Prva stran - WBC-INCO Net

combined with other electronic devices with the purpose of
better system performance.
The chosen PV array would have an array area of 54,2 m 2
and would consist of 43 modules. Because there is enough
space at the sheepfold, the size of the array is not limited by
the available land area. The roofs of the two small houses
could be also used for mounting the PV array, which in that
case could be divided in two separate parts, but bearing in
mind that the size of the array should not exceed
approximately half of the roof area. Where the PV arrays
would be installed is important when calculating the costs of
the supporting array equipment.
As stated before, the battery should have two days of
anatomy, which should provide reasonable availability for
the system. The battery that could be used for this
application would be with nominal voltage of 24V and
efficiency of 85%. The nominal battery voltage has no
influence on the energy predictions of the model used by the
software application. The use of additional diesel machine is
not taken in consideration because it was assumed that the
batteries would be able to provide enough reserve for the
system.
E. Cost analysis and financial summary
Using this software application, the initial costs for the
installation can be estimated. To perform these cost
analyses, data for possible prices referring to energy
equipment, balance of equipment, and miscellaneous are
needed. The compilation of these data for Macedonia was
especially difficult as the penetration of PV equipment on
the market is quite low, so hardly any reference values exist.
The basic energy equipment in this case includes the PV
modules, while the balance of equipment includes the
module support structure, the inverter, the batteries as well
as the other electrical equipment. The costs for system
installation and transport are also considered when the
initial costs are calculated. The initial costs for the prefeasibility
study were calculated using average market
prices [6] for all equipment which could be installed on site.
The costs for preparing and developing the pre-feasibility
study at this stage were not considered.
When performing cost analyses, it is important to stress
out what conventional sources would be replaced with the
proposed PV system. Two possible cases for the selected
target location were analyzed:
• replacement of a diesel aggregate; and
• avoiding grid extension.
1) Replacement of a Diesel Aggregate,
When replacing a base system, which in this case is a
diesel aggregate, with a PV system, the specific fuel
consumption needed to provide given amount of electrical
energy is directly related to the avoided cost of energy. The
calculations were made assuming that the avoided cost of
energy is 0,7 €/L (approx. 2,6 €/gal). These values,
including the renewable energy delivered by the system are
used by the software to calculate the annual energy savings.
Several economic parameters like: energy cost escalation
rate, inflation, discount rate etc are used by the model to
obtain the cumulative cash flow for the proposed project.
The calculations started assuming energy escalation rate of
5%, inflation rate of 1% and discount rate of 8%. The
project life should span over 30 years.
The cumulative cash flow for a PV system which replaces a
diesel aggregate is shown on figure 4.
Cumulative cash flow (EUR)
200000
150000
100000
50000
0
-50000
-100000
-150000
1 4 7 10 13 16 19 22 25 28 31
Years
Fig. 4. Cumulative cash flow when PV system replaces a diesel aggregate
The cash flow analysis shows that the positive cash flow
would be achieved after more than nineteen years. The
model calculates the number of years to positive
(cumulative) cash flow, which represents the length of time
that it takes to recoup the initial investment out of the
project cash flows generated. The year-to-positive cash
flow considers project cash flows following the first year as
well as the leverage (level of debt) of the project, which
makes it a better time indicator of the project merits than the
simple payback.
In this case further sensitivity analysis was performed
because of the uncertainty of the used economical
parameters, especially concerning the avoided costs of
energy. The years-to-positive cash flow for the different
assumed values for the avoided and initial costs are shown
in figure 5. The changes of the avoided cost of energy and
initial costs were made with 10% step change. The
sensitivity analyses show that the change of fuel price would
certainly affect the year to positive cash flow. Bearing in
mind the big changes in fuel prices in the last two years, it
becomes hard to predict how they would change in
future
Years
30
25
20
15
10
5
0
-20% -10% 0% 10% 20%
2,08 2,34 2,6 2,86 3,12
Avoided costs of energy (EUR/gal),
10% step change
105.245 -20%
118.400 -10%
131.556 0%
144.712 10%
157.867 20%
Initial
costs(EUR),
with 10% step
change
Fig. 5. Sensitivity analysis graph showing the year-to-positive cash flow
when the avoided costs of energy and the initial costs are changed with
10% step change
4