Experimental and simulated Performance of Hot Mirror Coatings in a Parabolic Trough Receiver

Khaled Mohamad; P. Ferrer; V.S Kaluba

REVIEW 4 major objections 6 minor 39 references

Experimental and simulated Performance of Hot Mirror Coatings in a Parabolic Trough Receiver

T0 review · 4 major / 6 minor · reviewed 2026-08-14 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read Hot mirror coatings can push parabolic trough receiver temperatures past 700 K while keeping the glass cover cool, experiments and simulations show.

desk verdict A useful IR-reflection-only validation of a hot-mirror receiver model, but the leap to transparent coatings above 700 K rests on physics the experiment never exercised. read the letter →

arxiv 1908.00866 v1 pith:EWVULXI4 submitted 2019-08-02 physics.app-ph

V.S Kaluba , Khaled Mohamad , P. Ferrer This is my paper · ORCID

classification physics.app-ph

keywords parabolictroughcollectorhotmirrorcoatinginfraredradiationlossselectiveabsorberindiumtinoxidereceiverheatretentionsolarthermalsimulationtransferfluidtemperature

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

Thermal radiation is the dominant heat-loss channel from a parabolic trough receiver at high temperatures, and the usual remedy—a selective coating on the absorber pipe—becomes chemically and thermally unstable above roughly 500 °C. This paper argues that a hot mirror coating on the inside of the glass cover, which lets sunlight through but reflects infrared emission back to the absorber, can retain heat without that ceiling. The argument combines an indoor experiment with an infrared-reflective sheet and a finite-volume simulation: the hot-mirror absorber ran about 100 °C hotter than the bare unit at 500 W/m power density, and simulated temperatures matched the measurements within a few percent (chi-squared p-values from 0.80 to 0.995), with the simulation underestimating performance. The validated model then predicts that an indium-tin-oxide (ITO) hot mirror lets the heat-transfer fluid exceed 700 K—stagnation above 1200 K—while the glass cover stays below 570 K. If correct, hot mirror receivers open a route to direct high-temperature process heat and higher thermodynamic efficiency, even though a conventional selective coating remains more efficient where its temperature limit is not exceeded.

What carries the argument

The load-bearing mechanism is the hot mirror itself: a glass-cover coating that transmits visible sunlight but reflects infrared emission from the absorber pipe back onto the pipe for reabsorption. The quantitative argument is carried by a finite-volume energy-balance model that breaks the absorber pipe, glass cover, and heat-transfer fluid into control volumes along circumference and length, and enforces steady-state conservation of conduction, convection, radiation, and solar absorption in every element, tracking up to two successive infrared reflections between surfaces. The model is validated against an indoor electrically heated receiver whose surrogate hot mirror is an aluminum sheet with infrared reflectivity about 0.92; after validation, the same model is run with a non-uniform solar flux distribution and reference trough design parameters to compare ITO, gold, and silver coatings.

What would settle it

Take a receiver with an actual ITO hot-mirror coating on the glass cover, illuminate it with concentrated sunlight or a solar simulator using the non-uniform flux profile assumed in the simulations, and compare measured heat-transfer-fluid temperatures with the model's predictions; if temperatures fall more than about 6% below prediction at high power, or if the coating's visible transmissivity degrades after sustained operation above 700 K, the central claim would be undercut.

Watch

Extended reading notes

Core claim

On the paper's own terms, the central discovery is that an infrared-reflective "hot mirror" on the glass cover of a parabolic trough receiver is a workable alternative to selective absorber coatings for reaching high heat-transfer-fluid temperatures. The experiment demonstrates greater heat retention—about 100 °C higher absorber temperature at 500 W/m with the mirror than without—and the simulation reproduces the measured receiver temperatures closely enough (glass-cover p-values above 0.995, absorber p-value 0.80) that the authors call the model "reasonably accurate" and note it slightly underestimates performance. In the realistic simulations, ITO is the best hot mirror material: with roughly 80% visible transmissivity and 85% infrared reflectivity, it reaches stagnation temperatures above 1200 K while the glass cover remains below 570 K, well within the coating's stability range. The paper also concludes that visible transparency contributes more to efficiency than infrared reflectivity, while infrared reflectivity is what raises the temperature ceiling, and that a selective coating plus hot mirror combination offers no clear advantage over either alone.

