PD ISO/TR 9901:2021 pdf download

PD ISO/TR 9901:2021 pdf download.Solar energy – Pyranometers – Recommended practice for use. 4 Selection of pyranometers and accessories 4.1 General A pyranumeter performs a hemispherical Irradlance measurement In W/m2. It Is Important to realize that in many applications br example when working according to monitoring standards LIC 017241 .1 i, ASTM G193 I 22 1 and WMOF I a measurenwnt are accompanied by a time stamp. Roth the irradiance and the rime cramp have a measurement uncertainty. See 52.52 and 5.6 for more details on uncrtai nty evaluation. The pyranomete’r selection Is often based on the wIsh 10 attain a certain measurement uncertainty. There also may be other conslderations a) Task•spccilk criteria, such a maximum response time, or the rrquirenwnt to comply with a standard. b) Operational cntena, such as dimensions, weight, stability, measures to mitigate dew, frost, precipitation and wiling, and maintenance requirements of the instrurnrnt and accessories. c) Economic criteria, costs of mechanical and electrical integration in a system depend on the instrument characteristics. Also costs o recalibration, inspection and maintenance may be considered. When selecting an instrument there are two common ways to make a choice, described in the following clauses: — related to the pyranometer accuracy dass; — related to the specilications of the pyl-anometer and its accessories. 4.2 Pyranometer selection based on accuracy dass In some applications the choice of instrument is driven by the pyranometer accuracy class. The class is often, but not necessarily related to the type. i.e. the technology used (e.g. with photodiode or thermoplie sensors). The choice of a certain accuracy class Is often driven by the requirements of standards Table 1 summarizes the required pyranometer accuracy class for the most common application of PV system performance monitoring according to JEC. NOTE IEC b1724-l is du, for revIan in 2021. and ra’qwremenls will possibly change liQQ6O2Q1U defInes 3 pyranosneter classes, A, Rand C. These classes are accuracy classes, which arc defined by ICGM 200:2012 to meet stated metrological requirements that are intended to keep measurement errors or instrumental uncertainties within specified limits under specified operating conditsonsi 24 I. The accuracy classification as used In ISLL9O6O dues not by definition mean that a higher class pyraisomcter will provide a higher accuracy meaxurenwnt: this entirely depends on the application Besides dassilication as class A, B, and C. I0fQ makes a further distinction between 2 maIn types and an independent sub’category: — spectrolfr,flot...