Environmental Engineering Reference
In-Depth Information
In this situation, an economic analysis, performed by calculating the cash flow
and the pay-back-period (PBP) of the investment for the installation of a BACS,
becomes a very important tool for making plausible hypotheses on their com-
mercial widespread in the medium-term.
The cash flows depend on several factors such as the initial thermal and electric
demand of the house, the electricity purchase cost, the cost of the fuel for the
heating system, the kind of HVAC system, the maintenance and management
costs.
All these factors can be translated into cash flows Ct* by means of the fol-
lowing equation obtained by adding algebraically all the costs Ci and all the profits
Pi related to the generic t-th year:
C
t
¼
X
i
P
i
;
t
X
i
C
i
;
t
ð
6
:
1
Þ
In order to carry out a realistic analysis, the cash flows are annualized using the
classical expression derived by Feibel (
2003
):
C
t
ð
1
þ
i
Þ
t
C
t
¼
ð
6
:
2
Þ
where i is the inflation rate.
Equation (
6.2
) allows to obtain the equivalent present value of the cash flow of
the t-th year.
4
6.5
Tools for Extensive Evaluations of Energy Efficiency Due
to Passive Measures: The ''Passivhaus'' Standard
In the above sections, the regulatory framework justifying the approach for the
evaluation of the economic impact of some active measures for improving energy
efficiency have been presented. In this section, the regulatory framework and
scientific background for the economic evaluation of the impact of passive mea-
sures is presented. Tools to make such assessments can be found within the Italian
standard UNI TS 11300 and within the Italian regulatory framework from the
AEEG (Authority for Electrical Energy and Gas), but since they derive from
extensive studies, they can easily used in other national contexts showing similar
climatic features. In the last 10 year in North Europe Countries, especially in
Germany, a great interest rises towards the constructive standard of the so-named
Passivhaus. A Passivhaus is a building able to assure comfort conditions during
winter period, without a traditional heating system. In order to attain this result, the
yearly energy request for heating must not overcome 15 kWh/m
2
year.
4
For example, if i = 5 %, a cash flow C
t
* = 1,000 € produced at the 10th year is equivalent to
614 € at year 0.