Load-bearing premise

The entire high-temperature prediction rests on the assumption that an opaque aluminum sheet with about 92% infrared reflectivity, heated electrically indoors, stands in for a real transparent hot mirror coating under concentrated sunlight, so the validation covers only infrared reflection and not visible transmission or realistic flux non-uniformity.

Editorial extensions

If this is right

With a validated model, hot mirror receivers can be designed to deliver heat-transfer-fluid temperatures above 700 K, with ITO reaching stagnation temperatures above 1200 K, enabling direct use in high-temperature industrial processes.
ITO outperforms both gold and silver as a hot mirror material; gold and silver lose so much visible light that they trail even a bare receiver over the first several hundred meters.
For material design, visible transmissivity is the more important property for overall efficiency, while infrared reflectivity sets the ceiling on achievable fluid temperature.
A modern selective coating still beats every simulated hot mirror on efficiency, peaking near 37% versus about 31% for ITO, so hot mirrors are a complement rather than a replacement for selective coatings.
Because selective and hot mirror coatings dominate in different temperature ranges, a receiver segmented by length could use each where it performs best.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

The indoor experiment tests only the infrared-reflection half of a hot mirror's function; the predicted benefits of real transparent coatings such as ITO therefore remain unverified under concentrated, non-uniform sunlight until an outdoor test with an actual coating is run.
The finding that visible transparency dominates efficiency suggests that adding antireflection layers to ITO—or choosing a composite hot mirror with higher solar transmissivity—could close much of the efficiency gap with selective coatings.
If the glass cover indeed stays below 570 K while the absorber runs above 1000 K, hot mirror receivers could relax constraints on glass and sealing materials, potentially lowering receiver cost.
The same energy-balance machinery could be applied to cavity receivers or concentrating photovoltaic-thermal systems, where recycling infrared radiation back to a hot emitter is also the key loss-reduction step.

Share X Bluesky LinkedIn Reddit HN

Signed reviews

No signed human review yet.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

Short version: this is a useful experimental check of the IR-reflection half of a hot-mirror receiver model, but the paper overreaches when it lets that check validate transparent coatings at 700 K plus.

What's new: the indoor experiment using an opaque aluminum sheet (IR reflectivity ~0.92) inside an electrically heated receiver is a real, independent test of the model's IR-reflection treatment, and the agreement (chi-squared p>0.8, max 6% divergence) is decent. The parameter sweep over ITO, gold, silver, and the hypothetical H1/H2 pair is a legitimate extension of earlier modeling by Grena, Cyulinyana/Ferrer, and the authors' own [23]. No fitted constants are introduced to force the match, so the validation is not circular.

Where it's soft: the surrogate does not transmit visible light, so the experiment never constrains the model's visible-transmission and glass-absorption channels. Section 4's predictions, including ITO stagnation above 1200 K, depend precisely on those unexercised channels. The paper explicitly says the sheet's opacity was immaterial because only IR reflection was tested, which is honest but doesn't make the high-temperature predictions any less extrapolated. Also, one data point was dropped from the chi-squared test to get p>0.80, the reported figures don't show error bars, and the simulation under-predicts at high temperatures. None of these are fatal; they all point the same direction: the validation covers less than the conclusions claim.

The selective-coating comparison is fairly done, and the paper itself concedes a modern selective coating beats ITO on efficiency, with hot mirrors attractive mainly for high-temperature process heat. That is a measured and credible conclusion.

Bottom line: somebody modeling receiver heat transfer will get value from the experimental setup and the honest comparison. It deserves serious peer review, but a referee should push for either additional validation of the visible-transmission channel (for example a transparent hot-mirror sample at lower temperature) or a much more careful qualification of the 700 K claim.

