Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
  • H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
  • H02S40/40—Thermal components
  • H02S40/44—Means to utilise heat energy, e.g. hybrid systems producing warm water and electricity at the same time
• • 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
  • F24S23/30—Arrangements for concentrating solar-rays for solar heat collectors with lenses
  • F24S23/31—Arrangements for concentrating solar-rays for solar heat collectors with lenses having discontinuous faces, e.g. Fresnel lenses
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S30/00—Arrangements for moving or orienting solar heat collector modules
  • F24S30/40—Arrangements for moving or orienting solar heat collector modules for rotary movement
  • F24S30/42—Arrangements for moving or orienting solar heat collector modules for rotary movement with only one rotation axis
  • F24S30/428—Arrangements for moving or orienting solar heat collector modules for rotary movement with only one rotation axis with inclined axis
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F77/00—Constructional details of devices covered by this subclass
  • H10F77/40—Optical elements or arrangements
  • H10F77/42—Optical elements or arrangements directly associated or integrated with photovoltaic cells, e.g. light-reflecting means or light-concentrating means
  • H10F77/484—Refractive light-concentrating means, e.g. lenses
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F77/00—Constructional details of devices covered by this subclass
  • H10F77/40—Optical elements or arrangements
  • H10F77/42—Optical elements or arrangements directly associated or integrated with photovoltaic cells, e.g. light-reflecting means or light-concentrating means
  • H10F77/488—Reflecting light-concentrating means, e.g. parabolic mirrors or concentrators using total internal reflection
• • 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
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B10/00—Integration of renewable energy sources in buildings
  • Y02B10/20—Solar thermal
• • 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
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B10/00—Integration of renewable energy sources in buildings
  • Y02B10/70—Hybrid systems, e.g. uninterruptible or back-up power supplies integrating renewable energies
• • 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
• • 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
  • Y02E10/47—Mountings or 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
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/52—PV systems with concentrators
• • 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
  • Y02E10/60—Thermal-PV hybrids

