at the end of the first period. This is shown in Figure 6.2, where the feedstock
remaining at the end of the year, from the June to September harvest, continues
to be available into the next year, until finally running out in April. If there
continues to be an excess of feedstock at the start of the next harvest period, the
process will not be able to exceed its maximum feed rate, so there will continue
to be an excess of feedstock, and production will be constant throughout the
year. Care should be taken to match the feedstock availability to the process
feedstock feed rate (kg/hr), either to ensure that all of the available feedstock is
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