WO2013183067A2 - An improved heat collection element for linear collector - Google Patents

An improved heat collection element for linear collector Download PDF

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Publication number
WO2013183067A2
WO2013183067A2 PCT/IN2013/000357 IN2013000357W WO2013183067A2 WO 2013183067 A2 WO2013183067 A2 WO 2013183067A2 IN 2013000357 W IN2013000357 W IN 2013000357W WO 2013183067 A2 WO2013183067 A2 WO 2013183067A2
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WO
WIPO (PCT)
Prior art keywords
collection element
heat collection
inlet
groove
outlet
Prior art date
Application number
PCT/IN2013/000357
Other languages
French (fr)
Other versions
WO2013183067A3 (en
WO2013183067A4 (en
Inventor
Sharad Bhupendrabhai PAREKH
Original Assignee
Parekh Sharad Bhupendrabhai
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Filing date
Publication date
Application filed by Parekh Sharad Bhupendrabhai filed Critical Parekh Sharad Bhupendrabhai
Publication of WO2013183067A2 publication Critical patent/WO2013183067A2/en
Publication of WO2013183067A3 publication Critical patent/WO2013183067A3/en
Publication of WO2013183067A4 publication Critical patent/WO2013183067A4/en

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S10/00Solar heat collectors using working fluids
    • F24S10/70Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits
    • F24S10/74Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits the tubular conduits are not fixed to heat absorbing plates and are not touching each other
    • F24S10/744Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits the tubular conduits are not fixed to heat absorbing plates and are not touching each other the conduits being helically coiled
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S10/00Solar heat collectors using working fluids
    • F24S10/40Solar heat collectors using working fluids in absorbing elements surrounded by transparent enclosures, e.g. evacuated solar collectors
    • F24S10/45Solar heat collectors using working fluids in absorbing elements surrounded by transparent enclosures, e.g. evacuated solar collectors the enclosure being cylindrical
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S20/00Solar heat collectors specially adapted for particular uses or environments
    • F24S20/20Solar heat collectors for receiving concentrated solar energy, e.g. receivers for solar power plants
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S23/00Arrangements for concentrating solar-rays for solar heat collectors
    • F24S23/70Arrangements for concentrating solar-rays for solar heat collectors with reflectors
    • F24S23/74Arrangements for concentrating solar-rays for solar heat collectors with reflectors with trough-shaped or cylindro-parabolic reflective surfaces
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S23/00Arrangements for concentrating solar-rays for solar heat collectors
    • F24S23/70Arrangements for concentrating solar-rays for solar heat collectors with reflectors
    • F24S23/79Arrangements for concentrating solar-rays for solar heat collectors with reflectors with spaced and opposed interacting reflective surfaces
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S40/00Safety or protection arrangements of solar heat collectors; Preventing malfunction of solar heat collectors
    • F24S40/80Accommodating differential expansion of solar collector elements
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S80/00Details, accessories or component parts of solar heat collectors not provided for in groups F24S10/00-F24S70/00
    • F24S80/70Sealing means
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S25/00Arrangement of stationary mountings or supports for solar heat collector modules
    • F24S25/60Fixation means, e.g. fasteners, specially adapted for supporting solar heat collector modules
    • F24S2025/6004Fixation means, e.g. fasteners, specially adapted for supporting solar heat collector modules by clipping, e.g. by using snap connectors
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S25/00Arrangement of stationary mountings or supports for solar heat collector modules
    • F24S25/60Fixation means, e.g. fasteners, specially adapted for supporting solar heat collector modules
    • F24S2025/6011Fixation means, e.g. fasteners, specially adapted for supporting solar heat collector modules by welding or brazing
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/40Solar thermal energy, e.g. solar towers
    • Y02E10/44Heat exchange systems

Definitions

  • the present invention relates to an improved heat collection element for Linear Solar Collector.
  • the present invention relates to an improved heat collection element for Linear Solar Collector to achieve medium operation range with high efficiency at low cost.
  • Non conventional energy sources including solar, wind, biomass, ocean and geo thermal are eco-friendly and economical alternative to the use of fuel for production of process heat and electricity.
  • solar energy can be directly and efficiently used to generate heat as well as electricity.
  • it can be utilized on site as solar energy is available everywhere without major variations in proportion.
  • Solar energy is available in two forms - heat energy and light energy.
  • the heat energy can be collected by using various collection techniques according to application.
  • the solar energy harnessing technology for thermal energy (heat) is known as Solar Thermal
  • the Solar Thermal System mainly consists of three stages: 1. Collection - to collect the available solar energy in most efficient way.
  • Mainly solar collectors are used to collect the solar energy.
  • the solar energy from sun is reflected using reflective means such as mirrors arranged such that the resulting reflected rays are focused at focal point of the collector; where the heat energy of the said reflected rays it transmitted to a Heat Transfer Fluid to utilize it further.
  • Heat Transfer Fluid refers to any kind of liquid or gaseous fluid utilized to carry energy from the collector to the storage.
  • the selection of heat transfer fluid depends on the utility and the type system.
  • Utilization - utilizing the stored thermal energy in efficient way examples include solar air condition via absorption chiller, solar hot water, solar distillation etc.
  • the present invention relates to solar thermal collectors for efficient collection of the solar rays.
  • Solar thermal collectors are solar collectors that are designed to collect heat by absorbing sunlight.
  • CPC Compound Parabolic Collectors
  • Point Concentric e.g. Dish Collector
  • solar thermal collectors are classified as:
  • Low-temperature collectors are flat plates generally used to warm up the water or other fluids or air e.g.: heating swimming pools.
  • Medium- temperature collectors are also usually flat plates but the operation ranges is higher and are used for heating water or air for residential and commercial use.
  • High-temperature collectors concentrate sunlight using mirrors or lenses and are generally used for electric power production and processes heat generation.
  • Solar thermal systems with a medium operating temperature range is usually required for roof-top type collectors and for other common industrial applications and their operational temperature range is generally between 150 - 350 °C.
  • Flat Plate Collectors as well as Linear Concentric Collectors can be used for achieving such operating temperature range.
  • the present invention relates to Linear Collectors which include: Parabolic Trough Collector and Compound Trough Collector etc.
  • Solar Thermal Collector comprises of:
  • the assembly includes a tracking mechanism that tracks the sun for maximum utilization of available solar energy and is supported by a support structure.
  • the technology is used for heating Heat Transfer Fluid or energy from the scalding liquid is used to produce steam.
  • Common Heat Transfer Fluids for medium temperature range include water-glycol mixture, Thermic Fluid, Refrigerant.
  • a selective coating is applied on the Receiver.
  • the selective coating is a special paint that absorbs radiation of one wavelength (example - sunlight) but emits little radiation of another wavelength (example - infrared); this way most of the radiation that falls onto the collector is turned into heat.
