Solar stations have been deployed in 9 sites across Mauritius, 2 Sites in Rodrigues and 1 site in Agalega in order to measure the following quantities: global horizontal irradiance (GHI), plane of array irradiance (PoA), ambient temperature and cell temperature. These parameters are essential for design, evaluation and financial appraisal of PV systems and projects.
GHI is measured at high frequency sampling rate of one minute using ISO 9060 secondary standard broadband EKO MS 802 pyranometers. PoA irradiance is measured using Si-O2-Pt mono-Si reference with integrated cell temperature sensor. Ambient temperature is measured with the aid of temperature sensors. Frequency of measurement has been adjusted to 1 minute. The sensors at each station are connected to a signal conditioning element and a web based data logger that transmit all measured data to a central server located at the University of Mauritius. The data are then processed and used to generate GIS solar maps for Mauritius, Rodrigues and Agalega
The base station consists of the following parts:
NESA model TMF100 is a multifunctional data acquisition terminal which is used as a programmable data acquisition switchboard peripheral for environmental monitoring and distance-control networks.
A pyranometer is a solar radiation sensor which produces an electric signal equivalent to solar power received from whole range of wavelengths of radiation. The MS-802 highest class ISO Secondary Standard is used for the most demanding applications in PV, Meteorology, field research and solar radiation monitoring of global, tilted and diffuse irradiance. It is a thermopile type pyranometer which has a 180 degree field-of-view for measuring the hemispheric solar radiation with a cosine-weighting function. Thermopile, which has a flat spectral response at all wavelengths, is integrated as a sensor. Thermopiles generate electricity by thermo-electric effect, which is caused by the temperature difference between hot and cold junctions. Solar irradiance is obtained by measuring voltage from the thermopile sensor. Glass dome to reject infrared radiation of wavelength above 3um is necessary for thermopile type sensors. Otherwise, these sensors would detect all infrared radiation as well as solar radiation. Double-dome construction is designed to eliminate secondary thermal radiation effects caused by cooling of the outer dome.
A reference cell is a radiation sensor which operates just like a solar cell. It produces a signal equivalent to solar power from a limited range of wavelengths. Silicon irradiance sensors (Si sensor) show a cost-effective, but rugged and reliable solution for the measurement of solar irradiance, especially for the monitoring of Photovoltaic (PV) systems. Based on the construction of the sensor element corresponding to a PV module they are ideal as reference for the monitoring of PV systems. Especially the spectral response comparable to PV modules as well as the similar inclination error (incident angle modifier) allow an exact analysis of PV energy yields using Si sensor data.
Additionally to the irradiance measurement the silicon sensors with the extension “-T” are able to measure the temperature of the solar cell using a temperature sensor laminated to the back of the cell. This solar cell temperature can approximately be used as module temperature.
Ambient temperature is measured with a platinum thermistor Pt100 1/3DIN (100Ω@0°C) sensible to temperature variations in accordance to the response curve described in DIN 43760 norms. Pt100 resistance measure is converted, through 4-wire connection, in an electrical signal normalized in current or voltage, linearly variable with temperature.
The reference cells are calibrated as per IEC 60904-3 under outdoor conditions. The thermopile pyranometers are calibrated as per ISO 9847 – Calibration of Pyranometer using reference Pyranometer and as per ISO 9846 - Calibration of Pyranometer using pyrheliometer.
The base stations have been deployed within the premises of CEB at the following sites: