Whitepaper - Real World Performance

Real world performance exceeds expectations
REC is commied to providing high-performance solar energy solutions and long term value for
solar system owners. Being certain of performance in the field is critical for system owners to
realize returns on project investments. REC outperforms PVsyst predictions to provide value
beyond expectations.
Planning a solar installation
Most solar modules are sold by wa class, also referred to as the
module’s “nameplate” rating , which states the nominal power rating
of a module as tested under prescribed factory conditions. However,
test conditions rarely reflect the real world. The actual output of an
installed solar module is far more involved than STC conditions as it
depends upon local weather, system design characteristics and many
other factors. Far more significant to the photovoltaic systems’s
value than the “nameplate” waage is the reliability of energy
production, as the energy volume produced over the plant’s lifetime
is a critical input for determining revenue stream and project returns.
It is of vital importance for predicted values to be closely matched to
actual performance.
When it comes to predicting the yield of a PV plant, there are a number
of simulation methods that can be utilized. PVsyst is one of the most
well-known soware programs recognized by project developers and
financial institutions worldwide for producing reliable yield profiles
given the right input data. To demonstrate the accuracy of PVsyst in
projecting yield performance, we have compared predicted figures
to those actually generated on our rooop systems at our integrated
wafer, cell and module manufacturing facility in Tuas, Singapore.
Results show that actual yields can be in excess of five percent above
PVsyst predictions. This is in-line with findings from REC installations
in Europe, where performance ratios are .  . percent above
projections
1
.
Background
At REC’s integrated manufacturing facility in Singapore, a  kW
array comprised of REC AE modules was been installed on the
wafer plant rooop. Installed in January , the array is tilted at
an angle of ° to the horizontal and is split between north and south
facing roofs.  kW of the array is accurately monitored by Solar
Energy Research Institute of Singapore (SERIS). The monitored
array is divided into sections ranging from .  . kW each and
the monitoring system records irradiance at the module plane, cell
temperature and inverter AC output at one minute intervals.
1European assessed sites include Luxel, France ( sites); Bero II, Italy ( sites); Bero III,
Italy ( sites) and Ikea Freiburg, Germany.
The full year’s data for  was provided by SERIS, which enabled
the investigation to determine the actual performance against that
predicted by PVsyst. Due to a disruption in the data recording, the
months of June and July were not appropriate for assessment and
hence were excluded from the analysis. Two sections of the array
were affected by extreme soiling contamination (from a waste stream
now removed from the plant) and therefore have been removed from
the analysis.
The PVsyst simulation
Care was taken when conducting the simulation to minimize
assumptions fed into the model so as to provide an accurate
prediction over the year. Since recorded irradiation and module
temperature were used, this is considered a ‘weather normalized’
prediction, where discrepancies between assumed and actual weather
conditions are avoided.
Measured system performance
Performance ratio (PR) is one of the most important measures for
comparing system performances from one location to another,
independent of irradiance. It is defined as the ratio of actual
measured output over a given period of time divided by the nominal
power (nameplate rating) during that time. All three sections studied
had high performance ratios of  percent or above (as shown in the
graph overleaf).
The high PR of REC modules is a paern replicated in the  Photon
Laboratory Field Performance Test of  different modules from 
separate leading manufacturers. Based in Germany, and therefore in
a temperate climate, REC modules had the highest PR relative to the
competition of . percent and produced six percent more power
than the test average. This is aributed to REC’s anti-reflection
coating and excellent low-light performance.
Input variable Value Source
System location Tuas, Singapore REC Integrated Facility
Irradiation data Global at tilt As recorded by SERIS at
 min. intervals
Module temperature Reference
modules
As recorded by SERIS
Modules . kW REC AE
Inverter  kW SMA TL  &
TL 
Module efficiency
loss
. Reflective of  year’s
degradation
DC losses . Design assumption
Module mismatch
loss
. Simulated by REC
Soiling loss  Assumption
Reflection profile REC AR coating As generated by SERIS
Key inputs used in the PVsyst simulation
The complete system installed at REC’s integrated manufactuing facility in Tuas,
Singapore.