ASTM E905-87(2007)

Standard Test Method for Determining Thermal Performance of Tracking Concentrating Solar Collectors

SCOPE
1.1 This test method covers the determination of thermal performance of tracking concentrating solar collectors that heat fluids for use in thermal systems.
1.2 This test method applies to one- or two-axis tracking reflecting concentrating collectors in which the fluid enters the collector through a single inlet and leaves the collector through a single outlet, and to those collectors where a single inlet and outlet can be effectively provided, such as into parallel inlets and outlets of multiple collector modules.
1.3 This test method is intended for those collectors whose design is such that the effects of diffuse irradiance on performance is negligible and whose performance can be characterized in terms of direct irradiance.
Note 1—For purposes of clarification, this method shall apply to collectors with a geometric concentration ratio of seven or greater.
1.4 The collector may be tested either as a thermal collection subsystem where the effects of tracking errors have been essentially removed from the thermal performance, or as a system with the manufacturer-supplied tracking mechanism.
1.4.1 The tests appear as follows:SectionLinear Single-Axis Tracking Collectors Tested as Thermal Collection Subsystems11-13System Testing of Linear Single-Axis Tracking Collectors14-16Linear Two-Axis Tracking and Point Focus Collectors Tested as Thermal Collection Subsystems17-19System Testing of Point Focus and Linear Two-Axis Tracking Collectors20-22
1.5 This test method is not intended for and may not be applicable to phase-change or thermosyphon collectors, to any collector under operating conditions where phase-change occurs, to fixed mirror-tracking receiver collectors, or to central receivers.
1.6 This test method is for outdoor testing only, under clear sky, quasi-steady state conditions.
1.7 Selection and preparation of the collector (sampling method, preconditioning, mounting, alignment, etc.), calculation of efficiency, and manipulation of the data generated through use of this standard for rating purposes are beyond the scope of this test method, and are expected to be covered elsewhere.
1.8 This test method does not provide a means of determining the durability or the reliability of any collector or component.
1.9 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.10 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 28-Feb-2007
• ICS: 27.160 - Solar energy engineering
• Technical Committee: E44 - Solar, Geothermal and Other Alternative Energy Sources

Relations

• Replaces: ASTM E905-87(2001) - Standard Test Method for Determining Thermal Performance of Tracking Concentrating Solar Collectors
• Effective Date: 01-Mar-2007

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E905 − 87 (Reapproved 2007)
StandardTest Method for
Determining Thermal Performance of Tracking
Concentrating Solar Collectors
This standard is issued under the fixed designation E905; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.7 Selection and preparation of the collector (sampling
method, preconditioning, mounting, alignment, etc.), calcula-
1.1 This test method covers the determination of thermal
tion of efficiency, and manipulation of the data generated
performanceoftrackingconcentratingsolarcollectorsthatheat
through use of this standard for rating purposes are beyond the
fluids for use in thermal systems.
scope of this test method, and are expected to be covered
1.2 This test method applies to one- or two-axis tracking
elsewhere.
reflecting concentrating collectors in which the fluid enters the
1.8 This test method does not provide a means of determin-
collectorthroughasingleinletandleavesthecollectorthrough
ing the durability or the reliability of any collector or compo-
a single outlet, and to those collectors where a single inlet and
nent.
outlet can be effectively provided, such as into parallel inlets
and outlets of multiple collector modules. 1.9 The values stated in SI units are to be regarded as the
standard. The values given in parentheses are for information
1.3 This test method is intended for those collectors whose
only.
design is such that the effects of diffuse irradiance on perfor-
1.10 This standard does not purport to address all of the
mance is negligible and whose performance can be character-
safety concerns, if any, associated with its use. It is the
ized in terms of direct irradiance.
responsibility of the user of this standard to establish appro-
NOTE 1—For purposes of clarification, this method shall apply to
priate safety and health practices and determine the applica-
collectors with a geometric concentration ratio of seven or greater.
bility of regulatory limitations prior to use.
