IEC 60904-4:2009 pdf download – Photovoltaic devices – Part 4: Reference solar devices – Procedures for establishing calibration traceability
This part of lEC 60904 sets the requirements for calibration procedures intended to establishthe traceability of photovoltaic reference solar devices to Sl units as required by IEC 60904-2.
This standard applies to photovoltaic (PV) reference solar devices that are used to measurethe irradiance of natural or simulated sunlight for the purpose of quantifying the performanceof PV devices. The use of a PV reference solar device is required in the application oflEC 6o904-1 and lEC 60904-3.
This standard has been written with single junction PV reference solar devices in mind,inparticular crystalline Silicon. However, the main part of the standard is sufficiently general toinclude other technologies. The methods described in Annex A, however, are limited to singlejunction technologies.
Normative references
The following referenced documents are indispensable for the application of this document.For dated references, only the edition cited applies.For undated references, the latest editionof the referenced document (including any amendments) applies.
IEC 60904-2,Photovoltaic devices – Part 2: Requirements for reference solar devices
ISO/IEC 17025，General requirements for the competence of testing and calibrationlaboratories
Iso 9059，Solar energy – Calibration of field pyrheliometers by comparison to a referencepyrheliometer
Iso 9846, Solar energy – Calibration of a pyranometer using a pyrheliometer
ISo/IEC Guide 98-3: 2008, Uncertainty of measurement – Part 3: Guide to the expression ofuncertainty in measurement(GUM: 1995)
3Terms and definitions
For the purposes of this document, the following terms and definitions apply.
NOTE The different reference instruments for the traceability chain of solar irradiance are defined in this Clause.Table 1 lists and compares them with those in use for time. Figure 1 shows schematically the most commontraceability chains, based on the methods described in AnnexA.
3.1
primary standard
a device， which implements physically one of the Sl units or directly related quantities.Theyare usually maintained by national metrology institutes (NMIs) or similar organisationsentrusted with maintenance of standards for physical quantities. Often referred to also just asthe uprimaryw, the physical implementation is selected such that long-term stability, precision and repeatability of measurement of the quantity it represents are guaranteed to the maximumextent possible by current technology.
NOTE The World Radiometric Reference (WRR) as realized by the World Standard Group (wsG) of cavityradiometers is the accepted primary standard for the measurement of solar irradiance.
3.2
secondary standard
a device,which by periodical comparison with a primary standard,serves to maintainconformity to Sl units at other places than that of the primary standard. It does not necessarilyuse the same technical principles as the primary standard,but strives to achieve similar long-term stability， precision and repeatability.”
NOTE Typical secondary standards for solar irradiance are cavity radiometers which participate periodically(normally every 5 years) in the International Pyrheliometer Comparison (IPC) with the wSG.
3.3
primary reference
the reference instrument which a laboratory uses to calibrate secondary references. lt iscompared at periodic intervals to a secondary standard.Often primary references can berealised at much lower costs than secondary standards.
NOTE Typically a solar cell is used as a reference solar device for the measurement of natural or simulated solarirradiance.
3.4
secondary reference
the measurement device in use for daily routine measurements or to calibrate workingreferences,calibrated at periodic intervals to a primary reference.
NOTE The most common secondary references for the measurement of natural or simulated solar irradiance aresolar cells and solar modules.
3.5
traceability
the requirement for any PV reference solar device, to tie its calibration value to Sl units in anunbroken and documented chain of calibration transfers including stated uncertainties.
NOTE The WRR has been compared twice to the Sl radiometric scale and shown to be within their mutualuncertainty levels. Therefore traceability to WRR automatically provides traceability to sI units. However, theuncertainty of the ratio WRR/Sl units needs to be taken into account. The World Radiation Center (WRC)recommends a rectangular uncertainty distribution with 0,3 % half-width. A third comparison is currently underwayand should be published in the future.
J.Romero,N.P. Fox,C.Frohlich metrologia 28 (1991)125-8J.Romero,N.P.Fox,C.Frohlich metrologia 32 (1995/1996y 523-4
