PVSyst is a standard tool for determining the generation from a solar plant, however there is little standardisation over the losses to be assumed. Based on Gensol's experience, every loss has been analysed & through this document we are indicating on the loss percentage to be assumed.

1. Generation Assessment and Loss Justification
The generation was estimated considering 315Wp modules of a reputed
make and 1MW solar inverter of a reputed make as initial design inputs for
conducting the simulations.
The project uses a seasonal tilt system for with 7.5m pitch.
The DC to AC overloading that has been decided as a design parameter is
25%.
The typical loss breakdown is as shown below with relevant justifications
Table 1: Justification of PVSyst Losses
S.No. Parameter Measure Justification
1. PV Syst Version 6.41
Latest version of PVSyst simulation tool has
been used
2. Tilt Angle/Tracking Angle 5 o and 30 o
For seasonal tilt, the aforementioned tilt angles
for summer and winter have been assumed.
3. Pitch(m) 7.5
Considering the overloading of 25%, and
corresponding land usage and generation
optimization, the pitch values given here came
out to be optimal
4. Shading
-0.2% (5 o)
Near shading is caused by inter row distance
and due to tall objects like control rooms and
lightening arrestors. For shading from tall
objects, sufficient spaces are left by conducting a
shadow estimation study so as to keep the PV
array shadow free during generation hours. The
near shading loss due to inter row spacing is
however determined by PVSyst as per the
design pitch considered. In the case of seasonal
tilt, the shading losses are low for summer tilt
and is higher for winter tilt. However, the
average shading loss will fall somewhere in
between the two values.
-3.7% (30 o)
5. Incidence Angle Modifier
-2.2% (5 o)
IAM loss accounts for losses in radiation
penetrating the front glass of the PV
modules due to angles of incidence other than
perpendicular. The loss figures is a module
dependent parameter and is calculated by the
PVSyst as per the module chosen.
-3.3% (30 o)

2. 6. Soiling Loss -1.5%
This is the loss due to dust and bird droppings
on the PV modules depending on the
environmental conditions, rainfall frequency
and on the plant’s O&M module cleaning
strategy.
To assure the maintenance of soiling losses
below 1.5%, a novel soilingestimation setup will
be setup at plant during O&M consisting of two
PV strings. One of the PV strings will be cleaned
on a daily basis, while the other one will not be
cleaned. Once, the difference between
performance of the two strings will start
touching 1.25%, a module cleaning cycle of the
entire plant will be initiated, thus ensuring
soiling loss in line with the design assumption.
7. Module Temperature Loss -9.5% (Seasonal)
The characteristics of a PV module are
determined at standard temperature conditions
of 25˚C. Considering the temperature coefficient
of the 315Wp modules selected, the module
performance decreases by -0.40% for every oC
rise in cell temperature.
Module temperature loss is computed by the
PVSyst by considering the temperature profile
of the location as per the meteo database. Since,
the site is located in Rajasthan, a desert region
with high temperatures, and the high
temperature losses calculated are representative
of the high temperature profile.
8. Module Quality Loss +0.4%
PV modules generally deviate from the
manufacturer’s technical specifications. The
315W modules considered here are supplied
with a positive Power tolerance of 0 to 3%. The
developer has thus considered a quality gain of
0.4%, although on a conservative side so as to
account for other contingencies in generation
estimation.
9.
First Year Module
Degradation (under Light
Induced Degradation(LID))
-1.5%
The performance of PV modules degrades over
the time. The degradation is most significant
during few hours of first exposure of PV
modules to light. This phenomenon is known as
Light Induced Degradation (LID). Factors
affecting the degree of degradation include the
quality of materials used in manufacture, the
manufacturing process and the quality of
assembly and packaging of cells into the
modules.
The first year degradation considering LID and
annual degradation is guaranteed to be less than
2.5% in the datasheet. However, as per the
general industry experience, the first year
degradation for Tier-1 modules has typically
been observed between 0.8% to 1.5%. Hence, the
first year module performance degradation has
been considered as 1.5% here.