1.4 The collector may be tested either as a thermal collec-
tion subsystem where the effects of tracking errors have been
2. Referenced Documents
essentially removed from the thermal performance, or as a
2.1 ASTM Standards:
system with the manufacturer-supplied tracking mechanism.
E772Terminology of Solar Energy Conversion
1.4.1 The tests appear as follows:
2.2 Other Standard:
Section
Linear Single-Axis Tracking Collectors Tested as
ASHRAE 93-86,Methods of Testing to Determine the
Thermal Collection Subsystems 11–13 3
Thermal Performance of Solar Collectors
System Testing of Linear Single-Axis Tracking Collectors 14–16
Linear Two-Axis Tracking and Point Focus Collectors
NOTE 2—Where conflicts exist between the content of these references
Tested as Thermal Collection Subsystems 17–19
and this test method, this test method takes precedence.
System Testing of Point Focus and Linear Two-Axis
NOTE3—Thedefinitionsanddescriptionsoftermsbelowsupersedeany
Tracking Collectors 20–22
conflicting definitions included in Terminology E772.
1.5 This test method is not intended for and may not be
applicable to phase-change or thermosyphon collectors, to any
3. Terminology
collector under operating conditions where phase-change
3.1 Definitions:
occurs, to fixed mirror-tracking receiver collectors, or to
3.1.1 area, absorber, n—total uninsulated heat transfer sur-
central receivers.
face area of the absorber, including unilluminated as well as
1.6 This test method is for outdoor testing only, under clear
illuminated portions. (E772)
sky, quasi-steady state conditions.
1 2
This test method is under the jurisdiction of ASTM Committee E44 on Solar, For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Geothermal and OtherAlternative Energy Sourcesand is the direct responsibility of contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Subcommittee E44.05 on Solar Heating and Cooling Systems and Materials. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved March 1, 2007. Published April 2007. Originally the ASTM website.
approvedin1982.Lastpreviouseditionapprovedin2001asE905–87(2001).DOI: Available from the American Society of Heating, Refrigerating, and Air
10.1520/E0905-87R07. Conditioning Engineers, Inc., 1791 Tullie Circle, N.E. Atlanta, GA 30329.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E905 − 87 (Reapproved 2007)
3.1.2 collector, point focus, n—concentrating collector that from the sun’s rays; or the time required for ∆t to increase to
a
concentrates the solar flux to a point. (E772) 90% of its value under quasi-steady state conditions after the
shaded collector at equilibrium is exposed to irradiation.
3.1.3 collector, tracking, n—solar collector that moves so as
to follow the apparent motion of the sun during the day, 3.2.10 quasi-steady state, n—refers to that state of the
rotating about one axis or two orthogonal axes. (E772) collector when the flow rate and inlet fluid temperature are
constant but the exit temperature changes “gradually” due to
3.1.4 concentration ratio, geometric, n—ratio of the collec-
the normal change in solar irradiance that occurs with time for
tor aperture area to the absorber area. (E772)
clear sky conditions.
3.1.5 quasi-steady state, n—solar collector test conditions
3.2.10.1 Discussion—It is defined by a set of test conditions
when the flow rate, fluid inlet temperature, collector
described in 10.1.
temperature, solar irradiance, and the ambient environment
3.2.11 solar irradiance, direct, in the aperture plane,
have stabilized to such an extent that these conditions may be
n—direct solar irradiance incident on a surface parallel to the
considered essentially constant (see Section 8).
collector aperture plane.
