1、BSI BS*7b2L 93 Lb24bbS 0325945 407 m BRITISH STANDARD Method for Calibrating field Pyranometers by comparison to a reference Pyranometer UDC 551.521.1 : 535.231.6.089.6 BS 7621 : 1993 IS0 9847 : 1992 BSI BS+7b2L 93 = Lb24bb 0325946 343 = BS 7621 : 1993 Committees responsible for this British Standar
2、d I The preparation of this British Standard was entrusted by the Refrigeration Heating and Air Conditioning Standards Policy Committee (RHE/-) to Technical Committee RHEIBS, upon which the following bodies were represented: Association of Consulting Engineers British Precast Concrete Federation Ltd
3、. Chartered institution of Building Services Engineers Consumers Association Copper Development Association Cranfield Institute of kchnology Department of the Environment Department of the Environment (Building Research Establishment) Institution of Gas Engineers international Solar Energy Society N
4、ational Centre for Alternative kchnology Royal Institute of British Architects Solar Trade Association Swimming Pool and Allied Trades Association Ltd. University College Cardiff University of Ulster Water Byelaws Advisory Service This British Standard, having been prepared under the direction of th
5、e Refrigeration Heating and AU Conditioning Amendments issued since publication Standards policy Committee, was published under the Amd. No. Date Text affected authority of the Standards Board and comes into effect on 16 January 1993 O MI 1993 The foiowing BSI references relate to the work on this s
6、tandard: Committee reference RHEIZS Draft for comment 9W77417 Dc ISBN O MIO 21024 6 BSI BSx7621 93 m 1b24bb9 0325947 28T m BS 7621 : 1993 Contents Committees responsible National foreword Introduction page Inside front cover ii iii Method 1 Scope 2 Normative references 3 Definitions 4 Apparatus 6 Ca
7、libration procedure 6 Certificate of calibration 7 Precision and accuracy Annexes A (informative) Calibration devices using artificial sources 8 C (informative) Computation of daily average solar angle 13 D (informative) Procedure to determine the ratio of the directional response 14 E (informative)
8、 Bibliography 15 B (informative) Interferences and precautions 11 c i BSI BS+b2L 93 m Lb24669 0325948 LLb m BS 7621 : 1993 National foreword ii This British Standard has been prepared under the direction of the Refrigeration Heating and Air Conditioning Standards Policy Committee and is identical wi
9、th IS0 9847 : 1992 Solar energy - Calibmtim of field pyranmwters by mparison to a reference pymnomder, published by the International Organization for Standardization (ISO) and prepared by Technid Committee ISO/TC 180, Solar heating, in which the UK played an active part. Cross-reference The Technic
10、al Committee has reviewed the provisions of IS0 9060 : 1990, to which normative reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. Compliance with a British Standard does not of itself confer immunity from legal obligations. r BSI BSt76
11、2L 93 m Lb24bb9 0325949 052 m Introduction Accurate and precise measurements of the irradiance of the global (hemispherical) solar radiation are required in a) the determination of the energy available to flat-plate solar collec- tors, b) the assessment of irradiance and radiant exposure in the test
12、ing of solar and non-solar-related materials technologies, and c) the assessment of the direct versus diffuse solar components far energy budget analysis, geographic mapping of solar energy, and as an aid in the determination of the concentration of aerosol and particulate pollution and the effects
13、of water vapour. Although meteorological and resource assessment measurements gen- erally require pyranometers oriented with their axis vertical, appli- cations associated with flat-plate collectors and the study of the solar exposure of related materials require calibrations of instruments tilted a
14、t a predetermined non-vertical orientation. Calibrations at fixed tilt an- gles have applications which seek state-of-the-art accuracy, requiring corrections for cosine, tilt and azimuth. BSI BS*762L 93 1624667 0325950 874 - INTERNATIONAL STANDARD IS0 9847:1992(E) Solar energy - Calibration of field
15、 Pyranometers by comparison to a reference Pyranometer 1 Scope 1.1 This International Standard specifies two pre- ferred methods for the calibration of field pyrano- meters using reference Pyranometers. 1.2 One method, the outdoor calibration or type I, employs solar radiation as the source, while t
16、he other method, the indoor calibration or type II, em- ploys an artificial radiation source. 1.2.1 The outdoor calibration of field Pyranometers may be performed with the Pyranometer in a hori- zontal position (Le. zero tilt) (type la), in a tilted position (type Ib), or at normal incidence (type I
17、C) maintaining the receiver surface perpendicular to the suns beam component. 1.2.2 The indoor calibration of field Pyranometers may be performed using an integrating sphere with shaded (type Ila) or unshaded (type Ilb) lamp(s), or at normal incidence (type Ilc) frequently using an optical bench to
18、present the receiver surface per- pendicular to the beam of the lamp. Types Ila and Ilb correspond to an outdoor cali- bration under conditions of overcast and sunny sky with large light cloud fields, respectively. Type Ilc is comparable with the normal incidence calibration of type IC. 1.3 The meth
