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WO1989008271A1 - Transformation d'energie solaire a flux intense - Google Patents

Transformation d'energie solaire a flux intense Download PDF

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Publication number
WO1989008271A1
WO1989008271A1 PCT/US1989/000878 US8900878W WO8908271A1 WO 1989008271 A1 WO1989008271 A1 WO 1989008271A1 US 8900878 W US8900878 W US 8900878W WO 8908271 A1 WO8908271 A1 WO 8908271A1
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WO
WIPO (PCT)
Prior art keywords
stage
concentrative
solar energy
solar
primary
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1989/000878
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English (en)
Inventor
Roland Winston
Philip L. Gleckmann
Joseph J. O'gallagher
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Arch Development Corp
Original Assignee
Arch Development Corp
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Filing date
Publication date
Application filed by Arch Development Corp filed Critical Arch Development Corp
Publication of WO1989008271A1 publication Critical patent/WO1989008271A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
    • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
    • F24S23/79—Arrangements for concentrating solar-rays for solar heat collectors with reflectors with spaced and opposed interacting reflective surfaces
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
    • G02B19/0019—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having reflective surfaces only (e.g. louvre systems, systems with multiple planar reflectors)
    • G02B19/0023—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having reflective surfaces only (e.g. louvre systems, systems with multiple planar reflectors) at least one surface having optical power
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
    • G02B19/0028—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed refractive and reflective surfaces, e.g. non-imaging catadioptric systems
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
    • G02B19/0038—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with ambient light
    • G02B19/0042—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with ambient light for use with direct solar radiation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S50/00—Arrangements for controlling solar heat collectors
    • F24S50/20—Arrangements for controlling solar heat collectors for tracking
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/40—Solar thermal energy, e.g. solar towers
    • Y02E10/44—Heat exchange systems

