A pyranometer is a solar irradiance sensor that measures solar radiation flux density (W/m²) on a planar surface.
Widely used within the solar energy sector, pyranometers provide high-quality data for feasibility studies and monitoring photovoltaic performance of established solar projects.
Modern pyranometers utilise a thermopile sensor (collection of thermocouples which turn thermal energy in to a small electrical current). However, silicon semiconductor sensors are also utilised in some pyranometers. Thermopile sensors absorb a greater spectrum of solar radiation and have a near-perfect cosine response. As a result, they are considered superior. Kipp and Zonen CMP and SMP pyranometers use thermopile sensors.
How does a Pyranometer work?
Thermopiles’ black coating absorbs all solar radiation. The absorbed radiation causes a temperature difference between the hot and cold junctions of the thermopile. Which in turn, generates a very small voltage proportional to the solar radiation absorbed. Therefore, a greater temperature difference produces a larger voltage output. However, output on a sunny day may only reach 10mV.
A prominent feature of thermopile pyranometers is the glass dome. These allows full 180° of solar radiation to reach the sensor. The dome acts as a radiation shield against convection consequently maintaining the temperature difference between the ‘hot’ and ‘cold’ junctions of the thermopile.
Where to use a pyranometer
Pyranometer precision is classified by three standards; Class A, B and C. Previously named; secondary standard, first class and second class.
Class A (Secondary Standard) pyranometers have the highest standard and produce the most accurate data. Subsequently, large solar farms and meteorological weather stations utilise them.
Class C pyranometers are slightly less stable and as a result, produce slightly less accurate data. Consequently, they are ideal for none critical observations and building automation, where the accuracy of data is not vital
Pyranometers capture 180° of solar radiation allowing their orientation on solar farms to be in the same plane of array as the photovoltaic panels. Pyranometers positioned horizontally measure global horizontal irradiance. GHI is a useful metric for the planning of solar farm locations.
Bi-facial panels (photovoltaic panels which have two sides to capture direct radiation and radiation reflected radiation off the ground) utilise pyranometer mounted ‘back to back’, which forms an Albedometer. This defines the ratio of irradiance reflected to the irradiance received by a surface.
To adapt to the various uses Kipp and Zonen produce two ranges of pyranometers the CMP and SMP.
For remote areas with no power source, CMP pyranometers are ideal, as they use the electrical energy generated in the thermopile to provide a very small analogue output (V or mA) which can be read by data loggers with an accuracy better than 10 microvolts.
For facilities requiring sensors compatible with a SCADA system then the SMP range is best. With both analogue and RS 485 Modbus outputs the SMP pyranometers can easily be integrated.
If you would like advice on which pyranometer would suit your specific application then please contact us for information.
To provide an idea of how the class and the accuracy of the sensors change we have provided the specifications table for the Kipp and Zonen SMP and CMP range of pyranometers.
PYRANOMETER SMP SERIES |
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| SPECIFICATION | SMP3 | SMP6 | SMP10/SMP11 | SMP21 | SMP22 |
| Classification to ISO 9060:1990 | Class C | Class B | Class A | Class A | Class A |