  • Linear troughs, Parabolic troughs and dishes use mirrors shaped like parabolas, as reflectors to focus incoming radiant energy onto a receiver; a pipe filled with fluid known as Heat Transfer Fluid that runs down the center of a trough.
  • the trough is usually aligned on a north-south axis, and rotated to track the sun as it moves across the sky each day.
  • the receiver serves to be the heart of solar collectors i.e. Receiver is considered the heart of the system that collects the reflected rays and transmits the heat to the heating fluid.
  • the Receivers used in Linear Collectors are generally tubular and are made of metal, usually steel with a diameter of 70 - 100 mm.
  • the Temperature Range of a solar collector mainly depends on the concentration ratio which is the ratio between the collector aperture area and the total area of absorber tube.
  • concentration ratio is directly proportional to the aperture area and the absorber area. Usual value of the concentration ratio is about 20, although the maximum theoretical value is in the order of 70-100.
  • the Efficiency of a solar collector is largely associated with a receiver of the collector.
  • the solar collector generally losses efficiency from the receiver in terms thermal loss.
  • the Flat plate collectors have aperture area equal to receiver area and so the area that can lose energy is large and in turn large amount of energy is lost. While in the case of linear collectors, aperture area is much higher than the receiver area and mainly depends on concentration ratio of the collector. Further, winds are the major sources that take away the heat energy.
  • tubular Receiver made up of steel with a diameter of 70 - 100 mm, coated with physical vapor deposited absorbing resin.
  • the said Receiver is enveloped by glass tube in order to decrease thermal losses by convection and radiation.
  • the said Glass tube and the said Receiver are fixed by means of metal-glass seal. Expansion bellows is provided on both the ends to avoid breakage in glass tube due to expansion of metal tube when operated on high temperature.
  • the space between absorber pipe and glass cover is sometimes evacuated to reduce convection losses.
  • the diameter of glass cover may be about 10 cm and that of Metal receiver tube of Receiver is about 7 cm.
  • the usual length of such Receiver is 2 to 4 meter. That is, the standard Receiver or receiver available in market has standard dimension of 4 meter with higher cost, which is not feasible for medium range solar concentric collector, having lesser concentration ratio.
  • tubular collection element being of 70mm- 100mm, has higher mass per unit area at same collection field and hence the time to heat the fluid also more. This is also not economically viable.
  • the aforementioned inventions have many constraints like space availability, continuous mass flow rate, cost per collector etc.
  • the said receivers disclosed therein are larger in length i.e. up to 4 meters, which at times become difficult to transport.
  • the US patent application number US 2011/0017273 Al discloses "A system for concentrating solar energy".
  • the applicant of the aforementioned US patent application therein suggests using helical coil in place of tubular receiver arrangement, which reduces the mass per unit aperture area for collector having lesser concentration ratio.
  • the said system has a single side output and input, which makes it incompatible to fix multiple units in series for larger aperture length, or it may need complex piping arrangement for Heat Transfer Fluid circulation in series installation.
  • it does not have any specific mounting and fitting arrangement which makes it incompatible to connect with other such units thereby limiting the said invention to the single unit as per the matter disclosed therein.
  • there are no provisions of glass or outer receiver cover which significantly increases the losses due to the wind as the thermal conductivity of the metal is much higher the wind carries away enormous amount of collected heat with it.
  • a glass cover started to be used covering the metal receiver.
  • the glass cover allowed the thermal energy to pass inside but acts as a barrier between the metal pipe and the wind helping to conserve the heat.
  • the glass cover with the receiver inside is covered with the side covers.
  • the air that persists inside after closing the said glass cover acts as a insulator in transfer of heat from the glass cover to the metal pipe thereby decreases the efficiency of the receiver as a whole.
  • the loss of vacuum is significant problem in such collector at time of thermal or mechanical failure.
  • the loss of vacuum also allows the air to space, which carries away the heat with it to free space.
  • the said receiver also requires replacing the whole receiver in cases of damage.
  • US Patent application number 2010/0325889 by David Buttors disclosing "Apparatus and method for joining solar receiver tubes” and US Patent application number 2011/0049106 Al by Davis Buttors disclosing "Apparatus and method for field welding solar receiver tubes” show the methods of joining two receiver tubes at the solar field.
  • the collector having high concentration ratio with large solar fields requires joining of a number of solar collectors in a series, thereby requiring the joining of a number of receivers.
  • the reference patents show the method and apparatus needed for such joining.
  • the application such as rooftop type collectors needs easy mounting and connection of the receiver.
  • the existing collector needs special welding and joining procedure for the connection of two Receivers. It is not feasible to setup such plant on site like roof.
  • US Patent application number 201 1/0049106 Al discloses "Apparatus and method for field welding solar receiver tubes”.
  • the said patent application further discloses the requirement of special apparatus to hold and join the two receiver tubes.
  • the orbital welding required for joining two receiver tubes needs to hold them with the help of special apparatus.
  • special apparatus There, it is also necessary to take special precaution during the joining procedure.
  • in case of replacement of the receiver it needs the complex operational sequence.
  • Receivers are tubular and provides less surface area to the heating fluid compared to a coil type Receiver.
  • the main object of the present invention is to provide an improved Heat Collection Element for Linear Collector to achieve medium operation range with high efficiency at low cost.
  • Another object of the present invention is to provide an improved Heat Collection Element for Linear Collector that is coil shaped which provides increased surface area to the heating fluid.
  • Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which has a lesser startup time.
  • Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which provides flexibility in temperature range and flow rate.
  • Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which has lesser breakage problems.
  • Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector wherein the smaller size of the collector makes it more viable and feasible for roof-top type collector application apart from industrial uses.
  • Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which is easy to transport.
  • Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which is easy to manufacture and repair.
  • Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which can be assembled and repaired on site.
  • Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which does not involve any special welding requiring skill and adding up of cost.
  • Yet another object of the present invention is to an improved Heat Collection Element for Linear Collector wherein the secondary reflector helps in increasing the efficiency of the said Heat Collection Element.
  • Yet another object of the present invention is to an improved Heat Collection Element for Linear Collector which has a lower manufacturing cost.
  • Fig 2A Shows the typical solar collection arrangement.
  • Fig 2B Shows the relative positioning of the secondary reflector according to the present invention with the primary reflector.
  • Fig 3 Shows various linear concentric type profiles of parabolic troughs of the collector.
  • Fig 4A Shows the single pass Helical Coil.
  • Fig. 4B Shows the multi-pass Helical Coil.
  • Fig 4C Shows the Cross Section of various possible Helical
  • Fig 5 Shows the cross section and front view of end cover.
  • Fig 6 Shows the isometric view with cross section of end cover.
  • Fig 8A Shows the front view of the secondary reflector with a clipping arrangement.
  • Fig 8B Shows the side view of the secondary reflector with a clipping arrangement.
  • Fig 8C Shows the isometric view of the secondary reflector with a clipping arrangement.
