Calculate Direct-Normal Irradiance (DNI) with the SPN1 Sunshine Pyranometer

0

Source: Delta-T Devices Ltd.

Photovoltaic developers and triallists find the SPN1 Sunshine Pyranometer a valuable tool for research and for performance validation.

When making PV investments, it is essential to identify the best locations. An SPN1 can be used to quantify the available global and diffuse radiation at potential sites. Later, after an installation has been completed and power is being generated, the SPN1 can help to monitor the short and long term efficiency of the panels, and these results can be fed back into improved PV panel design.

The key advantage of the SPN1 Sunshine Pyranometer is that it measures global (total) and diffuse radiation, and sunshine state – all in one instrument. It is also easy to use and needs no routine adjustment or polar alignment.

Output from an SPN1 Sunshine Pyranometer allows calculation of DNI (Direct-Normal Irradiance) in sun tracking, horizontal and tilted installations. It is a common practice to compare solar panel efficiency to DNI, particularly in solar energy field trials.

The SPN1 is a meteorological class instrument designed for long-term outdoor exposure, and is an affordable and effective alternative to traditional shade-ring pyranometers, the Campbell-Stokes and other sunshine recorders. It also provides some of the functionality of expensive pyrheliometers.

  • Global (total) and diffuse horizontal irradiance in W.m-2
  • DNI (Direct-Normal Irradiance) calculation
  • Sunshine threshold to WMO definition: >120 W.m-2 in the direct beam
  • No moving parts, no shade rings, no motorised tracking needed
  • No routine adjustment or polar alignment needed
  • Works at any latitude

The unique design of the SPN1 Sunshine Pyranometer uses a patented array of thermopile sensors and a computer-generated shading pattern to measure the direct and diffuse components of incident solar radiation. The shading pattern and thermopiles are arranged so that at least one thermopile is always fully exposed to the solar beam, and at least one is fully shaded from it, regardless of the position of the sun in the sky. A microprocessor derives the global and diffuse radiation values, which allows an estimate of the direct beam, and hence sunshine hours, to be calculated. The SPN1 Sunshine Pyranometer is protected by patents EP 1012633 & US 6417500.

The Sunshine Pyranometer provides 2 voltage outputs for global and diffuse energy, and a digital output of sunshine state for data logging. Delta-T Devices’ reliable low cost logging solution for the SPN1 is the GP1 Data Logger.

The SPN1 has a precision ground glass dome and uses wideband thermopile sensors; it achieves a near ideal spectral and cosine response. The internal heater keeps the Sunshine Pyranometer clear of dew, ice and snow down to –20°C, ensuring reliable readings in difficult climatic conditions.

In summary, the SPN1 Sunshine Pyranometer is a high performance instrument offering a unique combination of solar radiation measurements in a single, rugged, low maintenance device, making it ideal for PV applications.

Customer comments

No comments were found for Calculate Direct-Normal Irradiance (DNI) with the SPN1 Sunshine Pyranometer. Be the first to comment!