| Analogue output • V-version | 0 to 1V | 0 to 1V | 0 to 1V | 0 to 1V | 0 to 1V |
| Analogue output range | -200 to 2000W/m² | -200 to 2000W/m² | -200 to 2000W/m² | -200 to 2000W/m² | -200 to 2000W/m² |
| Analogue output • A-version | 4 to 20mA | 4 to 20mA | 4 to 20mA | 4 to 20mA | 4 to 20mA |
| Analogue output range* | 0 to 1600W/m² | 0 to 1600W/m² | 0 to 1600W/m² | 0 to 1600W/m² | 0 to 1600W/m² |
| Serial output | RS-485 Modbus® | RS-485 Modbus® | RS-485 Modbus® | RS-485 Modbus® | RS-485 Modbus® |
| Serial output range | -400 to 2000W/m² | -400 to 2000W/m² | -400 to 4000W/m² | -400 to 4000W/m² | -400 to 4000W/m² |
| Response time (63 %) | < 1.5 s | < 1.5 s | < 0.7 s | < 0.7 s | < 0.7 s |
| Response time (95 %) | < 12 s | < 12 s | < 2 s | < 2 s | < 2 s |
| Spectral range (20 % points) | 285 to 3000nm | 270 to 3000nm | 270 to 3000nm | 270 to 3000nm | 210 to 3600nm |
| (50 % points) | 300 to 2800nm | 285 to 2800nm | 285 to 2800nm | 285 to 2800nm | 250 to 3500nm |
| Zero offsets (unventilated) | |||||
| (a) thermal radiation (at 200 W/m²) | < 15W/m² | < 10W/m² | < 7 W/m² | < 7 W/m² | < 3 W/m² |
| (b) temperature change (5 K/h) | < 5W/m² | < 4W/m² | < 2 W/m² | < 2 W/m² | < 1 W/mm² |
| Nonstability (change/year) | < 1% | < 1% | < 0.5% | < 0.5% | < 0.5% |
| Non-linearity (100 to 1000 W/m²) | < 1.5% | < 1% | < 0.2% | < 0.2% | < 0.2% |
| Directional response (up to 80 ° with 1000 W/m beam) | < 20W/m² | < 15W/m² | < 10 W/m² | < 10W/m² | < 5 W/m² |
| Temperature response | < 2% (-20 °C to +50 °C) | < 1.5% (-20 °C to +50 °C) | < 1% (-20°C to +50 °C) | < 0.3% (-20°C to +50 °C) | < 0.3% (-20°C to +50 °C) |
| < 4% (-40 °C to +70 °C) | < 3% (-40 °C to +70 °C) | < 2% (-40 °C to +70 °C) | < 0.3% (-40 °C to +70 °C) | < 0.3% (-40 °C to +70 °C) | |
| Spectral selectivity (350 to 1500 nm) | < 1% | < 1% | < 1% | < 1% | < 2% |
| Tilt response (0 ° to 90 ° at 1000 W/m²) | < 1% | < 1% | < 0.2% | < 0.2% | < 0.2% |
| Field of view | 180 ° | 180 ° | 180 ° | 180 ° | 180 ° |
| Accuracy of bubble level | < 0.2 ° | < 0.1° | < 0.1 ° | < 0.1 ° | < 0.1 ° |
| Power consumption (at 12 VDC) | V-version: 55mW | V-version: 55mW | V-version: 55mW | V-version: 55mW | V-version: 55mW |
| A-version: 100mW | A-version: 100mW | A-version: 100mW | A-version: 100mW | A-version: 100mW | |
| Software, Windows™ | Smart Sensor Explorer Software, for configuration, test and data logging. | Smart Sensor Explorer Software, for configuration, test and data logging. | Smart Sensor Explorer Software, for configuration, test and data logging. | Smart Sensor Explorer Software, for configuration, test and data logging. | Smart Sensor Explorer Software, for configuration, test and data logging. |
| Supply voltage | 5 to 30VDC | 5 to 30VDC | 5 to 30VDC | 5 to 30VDC | 5 to 30VDC |
| Detector type | Thermopile | Thermopile | Thermopile | Thermopile | Thermopile |
| Operating and storage temperature range | -40 °C to +80 °C | -40 °C to +80°C | -40 °C to +80 °C | -40 °C to +80 °C | -40 °C to +80 °C |
| Humidity range | 0 to 100% | 0 to 100% | 0 to 100% | 0 to 100% | 0 to 100% |
| MTBF (Mean Time Between Failures) | > 10 years | > 10 years | > 10 years | > 10 years | > 10 years |
| Ingress Protection (IP) rating | 67 | 67 | 67 | 67 | 67 |
| Onsite pyranometer uncertainty | Calculate with Suncertainty App | Calculate with Suncertainty App | Calculate with Suncertainty App | Calculate with Suncertainty App | Calculate with Suncertainty App |