  • Fig 9A Shows the isometric view of Joining Piece from the right hand side illustrating the Outlet Facing Side of the said Joining Piece.
  • Fig 9B Shows the isometric view of Joining Piece from the left hand side illustrating the Inlet Facing Side of the said Joining Piece.
  • Fig 10A Shows the front view cross section view of interconnection of a Heat collection element unit with another such adjacent unit using a joining piece.
  • Fig 10B Shows the side view cross section view of interconnection of a Heat collection element unit with another such adjacent unit using a joining piece.
  • Fig 12 Shows the front view and the side view of the O Ring.
  • the present invention provides an improved Heat Collection Element for medium operation range Linear Solar Collector suitable for roof-top type collectors.
  • the present invention mainly embodies an improved Heat Collection Element (1) for Linear Solar Collector which mainly comprises of: a helical coil (4);
  • the said Heat Collection Element (1) has one end of it that acts as Inlet (2) for the Heat Transfer Fluid and the opposite end act as an Outlet (3).
  • a hollow Helical Coil (4) made of metal such as copper, with a selective coating is provided to enhance absorption of solar energy.
  • the said Helical Coil (4) has Expansion Compensating Mechanism (5) on ends that have a spaced pitch between the helical turns wherein the suggested value of the said Expansion Compensating Mechanism (5) is between 0.1L to 0.2L on both the ends.
  • a Glass Cover (6) is provided to cover the said hollow Helical Coil (4) and thereby to avoid the energy loses from the said Helical Coil (4).
  • the said Glass Cover (6) is provided with the Second Threaded Groove (2f) on Inlet (2) and Fourth Threaded Groove (3f).
  • End Covers (2a and 3a) are provided for closing the said Glass Cover (6) with the said hollow Helical Coil (4) inside where, an Inlet End Cover (2a) is provided at Inlet (2) end and Outlet End Cover (3a) is provided at the Outlet (3) end.
  • the said Inlet End Cover (2a) consists of a First Threaded Groove (2c) for fixing the said Inlet End Cover (2a) with the Second Threaded Groove (2f) of the said Glass Cover (6).
  • the said Inlet End Cover (2a) consists of a First Hole (2b) to allow the traversing of the said Inlet Connection Hose (2h); a Second Groove (2j) for fixing the said Inlet End Seal (2d) and a First Extruded Part (2g) with a Third Groove (2k).
  • the said Outlet End Cover (3a) is used to close the said Glass Cover (6) at Outlet (3) whereby the said Outlet End Cover (3a) consists of a Third Threaded Groove (3c) for fixing the Outlet End Cover (3a) with the Fourth Threaded Groove (3f) of the said Glass Cover (6).
  • the said Outlet End Cover (3a) consists of a Third Hole (3b) to allow the traversing of the said Outlet Connection Hose (3h); a Sixth Groove (3j) for fixing the Outlet End Seal (3d) and a Second extruded part (3g) with a Seventh Groove (3k).
  • a Space (7) between the said Glass Cover (6) and the said Helical Coil (4) is filled with heat conductive gases like argon.
  • Inlet End Seal (2d) and an Oxitlet End Seal (3d) are provided inside the said Inlet End Cover (2a) and Outlet End Cover (3a) respectively for : avoiding the leakage of said gases.
  • the said . End Seals are of the material such as high temperature resistant rubber.
  • the said Inlet End Seal (2d) is provided with a Second Hole (2e) for allowing the traversing of the said Inlet Connection Hose (2h) and a Fourth Groove (21) to fix on the said Second Groove (2j) of the said Inlet End Cover (2a) while the said Outlet End Seal (3d) is provided with a Fourth Hole (3e) to allow traversing of the said Outlet Connection Hose (3h) and a Eighth Groove (31) to fix with the Sixth .Groove . (3j) of the said Outlet End Cover (3a).
  • a Secondary Reflector (8) is fixed on outer side on the Glass Cover (6) of the said Heat Collection Element " ( 1) and is provided for facilitating the capturing of the reflected rays that bypasses the said Helical Coil
  • the said Secondary Reflector (8) is a Reflective sheet curved in compound parabolic shape.
  • a Clipping Arrangement (9) is provided for fixing the said a Secondary Reflector (8).
  • the said Clipping Arrangement (9) is preferably made of non-corrosive metal having weather proof Coating to protect it from climatic variation. ⁇
  • a Joining Piece ( 12) is provided to facilitate interconnection of two '
  • the said Joining piece ( 12) has an Upper section ( 12a), a Lower section (12b) and a Third extruded part ( 12c).
  • the said Upper section ( 12a) and the said Lower section ( 12b) are joined together with bolt and nut ( 12k) at Fifth Hole ( 12d) and the said lower section ( 12b) and the said Third extruded part ( 12c) are permanently attached.
  • the said Joining Piece (12) has an Outlet Facing Side ( 12A) that faces the Outlet (3) of a Heat Collection Element ( 1) in a series and an Inlet Facing Side ( 12B) that faces the Inlet (2) of adjacent Heat Collection Element ( 1) in a series.
  • the said Joining Piece ( 12) is provided with a Sixth Hole ( 12e), on the said Outlet Facing Side ( 12A) which fixes with the Outlet Connection Hose (3h) of one unit of the said Heat Collection Element ( 1) whereby the proper fixing of the said Sixth Hole ( 12e) and the said Outlet Connection Hose (3h) is facilitated by a First O ring (14a) between a ninth groove (12f) at the said Sixth Hole (12e) and a Fifth Groove (3i) at the Outlet Connection Hose (3h).
  • An Eighth Hole (121) is provided on the said Inlet Facing Side (12B) of the said Joining Piece (12) which fixes with the Inlet Connection Hose (2h) of adjacent unit of Heat Collection Element (1) and the proper fixing of the said Eighth Hole (121) and the said Inlet Connection Hose (2h) is facilitated by a Second O ring (14b) between a eleventh groove (12m) at the said Eighth Hole (121) and First Groove (2i) of the said Inlet Connection Hose (2h).
  • a Seventh Hole (12g) is provided on the said Outlet Facing Side (12A) for fixing the said Outlet End Cover (3a) of one unit of the said Heat Collection Element (1) whereby the proper fixing of the said Seventh Hole (12g) the said Outlet End Cover (3a) is facilitated by a Third O ring (14c) between a tenth groove (12i) at the said Seventh Hole (12g) and a Third Groove (2k) at the Outlet End Cover (3a).
  • a Ninth Hole (12n) is provided on the said Inlet Facing Side (12B) for fixing the said Inlet End Cover (2a) of adjacent unit of Heat Collection Element (1) whereby the proper fixing of the said Ninth Hole (12n) and the said Inlet End Cover (2a) is facilitated by a Fourth O ring (14d) between a Twelfth Groove (12o) at the said Ninth Hole (12n) and a; Seventh Groove (3k) at the said Inlet End Cover (2a).
