1、Designation: E1084 86 (Reapproved 2015)Standard Test Method forSolar Transmittance (Terrestrial) of Sheet Materials UsingSunlight1This standard is issued under the fixed designation E1084; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revi
2、sion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of solartransmittance (terrestrial) of materials in sheet fo
3、rm by using apyranometer, an enclosure, and the sun as the energy source.1.2 This test method also allows measurement of solartransmittance at angles other than normal incidence.1.3 This test method is applicable to sheet materials that aretransparent, translucent, textured, or patterned.1.4 This st
4、andard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Terminology2.1 Definiti
5、ons:2.1.1 pyranometer, na radiometer used to measure thetotal solar radiant energy incident upon a surface per unit timeper unit area. This energy includes the direct radiant energy,diffuse radiant energy, and reflected radiant energy from thebackground.2.1.2 solar reflectance, nthe ratio of reflect
6、ed to incidentsolar flux.2.1.3 solar transmittance, nthe ratio of transmitted toincident solar flux.2.2 Definitions of Terms Specific to This Standard:2.2.1 solar flux, nthe total radiation from the sun, bothdirect and diffuse.3. Summary of Test Method3.1 Using a pyranometer to measure the solar irr
7、adiance, thetest specimen is inserted in the path of the rays from the sun tothe pyranometer. An enclosure with a nonreflecting bottom isused to avoid measuring flux from around the edges of thespecimen or from multiple reflections between the box and thespecimen. The transmittance is the ratio of t
8、he flux measuredwith the specimen in the light path to the flux measured withoutthe specimen in the path.4. Significance and Use4.1 Solar transmittance is an important factor in the admis-sion of energy through fenestration, collector glazing, andprotective envelopes. This test method provides a mea
9、ns ofmeasuring this factor under fixed conditions. While the datamay be of assistance to designers in the selection and specifi-cation of glazing materials, the solar transmittance is notsufficient to define the rate of net heat transfer withoutinformation on other important factors.4.2 This test me
10、thod has been found practical for bothtransparent and translucent materials, as well as for those withtransmittance reduced by highly reflective coatings. This testmethod is particularly applicable to the measurement oftransmittance of inhomogeneous, fiber reinforced, patterned, orcorrugated materia
11、ls since the transmittance is averaged over alarge area.4.3 This test method may be used to measure transmittanceof glazing materials at angles up to 60 off normal incidence.NOTE 1A technique similar to the one described but using apyrheliometer has been used for the measurement of specular solarref
12、lectance; however, there is insufficient experience with this techniquefor standardization at present.5. Apparatus5.1 EnclosureThe required apparatus is a box capable ofsupporting a 0.60 m (24 in.) square specimen. The box shallhave a square, clear aperture of no less than 0.50 m by 0.50 m(20 in. by
13、 20 in.). The enclosure shall have provisions to holdspecimens planar across the aperture with the additionalcapability to remove and replace the specimen easily during themeasurement process. It shall also have the capability to movethe specimen across the aperture in a systematic way. Lightbaffled
14、 air vents at the top and bottom of the enclosure arerecommended to aid cooling of all components when aspecimen is in place.The inside of the box shall have side wallscovered with mirrors having specular, solar reflectance greaterthan 0.85 that extend from the opening down to the plane of the1This
15、test method is under the jurisdiction of ASTM Committee E44 on Solar,Geothermal and OtherAlternative Energy Sources and is the direct responsibility ofSubcommittee E44.05 on Solar Heating and Cooling Systems and Materials.Current edition approved March 1, 2015. Published April 2015. Originallyapprov
16、ed in 1986. Last previous edition approved in 2009 as E108486(2009). DOI:10.1520/E1084-86R15.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1sensor element. The rest of the inside of the box shall beblackened so that its solar reflect
17、ance is less than 0.10. Atypical unit is shown in Fig. 1.NOTE 2Mirrors having the necessary specular reflectance are brightanodized aluminum lighting sheet, aluminized polymer films, and con-ventionally mirrored glass. For highly diffusing materials, a box with thespecified aperture and blackened si
18、de walls, the test method couldunderestimate the transmittance by up to 0.03. Using highly reflecting sidewalls on the interior of the enclosure reduces this error for such materialsto less than 0.01 transmittance unit. For highly specular materials, thiserror is negligible.NOTE 3For an enclosure wi