Referee Report

4 major / 6 minor

Summary. The paper presents a mathematical model, previously developed in [23], for heat transfer in a parabolic trough receiver unit with a hot mirror coating on the inner side of the glass cover. The model is adapted to an indoor electrically heated receiver unit and validated against experiments using a bare receiver and a receiver whose glass cover is lined with an opaque aluminum sheet of IR reflectivity about 0.92, described as a surrogate for a hot mirror. The simulation agrees with measured temperatures to within about 6%, with chi-squared p-values reported between 0.80 and 0.995. Based on this validation, the paper simulates the performance of realistic hot mirror coatings (ITO, gold, silver) under concentrated solar flux with the Jeter non-uniform flux distribution, concluding that ITO allows heat-transfer-fluid temperatures above 700 K, with stagnation temperatures above 1200 K. The paper also compares hot mirror coatings with conventional selective absorber coatings and with two hypothetical coatings H1 and H2 that isolate the effects of IR reflectivity and visible transmissivity.

Significance. If the validation were complete, the paper would provide a useful design tool for a less-explored route to high-temperature parabolic trough operation: placing an IR-reflecting, visible-transmitting hot mirror on the glass cover instead of (or in addition to) a selective absorber coating. The experimental dataset for the surrogate IR reflector is novel, the model is not fitted to the validation data, and the parameter tables (Tables 1, 2, and 4) make the simulations reproducible. The comparison to existing selective coatings (Section 4.C) is a useful practical benchmark. However, the central experimental validation covers only the IR-reflection path; the visible-transmission path, which is decisive for the Section 4 predictions, is not exercised by the indoor experiment. The overstated reach of the validation is the main weakness.

major comments (4)

[3.1.C] The experimental surrogate is an opaque aluminum sheet with IR reflectivity of about 0.92, not a transparent hot mirror. The paper explicitly states that 'the sheet is not transparent to solar radiation, however, this was immaterial, since in the experiment the effects of IR reflectivity were tested, not of solar transparency.' This is a load-bearing limitation: the indoor experiment has no solar flux passing through the glass cover, so the model's treatment of visible transmission, glass-cover solar absorption, and non-uniform concentrated flux is unconstrained by the reported chi-squared agreement. Section 4 then uses the same model to predict ITO reaching stagnation temperatures above 1200 K and HTF temperatures above 700 K, claims that depend precisely on the visible-transmission channel that the experiment never tests. Please either provide independent validation of the visible-transmission channel (e.g., outdoor or solar-simulator experiments with a transparent hot mirror), or revise the claims in the abstract and Section 4 to explicitly state that the >700 K predictions rest on simulation alone, not on the experimental validation.
[3.1.C] The reported absorber-pipe chi-squared p-value for the hot mirror case is '>0.80', but this is obtained only after excluding the 44°C data point as an outlier, with no statistical or physical justification given. Post-hoc removal of a data point from a goodness-of-fit test inflates the reported p-value and weakens the claim of agreement. Additionally, no error bars are shown in Figures 4 and 5, and the chi-squared calculation is not described (e.g., which uncertainties were used). Please provide a transparent description of the chi-squared procedure, the justification for outlier exclusion, and error bars on the experimental data points.
[4.A] The simulation is validated only up to approximately 500°C (about 773 K) for the absorber pipe, and even there the model under-predicts the experimental temperature by up to 6%, attributed to 'temperature dependent simulation parameters.' The Section 4 predictions for ITO extend to HTF temperatures above 700 K and stagnation temperatures above 1200 K, far beyond the validated range. The systematic under-prediction at the high end of the experimental range means the extrapolation is not conservative. Please state the validated temperature range explicitly when presenting the Section 4 results, and discuss how the known under-prediction bias affects the ITO stagnation-temperature and efficiency claims.
[2] The model truncates radiation exchange after two consecutive reflections (Section 2) and uses a gray-body treatment for the absorber pipe (Table 2). The experimental aluminum sheet is an opaque specular reflector, whereas the simulated ITO, gold, and silver coatings are transparent in the visible with angle-dependent properties implied by thin-film multilayers. It is not demonstrated that two-reflection truncation and gray-body assumptions remain accurate for the multilayer transparent coatings at the high temperatures of Section 4. Please add a sensitivity test or a justification that the truncation error is negligible for the coating configurations considered.