| Recommended applications | Economical solution for efficiency and maintenance monitoring of PV power installations, routine measurements in weather stations, agriculture, horticulture and hydrology. | Good quality measurements for Solar Monitoring, hydrology networks, greenhouse climate control. | High performance for PV panel and thermal collector testing, solar energy research, solar prospecting, materials testing, advanced meteorology and climate networks. | Meteorological networks, reference measurements in PV monitoring, extreme climates, polar or arid. | Scientific research requiring the highest level of measurement accuracy and reliability under all conditions. |
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PYRANOMETER CMP SERIES |
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| SPECIFICATION | CMP3 | CMP6 | CMP10/CMP11 | CMP21 | CMP22 |
| Classification to ISO 9060:1990 | Class C | Class B | Class A | Class A | Class A |
| Sensitivity | 5 to 20µV/W/m² | 5 to 20µV/W/m² | 7 to 14µV/W/m² | 7 to 14µV/W/m² | 7 to 14µV/W/m² |
| Impedance | 20 to 200Ω | 20 to 200Ω | 10 to 100Ω | 10 to 100Ω | 10 to 100Ω |
| Expected output range (0 to 1500 W/m) | 0 to 30mV | 0 to 30mV | 0 to 20mV | 0 to 20mV | 0 to 20mV |
| Maximum operational irradiance | 2000 W/m² | 2000 W/m² | 4000 W/m² | 4000 W/m² | 4000 W/m² |
| Response time (63 %) | < 6 s | < 6 s | < 1.7 s | < 1.7 s | < 1.7 s |
| Response time (95 %) | < 18 s | < 18 s | < 5 s | < 5 s | < 5 s |
| Spectral range (20 % points) | 285 to 3000nm | 270 to 3000nm | 270 to 3000nm | 270 to 3000nm | 210 to 3600nm |
| (50 % points) | 300 to 2800nm | 285 to 2800nm | 285 to 2800nm | 285 to 2800nm | 250 to 3500nm |
| Zero offsets (unventilated) | |||||
| (a) thermal radiation (at 200 W/m²) | < 15 W/m² | < 10W/m² | < 7W/m² | < 7W/m² | < 3W/m² |
| (b) temperature change (5 K/h) | < 5 W/m² | < 4 W/m² | < 2W/m² | < 2W/m² | < 1W/m² |
| Nonstability (change/year) | < 1% | < 1% | < 0.5% | < 0.5% | < 0.5% |
| Non-linearity (100 to 1000 W/m²) | < 1.5% | < 1% | < 0.2% | < 0.2% | < 0.2% |
| Directional response (up to 80 ° with 1000 W/m beam) | < 20 W/m² | < 20 W/m² | < 10 W/m² | < 10 W/m² | < 5W/m² |
| Spectral selectivity (350 to 1500 nm) | < 3% | < 3% | < 3% | < 3% | < 3% |
| Tilt response (0 ° to 90 ° at 1000 W/m²) | < 1% | < 1% | < 0.2% | < 0.2% | < 0.2% |
| Temperature response | < 5% (-10 °C to +40 °C) | < 4% (-10 °C to +40 °C) | < 1% (-10 °C to +40 °C) | < 1% (-20 °C to +50 °C) | < 0.5% (-20 °C to +50 °C) |
| Field of view | 180 ° | 180 ° | 180 ° | 180 ° | 180 ° |
| Accuracy of bubble level | < 0.2 ° | < 0.1 ° | < 0.1 ° | < 0.1 ° | < 0.1 ° |
| Temperature sensor output | NA | NA | NA | 10 k Thermistor (optional Pt-100) | 10 k Thermistor (optional Pt-100) |
| Detector type | Thermopile | Thermopile | Thermopile | Thermopile | Thermopile |
| Operating and storage temperature range | -40 °C to +80 °C | -40 °C to +80 °C | -40 °C to +80 °C | -40 °C to +80 °C | -40 °C to +80 °C |
| Humidity range | 0 to 100% | 0 to 100% | 0 to 100% | 0 to 100% | 0 to 100% |
| MTBF (Mean Time Between Failures) | > 10 years | > 10 years | > 10 years | > 10 years | > 10 years |
| Ingress Protection (IP) rating | 67 | 67 | 67 | 67 | 67 |
| Onsite pyranometer uncertainty | Calculate with Suncertainty App | Calculate with Suncertainty App | Calculate with Suncertainty App | Calculate with Suncertainty App | Calculate with Suncertainty App |
| Recommended applications | Economical solution for routine measurements in weather stations, field testing. | Good quality measurements for hydrology networks, greenhouse climate control. | Meteorological networks, PV panel and thermal collector testing, materials testing. | Meteorological networks, reference measurements in extreme climates, polar or arid. | Scientific research requiring the highest level of measurement accuracy and reliability. |