Definitions

  • the present invention relates generally to radiant energy concentration and more particularly to high flux solar energy transformation systems suitable for use as energy sources for. a variety of applications including laser pumping. Numerous potential applications exist for concentrated solar photothermal energy. As one example, solar energy has been proposed as an energy source for the pumping of (e.g., satellite-based) neodymium-doped YAG crystal lasers [see, e.g...
  • parabolic mirror forms an aplanatic image of the center of the sun in the center of its focal plane. It follows then from brightness conservation that the irradiance at the center of the image is given by
  • ⁇ is the Stefan-Boltzmann constant
  • T is the absolute temperature
  • ⁇ is the rim angle, i.e., the semi-angle subtended by the parabola from the center of the focal plane.
  • This concentration ratio is a maximum for a 45° rim angle, where it has a value of 11,500.
  • Non-imaging concen ⁇ trators are developed according to two basic design principles: the "extreme ray” or "maximum slope".prin ⁇ ciple (see, e.g., U.S. Letters Patent No.
  • Non-imaging concen ⁇ trators may optionally be "filled” with a refractive, "dielectric” fluid or formed from a refractive solid, allowing for enhancement in concentrative capacity [see, e.g., U.S. Letters Patent No. 4,240,692; Ning et al., J.Opt.Soc.Am., 26, 300-305 (1987); and Ning et al., J.Opt.Soc.Am., 26, 1207-1212 (1987)].
  • a refractive, "dielectric” fluid or formed from a refractive solid allowing for enhancement in concentrative capacity
  • Such composite devices when employed in solar furnace and photovoltaic transformation appli- cations, are generally designed to include relatively "fast" primary mirrors or lenses with focal ratios on the order of 0.5 to about 1.5 and non-imaging secondary concentrators with concentrative capacities on the order of 10 to 20.
  • Such systems would be capable of providing uniform concentration of solar flux with net solar intensification by factors in excess of those heretofore achieved.
  • multi ⁇ stage solar radiant energy transformation systems are provided which allow for solar energy intensification by factors well in excess of any heretofore achievable.
  • systems of the invention are seen to comprise a primary solar energy focusing device (pref ⁇ erably a mirror or lens) associated with a secondary, non-imaging energy concentrator (preferably shaped according to extreme ray or geometric vector flux-prin ⁇ ciples).
  • the secondary stage is disposed at or near the focus of the primary stage device to receive solar energy therefrom and the concentrative capacities of primary and secondary stages are selected and coordi ⁇ nated to allow for a minimum solar intensification of at least 2000 suns, uniformly distributed at the second stage energy exit aperture (i.e., distributed over an area intercepting 95 percent of the concentrated energy) .
  • Preferred systems readily achieve uniformly distributed concentrations of 10,000 suns or more, and those systems including a secondary concentrator which comprise a high refractive index solid or fluid refract- ing medium are capable of providing intensification of greater than the.46,000 sun theoretical maximum concen ⁇ tration in air.
  • the primary stage has a focal ratio of greater than 2.0 and the secondary stage is designed to concentrate by a factor of about 50 or more.
  • Refractive medium filled systems include solid or fluid media which preferably having a refractive index in excess of about 1.3.
  • Solid refractive non-imaging second stage concentrators may be provided which are totally internally reflective.
  • a presently preferred prototypical, embodiment of the systems of the invention comprises a primary focusing mirror device having a focal ratio of about 2.5.
  • a secondary non-imaging device filled with a refractive oil (having a refractive index of about 1.53) and designed for a concentration by a factor of about 60.
  • a refractive oil having a refractive index of about 1.53
  • this illustrative system allows for solar intensification of approximately 60,000 suns and a corresponding irradiance of about 5 kW cm .
  • Systems of the invention are readil applied as energy sources for laser pumping and in other photo- thermal energy utilization processes.
  • Figure 1 is a schematic representation of a two-stage system according to the invention
  • Figure 2 graphically represents irradiance distributions derived from a Monte Carlo raytrace pro- gram for primary and secondary stages of a device according to the invention
  • FIGS. 3 and 4 illustrate operation of a second stage device in practice of the invention.
  • Figures 5, 6 and 7 illustrate results of pro- cedures to determine exit irradiance in practice of the invention.
  • the present invention relates to multi-stage solar concentrator devices wherein the major concentra ⁇ tive elements include both focusing and non-imaging devices whose designs are selected and coordinated to achieve solar flux intensification approaching thermo- dynamic limits.
  • the assembly and operation of system components according to the invention is believed to be clearly illustrated by the following examples wherein Example 1 relates to the construction of a two-stage device and Example 2 relates to the use of the device to secure uniform irradiance over the entirety of the exit aperture of the secondary concentrator which is nearly four times the highest irradiation previously reported to have been achieved over an extremely limited area and well in excess of 20 times the irradiation reported to have been achieved over an area intercepting 95 percent of the solar energy.
  • EXAMPLE 1 Construction of a multi-stage apparatus according to the invention is illustrated in Figure 1, wherein the system 10 is seen to include, as a primary stage a focusing mirror 20, and as a secondary stage a non-imaging concentrator 30.
  • the primary stage mirror was a 40.6 cm parabolic telescope mirror, with a thickness to diameter ratio of 1:6.
  • the mirror is designed to have a rim angle of 11.5 degrees, gener ⁇ ating a focal ratio of 2.5 and a theoretical maximum concentrative capacity at its 0.98 diameter image of 730.
  • the mirror was held on an equatorial mount (not shown) which continuously tracks the sun, and supported on a Novak nine-point flotation mirror cell. Also attached to the mount was an Eppley normal incidence pyrheliometer (NIP) which continuously measured solar beam radiation. Focusing of the solar image on the secondary stage was done visually under attenuated light by adjusting a microscope focusing mechanism. The highest irradiance was achieved with a chemical silver coating on the primary. Because it would have reduced the broadband reflectivity, no protective dielectric overcoat was used on the silver. Protection was pro- vided instead by keeping the mirror in a nitrogen enriched environment.
  • Non-imaging concentrator 30 is disposed at the focal plane of mirror 10.
  • the secondary concentrator was designed according to the extreme ray non-imaging concentrator principle [as illustrated, for example, in Winston, SPIE Proceedings, 692, 224-226 (1986)] whereby one images the edge of the source at the edge of the exit aperture as illustrated in Figure 3.
  • the concentrator thus included a hollow vessel 31 fabricated from 99.9 percent pure silver which had been melted and hydraulically pressed onto a convex mandrel machined to a tolerance of a few thousandths of an inch.
  • the resulting vessel was 1.2 cm long, had an entrance aperture of 0.98 cm, an exit aperture of 1.27 mm and an acceptance angle of 11.5, resulting in a theoretical maximum concentration (air-filled) capacity of 59.7.
  • the vessel was then filled with immersion oil (1160, R.P. Cargille Laboratories , Cedar Grove, N.J.) which was selected for its high index of refraction and transmissivity over the solar spectrum.
  • the index of refraction was measured using a hollow prism spectro- graph at various visible wavelengths of mercury.
  • the infrared index was extrapolated using the Cauchy equa ⁇ tion and was found to range from 1.52 at 1000 nm to 1.56 at 400 nm.
  • the internal transmission of 1 cm of the oil was measured using a Perkin-Elmer Model 330 spectro- photometer and it was found that the solar average transmission for 1.2 cm of the oil (the oil depth in the secondary) was calculated to be 91%.
  • the vessel was capped by a plano-convex lens