3.1.6 Discussion—The exit fluid temperature will, under
3.2.12 solar irradiance, total, n—total solar radiant energy
these conditions, also be essentially constant (see ASHRAE
incident upon a unit surface area (in this standard, the aperture
93-86).
of the collector) per unit time, including the direct solar
3.2 Definitions of Terms Specific to This Standard:
irradiance, diffuse sky irradiance, and the solar radiant energy
3.2.1 altazimuthal tracking, n—continual automatic posi-
reflected from the foreground.
tioningofthecollectornormaltothesun’sraysinbothaltitude
3.2.13 thermal performance, n—rate of heat flow into the
and azimuth.
absorber fluid relative to the incident solar power on the plane
3.2.2 area, aperture (of a concentrating collector),
of the aperture for the specified test conditions.
n—maximum projected area of a solar collector module
3.3 Symbols:
through which the unconcentrated solar radiant energy is
2 2
A =collector aperture area, m (ft ).
a
admitted,includinganyareaofthereflectororrefractorshaded
2 2
A =absorber area, m (ft ).
by the receiver and its supports and including gaps between abs
2 2
A =ineffective aperture area, m (ft ).
reflector segments within a module. (E772) 1
C=geometric concentration ratio A /A , dimensionless.
a abs
3.2.3 clear-sky conditions, n—refer to a minimum level of
−1 −1
−2 −2 C =specific heat of the heat transfer fluid,J·kg ·° C
p
direct normal solar irradiance of 630 W · m (200 Btu · ft ·
−1 −1
(Btu · lb ·°F ).
−1
h ) and a variation in both the direct and total irradiance of
E =diffuse solar irradiance incident on the collector
s,d
less than 64% during the specified times before and during
−2 −1 −2
aperture, W · m (Btu · h ·ft ).
each test.
E =direct solar irradiance in the plane of the collector
s,D
3.2.4 end effects, n—inlinearsingle-axistrackingcollectors, −2 −1 −2
aperture, W · m (Btu · h ·ft ).
the loss of collected energy at the ends of the linear absorber
E =directsolarirradianceintheplanenormaltothesun,
s,DN
when the direct solar rays incident on the collector make a −2 −1 −2
W·m (Btu · h ·ft ).
non-zeroanglewithrespecttoaplaneperpendiculartotheaxis
E =globalsolarirradianceincidentonahorizontalplane,
s,2π
of the collector.
2 −1 −2
W·m (Btu · h ·ft ).
3.2.5 fluid loop, n—assembly of piping, thermal control,
E =totalsolarirradianceincidentonthecollectoraperture,
s,t
−2 −1 −2
pumping equipment and instrumentation used for conditioning
W·m (Btu · h ·ft ).
the heat transfer fluid and circulating it through the collector
f=focal length, m (ft).
during the thermal performance tests.
g=spacing between the effective absorbing surfaces of
adjacent modules, m (ft).
3.2.6 module, n—the smallest unit that would function as a
solar energy collection device. K=incident angle modifier, dimensionless.
L=length of reflector segment, m (ft).
3.2.7 near-normal incidence, n—angular range from exact
l =length of receiver that is unilluminated, m (ft).
normal incidence within which the deviations in thermal r
−1
m =mass flow rate of the heat transfer fluid, kg · s (lbm ·
performance measured at ambient temperature do not exceed
−1
h ).
62%, such that the errors caused by testing at angles other
−1
˙
Q =net rate of energy gain in the absorber, W (Btu · h ).
than exact normal incidence cannot be distinguished from
−1
˙
errors caused by other inaccuracies (that is, instrumentation Q =rate of energy loss, W (Btu · h ).
L
errors, etc.). r=overhang of the receiver past the end of the reflectors, m
(ft).
3.2.8 rate of heat gain, n—the rate at which incident solar
R(θ)=ratio of the rate of heat gain to the solar power
energy is absorbed by the heat transfer fluid, defined math-
incident on the aperture, dimensionless.
ematically by:
s=angle which the collector aperture is tilted from the
˙
Q 5 m˙C ∆t (1)
p a horizontal to the equator, and is measured in a vertical N-S
plane, degrees.
