We bought our first SPN1 by the middle of 2008, as the device seemed at first analysis to be well suited to our needs. We now know it is - and we now have 12 of them, hoping to reach 20 within 2 years
Patrick Jeanty, LE2P lab Research Engineer Lan Sun Luk. Jean Daniel, Professor in charge of RCI_GS Project. Morgane Barthod & Aude Zuliani, Master trainees
Energy, Electronics and Process Laboratory Université de la Réunion, Saint-Denis
SPN1 Sunshine Pyranometer
- Global (Total) and Diffuse irradiance in W.m-2
- WMO sunshine threshold: 120 W.m-2 direct beam
- DNI (Direct Normal Irradiance) calculations
- Sunshine status
- No moving parts, shade rings or motorised tracking
The SPN1 Sunshine Pyranometer is a meteorological class solar radiation measurement instrument with a precision ground glass dome, and is designed for long-term outdoor exposure. It is an affordable and effective alternative to shade-ring pyranometers, pyrheliometers and traditional sunshine recorders.
The SPN1 Sunshine Pyranometer is exceptionally easy to use; it needs no routine adjustment or polar alignment and works at any latitude.
An internal heater keeps the pyranometer dome clear of dew, ice and snow down to -20°C (in still air conditions), ensuring reliable readings in difficult climatic conditions. The SPN1 Sunshine Pyranometer is protected by patents EP 1012633 and US 6417500.
Direct and Diffuse Radiation
The SPN1 Sunshine Pyranometer uses an array of seven miniature thermopile sensors and a computer-generated shading pattern to measure the direct and diffuse components of incident solar radiation. The SPN1 Pyranometer computes direct radiation by subtracting the diffuse from the global (total) radiation.
The WMO threshold for bright sunshine is 120 W.m-2 in a plane perpendicular to the direct solar beam. The SPN1 Pyranometer uses an algorithm based on the ratio of direct to diffuse radiation, combined with their absolute values, to estimate sunshine duration to within a few percent of the WMO standard.
The SPN1 Sunshine Pyranometer does not need to be adjusted or repositioned to track the sun - a distinct advantage over devices with shadow rings. There are no complex electro-mechanical assemblies and no burnt paper tracks to interpret.
Outputs and Logging
The SPN1 Sunshine Pyranometer provides 2 analogue voltage outputs for global and diffuse radiation, and a digital output for sunshine duration, which can be connected to data loggers, such as the Delta-T Devices DL2e and the compact GP1.
Readings can also be obtained directly from the RS232 port and viewed/logged using the SunData software supplied.
The GP1 Data Logger from Delta-T Devices is a powerful general purpose data logger that provides a low cost logging solution for the SPN1 Sunshine Pyranometer.
The SPN1 is ideally suited to multiple solar radiation measurement application areas, including PV (photovoltaic) efficiency monitoring, air pollution studies, cloud cover research, ET and heat flux studies, canopy analysis, and building energy management systems. For further information please visit the SPN1 Resource Centre.
Evaluation of the SPN1 Sunshine Pyranometer for measuring Total Optical Depth
Over the last 2 years Prof Victor Estelle’s Solar Radiation Research group at the University of Valencia has been running an SPN1 alongside Cimel and Prede sun photometers to see how it compares with these higher precision but more complex instruments. Preliminary findings indicate a relatively good correspondence - scientific posters were presented at Skynet Rome 2016 and EGU Vienna 2016.
Download Application Note here
Direct-Normal Irradiance (DNI) is the amount of solar radiation arriving in unit time at the Earth's surface on a unit area perpendicular to the direction to the Sun. It is a common practice to compare solar panel efficiency to DNI, particularly in field trials. Output from an SPN1 allows calculation of DNI in sun tracking, horizontal and tilted installations.
Read more about the SPN1 Pyranometer and DNI Calculation in the "SPN1 Technical Fact sheet".
There are two ways to calculate DNI:
DNI Firmware: The SPN1 can calculate DNI. It requires firmware version 1.08 or later. The results are only available on the Serial output and requires the use of a Terminal program or similar to send RS232 commands and receive the results. For more information download Use of the DNI Function in SPN1 Firmware. To upgrade the SPN1 firmware to the required version 1.08 contact techsupport@delta-T.co.uk
- DNI Spreadsheet: You can download an Excel spreadsheet add-in to calculate DNI from the output of a horizontally mounted SPN1 Pyranometer, using data logged from either the analogue or serial outputs. The download is titled "Direct Normal Irradiance (DNI) Spreadsheet". It is downloadable from the Application Notes drop down menu on our Product Support Material page.
Read news on the SPN1 and DNI Calculation here.
SPN1 Sunshine Pyranometer - comparison with BF5 Sunshine Sensor
The SPN1 Pyranometer is a precision version of the BF5 Sunshine Sensor and although the two instruments have some features in common, there are important differences. These are summarised in the document: "SPN1 Sunshine Pyranometer Comparison with BF5 Sunshine Sensor." - downloadable from our Further Information section
(SPN1 Product Comparisons) to the left.
Please note that research literature sometimes refers to the SPN1 as the SPN1 Radiometer.