19、ods of calibration specified are traceable to the world radiometric reference (WRR); traceability to the International Pyrheliometric Scale of 1956 is not permitted. 1.4 This International Standard is applicable to most types of field Pyranometers regardless of the type of radiation receptor employe
20、d. In general, all Pyranometers used for long-term monitoring of inci- dent solar irradiance may be calibrated by using the described methods, provided that the reference Pyranometer lias been calibrated at essentially the same tilt from horizontal as the tilt employed in the calibration. NOTE 1 Pyr
21、anometers used for collector tests should be calibrated using a reference pyrheliometer (see IS0 9846). 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publi- cation, the edi
22、tions indicated were valid. All stan- dards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of ap- plying the most recent editions of the standards in- dicated below. Members of IEC and IS0 maintain registers of cu
23、rrently valid International Standards. IS0 9060:1990, Solar energy - Specification and classification of instruments for measuring hemispherical solar and direct solar radiation. IS0 9846:-”, Solar energy - Calibration of a Pyranometer using a reference Pyrheliometer. 3 Definitions For the purposes
24、of this International Standard, the following definitions apply. 3.1 altazimuth mount: A tracking mount capable of rotation about orthogonal altitude and azimuth axes; tracking may be manual or by a follow-the-sun servomechanism. (See also IS0 9846.) 3.2 global (solar) irradiance: Hemispherical sola
25、r irradiance received by a horizontal plane surface. (See also IS0 9060.) 1) To be published. 1 ES1 BS*762L 93 1624669 0325953 700 IS0 9847:1992(E) 3.3 integrating sphere hemisphere: A sphere hemisphere, generally from 1 m to 4 m in diam- eter, provided with a planar segment (usually a horizontal bo
26、ttom segment) on which to mount pyranometers (to be compared with an artificial light source), the sphere wall of which is coated with a flat, white pairit that is as lambertian as possible to provide uniform illumination. 3.4 pyranometer: Radiometer designed for meas- uring the irradiance on a plan
27、e receiver suiface which results from the radiant fluxes incident from the hemisphere above within the wavelength range 0.3 pm to 3 pm. (See also IS0 9060.) 3.5 field Pyranometer: Pyranometer usually meet- ing second class2) specifications or first class speci- fications, designed for field use and
28、(typically) continrioiic exposure. 3.6 reference Pyranometer: We1 I-m a i n ta i ned Pyranometer, selected for its stability and quality, used exclusively to calibrate other instruments. 3.7 test Pyranometer: Pyranometer being cali- brated, regardless of its classification or its photoreceptor type.
29、 3.8 tilt angle: Angle between the vertical and the Pyranometer axis (which is equal to thc angle be- tween the horizontal plane and the plane of the de- tector surface). 3.9 calibration factor: Multiplicator, used to derive the global solar irradiance from the measured out- put (voltage). The units
30、 are those of the reciprocal value of the responsivity (e.g. watts per square me- tre per microvolt). 4 Apparatus 4.1 Digital electronic readout device Any digital microvoltmeter having an accuracy of better than f 0.1 YO may be employed. Data loggers with print-out shall be capable of a measurement
31、 frequency of at least two per minute. A data logger having at least a three-channel capacity may be iisefu I. 4.2 Reference pyranometer The reference Pyranometer shall be specially se- lected, tested and maintained as follows. 2) For the classification of pyranometers, see IS0 9060. 4.2.1 For outdo
32、or calibration (type I) The reference Pyranometer for outdoor calibration (type I) should be typically of a higher class (in ac- cordance with the classification given in IS0 9060) than the test Pyranometer, and should exhibit a particularly high long-term stability. The depen- dence of its responsi
33、vity on temperature, irradiance, tilt and angles of incidence shall be determined.3) Within 12 months prior to its use for calibrating field pyranometers, the reference Pyranometer should it- self be recalibrated outdoors by comparison to a pyrheliometer (see IS0 9846). This recalibration should be
34、carried out under conditions typical of those in which the field Pyranometer and reference Pyranometer will be used. The calibration history of the reference pyranometer should be well docu- mented. If the measuring conditions duting calibration devi- ate strongly from those during the typical use o
35、f the field Pyranometer (by more than f 5 “C and I15“ azimuth angle), a reference Pyranometer of the same type that has been calibrated under similar conditions should be used. 4.2.2 For indoor calibration (type il) The reference Pyranometer for indoor calibration (type II) shall be of the same type
36、 as the test Pyranometer (to avoid errors that may be caused by the artificial radiation employed; these errors may arise mainly from imperfect homogeneity of the source beam or from an imperfect match to the solar spectrum). In addition, the Pyranometer shall meet the requirements specified in 4.2.