minor comments (6)

[Abstract] The abstract contains 'in a solar through receiver' which should read 'in a solar trough receiver.'
[Figure 12] The Figure 12 caption reads 'SC, SC+ITO, ITO' while the text in Section 4.C describes the scenarios as 'SC', 'SC+HM', and 'HM'. Please reconcile the notation.
[3.1.C] The text states the simulation underestimates experimental performance by 'at most 6% at around 500 Co'; please also give the corresponding temperature in kelvin to match the rest of the paper.
[4] The symbol 'q̇_AF,conv' in Equation (2) is defined after being used; please define all symbols at first use. Also, Equation (5) uses 'Tres' and 'THTF' with inconsistent subscript styles.
[References] Several references use abbreviated author names (e.g., 'P W and DY L', 'KS R and KR K'); these should be converted to a consistent journal style for completeness.
[4.B] The hypothetical materials H1 and H2 are useful for isolating parameter effects, but the text should state more clearly that they are not physical materials and that their parameter combinations may not be simultaneously realizable in practice.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: the simulation is validated against independent measurements with no fitted parameters; Section 4 predictions are extensions with a validation-scope caveat, not reductions to inputs.

full rationale

The paper's derivation chain is: (i) a finite-volume heat-balance model from the authors' prior work [23] is adapted to an indoor electrically heated receiver; (ii) measured temperatures for a bare receiver and a receiver with an IR-reflective aluminum sheet are compared with simulation using chi-squared goodness-of-fit tests; (iii) the same simulation, with Jeter solar flux, is used to compare ITO, gold and silver hot-mirror options. No parameter is fitted to the experimental data: the code is changed only to replace solar heating with electrical heat generation, and no prediction is defined in terms of the measured outcomes. The p-values are goodness-of-fit statistics, not calibration targets, so the Section 4 predictions do not reduce by construction to the experimental inputs. The only self-citations ([23], [27]) supply the code and prior modeling, but the indoor experiment is an independent check of that code's IR-reflection channel, and the quoted agreement is not forced by a fitted coefficient. The paper itself flags the key limitation in §3.1.C: 'The sheet is not transparent to solar radiation, however, this was immaterial, since in the experiment the effects of IR reflectivity were tested, not of solar transparency' — this is a genuine validation-coverage gap for the later transparent-coating predictions (visible transmission and glass solar absorption are not exercised by the experiment), but it is a correctness/extrapolation concern, not circularity. There is no uniqueness theorem imported from the authors, no ansatz smuggled via citation, no renaming of a known result, and no fitted input renamed as a prediction. The central experimental validation is self-contained against an independent measurement, and the Section 4 simulations follow from stated optical properties and a physical model. Score 0.

Assumptions & free parameters 4 free parameters · 6 assumptions · 1 invented entities

No free parameters are explicitly fitted to the experimental data, but many optical constants are selected from literature or datasheets, and the model relies on a two-reflection truncation and gray/diffuse assumptions. The central validation also leans on the equivalence between an opaque aluminum sheet and a transparent hot mirror, which is an assumption rather than a demonstrated fact.

free parameters (4)

Experimental surrogate IR reflectivity = 0.92 (from MIRO SUN Alanod datasheet)
The indoor validation depends on the reflectivity of the aluminum sheet, which was taken from manufacturer data rather than measured in the experiment.
Glass cover visible and IR optical properties for simulated coatings = e.g., ITO visible transmissivity 0.875, IR reflectivity 0.85; gold 0.44 and 0.78; silver 0.40 and 0.95 (Table 2)
The Section 4 predictions for ITO, gold and silver use literature values chosen by the authors; the central claim that ITO reaches high temperatures depends on these selected inputs.
Absorber pipe emissivity and reflectivity = 0.15 emissivity (Table 1); IR reflectivity 0.14 (Table 2)
The absorber is assumed gray and its optical properties are specified rather than measured for the simulated receiver; the validation experiment used an uncoated mild steel pipe with an unknown emissivity.
Hypothetical H1 and H2 optical properties = H1: visible transmissivity 0.875, IR reflectivity 0.95; H2: visible transmissivity 0.95, IR reflectivity 0.85 (Table 3)
These materials are introduced by hand to isolate the effects of visible transmissivity and IR reflectivity; they have no measured or physical realization.