19、th a highly reflecting bottom, themeasured transmittance could be greater than 0.05 too high due tomultiple reflections. A blackened bottom having less than 0.10 reflectancewill hold this error to less than 0.005 transmittance units.22Flat black paints are satisfactory for this purpose.Also, a linin
20、g of opaque blackvelvet cloth such as that available from photographic suppliers is suitable.(A) Specular mirror, 500 50 mm. (J) Standard 2 4 in. wood framing, 75 mm long (bottom to center of hole)(B) Nonreflecting, black bottom. Nontransmitting louvers or multiple layers of grillcloth that allow ai
21、r circulation into the enclosure are preferable.(K) Rectangular,34 in. plywood, 500 75 mm.(C) Pyranometer (L)12 2 in. carriage bolt with wing and washer.(D) Support shelf for pyranometer. The height of the shelf will depend on thepyranometer used.(M)34 in. iron pipe.(E) Semicircular disk 538 mm diam
22、eter out of34 in plywood. (N) U-bolts.(F) Semicircular tracker with scale (P) Primary tracking axis, aligned parallel to earths axis of rotation. The axis shallmake an angle with the vertical equal to the local latitude and point toward theNorth Star.(G) Lip of flange turned up to 20 mm to help supp
23、ort specimens (Q) C-clamp attached to arm to lock equatorial angle during measurements.(H) 50 mm flange bent out of sheet metal or cut from wood. Top surface ispainted back to prevent light entering enclosure due to multiple reflections fromaround the specimen edges.(R) Vertical support post approxi
24、mately1mlong. Made from standard 2 6 ftlumber.NOTE 1This apparatus consisting of enclosure, detector, and equatorial mount has been found acceptable for measuring solar transmittance of sheetmaterials. The majority of the pieces are cut from standard 2.4, 2 by 6, and34 in. plywood construction mater
25、ials.FIG. 1 Apparatus Consisting of Enclosure, Detector, and Equatorial MountE1084 86 (2015)25.2 Tracking:5.2.1 The enclosure shall be mounted in a manner thatallows repositioning approximately every 15 min in order totrack the sun. The use of an equitorial or altazmuth mount isrecommended and autom
26、atic solar tracker is optional.5.2.2 For manual tracking, an alignment device shall beused. Several acceptable devices are shown in Fig. 2.5.3 Sensor:5.3.1 The sensing element of this apparatus is a pyranometerthat shall meet WMO Class 2 specifications (1, 2).3The mostimportant characteristics for t
27、he pyranometer are as follows:5.3.1.1 a flat spectral sensitivity (62 %) over the regionfrom 300 nm to 3000 nm that encompasses nearly all theterrestrial solar flux;5.3.1.2 sensitivity that is isotropic except for the usualcosine response with altitude angle; and5.3.1.3 output linear to within 62 %
28、from 0 to 1000 W/m2or calibration curves accurate to within 62 % over the samerange. Additional desirable characteristics are relative short-time constants of a few seconds and good temperature stability.NOTE 4When using pyranometers meeting WMO Class 2 specifica-tions in this procedure, the inaccur
29、acies due to these sources are expectedto be less than 1 %. This is because relative, rather than absolute, readingsare made over a dynamic range that is small compared to the range of thesensor. The procedure and apparatus specified in this test methodminimize the thermal drift during the measureme
30、nts.5.3.2 The pyranometer shall be located so that the sensingthermopile (not the dome) is centered approximately 50 mm (2in.) below the plane of the rim of the box. Normally pyranom-eters have a 180 viewing angle, but when placed as described,the field angle to the midpoint of the edges of the test
31、 specimenis 157.5.3.3 For pyranometers with thermal control shields havinghigh reflectance, for example, the Eppley P.S.P.) it is importantthat the reflection from the pyranometer back toward the sheetmaterial under test be minimized. This can be done by coveringthe shield with a nonreflecting mater
32、ial or by mounting thepyranometer outside the enclosure with only the dome andsensor element projecting into the box.NOTE 5Mounting the pyranometer outside of the enclosure also3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.(a) Semicircle with scale (
33、b) 12.7mm(12 in.) ID pipe by 195 mm (7.67 in.) long.(A) Semicircle with 143 mm radius cut out of 150 300 mm piece of12to34 in.plywood.NoteRealign when direct from the solar disk no longer traverses the pipe.(B) Tape with 1 cm scale attached to inside of semicircle.(C) This opaque sheet (preferably m
34、etal) with 3 mm aperture centered above semicircle.NoteA displacement of the light beam coming through the aperture of 1 cm on the circumference of the semicircle equals 4 misalignment. This tracker is conve-nient for determining angles for off normal incidence measurements.(c) 9 mm diameter rod by