  • the said Third Extruded Part (12c) consists of Plurality of Holes (12j) for fixing the said Joining Piece (12) with a Mounting Arrangement (13).
  • Helical Coil (4) to be used when a high mass flow rate is required.
  • the said multi-pass Helical Coil (4) is made by bending plurality hollow metal pipe.
  • said multi-pass Helical Coil (4) has plurality of turns and plurality of starting points.
  • the bending of plurality of pipes (two or more) is done along the parallel axis with respect to each other.
  • the ends of the said Helical Coil (4) are welded respectively with Inlet Connection Hose (2h) and Outlet Connection Hose (3h) for the ingress and egress of the Heat Transfer Fluid.
  • the present invention embodies an improved Heat Collection Element (1) for Linear Solar Collector to achieve medium operation range with high efficiency at low cost.
  • FIG.1 shows cross section view of the present Heat Collection Element (1) according to present invention from Front (Fig 1A) and from Side (Fig IB).
  • the said Heat Collection Element (1) has a construction of component parts as described hereinafter.
  • One end of the said Heat Collection Element (1) acts as Inlet (2) for the Heat Transfer Fluid and the opposite end act as an Outlet (3).
  • a hollow Helical Coil (4) made by helically bending a hollow metal pipe which includes a copper pipe is inserted in to a Glass Cover (6). Bending the said metal pipe into the Helical Coil (4) increases the surface area and thereby the Heat Transfer Area for the Heat Transfer Fluid.
  • the helical turns of the said Helical Coil (4) have a higher pitch on the ends to provide an Expansion Compensating Mechanism (5) as described in Fig 4.
  • the said Helical Coil (4) has a selective coating to enhance absorption of solar energy.
  • the said Glass Cover (6) with the said Helical Coil (4) inside has an Inlet End Cover (2a) at Inlet (2) end and Outlet End Cover (3a) ' at the Outlet (3) end. Gases including Argon, which facilitate heat transfer from Glass Cover (6) to the Helical Coil (4), are filled in the Space (7) between the said Glass Cover (6) and the said Helical Coil (4).
  • An Inlet End Seal (2d) and an Outlet End Seal (3d) of the material such as high temperature resistant rubber is fixed inside the said Inlet End Cover (2a) and Outlet End Cover (3a) respectively for avoiding the leakage of said gases.
  • the said Helical Coil (4) is attached with an Inlet Connection Hose (2h) which in turn traverses through the First Hole (2 b) and the Second Hole (2e) provided respectively in the said Inlet End Cover (2a) and said Inlet End Seal (2d).
  • the said Inlet Connection Hose (2h) is provided for ingress of the Heat Transfer Fluid into the said Helical Coil (4).
  • an Outlet Connection Hose (3h) is attached to the said Helical Coil (4) at the opposite end and traverses through the Third Hole (3b) and Fourth Hole (3e) respectively provided in the said Outlet End Cover (3a) and Outlet End Seal (3d).
  • the said Outlet Connection Hose (3h) is provided for the egress of the said Heat Transfer Fluid.
  • a Secondary Reflector (8) is fixed on outer side on the Glass Cover (6) of the said Heat Collection Element (1) using Clipping Arrangement (9).
  • Fig. 1C shows the fragmented view of the present Heat Collection Element (1) according to present invention.
  • FIG. 2 shows the typical solar collection arrangement of linear concentric type profile.
  • the existing Receiver (1 1) is generally provided with a Receiver Metal Tube (11a) and a Receiver Glass Cover (l ib), fixed at the focal length of Primary Reflector ( 10) using a mounting arrangement.
  • the said Receiver Glass Cover (l ib) is provided to reduce the convective losses due to wind.
  • the said Primary Reflector (10) has Reflecting Sheet such as Mirror fixed on the Profiled Structure.
  • Fig 2B shows the relative positioning of the Secondary Reflector (8) according to the present invention with the primary reflector (10)
  • Fig. 3 shows the various linear concentric type profiles of parabolic troughs of the collector.
  • FIG. 3A shows parabolic troughs with a parabolic shape whose focal point is outside the parabola whereas Fig. 3B and 3C is a compound parabolic trough with a focal point inside the geometrical shape of the said parabolic trough type of collector. Variations in the shape of the troughs results in different concentrate type profiles of the collectors. Such variations in the profile increase aperture area for same reflector size and focus the reflected rays at focal line.
  • FIG. 4 shows Helical Coil (4) of Heat Collection Element (1).
  • the said Helical Coil (4) is made by helically bending a hollow metal pipe. Plurality of such hollow metal pipes is bent to form multi start helical structure. The selection for the said Helical Coil (4) to have single or multi turns depends upon the requirement of mass flow rate and temperature range.
  • Fig. 4A shows a single pass Helical Coil (4) with single turn; and the said Helical Coil (4) has a singular starting point.
  • the said Helical Coil (4) is welded at the ends respectively with Inlet Connection Hose (2h) and Outlet Connection Hose (3h).
  • FIG. 4B shows a multi-pass Helical Coil (4) with has dual turns and two starting points.
  • bending of plurality of pipes (two or more) is done along the parallel axis with respect to each other and has multiple starting points.
  • the ends of the said Helical Coil (4) are welded respectively with Inlet Connection Hose (2h) and Outlet Connection Hose (3h) for the ingress and egress of the Heat Transfer Fluid.
  • the Helical Coil (4) has Expansion Compensating Mechanism (5) on both the ends. For compensating expansion, it is preferred in the present invention to take spaced pitch between the helical turns of the said Helical Coil (4).
  • Expansion Compensating Mechanism (5) shall be between 0.1L to 0.2L on both the ends for the purpose of the present invention.
  • the said Expansion Compensating Mechanism (5) also facilitates absorption of thermal shocks.
  • the said Inlet Connection Hose (2h) and Outlet Connection Hose (3h) also has a First Groove (2i) and a Fifth Groove (3i) respectively for enabling connections with other unit of the Heat Collection Element (1).
  • Fig. 4C shows the Cross Section of various possible Helical Coils.
  • Fig. 5 and 6 refer to End Covers where Fig 5 shows cross section of front view of End Cover (2a and 3a) and Fig. 6 shows the isometric view with cross section of End Covers (2a and 3a).
  • the said Inlet End Cover (2a) is used to close the said Glass Cover (6) at Inlet (2) whereby the said Inlet End Cover (2a) consists of a First Threaded Groove (2c) for fixing the said Inlet End Cover (2a) with the Second Threaded Groove (2f) of the said Glass Cover (6) and the said Outlet End Cover (3a) is used to close the said Glass Cover (6) at ' Outlet (3) whereby the said Outlet End Cover (3a) consists of a Third Threaded Groove (3c) for fixing the Outlet End Cover (3a) with the Fourth Threaded Groove (3f) of the said Glass Cover (6).