  • the secondary stage was -assembled in the following sequence. First, the lens was mounted in between the empty vessel and a flange which has an aperture the size of the solar image.
  • a filter was constructed to remove light that would be absorbed by the oil in the secondary.
  • the ideal filter for this job consists of two thin anti- reflection coated glass windows surrounding an optimized thickness of the same oil used in the secondary. A 1 cm thickness was chosen on the basis of a tradeoff between lowering absorption in the secondary and maintaining a high throughput. The overall effect of the filter was to halve the absorption in the secondary while reducing the net transmission by only 3.7%.
  • thermodynamic limit By placing a noni aging secondary device 30 in the focal plane of the parabolic mirror 20, an irrad ⁇ iance at the thermodynamic limit can be produced uniformly over the entire exit aperture. Furthermore, because the secondary stage is filled with a material with index of refraction (n) greater than one, the ther- modynamic limit is increased by a factor of n . In a two-stage system, the secondary stage entrance aperture is made to coincide with the solar image, and the acceptance angle of the secondary is made to coincide with the rim angle of the primary and the etendue is conserved. The index of refraction and the acceptance angle of the secondary determine its concentration, according to the theoretical limit:
  • the net geometric concentration of a two-stage nonimag ⁇ ing concentrator is therefore the product of the con- centration of each stage.
  • the two-stage concentrator consisting of an 11.5° (f/2.5) rim angle primary mirror, and the second ⁇ ary stage filled with a medium having a refractive index of 1.53 allows a net geometrical concentration ratio of 102,000, the aberrations causing only a 4% reduction from the thermodynamic limit.
  • Figure 2 shows the results of irradiance dis ⁇ tributions for the secondary stage, non-imaging concen ⁇ trator as calculated with a Monte Carlo raytrace pro ⁇ gram.
  • the upper left plot depicts the entrance in posi- tion space with the circle corresponding to the entrance aperture; the upper right plot depicts the secondary stage exit in position space with the circle correspond ⁇ ing to the exit aperture; the lower left plot is of the secondary entrance in direction cosine space with the circle corresponding to the primary reflector rim angle; and, the lower right plot is of the secondary exit in direction cosine space with the circle corresponding to 90°. All four plots show a high degree of uniformity.
  • the spatial entrance distribution is slightly rounded as a result of limb darkening.
  • the uniformity at the exit is a consequence of two factors: the average brightness is nearly equal to the thermodynamic limit, and the local brightness must not exceed the limit.
  • the following example relates to projection and actual measurement of the efficiency in solar flux concentration of the prototype multi-stage system of Example 1.
  • Deviations from ideal performance resulting from the optical materials and design employed in assembly of the system of Example 1 were calculated as follows in order to ascertain the likely variance of actual solar energy incidence and geometric projec- tion.
  • the primary stage losses were an approxi ⁇ mately 3% loss due to reflection inefficiency of the primary mirror and an approximately 15% loss due to extensive, mirror shading as a result of extensive, substantially oversized support elements employed to support the secondary concentrator calorimeter measuring device between the mirror and the solar source.
  • the net primary receiver efficiency was 82.4%.
  • a preliminary measurement of the efficiency of the secondary stage was made with a solar cell optically coupled to the exit aperture and the secondary concen ⁇ trator in place at the primary mirror focal plane.
  • An unsilvered primary was used to keep the light level low. Reflection off the glass surface of the uncoated mirror was sufficient to make the measurement. The measurement agree with the above calculation within three percent.
  • the dewar In the calorimeter employed to measure exit irradiance, the dewar is filled to capacity with 70 ml of the same immersion oil contained in the secondary stage.
  • the dewar is covered by a flange made of G-10, a glass-epoxy composite having a thermal conductivity comparable to the oil.
  • Nonuniformity in the oil temperature is mini ⁇ mized by stirring continuously during an experimental run, using a magnetic bar which rotates on a shaft at the base of the dewar.
  • the bar is driven by another magnet fixed to a motor outside the dewar.
  • the heating • caused by the stirring process is negligible.
  • the heater employed for calibration was com ⁇ posed of Teflon sewn with nichrome wire, and had a resistance of 9 ohms.
  • the DC electrical power was determined from the product of the measured current and measured four-wire voltage.
  • thermocouples Two light-shielded nichrome-constantan thermo ⁇ couples were at different, shallow and deep positions in the oil. Without shielding, the thermocouples warm up very quickly from direct optical absorption. A third thermocouple is inserted tightly into the body of the cast silver secondary concentrator vessel.
  • a high irradiance testing procedure was per- formed by first measuring the temperature rise of the oil when the primary is illuminated. Typical warm-up curves are shown in Figure 5.
  • This Figure plots temp ⁇ erature versus time during solar heating with triangles, circles and crosses respectively indicating the- concen- trator vessel and shallow and deep thermocouple read ⁇ ings, and vertical bars indicating the opening and clos ⁇ ing of the primary mirror to sunlight.
  • the average rate of temperature rise, ⁇ T gun / ⁇ t was taken from the temp ⁇ erature at the starting point (primary open) and at the isothermal ending point (primary closed). Readings from the two thermocouples in the oil were averaged.
  • the final temperature was chosen low enough so that the oil refractive index and vessel reflectivity are not signi ⁇ ficantly reduced.
  • the boiling point of the oil is 370°C at one atmosphere pressure.
  • the average rate of temp- erature rise for this run was .2428° C/sec, and the average beam insolation was 888 Wm .
  • the heat transfer coefficient was determined by measuring the temperature rise of both the oil and secondary vessel while heat was being applied to the vessel by a soldering iron. The conditions were kept exactly the same as during the solar heating experi ⁇ ment: the dewar was upside-down, and the oil was stirred. The warm-up curves are shown in Figure 7. The temperature rises were calibrated by the electrical heater. A value for h of 947 ⁇ 100 m ⁇ 2 C "1 was obtained. Therefore, Q sun is 4.1 W and Q el is 1.3 W. With this (7%) correction, a value of P opt of 61.4 W is determined.
  • the irradiance ratio is defined as the ratio of the irradiance exiting the concentrator to the inci ⁇ dent direct irradiance as measured using a normal inci ⁇ dence pyranometer (NIP).
  • NIP normal inci ⁇ dence pyranometer
  • the NIP measures all of the incident irradiance contained within its 2.75° accept- ance angle and because the sun subtends only .27°, the NIP measurement includes circumsolar radiation.
  • the circumsolar to beam (circumsolar plus direct) ratio was measured using a solar cell. The cell was placed in the primary focal plane. A mask with an aperture equal to the size of the solar image was mounted on the cell.
  • the other end of the rod is either uncoated for an external output mirror or coated with a partially transparent dielectric mirror. .
  • the rod sides are uncoated and the rod maintains high pump con- centration using total internal reflection.
  • _ Preli ⁇ minary estimates- of substantial comparative efficiencies of solar pumped dye lasers in keeping with the invention (compared, for example, to argon ion pumped lasers) take into account the fact that the overall efficiency.of the system is essentially limited only by the efficiency of the dye laser component itself in solar pumped devices.
  • Skew ray losses may also be eliminated by flow line designs and intravessel reflec- tions would be made negligible through use of a totally internally reflective secondary concentrator. Net secondary stage efficiencies on the order of about 94% could thus be projected and the combined effect of both primary and secondary efficiencies could thus provide for a net system efficiency on the order of 85% rather than 62.4% achieved by the prototype.

