User manual Shadow ring for pyranometers

Warning statements Ensure that SHR02 is connected to the protective earth to reduce electrical shock risk and increase instrument operation reliability. Ensure that the installed pyranometer housing is connected to reduce electrical shock risk and increase instrument operation reliability.

1 Ordering and checking at delivery 8 1.1 Ordering industrial pyranometers 8 2 Instrument principle and theory 11 2.5 General usage recommendations 15 3 Standards and recommended practices for use 16 3.1 General rules for solar radiation measurement 16 3.2 Specific use in meteorology and climatology 16 3.3 Pyranometer classification standard 17 6.1 Recommended maintenance and quality assurance 34 7.1 Irradiance level too high 36 8.2 Adjustment table: sliding bar settings and corresponding correction factors 40

quantities symbol Global horizontal In-plane solar irradiance Gi Diffuse Horizontal Instrument dome radius r Shadow ring radius R Shadow ring rim height h Shadow ring width w Shadow ring sliding x Correction factor diffuse f radiation component Latitude of installation lat Solar declination angle dec Hour angle at sunset t0 in-plane portion diffuse portion value at a chosen reference condition obscured portion contribution related to instrument dome contribution assuming symmetrical instrument

Introduction SHR02 is a practical metal shadow ring that helps making diffuse solar irradiance measurements with pyranometers. The shadow ring, also known as a shadow band, prevents direct radiation from reaching the pyranometer, so that the shaded pyranometer measures diffuse radiation only. The combination of a shadow ring and a pyranometer is called a diffusometer by the ISO 9060:2018 standard. The compact SHR02, combined with a Hukx pyranometer, has several advantages over competing models. SHR02 is compatible with most Hukx pyranometers. Hukx pyranometers have very low zero offsets, so that...

Using SHR02 has several advantages: – relatively small size/light weight – low-investment alternative for a sun tracker with shading-disc – high accuracy when used with Hukx (low zero-offset) pyranometers – save costs on expensive external ventilation; compatible with SR30 with internal ventilation Suggested use of SHR02: – meteorological observations – building energy performance – solar energy studies Figure 0.2 Installation of the SHR02 shadow ring with a Hukx pyranometer is easy. The altitude of the sun varies throughout the year and this influences the shadow cast by the shadow ring. Aside...

Figure 0.3 Pyranometer example: SR15, combined with SHR02 forming a diffusometer.

The standard configuration of SHR02 is for use with SR15 / SR30 sensor. Common options are: - Mounting adapter for SR20 / SR22 / SR25. Specify PMA01 Table 1.1.1 Overview of versions in the BLK - GLD sticker series. (continued on next page). SHR02 Shadow ring for pyranometers, combined with a pyranometer forming a diffusometer (pyranometer is not included in SHR02 delivery) Arriving at the customer, the delivery should include: 2. 1 x tilt adjustment stage (with engraved rotation scale in °) with pyranometer mounting plate 3. 1 x central support, horizontal bar connected to pyranometer support...

For assembling and mounting the shadow ring, the following tooling is recommended: For leveling and/or adjusting the shadow ring, the following tooling is recommended: Consult your pyranometer user manual for tooling recommended for removal of the pyranometer feet.

2. thumbscrew for adjustment of sliding bars 3. screw for adjustment of tilt stage 6. tilt adjustment stage 7 screw for latitude adjustment 8. central support with horizontal bar connected to pyranometer support arm Understanding the basic set-up, working principles and operation of a shadow ring instrument is essential to attain accurate, reliable measurement data. This chapter describes the basic principles, the main sources of error in data and some practical considerations regarding installation and operation. A view angle is an important specification for a shadow ring instrument. The view...

Operating principles A shadow ring is used together with a pyranometer to measure diffuse global irradiance. Direct radiation from the sun is blocked by the ring. To achieve this the entire day, the ring is set up parallel to the equatorial plane; see Figure 2.2.1. This is practically done by setting the plane of the ring compared to the horizon under an angle equal 90 ° minus the local latitude in °. Figure 2.2.1 The principle of a shadow ring. During the seasons, the sun’s trajectory changes its position in the sky due to variation in the declination of the earth-sun system. The shadow ring...

Most shadow rings are used with the pyranometer mounted horizontally. Using the incorporated tilt adjustment stage, the pyranometer can also be mounted in a tilted position. In this case, the diffuse irradiance in the tilted plane is measured. To keep the pyranometer shaded, the ring must stay aligned with the equatorial plane. There are two main sources of error that may affect the accuracy of the diffuse irradiance component: – measurement errors – errors due to unintentional blockage by the ring Measurement errors, inherent to the type of pyranometer and data logger used, can generally be...

f = 2 (w+h |tan(dec)|) / (pi R) cos3(dec) [t0 sin(lat) sin(dec) + cos(lat) cos(dec) sin(t0)] with R the diameter of the ring, h the height of the rims on the ring, w the width of the ring, dec the declination, lat the latitude and t0 the hour angle at sunset and sunrise. Refer to the specification table in Chapter 4 for the instrument dimensions. For convenience, the table in Appendix 8.2 lists correction factors for a range of latitudes and declinations. There are more sophisticated correction models possible, but these depend on the local conditions and require more assumptions and tuning to...

This equation results in a symmetrical shading around the center of the pyranometer. In the table, a setting for every 1 ° in declination is computed. In general, there are two dates during the year at which the declination is the same. To improve on this, the asymmetrical projection of the half-sphere formed by the pyranometer dome can be taken into account as well. Since this projection depends on the angle of the sun with the horizontal this equation depends on the latitude and the declination. Given a setting xsymmetrical the amount xdome can be added to improve the ring adjustment: Xdome...