Definitions

• the present invention relates to an energy collection system.
• the invention has application for use with systems which convert solar energy to heat and/or electrical energy, such as with photovoltaic cells.
• photovoltaic cells PN cells
• BACKGROUND OF THE INVENTION It is known to use photovoltaic cells to produce electricity from photonic radiation received from the sun.
• the photovoltaic cells are conventionally mounted on a flat panel, beneath a protective glass layer, in an array which extends over substantially an entire face of the panel, in order to maximise electrical output.
• the panel may be mounted on a dual- axis tracking assembly to allow the panel to continually face the sun.
• the amount of light incident on each cell may be increased such as with a point focus concentrator lens over each cell but then there is a need to limit the extent of solar energy concentrated because of degradation of the PV cells due to varying energy intensities and/or temperature rise across a collection plane of each cell,
• a method of collecting and an energy collection system with a lens for concentrating radiation along an elongate region of a body which converts the radiation into electrical and/or heat energy is provided.
• the lens is designed to have a focal plane extending substantially normally of the lens such that incident radiation on a face of the lens is refracted in a manner substantially uniformly over the region.
• the lens is a Fresnel lens.
• a cradle is provided and adapted for use with a solar energy collection system, as described above, the cradle including a first wall, having a first surface which is provided substantially in line with a position of the sun at the winter solstice, a second wall having a second surface which is provided substantially in line with the position of the sun at the summer solstice.
• the first and second surfaces are at least partially light reflective.
• a tooth adapted for use with a lens in a solar energy collection system the tooth being designed in accordance with equation 1, 2 and/or 3 as disclosed herein.
• the lens concentrates the incident solar radiation onto the elongate region of a body adapted to convert the radiation into electrical and/or heat energy.
• the lens is supported on a cradle provided with pivot structure to allow for rotation generally only in an east/west direction, transverse to the elongate region, in order to track the incident radiation.
• Other aspects and preferred aspects are disclosed in the specification and/or defined in the appended claims, forming a part of the description of the invention.
• the concentrator can be designed to give a more even intensity of solar concentration across the PN cells.
• the particular shape of the cradle enables the use of single axis tracking, whilst still gaining relative improvements in efficiency in the use of the PN cells. This is due to the fact that the focused light travels up and down the array and reflective end walls throughout the year whilst still maintaining full illumination on the array. Any light incident on the reflective surfaces of the cradle walls will be reflected also onto the array with relatively minimal losses.
• Figure 1 is a diagrammatic perspective view of one embodiment of an energy collection system
• Figure 2 illustrates various views of one embodiment of a collector and body of the system of Figure 1
• Figure 3 is a diagram illustrating Fresnel's law of refraction
• Figure 4 is a cross-sectional view of a lens and photovoltaic array of the system of Figure 1, taken along the line A-A
• Figure 5 is a view similar to that of Figure 4, showing the affect of a change in direction of incident radiation
• Figure 6 illustrates various views of a light sensor for use in a tracking system
• Figure 7 is a chart illustrating power output of photovoltaic arrays.
• DETAILED DESCRIPTION One embodiment of the present invention includes 4 elements
• the system creates from the energy collected from the sun, heat and electrical energy through the use of a concentrator lens, cradle, photovoltaic cells and cooling tubes,
• Some of the particular aspects of the invention include the lens, collection cradle, the combination of pre-heating water by cooling the photovoltaic cells as a feed to the household hot water system and the ability to utilise a single axis method of tracking, •
• the Fresnel type lens concentrates the suns rays to increase the output efficiency with respect to cell area,
• the collection cradle is inclined appropriate to the latitude of it's location to give greater face to the north/south direction as appropriate, according to the geographic latitude of the location of the installation of the system.
• the cradle is capable of collecting and reflecting the sun's rays from the north or south direction to give a high intensity of sun without changing the inclination of the photovoltaic cells
• Water used to cool the photovoltaic cells can be circulated into a storage tank to provide preheated water for the household hot water system
• a drive system rotates the cradle using a tracking system to determine the direction of the cradle which will maximize the energy collection, and It has been found that design principles of a Fresnel lens can be applied in respect of the lens, collector and/or cradle of the present invention.
• the present invention utilises a particular design for the Fresnel lens.
• the Fresnel lens is designed, according to this embodiment, to give a maximum concentration of the sun's rays across the surface of each cell whilst maintaining a uniform intensity on the cells. This is achieved by designing the lens to have a focal plane perpendicular to the face of the lens. This overcomes concentration problems associated with non-uniform light intensities on the collection areas.
• the choice of Fresnel lens over a mirror or other lens also ensures uniform light projection due to clarity of imaged light.
• FIG. 4 shows a lens 10 with substantially saw-tooth shaped teeth either side of a middle region. The middle region has little, if any, concentration of light on the cells.
• fi - f n representing the focal length of the first to the nth tooth
• basic trigonometry is used to determine the angle between the image and the horizontal or the refractive surface, as per equation (2).
• the present invention can be used to design a lens and collector of various sizes and shapes.
• Equation (3) is a derivation of the law of refraction as stated previously.
• any Fresnel type lens can be designed.
• the Fresnel lens 10, designed for the collection system, is shown in Figure 4.
• the lens 10 is divided up into any number of sections "s". In a preferred form, there are ten sections "s", each focusing in ten different areas, each tooth in each section having a corresponding focal length. If ray tracing is used to determine the absolute focal point of the lens, a perpendicular focal area would be found. This differs from normal lenses as they generally all have a parallel focal plane. It has been found that with a perpendicular focal plane, a more uniform concentration of radiation can be achieved along and across the region 12 of the body 6.
• the lens 10 can focus radiation from across the face 11 of the lens 10 onto a substantially uniform elongate region of the array 8 of photovoltaic cells.
• the intensity of radiation applied to the region 12 is increased or magnified by a factor commensurate with the temperature of the cell or the desired heat required.
• the factor may be 11, depending on the characteristics required for a safe operating temperature of the elongate body, as compared to the intensity that would otherwise be available if light was simply allowed to be directly incident on that region, without being magnified by a lens.
• the collection cradle has parameters which are specific to the location on the earth's surface relative to the equator to maximise illumination on the PN array.
• This specific selection of array length increases the efficiency of the system, minimizing the light that has to be reflected onto the array.