  • the said Inlet End Cover (2a) consists of a First Hole (2b) to allow the traversing of the said Inlet Connection Hose (2h); a Second Groove (2j) for fixing the said Inlet End Seal (2d) and a First Extruded Part (2g) with a Third Groove (2k) while the said Outlet End Cover (3a) consists of a Third Hole (3b) to allow the traversing of the said Outlet Connection Hose (3h); a Sixth Groove (3j) for fixing the Outlet End Seal (3d) and a Second Extruded Part (3g) with a Seventh Groove (3k).
  • the said Third Groove (2k) and the said Seventh Groove (3k) are provided to fix an O ring.
  • the said O ring (14) ensures proper fixing different units of said Heat Collection Element (1) as described later.
  • Fig. 7 shows view of the End Seals (2d and 3d).
  • the said Inlet End Seal (2d) is provided with a Second Hole (2e) for allowing the traversing of the said Inlet Connection Hose (2h) and a Fourth Groove (21) to fix on the said Second Groove (2j) of the said Inlet End Cover (2a).
  • the Outlet End Seal (3d) is provided with a Fourth Hole (3e) to allow traversing of the said Outlet Connection Hose (3h) and a Eighth Groove (31) to fix with the Sixth Groove (3j) of the said Outlet End Cover (3a).
  • FIG. 8 shows the Secondary Reflector (8) with Clipping Arrangement (9).
  • the said Secondary Reflector (8) is a Reflective sheet curved in compound parabolic shape and facilitates capturing of the reflected rays that bypasses the said Helical Coil (4) of the said Heat Collection Element (1) and focuses it back to the said Heat Collection Element (1).
  • Fig. 8 A shows the front view of Secondary Reflector (8) with a Clipping Arrangement (9).
  • the said Clipping Arrangement (9) is permanently attached to the said Secondary Reflector (8).
  • Fig. 8B shows side view of the Secondary Reflector (8) with the said Clipping Arrangement (9).
  • Fig. 8C shows the isometric view of the Secondary Reflector (8) with a Clipping Arrangement (9).
  • Fig. 9 and 10 refers to the Joining Piece (12); Fig. 9 shows the isometric view of Joining Piece (12); where Fig. 9A shows the isometric view of Joining Piece (12) from the right hand side illustrating the Outlet Facing Side (12A) of the said Joining Piece (12) and Fig. 9B shows the isometric view of Joining Piece (12) from the left hand side illustrating the Inlet Facing Side (12B) of the said Joining Piece (12).
  • Fig. 10 shows the cross section front view (Fig. 10A) and cross section side view (Fig. 10B) of interconnection of two Heat Collection Element (1) using a Joining Piece (12).
  • a Joining piece (12) is provided to facilitate interconnection of two adjacent units of the said Heat Collection Element (1).
  • the said Joining Piece has an Upper section (12a), a Lower section (12b) and a Third extruded part (12c).
  • the said Upper section (12a) and the said Lower section (12b) are joined together with bolt and nut (12k) at Fifth Hole (12d) the said lower section (12b) and the said Third extruded part (12c) are permanently attached.
  • the said Joining Piece (12) has an Outlet Facing Side (12A) that faces the Outlet (3) of a Heat Collection Element (1) in a series and an Inlet Facing Side (12B) that faces the Inlet (2) of adjacent Heat Collection Element (1) in a series as clearly depicted in Fig. 10A.
  • the said Joining Piece (12) is provided with a Sixth Hole (12e), on the said Outlet Facing Side (12A) which fixes with the Outlet Connection Hose (3h) of one unit of the said Heat Collection Element (1).
  • the proper fixing of the said Sixth Hole (12e) and the said Outlet Connection Hose (3h) is facilitated by a First O ring (14a) between a ninth groove (12f) at the said Sixth Hole (12e) and a Fifth Groove (3i) at the Outlet Connection Hose (3h).
  • an Eighth Hole (121) is provided on the said Inlet Facing Side (12B) of the said joining piece (12) which fixes with the Inlet Connection Hose (2h) of adjacent unit of Heat Collection Element (1).
  • a Ninth Hole (12n) is provided on the said Inlet Facing Side (12B) for fixing the said Inlet End Cover (2a) of adjacent unit of Heat Collection Element (1).
  • the proper fixing of the said Ninth Hole (12n) and the said Inlet End Cover (2a) is facilitated by a Fourth O ring
  • the said Third Extruded Part (12c) consists of Plurality of Holes (12j) for fixing the said Joining Piece (12) with a Mounting Arrangement (13) as depicted in Fig. 1 1
  • FIG. 11 shows the Inter Connection of Heat Collection Element (1) in plurality, arranged in series using Joining Piece (12) and it's mounting using mounting arrangement (13).
  • FIG. 12 shows the front view and the side view of the O Ring.
  • the Heat Collection Element (1) for Linear Solar Collector disclosed hereinabove is fixed at a focal point of a linear collector.
  • Plurality of such Heat Collection Element (1) is interconnected in a series using Joining Piece (12) and is mounted using mounting arrangement (13).
  • the Heat Transfer Fluid enters in to the said Heat Collection Element (1) from the said Input Connection Hose (2h) and passes through the said Helical Coil (4) which is a single pass or a multi pass coil.
  • the said Helical Coil (4) gets heated as the rays get reflected from the collector and concentrate on it.
  • the reflected rays that circumvent due to the pitch distance gets collected by Secondary Reflector (8) and are focused back to the Heat Collection Element (1) thereby ensuring energy collection from complete set of rays available for efficient heating. Further, the resultant heated Heat Transfer Fluid moves out of the said Heat Collection Element (1) through Outlet Connection Hose (3h). Where the said collectors are in series; the said Heat Transfer Fluid moves out from Outlet Connection Hose (3h) of one Heat Collection Element (1) of the said collectors in series and enters in to the Inlet Connection Hose (2h) of another Heat Collection Element (1) of the collector adjacently attached to it.
  • the said Heat Transfer Fluid moves from First Heat Collection Element (1) to the adjacent and then to the next till the last unit in the series and the Heat Transfer Fluid gets heated attaining higher temperature from each of the said units of the Heat Collection Element (1) than the temperature attained in the previous unit.
  • the number of units of the Heat Collection Element (1) to be used depends on the requirement of temperature range and the volume.
  • the said Heat Collection Element (1) as described herein above works efficiently in the temperature range of 50-350°C as per the analysis shown below in the Graph 1.
  • the Graph 1 represents the temperature on its horizontal axis and the efficiency on vertical axis.
  • the curve representing the Flat Plate Collector which is generally used for temperature range of 50°C - 80°C shows that its efficiency suitable for temperature below 100°C, which decreases drastically with increase in temperature and mass flow rate.
  • Another curve representing the Evacuated Tube Collector which has lower thermal losses, is efficient for temperature range of 60°C-150°C.
  • the curve representing Parabolic Trough Collector with Existing Receiver shows that it is suitable for higher temperature range.