3.2.9 response time, n—time required for ∆ t to decline to
a
10%ofitsinitialvalueafterthecollectoriscompletelyshaded t =ambient air temperature, °C (°F).
amb
E905 − 87 (Reapproved 2007)
t =temperature difference across the absorber, inlet to the aperture. The departure of the optical response of the
∆ a
outlet, °C (°F). collector from the cosine response is determined by obtaining
t =temperature difference across the absorber inlet to the incident angle modifier data.The incident angle modifier is
∆ a,i
outlet at the time of initial quasi-steady state conditions, °C important in predicting such collector characteristics as all-day
(°F). thermal performance.
t =temperature difference across the absorber inlet to
∆ a,f
5. Significance and Use
outlet at the time final quasi-steady state conditions are
reached, °C (°F).
5.1 This test method is intended to provide test data essen-
t =temperature difference across the absorber inlet to
tial to the prediction of the thermal performance of a collector
∆ a,T
outlet at time T, °C (°F).
in a specific system application in a specific location. In
t =temperature of the heat transfer fluid at the inlet to the
addition to the collector test data, such prediction requires
f,i
collector, °C (°F).
validated collector and system performance simulation models
w=width of reflector segment, m (ft).
thatarenotprovidedbythistestmethod.Theresultsofthistest
β=solar altitude angle, degrees.
method therefore do not by themselves constitute a rating of
Γ(θ )=end effect factor, dimensionless.
the collector under test. Furthermore, it is not the intent of this
||
δ=solar declination, degrees.
test method to determine collector efficiency for comparison
θ=angle of incidence between the direct solar rays and the purposes since efficiency should be determined for particular
normal to the collector aperture, degrees.
applications.
θ , θ = angles of incidence in planes parallel and
|| '
5.2 This test method relates collector thermal performance
perpendicular, respectively, to the longitudinal axis of the
to the direct solar irradiance as measured with a pyrheliometer
collector, degrees.
with an angular field of view between 5 and 6°. The prepon-
θ =maximum angle of incidence at which all rays incident
ι
derance of existing solar radiation data was collected with
on the aperture are redirected onto the receiver of the same
instruments of this type, and therefore is directly applicable to
module, degrees.
prediction of collector and system performance.
θ' =minimum angle of incidence at which radiation re-
c
5.3 This test method provides experimental procedures and
flected from one module’s aperture is intercepted by the
calculation procedures to determine the following clear sky,
receiver of an adjacent module, degrees.
quasi-steady state values for the solar collector:
φ=solar azimuth angle measured from the south, degrees.
5.3.1 Response time,
5.3.2 Incident angle modifiers,
4. Summary of Test Method
5.3.3 Near-normal incidence angular range, and
4.1 Thermal performance is the rate of heat gain of a
5.3.4 Rate of heat gain at near-normal incidence angles.
collectorrelativetothesolarpowerincidentontheplaneofthe
NOTE 4—Not all of these values are determined for all collectors. Table
collector aperture. This test method contains procedures to
1 outlines the tests required for each collector type and tracking arrange-
measure the thermal performance of a collector for certain
ment.
well-defined test conditions. The procedures determine the
5.4 This test method may be used to evaluate the thermal
opticalresponseofthecollectorforvariousanglesofincidence
performance of either (1) a complete system, including the
ofsolarradiation,andthethermalperformanceofthecollector
tracking subsystems and the thermal collection subsystem, or
at various operating temperatures for the condition of maxi-
(2) the thermal collection subsystem.
mum optical response. The test method requires quasi-steady
5.4.1 Whenthistestmethodisusedtoevaluatethecomplete
state conditions, measurement of environmental parameters,
system, the test shall be performed with the manufacturer’s
and determination of the fluid mass flow rate-specific heat
tracker and associated controls, and thus the effects of tracking
product and temperature difference, ∆t , of the heat transfer
a
error on thermal performance will be included in the results.
fluid between the inlet and outlet of the collector. These
Linear single-axis tracking systems may be supplemented with
quantitiesdeterminetherateofheatgain, m˙C ∆t ,forthesolar
p a
the test laboratory’s tracking equipment to effect a two-axis
irradiance condition encountered. The solar power incident on
tracking arrangement.
the collector is determined by the collector area, its angle
5.4.2 When evaluat
...