37、1. 4.3 Integrating sphere or hemisphere For type Ila or Ilb calibration (see 5.3.1), an inte- grating sphere or hemisphere (see 3.3) is required. Suitable apparatus are described in annex A for in- formation. 4.4 Precision Calibration table A precision calibration table is required for all hori- zon
38、tal and fixed-angle tilt calibrations. It shall be level at O“ tilt (.e. horizontal) and shall be able to be tilted over a suitable range of angles from the horizontal with an uncertainty of less than 0,3“. NOTE 2 The deviation between the tilt angle of the ref- erence Pyranometer and that of the fi
39、eld Pyranometer should be not more than 0,l“ which means that the tilt of the pyranometerc has to be finely adjusted. If the cali- bration tables are mechanically and thermally stable it is necessary to check the tilt only after periods longer than a week. 3) Test methods to determine the dependence
40、 of the recponsivity of a Pyranometer on temperature, irradiance, tilt and angle of incidence will form the subject of a future International Standard. 2 BSI BS+7b21 93 lb24bbq 0325952 b47 4.5 Sun-tracking mount The mount, whether power driven or manually op- erated, shall be capable of maintaining
41、the refer- ence Pyranometer and all test pyranometers normal to the sun for the entire test period. The tracking precision shall be such that for all data-taking peri- ods, deviations from the exact normal to the sun do not exceed a) f 4“ where the reference and test pyranometers aie mounted on sepa
42、rate trackers; b) f 10“ where the reference and test pyrano- meters are mounted on the same tracker. NOTE 3 An altazimuth mount is preferred for pyrano- meters with a responsivity dependent on the altazimuth angle of the tilted receiver. The requirements for tracking a Pyranometer at normal incidenc
43、e are less stringent than those for tracking a pyrheliometer. For example, the cosine of 4“ is 0,997 6, and only an insignificant uncer- tainty in normal incident calibration will result from a de- viation of this magnitude. 5 Calibration procedure 5.1 General considerations A number of possible int
44、erferences and precautions relating directly to the methods specified in this In- ternational Standard are given for information in annex B. Particular care shall be taken to correct for zero off-sets. The off-set of signals of the reference and test Pyranometers shall be checked, as a minimum, at t
45、he start and the end of a measurement series, 5.2 Outdoor calibration (type I) 5.2.1 General (types la, Ib and IC) 5.2.1.1 Mount the reference Pyranometer and the test Pyranometer outdoors on a common calibration table for horizontal calibration (type la) and cali- bration at tilt (type Ib) and on a
46、n altazimuth or sun- pointing mount for normal-incidence calibration (type IC). Adjust both instruments to a common el- evation facing the equator. Ensure that the azimuth reference marks point in a common direction. NOTE 4 Convention is to use the electrical connector as the azimuth reference and t
47、o point it towards the equator avid downwards. 5.2.1.2 Adjust the calibration table to the required tilt (which may be O“) fi-om the horizontal. IS0 98471992(E) 5.2.1.3 Connect the reference and test pyrano- meters to their respective, or common, digital voltmeter, using proper shielding. Check the
48、instru- ments for electrical continuity, signal polarity, signal strength and stability. Clean the domes of the Pyranometers (see 1131). Check that the radiant fluxes of the foreground on both instruments are equal at the relevant tilt angle by transposing the positions of the Pyranometers. 5.2.2 Ho
49、rizontal calibration for meteorological and resource measurements (type la) 5.2.2.1 Stable cloudless sky conditions For stable cloudless sky conditions, simultaneously take instantaneous voltage readings on both instru- ments for a minimum of fifteen 10 min to 20 min measurement series, each consisting of 21 or more instantaneous readings. Take these measurement series over a 2 day to 3 day period, or over a longer period to cover a larger range of environmental conditions. Obtain data from early morning, through and including solar noon, to late afternoon to ensure that data a
