Prva stran - WBC-INCO Net

ecommended) in unheated part of the house. Hence, some
seasonal imbalance between the load L1 (approximately
constant) and PV supply is unavoidable, which will be
obviously larger in summer than in the winter part of the
year (Fig. 3).
Problem of the yearly imbalance of solar energy supply
can be reduced by appropriate inclination of the plane with
PV modules. Fig. 3 shows the available solar energy for
different tilts of this PV system.
Available Energy, Load (kWh)
100
90
80
70
60
50
40
30
20
10
0
500 Wp, mono Si
storage 400 Ah
0 deg
20 deg
40 deg
60 deg
90 deg
Load L1
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Fig.3: Available energy after all losses of the system have been subtracted,
in dependence of the inclination slope of the solar panels. Values relate to
the 500 Wp mono-Si plus 500 Ah battery system at the location Busevic.
Although tilting increases available solar energy by about
a factor of 2 in winter months in comparison with energy on
the horizontal plane, it is clear that tilting cannot solve the
yearly imbalance completely. The effect is aggravated by
the fact that percentage of diffuse radiation is high (Fig.2),
so the effect of tilting, which affects only the direct
component of global radiation, is strongly reduced.
Inclination toward south up to 30-40 o increases both the
total yearly irradiation per m 2 , and (especially) irradiation in
winter months. For even larger tilts the sum of solar energy
throughout the year decreases again (for tilt 90 o , it is 1/3
lower than for the optimal tilt.).
Hence, tilt of 40 o was selected as optimal, especially
since it also coincide to the tilt of the roof. Results of
detailed calculations for the 500 Wp system for tilt 40 o
toward the South are shown in Fig. 4. The following entities
were analyzed: theoretically maximal energy form PV array
(Edelivered), energy really available (Eavailable) after all
expected losses are taken into account (efficiency and
thermal coefficient of efficiency for the selected PV
modules, PV-array losses, battery charging losses and
system losses) and energy which, (for a given PV system
load, and solar delivered energy), is not utilized (Eunused)
for whichever reason, for example battery is full, etc. The
Euser, the energy actually used by the consumers, and
Emissing, the energy which user will not get from the solar
system; are calculated and compared with the first priority
load (Load L1) for each month of the typical year.
Energy (kWh/month)
100
90
80
70
60
50
40
30
20
10
0
mono Si, 40 o tilt
500W, 400 Ah
E delivered
E available
E unused
E Miss
E Used
Load L1
Jan Feb Mar Apr May Jun Jul Aug Sep Oct NovDec
Fig.4: Delivered, available and used solar energy at Busevic location, for a
small (0.5 kWp) PV system , together with first priority load, L1
The economic analysis of this specific basic system and
the price of PV-produced energy is calculated based on the
actual commercial prices in Croatia: 5,74 €/Wp, for PV
module (5 pieces of 100 Wp modules, high-priced but also
high quality and high efficiency module, having 20 year
warranty), 177 €/100 Ah battery (4 needed) and additional
600 € for frame (support) of modules, regulator, inverter,
setting, wiring and system integration. Calculations of
performance and economics using RETscreen simulation
program gave slightly more favorable (within 10 %) but
essentially the same results.
The needed investment amounts in total to 4128 € for this
basic system. If the purchase of the system is based on the
fully commercial basis, over the lifetime of the modules
(loan 8% over 20 year), taking into account the replacement
of batteries every 6 years and 1% for maintenance/year, the
total yearly cost (all taxes and expenses included) is 538
€/year. Energy cost per each solar produced and used kWh
(476 kWh/year) is 1.13 €/kWh. All these prices are, of
course, quite high. Still, when we compare the investment
into basic PV system with the price of bringing the grid to
this (or any other remote location, like those given in Table
II) it is obvious that such investment pays off, even in worst
case, i.e. on fully commercial bases. It is so not only for a
single remote house, but also for the cluster of houses in
some remote village. The prices can be somewhat lower if
lower quality (and lower efficiency) PV modules are used,
but then the area of modules needed for the same nominal
power is higher (for amorphous Si solar modules about 2.5x
larger area would be needed), and the system is less durable.
Some reduction of price can be also obtained by reducing
the size of the storage, although not more than 30% since
then the battery-full loses start to increase considerably
The financial aspects become much more attractive if
some incentives can be obtained – and that is possible up to
a very high percentage. According to the Croatian Law
about regions of special governmental care, LRSG [7], both
counties Donji Lapac and Plitvicka Jezera belong to the
first category (as well as territories within 15 km from the
Croatian border, etc)., and have a number of privileges. For
the considered case, the most interesting is the financial
support that local (regional) communities can obtain from
the Fond for the ecological protection and energy efficiency
(ZOFU, [8]) for activities and projects related to protection
of environment and renewable energy sources (Article 3).
According to the Article 23 of the same document, the
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