SUSTAINABLE USE OF ENVIRONMENTAL RESOURCES: OPTIMIZATION OF LOGISTICS OPERATIONS - Energy Research Developments: Tidal Energy, Energy Efficiency and Solar Energy - page 268

Figure 2.3. Main typologies of biomass present on the territory.
The biomass coming from the industrial scraps is used entirely (100%), while forest
biomasses are used according to the legislative constraints previously discussed.
Results
The considered optimization problems have been modelled through the use of an
optimization software ( Lingo 8.0 , Lindo Systems Inc.). First of all, the static optimization
problem has been solved for different plant capacities. That is to say, that the optimization
problem has been solved for different values of parameter CAP . For each run, the optimal
values of the decision variables and of the objective function has been found. Incrementing
CAP , if the available biomass is sufficient, the optimization problem is feasible, otherwise the
Lingo software finds a “not feasible solution”.
A sensitivity analysis of the cost function respect to the parameter that represents the
plant capacity ( CAP ) is carried out. This analysis has been carried out till the solution is
feasible. The solution is not feasible when there is not enough biomass to satisfy the capacity
under study, i.e. the sensitivity analysis is performed till a capacity that is not sustainable is
found. In the following, results for possible plant capacities ( CAP = 1 MW , 2 MW , 3 MW ,
etc.) are reported. The DSS has furnished feasible solutions till a plant capacity of 6 MW ,
without reaching the 7 MW capacity. With the only aim of testing the decision model, the
sensitivity analysis has been performed for values of CAP that do not correspond to real
installed plants. It can be seen that the optimization problem is feasible till CAP =6.42 MW . Of
course, CAP=6.42 MW cannot be a real plant capacity. This value should be observed only as
a result of the sensitivity analysis of the proposed decision model.
In table 2.1, the costs for the plant owner (regarding biomass collection and
transportation) are reported. They correspond to the optimal values of equation (4) for
different values of CAP . It is important to note that the value of the objective function is zero
for CAP = 1 MW and CAP = 2 MW because, in this case, the DSS selects only the scraps
coming from the private trader, whose unit costs are set equal to zero because.