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  • Life Sciences & Earth Sciences (AREA)
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Abstract

L'invention concerne des systèmes multi-étages (10) pour la transformation à flux intense d'énergie solaire permettant une intensification solaire uniforme par un facteur de 60 000 soleils ou plus. Des systèmes préférés utilisent un miroir de focalisation (20)en tant que dispositif de concentration primaire et un concentrateur de non-imagerie (30) en tant que dispositif de concentration secondaire, les capacités de concentration des étages primaire et secondaire (20, 30) étant choisis pour obtenir une intensification nette du flux solaire supérieure à 2000 sur 95% de la zone de concentration. Les systèmes de l'invention s'appliquent particulièrement bien comme sources d'énergie pour le pompage au laser et dans d'autres procédés d'utilisation de l'énergie photothermique.
PCT/US1989/000878 1988-03-04 1989-03-03 Transformation d'energie solaire a flux intense Ceased WO1989008271A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US16406988A 1988-03-04 1988-03-04
US164,069 1988-03-04

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WO1989008271A1 true WO1989008271A1 (fr) 1989-09-08

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2122268A4 (fr) * 2007-03-14 2014-02-19 Light Prescriptions Innovators Concentrateur optique, en particulier pour photovoltaïque solaire

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3624834A (en) * 1968-06-12 1971-11-30 Anvar Optical concentrator without flux loss
US4237332A (en) * 1978-09-26 1980-12-02 The United States Of America As Represented By The United States Department Of Energy Nonimaging radiant energy direction device
US4257401A (en) * 1980-01-02 1981-03-24 Daniels Ronald M Solar heat collector

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3624834A (en) * 1968-06-12 1971-11-30 Anvar Optical concentrator without flux loss
US4237332A (en) * 1978-09-26 1980-12-02 The United States Of America As Represented By The United States Department Of Energy Nonimaging radiant energy direction device
US4257401A (en) * 1980-01-02 1981-03-24 Daniels Ronald M Solar heat collector

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2122268A4 (fr) * 2007-03-14 2014-02-19 Light Prescriptions Innovators Concentrateur optique, en particulier pour photovoltaïque solaire

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Publication number Publication date
CA1330512C (fr) 1994-07-05

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