35、500 mm long centered on 80 mmdiameter white disk.NoteRealign when shadow of rod falls outside of white disk.NOTE 1The dimensions are chosen to provide 6 4 limits on deviations from normal to the sun. In (b) and ( c) care must be taken to mount the rodor pipe perpendicular to the surface of the enclo
36、sure.FIG. 2 Alignment Devices for EnclosureE1084 86 (2015)3reduces the heating load and cooling requirements for the pyranometer.6. Specimens6.1 The test specimens shall not be less than 0.60 by 0.60 m(24 by 24 in.). Care must be taken to prevent light leaks at theedges, especially if the cross-sect
37、ional shape of the specimen isnot flat. Also, if the cross-sectional shape is not flat or if thespecimen is patterned, a specimen enough larger to allowtranslation across the pyranometer by at least one period of theshape or pattern is required.7. Procedure7.1 Conduct the tests on a sunny day with n
38、o cloud coverwithin 615 of the sun and a minimum normal solar irradianceof 700 W/m2 and constant to within 1 % during the individualtests. Conduct testing as close to solar noon as possible but nomore than 3 h before or after solar noon.7.2 Set up apparatus at a location where no prominentstructure
39、or vegetation is nearby in the pyranometers field ofview.7.3 Align the box aperture to within 4 of the normal to thesuns rays, and measure the solar flux with no specimen inplace.Allow adequate time for the trace or reading to stabilize.7.4 Place the test specimen on the box and measure thetransmitt
40、ed solar flux, again allowing adequate time for thetrace or reading to stabilize.NOTE 6Operate the pyranometer as directed by its manufactureexcept that horizontal mounting requirements must be ignored. Longresponse times are undesirable because of the potential measurement errordue to changing irra
41、diance and the inconvenience of slow samplethroughput. The manufacturer shall be consulted if response times otherthan original provided are desired.7.5 Compute the solar transmittance of the test specimen asthe ratio of the flux measured when the test specimen is placedbetween the sun and the senso
42、r to the flux measured by thesensor with no test specimen in place.NOTE 7For a sensor with linear response, the ratio is equal to the ratioof the output signals with and without the specimen in place.7.6 Repeat the steps in 7.3 and 7.4 a minimum of five timesor until the estimated standard deviation
43、 of the average valuefor the calculated transmittance is acceptable. Make eachmeasurement with the specimen in a different location.7.7 Compute the estimated standard deviation of the aver-age transmittance of the specimen using the following equa-tion:Sr5!(j51n 2 j!2n!n 2 1!(1)where:Sr= the estimat
44、ed standard deviation of the average, = the average transmittance,j = the jth individual measurement of the transmittance,andn = the number of individual measurements made.7.8 Align the apparatus, at least every 15 min.7.9 When measuring corrugated or nonuniformly transmit-ting specimens, translate
45、the specimen in such a way as toobtain an average value for the transmittance. Since a system-atic translation over one period of structure is required, it ispermissible to perform the step in 7.3. Then take severalmeasurements with sample on the box (8.4) before repeatingthe step in 7.3, provided t
46、hese before and after readings are inclose agreement.NOTE 8Do not leave the specimens on the box for periods longer than10 min since it may cause overheating of the sensor, resulting in nonlinearresponse or even permanent damage.7.10 Measurement of the solar transmittance of sheet mate-rials at angl
47、es up to 60 off normal incidence is also permittedby this test method. To do this, align the box aperture withrespect to the solar angle to provide the desired incidenceangle, and follow the steps in 7.4 to 7.7.8. Report8.1 The report shall include the following information:8.1.1 The source and iden
48、tity of the test specimen,8.1.2 A complete description of the test specimen, that is,thickness, cross-sectional shape, color, size, translucent ortransparent, type of material.8.1.3 The orientation of the sample based on any nonuni-formity or anisotropy such as surface coatings, exposed surfacefiber
49、 orientation, color bands, etc. during each measurement.8.1.4 For each angle of incidence used, report the followinginformation.8.1.4.1 The angle of incidence.8.1.4.2 The solar transmittance as the average of the five ormore measurements to the nearest 0.01 transmittance unit.8.1.4.3 The estimated standard deviation of the averagecalculated as in 7.7.8.1.4.4 The number of measurements used in the computa-tion.8.1.5 The place, date, and time of the test.8.1.6 The solar irradiance as measured in 7.3.8.1.7 Type, model, serial number,
