Irradiance sensors

SolarSAT is capable of determining the energy expected from a photovoltaic plant starting from the information about solar energy that effectively impinges on the PV panel. SolarSAT can evaluate such solar energy either by using solar irradiance data acquired in real time by satellites or by measuring it with a dedicated irradiance sensor.
The SolarSAT irradiance sensor, available in several versions, is installed at the PV plant and is managed by a SolarSAT data logger (SuperLog or LightLog models) which provides data acquisition and transmission to the SolarSAT control station via GPRS or Ethernet link.

The robust and reliable Silicon sensor for the measurement of solar irradiance on a PV plant

Working principle

A silicon solar cell can be used as an irradiance sensor, because the short-circuit current is proportional to irradiance. The sensors are build out of a monocrystalline solar cell connected to a shunt. Due to the low resistance of the shunt the cell is working near the short circuit. The sensors have an active temperature compensation (TC) that allows an high precision in measuring irradiance. The compensation is realized by using a specific temperature sensor laminated to the rear side of the solar cell.

Mechanical construction

SolarSAT irradiance sensors are built in several models, having internal or external power supply, with different output signals, among which an optional one is for the measurement of cell temperature.
The solar cell is embedded in Ethylen-Vinyl-Acetat (EVA) between glass and Tedlar. The laminated cell is integrated into a case of powder-coated aluminium. Therefore the sensor construction is comparable to that of a standard PV module. The electrical connection is realized by a waterproof (IP65) connector.

Calibration

All sensors are calibrated in simulated sunlight against a reference cell. The reference cell is calibrated against a secondary standard pyranometer (Kipp & Zonen, type CM 11), which is yearly recalibrated by using a DKD service (German Calibration Service). Once that the sensor is installed by the plant, the SolarSAT service also allows a periodical check of its calibration by comparison with satellite data.

Temperature measurement

Additionally to the irradiance measurement the sensors with the extension “-T” are able to measure the temperature of the solar cell, which is close to that of PV modules. Therefore a temperature sensor is laminated to the rear side of the cell.

General informations

Solar cell	Monocrystalline silicon (50 mm x 33 mm)
Corrente di shunt	0,1 Ω (TC = 20 ppm / °K)  with 1 V output
	0,12 Ω (TC = 20 ppm / °K) with 10 V output
Operating temperature	- 20 °C ÷ 70 °C
Electrical connection	done by a waterproof connector
Case, protection mode	Powder-coated aluminium, IP 65
Dimension,weight	145mm x 83mm x 39mm, appr. 250 g

Accuracy

Irradiance

Error with temperature compensation (*)	± 5 %
Linearity pf the electronic circuit	± 0,3% from reading for 50 ÷ 1300 W/m2

(*) compared to pyranometer within the temperature range of -20 °C ÷ 70 °C

Temperature

Accuracy at 25 °C	± 1,5 °C
Linearity	± 0,5 °C
Error at minimum and maximum temperature	± 2,0 °C

Sensors models

Model	Supply	Irradiance			Cell temperature
		Range	Output Signal	Temperature Compensation	Range	Output Signal
SS-RAD-01-TC	Li internal battery	0 ÷1000 W/m2	0 ÷1 V	yes	-	-
SS-RAD-01-TC-ext	5 ÷ 28 Vdc	0 ÷1000 W/m2	0 ÷1 V	yes	-	-
SS-RAD-01-TC-T	5 ÷ 28 Vdc	0 ÷1000 W/m2	0 ÷1 V	yes	-20 ÷ 100 °C	1,235V +T [°C] 10mV/°C
SS-RAD-10-TC	12 ÷ 28 Vdc	0 ÷1000 W/m2	0 ÷10 V	yes	-	-

Temperature sensors

Temperature contact probe SS-PVTEMP-01

The contact probe SS-PVTEMP-01 measures the temperature of photovoltaic modules in a plant. The sensible element is inserted into an aluminium plate having one side free and the other covered with silicon rubber. Putting the free side in contact with the measuring surface allows for a very precise temperature measurement, as the remaining part of the probe is thermally isolated from the environment.
It is available in two versions: with and without power supply.

SS-PVTEMP-01 technical data

	SS-PVTEMP-01-A	SS-PVTEMP-01-P
Power supply	+12 Vdc ± 10%	-
Output	0÷5 Vdc	Ohm
Contacts(*)	Supply (1)	PT100 side 1 (red)
	Ground (2)	PT100 side 2 (white)
	Output (3)
Sensor type	PT100 ohm @ 0°C
Precision	< 0.5 °C (according to IEC 751 class B)
Measurement range	-30 ÷ 70 °C
Time constant	60 s
Protection level	IP65
Core material	Aluminium
Case material	ABS
Fixing	Gluing

(*) electrical contacts are done at the terminal blocks within the waterproof ABS case.

External temperature probe SS-ENTEMP-01

The probe SS-ENTEMP-01 measures the outdoor environmental temperature. The sensible element is inserted into a steel block, glued with thermally conductive resin to ensure a reliable measurement. The two plates over the sensor ensure a correct measure in every fixing condition, avoiding exposure to direct sunlight.
It is available in two versions: with and without power supply.

SS-ENTEMP-01 technical data

	SS-ENTEMP-01-A	SS-ENTEMP-01-P
Power supply	+12 Vdc ± 10%	-
Output	0÷5 Vdc	Ohm
Contacts (*)	Supply (1)	PT100 side 1 (red)
	Ground (2)	PT100 side 2 (white)
	Output (3)
Sensor type	PT100 ohm @ 0°C
Precision	< 0.5 °C (according to IEC 751 class B)
Measurement range	-30 ÷ 70 °C
Time constant	60 s
Protection level	IP65
Core material	ABS

(*) electrical contacts are done at the terminal blocks within the waterproof ABS case.

Anemometer

 

Wind speed and direction sensor SS-WIND-01

The SS-WIND-01 system is composed of a cup anemometer that senses wind intensity and direction. The sensor measuring wind speed is made of a rotating shaft housing three calibrated cups whose rotation operates a reed contact. The sensor detecting wind direction is composed of a wind vane rotating with a potentiometer cursor. Both sensors are in compliance with WMO standards. The system is supplied by 5 Vdc., has a global maximum consumption of 20 mA, provides two voltage outputs in the range 0-5V, one for each physical measurement.

SS-WIND-01 technical data

	Wind speed	Wind direction
Operational range	---	0 ÷ 78 m/s
Measurement range	0 ÷ 280 m/s	0 ÷ 360°
Typical precision	±5%	±7 %
Resolution	0,1 m/s	1 %
Threshold	0,2 m/s	---
Supply	+5 Vdc	+5 Vdc
Output	5÷0 Vdc digital (*)	0÷5 Vdc analog
Contacts	Supply(1)
	Wind direction (analog) (2)
	Wind speed (digital) (3)
	Ground (4)
Environmental conditions
Temperature	-20 ÷ 70 °C
Humidity	90% without drew
Altitude	not applicable
Protection level	IP55

(*) normally at 5 V; a pulse down to 0 V is produced at every cup revolution

SS-WIND-01 calibration

The device is calibrated in laboratory, so to guarantee measurement reliability for a period of about 12 months. During such period several in-field controls should be done, aimed at instrumentation cleaning (removal of leaves, dust, etc.) and at verifying their correct operation. Such controls are to be done every three months approximately. After two years from installation it is advisable to perform a new in-laboratory calibration to prolong measurement and operational reliability.