SEMS Spectral System

Exclusive Novelty-Real Time Measurement
Continuous measurement of Spectral Solar Irradiance in the range of 280 - 4000 nm with a resolution of 1 nm and data transmission in real time to obtain the Spectral Correction Factor-SCF and the corrected PR.


Solar Spectral Measurement System for the automatic calculation in real time, of the Spectral Correction Factors (SCF), to be used for obtaining the adjusted/corrected value of the Performance Ratio PR in PV solar power plants.

The SEMS Spectral System of GEONICA allows the measurement of the following spectral components of solar irradiance:

  • Global Horizontal Spectral Irradiance (GHSI) or in the plane of array (POA)
  • Direct Normal Spectral Irradiance (DNSI)

For the measurement of spectral irradiance in the horizontal plane or in the plane of array, the SEMS Spectral System uses the spectral pyranometer model GEO-SIM-GPV

SEMS Spectral System

For the measurement of the Direct Normal Spectral Irradiance, the SEMS Spectral System uses the GEO-SIM-D2 spectral pyrheliometer, mounted on GEONICA’s solar trackers models SunTracker-2000 or SunTracker-3000, for perfect continuous pointing to the sun.


The photovoltaic (PV) world is spectral, so it is essential to measure its parameters accordingly


The solar spectrum, showing the attenuating effects of various atmospheric components. The overall shape represents the sun’s spectrum in space. The white area represents the remaining parts of sun’s spectrum we observe on Earth.

The solar spectrum is very useful for a large number of scientific studies of the atmosphere, as well as for many other applications in agriculture and other sciences, but it is of special interest in relation to the calculation of the solar energy resource in photovoltaic solar power plants (PV), since each type of solar panel responds differently to the incident photon energy, always depending on the solar spectrum at each moment.

The sun is spectral and solar panels are also spectral, so it was necessary to find an adequate technological solution such as that offered by our SEMS Spectral System, capable of solving in the most advanced way what no other manufacturer can offer, that is, the calculation in real time, of the Spectral Correction Factor (SCF).

What is the Spectral Correction Factor?


GHI weighted monthly spectral correction factors for polysilicon and CdTe solar panels, calculated from GEO-SIM-GPV spectral pyranometer data, measured in Ottawa Canada from Jan 2018 – Aug 2019. A SCF of 1.04 represents a 4% boost in PV panel performance due to local spectral effects.

The Spectral Correction Factors SCF, quantify the changes in the performance of the photovoltaic solar panel due to the difference between the spectrum of the sun at each moment of the day and the reference spectrum under which all solar panels are classified. Spectral effects can approach 15-20% instantaneously and 3-5% on average for a whole year, relative to the energy generated by the plant.

Therefore, the Spectral Correction Factors SCF should be used to calculate the "adjusted or corrected" performance of the plant, that is, the Performance Ratio or PR, taking into account the influence that variations in the solar spectrum cause on the response of solar panels and, consequently, in the energy generated by the plant at all times.

It is not possible to obtain a value adjusted to the reality of the Performance Ratio (PR) of a photovoltaic solar power plant, if the spectral correction factor SCF is not taken into account for its calculation.

For this, the SEMS Spectral System incorporates the new, revolutionary and exclusive, spectral Pyranometer model GEO-SIM-GPV, which provides, first, the measurement of Global Irradiance in the plane of interest and, additionally, the solar spectrum in real time, over the entire range from 280 to 4000 nm, with a resolution of 1 nm.

How does the SEMS Spectral System calculate the value of the Spectral Correction Factor (SCF) according to the data provided by the GEO-SIM-GPV spectral Pyranometer in real time, and then apply it to calculate the adjusted performance Ratio (PR) of the plant ?

The corresponding equations are listed below:

1.) First step, SCF calculation:

SEMS Spectral System

A = Spectral Response of the PV panel
B = Reference Spectra (AM1.5G)
C = Measured Spectra by GEO-SIM-GPV sensor

2.) Second Step, unadjusted PR value:

SEMS Spectral System

G = Broadband solar irradiance
A = Area of panels
𝑟𝑇 = Panel efficiency at temperature T

3.) Third Step, calculation of the adjusted PR:

SEMS Spectral System

Once the SCF has been obtained, it can also be used for the predictive calculation of the plant's energy production, according to the following equation:

Adjusted prediction of plant power generation:

SEMS Spectral System

PSTC = Panel nameplate power
δ = Temperature coefficient
Tcell, Tref = Temperature of the cell and reference temperature (25 ºC)
G, GSTC = Site irradiance (from a pyranometer) and reference irradiance (1000 W/m2)
SCF = Spectral correction factor, a scalar to correct for spectral shape variance from AM1.5G

In addition to being able to adjust the calculation of the performance of photovoltaic solar power plants, that is, the Performance Ratio (PR), by introducing the SCF spectral correction factors, the information obtained through the SEMS-Spectral System allows optimizing other many aspects of the management of solar power plants, since, by means of this information, a series of adjustments and calculations can also be carried out, such as those indicated below Read more ...