  • Trough Collector with the present improved Heat Collection Element (1) shows its broad coverage range from temperatures from 50°C- 350°C that is the present improved Heat Collection Element (1) provides an advantage over Flat Plate Collectors, Evacuated Tube Collectors as well as Parabolic Trough Collector with Existing Receiver. Additionally, the said curve for Parabolic Trough Collector with the present improved Heat Collection Element (1) represents higher efficiency as compared to the Parabolic Trough Collector with Existing Receiver in the medium temperature range proving it to be more efficient and suitable for medium temperature operation range for linear collectors including parabolic troughs. Also, the present improved Heat Collection Element (1) covers a lower working temperature range due to the coil type arrangement and presence of highly conductive gases respectively. This makes it suitable for collectors including roof-top type collectors required for the medium temperature range of 50°C-350°C and medium mass flow rate.
  • the proposed invention is highly efficient and feasible for medium temperature operation range i.e. for 50°C-350°C temperatures.
  • the coiled shape of the Heat Collection Element of the present invention provides maximum surface area to the Heating Transfer Fluid increasing its efficiency.
  • the Heat Collection Element of the present invention is narrow and hence circulates lesser volume of heating fluid at a time and hence the startup time is less for the system.
  • the helical coil of the present invention can be single start or multi start, which helps to adjust the range of flow rate as well as the range of temperature of the Heat Transfer Fluid according to the requirement.
  • the helical coil of the present invention has spaced pitch at its end, helping to overcome the expansion of coil during heating at higher temperature.
  • Small size of the present invention also facilitates easy manufacture, mounting, installation and transportation.
  • the end covers of the Heat Collection Element in the present invention itself has fitting and mounting arrangement which helps for easy mounting of the Heat Collection Element on collector using joining piece.
  • the helical coil of the present invention itself has connection arrangements facilitating connection with other units.
  • the secondary reflector of the present invention redirects deflected rays to the Heat Collection Element that initially did not reach or hit the said Heat Collection Element.
  • the present invention has a lower manufacturing cost.

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Abstract

The present invention provides improved Heat Collection Element (1) for Linear Solar Collector for temperature range 50°C-350°C. It comprises of Helical Coil (4) with spaced pitch of its helical turns on ends providing Expansion Compensating Mechanism (5); Glass Cover (6) to avoid thermal losses; Space between said Helical Coil (4) and said Glass Cover (6) filled with heat conductive gases; End Covers (2a and 3a) to close said Glass Cover (6); End Seals (2d and 3d) to avoid leakage of gases; Connection Hose (2h and 3h) for ingress and egress of Heat Transfer Fluid; secondary reflector (8) for reflecting back the rays that bypasses Helical Coil (4); Clipping Arrangement (9) for fixing said Secondary Reflector (8) on said Glass cover (6); Joining Piece (12) to facilitate interconnection of two units of said Heat Collection Element (1) when arranged in plurality in series; and mounting arrangement (13) to mount said series at site.

Description

Description
AN IMPROVED HEAT COLLECTION ELEMENT FOR LINEAR COLLECTOR
FIELD OF INVENTION
The present invention relates to an improved heat collection element for Linear Solar Collector. In particular, the present invention relates to an improved heat collection element for Linear Solar Collector to achieve medium operation range with high efficiency at low cost.
BACKGROUND OF THE INVENTION
Industrialization was followed by ever increasing demand for heat and electricity. Majority of industries including textile, food and chemical industries widely need process heat and electricity for their day to day operation. Usually industries use conventional energy sources like coal and wood to produce process heat leading to an increase in the fuel consumption. Other small scale industries and household purposes require electricity. In addition to the environmental concerns, costs have become a major economic concern in using conventional energy sources.
Non conventional energy sources including solar, wind, biomass, ocean and geo thermal are eco-friendly and economical alternative to the use of fuel for production of process heat and electricity. Unlike other sources, solar energy can be directly and efficiently used to generate heat as well as electricity. Moreover, mostly, it can be utilized on site as solar energy is available everywhere without major variations in proportion. Solar energy is available in two forms - heat energy and light energy. The heat energy can be collected by using various collection techniques according to application. The solar energy harnessing technology for thermal energy (heat) is known as Solar Thermal
Energy (STE).
The Solar Thermal System mainly consists of three stages: 1. Collection - to collect the available solar energy in most efficient way.
Mainly solar collectors are used to collect the solar energy. The solar energy from sun is reflected using reflective means such as mirrors arranged such that the resulting reflected rays are focused at focal point of the collector; where the heat energy of the said reflected rays it transmitted to a Heat Transfer Fluid to utilize it further.
Here, the Heat Transfer Fluid refers to any kind of liquid or gaseous fluid utilized to carry energy from the collector to the storage. The selection of heat transfer fluid depends on the utility and the type system.
Storage - storage of collected energy
Utilization - utilizing the stored thermal energy in efficient way. Examples include solar air condition via absorption chiller, solar hot water, solar distillation etc. The present invention relates to solar thermal collectors for efficient collection of the solar rays. Solar thermal collectors are solar collectors that are designed to collect heat by absorbing sunlight.
Different types of solar collectors available are:
1. Non Concentric Type
> Flat Plate Collector (FPC)
> Evacuated-tube collectors (ETC)
> Heat Pipe Evacuated-tube collectors (Heat pipe ETC)
2. Concentric Type
a. Linear Concentric
i. Parabolic Through Collectors (PTC)
ii. Compound Parabolic Collectors (CPC)
b. Point Concentric (e.g. Dish Collector)
As per requirement of application, solar thermal collectors are classified as:
1. Low- temperature solar thermal collectors,
2. Medium-temperature solar thermal collectors,
3. High-temperature collectors.
Low-temperature collectors are flat plates generally used to warm up the water or other fluids or air e.g.: heating swimming pools. Medium- temperature collectors are also usually flat plates but the operation ranges is higher and are used for heating water or air for residential and commercial use. High-temperature collectors concentrate sunlight using mirrors or lenses and are generally used for electric power production and processes heat generation.
Solar thermal systems with a medium operating temperature range is usually required for roof-top type collectors and for other common industrial applications and their operational temperature range is generally between 150 - 350 °C. Flat Plate Collectors as well as Linear Concentric Collectors can be used for achieving such operating temperature range. The present invention relates to Linear Collectors which include: Parabolic Trough Collector and Compound Trough Collector etc.
Generally, Solar Thermal Collector comprises of:
1. Reflector,
2. Receiver
3. Support structure; and
4. Tracking Mechanism
Mirrored surfaces of the reflectors concentrate sunlight onto a Receiver, which superheats a liquid - Heat Transfer Fluid. The assembly includes a tracking mechanism that tracks the sun for maximum utilization of available solar energy and is supported by a support structure. The technology is used for heating Heat Transfer Fluid or energy from the scalding liquid is used to produce steam. Common Heat Transfer Fluids for medium temperature range include water-glycol mixture, Thermic Fluid, Refrigerant. To enhance the absorption of the solar energy i.e. heat, a selective coating is applied on the Receiver. The selective coating is a special paint that absorbs radiation of one wavelength (example - sunlight) but emits little radiation of another wavelength (example - infrared); this way most of the radiation that falls onto the collector is turned into heat.