assumptions (6)

domain assumption Steady-state energy balance with negligible thermal capacitance and control-volume discretization.
Section 2 imposes Eq. (1) on every control volume under steady state; experiments wait up to about three hours for equilibrium, but axial conduction and circumferential non-uniformities are simplified.
ad hoc to paper Radiation exchange can be truncated after two consecutive reflections.
Section 2 states 'Up to two consecutive reflections are taking into account'; no convergence study is shown to justify this truncation for the multi-bounce receiver cavity.
domain assumption The absorber pipe and coatings are gray and diffuse with constant spectral values in Tables 1 to 4.
Section 3.1.C states the bare pipe 'is assumed gray in its spectral characteristics'; actual spectral selectivity and directional dependence are not modeled.
ad hoc to paper The opaque aluminum sheet used in the experiment behaves equivalently to a transparent hot mirror coating for model validation.
Used in Section 3.1.C; the sheet tests IR reflection only, while the model also treats visible transmission as part of the hot mirror concept.
domain assumption The Gnielinski correlation accurately describes convection inside the absorber pipe.
Section 2 cites Gnielinski [24]; validity depends on Reynolds and Prandtl ranges and surface roughness, which are not checked in the paper.
domain assumption The Jeter solar flux distribution accurately represents concentrated solar flux for the LS2 geometry.
Section 3.1.D uses Jeter [28] for the non-uniform heat flux; the experimental validation used symmetric electrical heating, so this distribution is not validated experimentally.

invented entities (1)

Hypothetical hot mirror materials H1 and H2
purpose: Isolate the effects of high IR reflectivity versus high visible transmissivity on receiver performance.
No physical realization or measured spectra are provided; the optical properties are chosen by hand in Table 3 to bracket behavior.

how reviews work

0 comments

Cite this review

Pith. "Pith review of Experimental and simulated Performance of Hot Mirror Coatings in a Parabolic Trough Receiver." pith.science (2026). https://pith.science/paper/EWVULXI4

@misc{pith2026190800866,
  author       = {Pith},
  title        = {Pith review of: Experimental and simulated Performance of Hot Mirror Coatings in a Parabolic Trough Receiver},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/EWVULXI4}},
  note         = {Machine review of arXiv:1908.00866}
}

read the original abstract

Thermal radiation is the dominant heat loss mechanism for receiver units on a parabolic solar collector plant at high temperatures. Reduction of these losses is traditionally achieved through the use of an optically selective coating on the absorber pipe, which absorbs visible light well but emits poorly in the IR region. Another possibility is the use of a hot mirror coating on the glass cover of the receiver, which reflects thermal radiation back onto the absorber pipe for reabsorption. In this paper, novel experimental results of a receiver unit operating with a hot mirror coating is presented, and the results between a developed model and a simulation are compared. It is seen that the correspondence is encouragingly close (Chi-squared test p-values between 0.995 and 0.80), where the simulation underestimates the experimental performance. Further, simulations to investigate the performance of various candidates for hot mirror coating (ITO, Gold and Silver) in solar through the receiver are presented, where it is seen that the hot mirror coating has access to higher temperature regions (above 700K). Lastly, simulation of the effects of variation of some optical parameters on overall plant efficiency, and comparison to existing selective coatings is presented.

