Page 245 - Biofuels for a More Sustainable Future

220 Biofuels for a More Sustainable Future

Fig. 7.1 The examined plant.

In order to refer the results of the analysis to the selected functional unit
(1MJ of exergy), the exergy produced during the system life cycle needs to
be calculated.
The exergy content of the energy produced by the tri-generation plant
can be defined as the sum of electricity plus the useful thermal energy times a
Carnot coefficient. This factor is 1 for electricity considering that this form
of energy can theoretically be entirely converted into work in a reversible
machine. For thermal and refrigeration energy, the corresponding exergy
(E) depends on the temperature of the delivered thermal fluid and the dead
state temperature and it can be calculated by means of Eq. (7.1):

T 0
E ¼ Q ∗ 1 (7.1)
T 1