Household Electrical Consumptions Modeling and Management Through Neural Networks and Fuzzy Logic Approaches - Complex System Modelling and Control Through Intelligent Soft Computations - page 455

E t ¼ C t min ð F t ; W t Þ ð 27 Þ

where F t and W t are respectively the injected and withdrawn electricity in KWh and
C t represents a coef cient comprehensive of the electricity cost and net services cost

in eur/KWh. For the global cost of the PV plant, an average of the main solar
installer prices in the considered area has been considered.

7.1 Economical Analysis

The cost-benefit analysis (CBA) is a financial valuation technique used to predict
the effects of a project, a program or an investment, verifying its bene ts. CBA, as

an alternative to traditional methods of economic analysis, represents also a method
of ex-ante evaluation by external parties that have to decide on the

financial via-

bility of an investment or have to choose how to allocate scarce financial resources

among different possible investments.
To evaluate the economic convenience of PV systems on the considered building
we carried out the CBA of different sizes of PV plants to choose the best one. The
discounted cash

flows generated from each investment have been calculated for
20 years, equal to the period in which PV module producers guarantee at least 80 %
of their initial performance. The net present value (NPV), calculated for each PV
plant size, is:

fl

X

K

C t

NPV ¼ ð 28 Þ

t

ð 1 þ r Þ

t ¼ 0

where C t is the cash flow at time t, r the discount rate (equal to 5 % in our case) and

K the considered lifetime of the investment. The cash

fl

fl ow C t is the difference

between the discounted annual cash in ows O t . In particular I t consists

of the annual directly saved energy by self consumption (considering a 3 % annual
increase of the unitary energy price), the net metering contribution E t and government
contributions (50 % of the plant cost in taxes deduction for the

fl ows I t and out fl

rst 10 years).
O t consists instead of the initial cost of the plant (we consider an investment
made only with own capital) and the annual maintenance costs (0.5 % of the initial
cost per year). Considering that NPV calculation strongly depends on the used
reference discount rate r used (for which the same investment may be convenient or
less in relation to its value) it is useful to consider as financial indicator also the IRR
(internal rate of return), calculated as the rate r * for which results:

r Þ ¼ NPV ð 0 ð 29 Þ

Table 6 reports the unitary costs (Cost), the self consumption percentages of two
simulated scenarios (user performing EM actions and user maintaining the same
behavior) and CBA results for different PV plant sizes in the analyzed case study.