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

39 extracted references · 39 canonical work pages

[23]

Kennedy C E 2002 Review of mid-to high-temperature solar selective absorber materials (National Renewable Energy Lab., Golden, CO.(US))

work page 2002
[1]

hot mirror

Introduction Parabolic trough collectors (PTC) are amongst the most mature commercially developed solar power technologie s [1]. They operate by focusing solar radiation along a line onto a receiver unit which exchanges h eat with a circulating heat transfer fluid (HTF). The heat gained by the HTF can be used either directly or for electricity production ...

work page
[2]

local” efficiency for any CV element is 𝜂𝐶𝑉 = (𝑞̇𝐴𝐹,𝑐𝑜𝑛𝑣)𝑗 (𝑞𝑠𝑜𝑙)𝑗 (3) where 𝑞𝑠𝑜𝑙 the incident solar flux, and (𝑞̇𝐴𝐹,𝑐𝑜𝑛𝑣)𝑗 is defined by equation ( 2). The “integrated

Mathematical Model A model was developed that describes the different heat transfer interactions inside receiver unit, allowing for a hot mirror coating on the inside of the glass cover. In this section, this model is briefly described. More detail can be found in Reference [23]. The physical basis for our model uses energy conservation for the thermal in...

work page
[3]

ho t mirror

Experiment and code validation 3.1. Experimental analysis A receiver unit was constructed in order to validate the theory and simulation described in the previous section. The unit was constructed as it would be used in a functional PTC but was heated by heating elements situated inside the absorber tube, as opposed to from the outside by concentrated sun...

work page
[4]

However, to obtain a good IR reflectivity (>80%), the solar transmissivity of a simple metal layer becomes quite limited (less than 40%)

Thin metal layers: A good IR reflector can be made by depositing on the glass substrate a thin metal film, made of a metal with a low IR emissivity, such as silver, gold, copper, or aluminum. However, to obtain a good IR reflectivity (>80%), the solar transmissivity of a simple metal layer becomes quite limited (less than 40%). Silver has a higher solar t...

work page
[5]

A 200nm film of Indium Tin Oxide (In2O3:Sn) has a solar transmissivity of about 80%, with an IR -reflective coefficient of 75%

Doped semiconductors with an appropriate band gap: Compared to metal films, doped semiconductor thin layers have usually a lower IR -reflective coefficient (usually less than 85%) but they have a better transparency for the visible light (up to 80%). A 200nm film of Indium Tin Oxide (In2O3:Sn) has a solar transmissivity of about 80%, with an IR -reflectiv...

work page
[6]

Composite layers are usually made by a th in noble metal layer between transparent dielectric layers

Composite layers: The solar transmissivity of a metal thin film can be increased using a material with high refractive index as an antireflective layer. Composite layers are usually made by a th in noble metal layer between transparent dielectric layers. The solar transmissivity can be increased above 70%, but the realization is more difficult, since diff...

work page
[7]

Simulation Results A. Comparative performance of hot mirror coatings Simulations were constructed for the different coating materials: bare, ITO, Gold and Silver subject to th e parameters of Table 1 and Table 2. T he question of how the different coatings affect a variety of parameters such as the thermal distribution of the HTF along the length, the the...

work page

Show all 39 references

[8]

Conclusion The experimental results from the bare and hot mirror coated receiver unit indicated that the hot mirror system was capable of greater heat retention, which was evident by the higher temperature that was reached, around 100oC at 500 W/m power density. Further, the C...
[9]

IER 1–86

Porta F L 2005 Technical and economical analysis of future perspectives of solar thermal power plants Rep. IER 1–86

2005
[10]

Cohen Gilbert E, Kearney D W and Kolb G J 1999 Final report on the operation and maintenance improvement program for concentrating solar power plants (Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA)

1999
[11]

Fuqiang W and Ziming C 2017 Progress in concentrated solar power technology with parabolic trough collector system: A comprehensive review Renew. Sustain. Energy Rev. 79 1314–28

2017
[12]

Energy 102 449–60

P W and DY L 2013 Numerical study of heat transfer enhancement in the receiver tube of direct steam generation with parabolic trough by inserting metal foams Appl. Energy 102 449–60

2013
[13]

Energy 77 308–19

KS R and KR K 2015 Experimental investigation of porous disc enhanced receiver for solar parabolic trough collector Renew. Energy 77 308–19

2015
[14]