Solar reflectors are classified based on how they concentrate solar energy. The three most common types are: • Linear troughs,
• Parabolic dishes and
• Power towers. Linear troughs, Parabolic troughs and dishes use mirrors shaped like parabolas, as reflectors to focus incoming radiant energy onto a receiver; a pipe filled with fluid known as Heat Transfer Fluid that runs down the center of a trough. The trough is usually aligned on a north-south axis, and rotated to track the sun as it moves across the sky each day. Hence the receiver serves to be the heart of solar collectors i.e. Receiver is considered the heart of the system that collects the reflected rays and transmits the heat to the heating fluid. The Receivers used in Linear Collectors are generally tubular and are made of metal, usually steel with a diameter of 70 - 100 mm.
The Temperature Range of a solar collector mainly depends on the concentration ratio which is the ratio between the collector aperture area and the total area of absorber tube. The concentration ratio is directly proportional to the aperture area and the absorber area. Usual value of the concentration ratio is about 20, although the maximum theoretical value is in the order of 70-100.
The Efficiency of a solar collector is largely associated with a receiver of the collector. The solar collector generally losses efficiency from the receiver in terms thermal loss. The Flat plate collectors have aperture area equal to receiver area and so the area that can lose energy is large and in turn large amount of energy is lost. While in the case of linear collectors, aperture area is much higher than the receiver area and mainly depends on concentration ratio of the collector. Further, winds are the major sources that take away the heat energy. PRIOR ART OF THE INVENTION
Most common systems in the closest prior arts for the present invention include tubular Receiver made up of steel with a diameter of 70 - 100 mm, coated with physical vapor deposited absorbing resin. The said Receiver is enveloped by glass tube in order to decrease thermal losses by convection and radiation. The said Glass tube and the said Receiver are fixed by means of metal-glass seal. Expansion bellows is provided on both the ends to avoid breakage in glass tube due to expansion of metal tube when operated on high temperature. The space between absorber pipe and glass cover is sometimes evacuated to reduce convection losses. The diameter of glass cover may be about 10 cm and that of Metal receiver tube of Receiver is about 7 cm. The usual length of such Receiver is 2 to 4 meter. That is, the standard Receiver or receiver available in market has standard dimension of 4 meter with higher cost, which is not feasible for medium range solar concentric collector, having lesser concentration ratio.
The patent applications US 2007/0034204 by schott and US2012/0247456 Al by abengoa respectively disclose "Tubular radiation absorbing device for solar heating applications" and "Method for producing a solar power receiving tube and resulting tube". Both the aforementioned US patent applications describe the.^existing solar receiver technology. The said technology disclosed therein involves two basic tubes, one of the said tubes made of borosilicate glass and the other of metal. The said tubes are joined together with the help of expansion compensation system or bellow. The standard length of such tube is 4 m with inner metal tube diameter of 70-100 mm. The passage between said glass and metal is vacuumed to reduce the thermal losses of receiver. Here, tubular collection element being of 70mm- 100mm, has higher mass per unit area at same collection field and hence the time to heat the fluid also more. This is also not economically viable. In addition, for the application such as roof top collection, the aforementioned inventions have many constraints like space availability, continuous mass flow rate, cost per collector etc. Also, the said receivers disclosed therein are larger in length i.e. up to 4 meters, which at times become difficult to transport.
The US patent application number US 2011/0017273 Al discloses "A system for concentrating solar energy". The applicant of the aforementioned US patent application therein suggests using helical coil in place of tubular receiver arrangement, which reduces the mass per unit aperture area for collector having lesser concentration ratio. However, the said system has a single side output and input, which makes it incompatible to fix multiple units in series for larger aperture length, or it may need complex piping arrangement for Heat Transfer Fluid circulation in series installation. In addition, it does not have any specific mounting and fitting arrangement which makes it incompatible to connect with other such units thereby limiting the said invention to the single unit as per the matter disclosed therein. Also, there are no provisions of glass or outer receiver cover, which significantly increases the losses due to the wind as the thermal conductivity of the metal is much higher the wind carries away enormous amount of collected heat with it.
Further, again a reference is made to the aforementioned US patent application number 2012/0247456 Al, by abengoa, which discloses "Method for producing a solar power receiving tube and resulting tube". The said patent application suggests joining of metal tube and glass tube with the help of expansion compensating system or elbow thereby reducing the risks related to expansion of metal tube and losses of optical efficiency due to absorber coating degradation and failure of receiver resulting in thermal energy losses. However, the said invention fails to provide a solution to impacts of physical conditions like snow fall, damage due to accidental hitting of stones, balls etc leading to immediate system stoppage and requires the replacement of the whole receiver thereby having a direct impact on the economical feasibility of the system. This also needs significant maintenance and efforts to replace it. In addition, at time of physical failure it losses vacuum, which reduces the efficiency. And whole receiver needs to be replaced with new one as it is not possible to repair it at the site, which requires more maintenance resources.
In order to avoid the losses due to the wind, a glass cover started to be used covering the metal receiver. The glass cover allowed the thermal energy to pass inside but acts as a barrier between the metal pipe and the wind helping to conserve the heat. The glass cover with the receiver inside is covered with the side covers. The air that persists inside after closing the said glass cover acts as a insulator in transfer of heat from the glass cover to the metal pipe thereby decreases the efficiency of the receiver as a whole. As a solution to this problem was a suggestion of creating vacuum between the space between the metal receiver and the glass cover. The loss of vacuum is significant problem in such collector at time of thermal or mechanical failure. The loss of vacuum also allows the air to space, which carries away the heat with it to free space. The said receiver also requires replacing the whole receiver in cases of damage.
US Patent application number 2010/0325889 by David Buttors disclosing "Apparatus and method for joining solar receiver tubes" and US Patent application number 2011/0049106 Al by Davis Buttors disclosing "Apparatus and method for field welding solar receiver tubes" show the methods of joining two receiver tubes at the solar field. The collector having high concentration ratio with large solar fields requires joining of a number of solar collectors in a series, thereby requiring the joining of a number of receivers. The reference patents show the method and apparatus needed for such joining. The application such as rooftop type collectors needs easy mounting and connection of the receiver. The existing collector needs special welding and joining procedure for the connection of two Receivers. It is not feasible to setup such plant on site like roof.