• the indirect illumination of the array by light reflected off the side walls of the cradle onto the array increases the efficiency that would otherwise apply if only the light directly illuminating the array was used.
• FIG. 1 and 2 A particular configuration of the energy collection system 1 is shown in Figures 1 and 2 as including a collector 2, in the form of a cradle 3 with reflective walls 4, for concentrating radiation 5 onto a body 6 at a base 7 of the cradle 3.
• the body 6 preferably carries an elongate strip or array 8 of photovoltaic cells and is provided with suitable electrical comiections (not shown) to allow the body to be readily inserted and/or removed and replaced in the base 7, in a cartridge like manner.
• the lens 10 is provided over the cradle 3 to assist in concentrating the radiation 5, which is incident on a face 11 thereof, onto an elongate region 12 of the body 6.
• the lens preferably has a focal plane extending in a direction away from the lens
• the cradle may also have the following:
• a first wall having a first surface which is provided substantially in line with the position of the sun at the winter solstice
• the cradle is preferably also adapted to have the lens span entirely between the first and second walls.
• the first and second walls are disposed at an angle in the range of 90 to 130 degrees relative to a flat surface of the body.
• the first and second walls are disposed at an angle of substantially 115 degrees to the horizontal.
• the positioning of the region 12 is shown in Figure 4 in a centralised location relative to the body 6, due to the radiation 5 being incident on the lens 10 from a substantially normal direction. If the direction of the incident radiation is changed, such as indicated by arrows 13 or 14 in Figure 5, the region 12 would simply travel to the right or left respectively, as viewed.
• the total length of the body 6 and associated array 8 may therefore be determined by reference to the maximum directional change in the incident radiation 5.
• the body 6 and related elongate region 12 may be arranged to extend in a generally north/south direction such that any seasonal variation in the positioning of the sun will be automatically accommodated in the system 1 by virtue of the region 12 simply travelling up and down the extent of the body 6.
• the system 1 will, however, preferably actively track the sun from east to west.
• pivots 15, 16 are provided, as shown in Figure 1, to couple the cradle 3 to support structure 17 such that the cradle 3 is able to pivot about an axis 18 which is transverse to a longitudinal direction of the body 6 and elongate array 8.
• the system 1 may include a tracking mechanism
• a heat transfer assembly may be provided which includes cooling water tubes (not shown) located in the base and on the sides of the cradle. Water is circulated through the tubes at a rate which keeps the photovoltaic cells and cradle surface at an acceptable temperature, for example, 60 degrees Celsius. This water is returned to a header tank and is used for example as feedwater for a hot water system of a building or other building / process systems requiring heat energy. Through this process, significant solar energy is converted into heat energy by the system giving additional useful energy not otherwise achieved from the current large flat PN arrays which are used.
• the arrangement 20 includes two light sensitive resistors 21, 22 positioned on either side of a shading fin 23, which extends in a north/south direction.
• the sun When resistance in one of the resistors changes, the sun is assumed to have moved to one side or the other of the shading fin 23 and the cradle 3 may then be driven in the appropriate direction to realign the shading fin 23 with the sun and equalise the resistive load in each resistor 21, 22. Tolerances may be introduced to govern when the mechanism will and won't drive, in order to accommodate minor changes in environmental circumstances which may affect the amount of light falling on either of the resistors 21, 22. The mechanism may also be subject to set drive times such as for morning and night. 6. RESEARCH RESULTS It may be appreciated from the above that significant solar energy is gained by utilising the system 1, which would not otherwise be obtained using the current flat panel photovoltaic arrays.
• tracking systems are not generally used with photovoltaic panels because of the relatively high parasitic power losses involved, high equipment costs and generally low reliability because dual- axis tracking is required.
• Tracking systems are typically not used in standard systems because of the relatively high parasitic losses involved, the high relative cost and generally low reliability because two axis tracking is required.
• the concentrator system as described here increases the electrical output, for the given collection area, by an average of 72%, giving effectively 29% efficiency. Not only will the concentrator increase electrical output by 12% compared with the tracking flat solar panel, but because only a strip of cells is used, compared with a whole array of cells for the conventional panel, the system cost is reduced by at least 50% (depending on manufacturing quantities).
• This price reduction is a combination of the reduced quantity of PN cells and less equipment and materials for the tracking system.
• the system achieves a cell output efficiency, in excess of the most efficient photovoltaic cells commercially available at much lower price.
• a comparison of the output powers for a flat plate panel, a tracking flat plate and the present concentrator is shown below. This shows a 50-60% improvement between flat plate and tracking flat plate systems, but for the concentrator system (for which the improvement would be 72% for the same collector area) the increase in power output per cell is increased approximately 5 times.
• the concentrator will virtually allow 90% of the energy collected to be obtained. This is significantly greater than could be obtained for a tracking plate panel used with a solar water heating system.
• the system 1 has been found to increase electrical output, for the given collection area, by an average of 72%, giving effectively 29% cell efficiency. More particularly, a comparison of the output powers for a flat panel, a tracking flat panel and the system 1 is shown in Figure 7.
• Graph 28 illustrates the output for a flat panel without tracking.
• Graph 29 illustrates the power output for a flat panel with dual-axis tracking, which shows a 50-60% improvement over the graph 28.
• Graph 30 represents the output from system 1, which shows improvement of 72% for the same collector area as the panel.
• the power output per cell is increased approximately 5 times. Aside from providing an increase in electrical output by an additional 12%, as compared with the tracking solar panel, the system 1 can also offer considerable manufacturing savings.

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• Engineering & Computer Science (AREA)
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• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Thermal Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Photovoltaic Devices (AREA)

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Cited By (17)

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• 2004
  • 2004-12-09 EP EP04802036A patent/EP1844267A4/en not_active Withdrawn
  • 2004-12-09 AU AU2004297292A patent/AU2004297292B2/en not_active Ceased
  • 2004-12-09 US US11/721,152 patent/US20090223553A1/en not_active Abandoned
  • 2004-12-09 CA CA2590165A patent/CA2590165C/en not_active Expired - Fee Related
  • 2004-12-09 WO PCT/AU2004/001734 patent/WO2005057092A1/en not_active Ceased
  • 2004-12-09 CN CN2004800448493A patent/CN101147032B/zh not_active Expired - Fee Related
  • 2004-12-09 JP JP2007544691A patent/JP2008523593A/ja not_active Withdrawn

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