SE G and AA R 2017 Numerical thermal study on effect of porous rings on performance of solar parabolic trough collector Appl. Therm. Eng. 118 807–16

2017
[15]

Energy 136 989–1003

A M and T B-O 2014 Heat transfer and thermodynamic performance of a parabolic trough receiver with centrally placed perforated plate inserts Appl. Energy 136 989–1003

2014
[16]

HM S and E B 2015 Investigation of heat transfer enhancement in a new type heat exchanger using solar parabolic trough systems Int. J. Hydrog. Energy 40 15254–66

2015
[17]

Z H and ZY L 2017 Numerical investigations on fully-developed mixed turbulent convection in dimpled parabolic trough receiver tubes Appl. Therm. Eng. 114 1287–99

2017
[18]

ZD C and YL H 2012 Numerical study of heat transfer enhancement by unilateral longitudinal vortex generators inside parabolic trough solar receivers Int. J. Heat Mass Transf. 55 5631–41

2012
[19]

Energy 164 411–24

W F and L Q 2016 Parabolic trough receiver with corrugated tube for improving heat transfer and thermal deformation characteristics Appl. Energy 164 411–24

2016
[20]

W F and T Z 2016 Heat transfer performance enhancement and thermal strain restrain of tube receiver for parabolic trough solar collector by using asymmetric outward convex corrugated tube Energy 114 275–92

2016
[21]

Energy 94 213–22

E B and C T 2016 Thermal enhancement of solar parabolic trough collectors by using nanofluids and converging-diverging absorber tube Renew. Energy 94 213–22

2016
[22]

Hassani S, Saidur R, Mekhilef S and Hepbasli A 2015 A new correlation for predicting the thermal conductivity of nanofluids; using dimensional analysis Int. J. Heat Mass Transf. 90 121–30

2015
[24]

Granqvist C G 1985 Spectrally Selective Coatings for Energy Efficiency and Solar Applications Phys. Scr. 32 401

1985
[25]

Non-selective and energy control films Sol

Lampert C M 1979 Coatings for enhanced photothermal energy collection II. Non-selective and energy control films Sol. Energy Mater. 2 1–17

1979
[26]

ASE Archimede Solar Energy
[27]

Canan K 2013 Performance analysis of a novel concentrating photovoltaic combined system Energy Convers. Manag. 67 186–96

2013
[28]

Energy Mater

Miller D C, Khonkar H I, Herrero R, Antón I, Johnson D K, Hornung T, Schmid-Schirling T, Vinzant T B, Deutch S, To B, Sala G and Kurtz S R 2017 An end of service life assessment of PMMA lenses from veteran concentrator photovoltaic systems Sol. Energy Mater. Sol. Cells 167 7–21

2017
[29]

Grena R 2011 Efficiency Gain of a Solar Trough Collector Due to an IR-Reflective Film on the Non- Irradiated Part of the Receiver Int. J. Green Energy 8 715–33

2011
[30]

Cyulinyana M C and Ferrer P 2011 Heat efficiency of a solar trough receiver with a hot mirror compared to a selective coating South Afr. J. Sci. 107 01–07

2011
[31]

Kaluba V S and Ferrer P 2016 A model for hot mirror coating on solar parabolic trough receivers J. Renew. Sustain. Energy 8 053703

2016
[32]

Gnielinski V 1975 New equations for heat and mass transfer in the turbulent flow in pipes and channels NASA STIrecon Tech. Rep. A 75 8–16

1975
[33]

Pech A J and Soberanis M E 2012 Efficiency curves analysis of a parabolic trough solar collector in the Yucatan Peninsula J. Renew. Sustain. Energy 4 021203

2012
[34]

Forristall R 2003 Heat transfer analysis and modeling of a parabolic trough solar receiver implemented in engineering equation solver (National Renewable Energy Lab., Golden, CO.(US))

2003
[35]

Energy 238 1250–1257

Mohamad K and Ferrer P 2019 Parabolic trough efficiency gain through use of a cavity absorber with a hot mirror Appl. Energy 238 1250–1257

2019
[36]