3. 10.
Module Array Mismatch
Loss
-0.8%
Mismatch losses represent the mismatch in
current/voltage of modules in a string due to
statistical variations. Typically, the mismatch
losses are considered as 1%. However, the loss
can be reduced by sorting the modules as per
current before factory dispatch. The modules
supplied at site with a 3-bin current sorting will
effectively reduce the mismatch losses. Hence,
we have considered the module mismatch losses
as 0.8%.
11. DC Ohmic Wiring Loss -1.5% (STC)
Electrical resistance in the wires between the
power available at the modules and at the
terminals of the array gives rise to ohmic losses
(I²R).
For well-designed plants, DC cabling losses at
STC vary from 1.2% to 1.5% at STC. We have
considered 1.5% as the DC Ohmic losses at STC.
The losses are at full load, and the PVsyst
computed the overall losses considering the
solar plant operates at partial loads most of the
times. The final loss then computed by PVSyst
corresponding to 1.5% loss at STC considering
the partial load profile of plant is 1.1%
12.
Inverter Loss during
Operation (Efficiency)
-1.7%
Inverters convert power from DC into AC at a
certain efficiency. This results in a loss of power
during conversion from AC to DC. The
efficiency curves are inverter dependent. In our
case, the inverters considered are 1000kW of a
reputed make. The efficiency loss has been
calculated by the PVSyst as per the
manufacturer provided efficiency curves of the
inverter and stands at around 1.7%.
13. Auxiliary Losses -0.6%
Various components of plants like inverters,
PLC, module cleaning system, plant lighting,
security systems etc and amenities like Air
conditioning, plumbing and others consume
electricity for their operation. This is known as
auxiliary loss. The auxiliary losses vary from
0.5% to 1% depending upon the size, design and
structure of the plant. Typically, small plants
require a higher percentage of auxiliary
consumption than bigger plants on relative
terms. Various measures such as night
disconnect, self-powered trackers, LED lighting,
have been considered in the design for reducing
auxiliary consumption. The auxiliary losses
have thus been reasonably considered at 0.6%
with sufficient margin.

4. 14. AC Ohmic Losses -0.5% (Full Load)
This includes ohmic losses in the cable from
inverter leading to the substation, and depends
on the sizingof cables during the design. During
the design of the plants, the AC cable sizing has
been done in such a way that the losses do not
exceed 0.5% in the AC side. Full load AC ohmic
losses of 0.5% have been considered,
corresponding to which PVsyst computes the
overall losses considering the solar plant
operates at partial loads most of the times. The
final loss then computed by PVSyst
corresponding to 0.5% loss at STC considering
the partial load profile of plant is 0.3%.
15. System Unavailability -0.5%
Downtime depends on the diagnostic response
time and stock of spare equipment. Further, loss
in generation due to unavailability of plant and
grid are also accounted for in downtime losses.
Typically, the unavailability is higher for smaller
plants, as compared to larger plants due to
relative impact of failure of a single component
on the entire plant availability. The O&M
scheme thought out also considers stocking of
inverter transformer, breaker, inverter IGBT
stacks, and modules, cables of all sizes,
consumables and on site deployment of service
persons of critical components like
transformers, inverters on site along with
regular manufacturer training of O&M
personnel. Large solar plants in solar parks are
now connected at 132kV to the grid which is
ultimately connected at 400kV to green corridor
grid network, which will be extremely stable
with very less downtime. Considering the
above, the system unavailability has been
considered as 0.5%
16. External Transformer Loss -1.6%
Large losses may rise in the transformer but are
generally less than 1% for each transformation
level. Given the fact that the plant will be
evacuating at 132kV, two levels of losses have
been considered; 1.0% for the intermediate
transformation at 33/11kV, and 0.6% (following
the GTP of the transformer to be used on-site)
for the second level of transformation at 132kV
in line with standard design practices.