PhD Thesis - Energy Systems Research Unit - University of Strathclyde

used in vehicles, for the production of heat, and, when necessary, turned back
into electricity via fuel cells.
Currently, communities of this type typically use diesel generators for electricity
generation (for which diesel must be imported) and many small local electricity
distribution networks already exist. It would, therefore, be prudent to assess the
feasibility of the local production of biodiesel from dedicated crops for use in
the existing plant. As diesel generators produce a substantial amount of waste
heat, the use of CHP in a district-heating scheme should also be considered.
Although the importation of methanol would still be required to allow biodiesel
manufacture, this would be roughly one tenth of the amount of diesel that would
otherwise need to be imported. Also, the glycerine produced by the
transesterification process is a valuable by-product, which may be exported or
used on the island to produce toiletries and cosmetics that may be exported or
sold alongside the local craftwork. As biodiesel and diesel can be mixed in an
engine with no ill effects, diesel may still be imported and used in the same
plant if a shortage should occur.
Another option for the production of a multi-purpose fuel from an energy crop
would be the fermentation of an extension to the currently grown grain crops to
produce ethanol. A by-product of this process would be a nutrient rich animal
feed that could be used on the farm, reducing the need to import feed. Such
energy crops could be grown on the 10% to 15% of the farmer’s land that is
required to be set-aside under European Union legislation, but can be used for
non-food production.
To reduce the amount of biodiesel or ethanol required, and therefore the amount
of land required, electricity and heat production from either of these fuels could
be supplemented by electricity from the intermittent sources outlined earlier. As
the heat demand is substantially larger than the electricity demand, some
electricity would be required to produce heat, and this supplementary electrical
heating could be used, in conjunction with heat storage, to help achieve a
desirable heat to electricity ratio, and allow the CHP plant to operate as
efficiently as possible. The use of multiple engine sets may also be appropriate
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