Energy 37 335–345

Jeter S M 1986 Calculation of the concentrated flux density distribution in parabolic trough collectors by a semifinite formulation Sol. Energy 37 335–345

1986
[37]

Dudley V E, Kolb G J, Mahoney A R, Mancini T R, Matthews C W, Sloan M and Kearney D 1994 Test Results: Segs Ls-2 Solar Collector (Sandia National Labs., Albuquerque, NM (United States))

1994
[38]

I - Selective absorbers Sol

Lampert C M 1979 Coatings for enhanced photothermal energy collection. I - Selective absorbers Sol. Energy Mater. 1 319–41

1979
[39]

Allegrezza M, Canino M, Bellettato M and Summonte C 2014 Transparent conducting oxides for high temperature processing Energy Procedia 44 23–31

2014

Pith tools

Reviewed August 14, 2026 · model on record in the stance chip above.

[1] [23]

Kennedy C E 2002 Review of mid-to high-temperature solar selective absorber materials (National Renewable Energy Lab., Golden, CO.(US))

work page 2002

[2] [1]

hot mirror

Introduction Parabolic trough collectors (PTC) are amongst the most mature commercially developed solar power technologie s [1]. They operate by focusing solar radiation along a line onto a receiver unit which exchanges h eat with a circulating heat transfer fluid (HTF). The heat gained by the HTF can be used either directly or for electricity production ...

work page

[3] [2]

local” efficiency for any CV element is 𝜂𝐶𝑉 = (𝑞̇𝐴𝐹,𝑐𝑜𝑛𝑣)𝑗 (𝑞𝑠𝑜𝑙)𝑗 (3) where 𝑞𝑠𝑜𝑙 the incident solar flux, and (𝑞̇𝐴𝐹,𝑐𝑜𝑛𝑣)𝑗 is defined by equation ( 2). The “integrated

Mathematical Model A model was developed that describes the different heat transfer interactions inside receiver unit, allowing for a hot mirror coating on the inside of the glass cover. In this section, this model is briefly described. More detail can be found in Reference [23]. The physical basis for our model uses energy conservation for the thermal in...

work page

[4] [3]

ho t mirror

Experiment and code validation 3.1. Experimental analysis A receiver unit was constructed in order to validate the theory and simulation described in the previous section. The unit was constructed as it would be used in a functional PTC but was heated by heating elements situated inside the absorber tube, as opposed to from the outside by concentrated sun...

work page

[5] [4]

However, to obtain a good IR reflectivity (>80%), the solar transmissivity of a simple metal layer becomes quite limited (less than 40%)

Thin metal layers: A good IR reflector can be made by depositing on the glass substrate a thin metal film, made of a metal with a low IR emissivity, such as silver, gold, copper, or aluminum. However, to obtain a good IR reflectivity (>80%), the solar transmissivity of a simple metal layer becomes quite limited (less than 40%). Silver has a higher solar t...

work page

[6] [5]

A 200nm film of Indium Tin Oxide (In2O3:Sn) has a solar transmissivity of about 80%, with an IR -reflective coefficient of 75%

Doped semiconductors with an appropriate band gap: Compared to metal films, doped semiconductor thin layers have usually a lower IR -reflective coefficient (usually less than 85%) but they have a better transparency for the visible light (up to 80%). A 200nm film of Indium Tin Oxide (In2O3:Sn) has a solar transmissivity of about 80%, with an IR -reflectiv...

work page

[7] [6]

Composite layers are usually made by a th in noble metal layer between transparent dielectric layers

Composite layers: The solar transmissivity of a metal thin film can be increased using a material with high refractive index as an antireflective layer. Composite layers are usually made by a th in noble metal layer between transparent dielectric layers. The solar transmissivity can be increased above 70%, but the realization is more difficult, since diff...

work page

[8] [7]

Simulation Results A. Comparative performance of hot mirror coatings Simulations were constructed for the different coating materials: bare, ITO, Gold and Silver subject to th e parameters of Table 1 and Table 2. T he question of how the different coatings affect a variety of parameters such as the thermal distribution of the HTF along the length, the the...

work page