US Patent application number 201 1/0049106 Al discloses "Apparatus and method for field welding solar receiver tubes". The said patent application further discloses the requirement of special apparatus to hold and join the two receiver tubes. The orbital welding required for joining two receiver tubes needs to hold them with the help of special apparatus. There, it is also necessary to take special precaution during the joining procedure. It is necessary to effectively join two Receivers in series but the application such as roof top type solar concentric collector needs simple joining procedure for effective and economical viability. It is also noticeable that the joining by such methods as mentioned herein above becomes permanent type joining. However, in case of replacement of the receiver it needs the complex operational sequence.
The ever increasing demand of non conventional energy, especially the solar energy, increases need of better collection techniques which obviates the problems of the prior art and are efficient, easily maintainable and economically viable. DISADVANTAGES OF PRIOR ART
Different types of Receivers are available depending upon the requirement of application. But each of them suffers from at least one of the following problems:
1. Presently available Receivers work successfully for collectors having temperature range of 550 °C and above, but when the same Receiver is used for temperature range of 50 °C - 350 °C, having less concentration ratio of the collector, the efficiency falls down
2. Most of them are not economically viable.
3. Most of Receivers are tubular and provides less surface area to the heating fluid compared to a coil type Receiver.
4. Most of them take more start up time to heat the Heat Transfer Fluid.
5. Most of them do not provide flexibility in adjustment of temperature range and flow rate.
6. Most of them cannot withstand higher working temperature, leading to breakage in the outer glass envelope due to expansion of the metal receiver tube of Receiver.
7. Most of them are very large in length i.e. 2-4 m and are not feasible for roof-top type collectors.
8. Larger size of most of them also leads to difficulties in manufacturing, mounting, installation and transportation.
9. Joining and Interconnection of units is difficult in most of them. 10. Most of them use separate fitting and mounting accessories adds on to cost and mounting difficulties. 11. In most of them, joining of two or more units together results in permanent type of joining and thus replacement of the receiver in such cases needs complex operational sequence.
12. Most of them are not possible to assemble on site.
13. Repairing the system including breakage or requiring replacements of parts is difficult or not possible on site.
14. Most of them require special welding attachment which requires much expertise skill which adds up cost.
15. Most of them fail to provide a solution to impacts of physical conditions like snow fall, damage due to accidental hitting of stones, balls etc leading to immediate system stoppage of the system.
16. Most of them require the replacement of the whole receiver thereby having a direct impact on the economical feasibility of the system.
17. In most of the collectors, there is no provision for redirecting the scattered and deflected rays.
18. Most of them have higher manufacturing cost.
19. Most of them can expose only 90 to 180 degree of reflector surface to the sun and thus only about l/3rd part of the receiver transfers the heat to Heat Transfer Fluid limiting the efficiency of the Receiver.
Hence, there is an unmet need of an improved Heat Collection Element for Solar Collectors that work efficiently at medium operation range, economical, smaller in size, easy to assemble, durable and suitable for roof-top type collectors. OBJECTS OF THE INVENTION
The main object of the present invention is to provide an improved Heat Collection Element for Linear Collector to achieve medium operation range with high efficiency at low cost.
Another object of the present invention is to provide an improved Heat Collection Element for Linear Collector that is coil shaped which provides increased surface area to the heating fluid.
Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which has a lesser startup time.
Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which provides flexibility in temperature range and flow rate.
Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which has lesser breakage problems.
Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector wherein the smaller size of the collector makes it more viable and feasible for roof-top type collector application apart from industrial uses.
Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which is easy to transport.
Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which is easy to mount. Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which is easy to install and connect with other units.
Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which is easy to manufacture and repair.
Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which can be assembled and repaired on site.
Yet another object of the present invention is to provide an improved Heat Collection Element for Linear Collector which does not involve any special welding requiring skill and adding up of cost.
Yet another object of the present invention is to an improved Heat Collection Element for Linear Collector wherein the secondary reflector helps in increasing the efficiency of the said Heat Collection Element.
Yet another object of the present invention is to an improved Heat Collection Element for Linear Collector which has a lower manufacturing cost.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure imgf000014_0001
Collection Element according to present invention from Side.
Fig 1C • Shows the fragmented view of the present Heat
Collection Element according to present invention.
Fig 2A Shows the typical solar collection arrangement.
Fig 2B Shows the relative positioning of the secondary reflector according to the present invention with the primary reflector.
Fig 3 Shows various linear concentric type profiles of parabolic troughs of the collector.
Fig 4A • Shows the single pass Helical Coil.
Fig. 4B : Shows the multi-pass Helical Coil.
Fig 4C • Shows the Cross Section of various possible Helical
Coils.
Fig 5 Shows the cross section and front view of end cover.
Fig 6 • Shows the isometric view with cross section of end cover.
Fig 7 • Shows the end seal.
Fig 8A • Shows the front view of the secondary reflector with a clipping arrangement.
Fig 8B • Shows the side view of the secondary reflector with a clipping arrangement.
Fig 8C Shows the isometric view of the secondary reflector with a clipping arrangement.
Fig 9A • Shows the isometric view of Joining Piece from the right hand side illustrating the Outlet Facing Side of the said Joining Piece.
Fig 9B Shows the isometric view of Joining Piece from the left hand side illustrating the Inlet Facing Side of the said Joining Piece.
Fig 10A Shows the front view cross section view of interconnection of a Heat collection element unit with another such adjacent unit using a joining piece.
Fig 10B Shows the side view cross section view of interconnection of a Heat collection element unit with another such adjacent unit using a joining piece.
Fig 11 Shows the Inter Connection of Heat Collection
Element in plurality, arranged in series using Joining Piece and its mounting using mounting arrangement.
Fig 12 Shows the front view and the side view of the O Ring.
SUMMARY OF THE INVENTION
The present invention provides an improved Heat Collection Element for medium operation range Linear Solar Collector suitable for roof-top type collectors.
Meaning of reference numerals used in figures used in Fig. l to 12:
1 : Heat Collection Element
2 : Inlet
2a : Inlet End Cover
2b : First Hole
2c : First Threaded Groove d Inlet End Seal
e Second hole
f Second Threaded Groove
g First Extruded Part
h Inlet Connection Hose
i First Groove
j Second Groove
k Third Groove
1 Fourth Groove
Outlet
a Outlet End Cover
b Third hole
c Third Threaded Groove
d Outlet End Seal
e * Fourth Hole
f Fourth Threaded Groove
g Second Extruded Part
h Outlet Connection Hose
i Fifth Groove
j Sixth Groove
k Seventh Groove
1 Eighth Groove
Helical Coil
Expansion Compensating Mechanism
Glass Cover
Space
Secondary Reflector
Clipping Arrangement
0 Primary Reflector
1 Receiver
1a Receiver Metal Tube l ib : Receiver Glass Cover
12 : Joining Piece
12A : Outlet Facing Side
12B : Inlet Facing Side
12a : Upper Section
12b : Lower Section
12c : Third Extruded Part
12d : Fifth Hole
12e : Sixth Hole
12f : Ninth Groove
12g : Seventh Hole
12i : Tenth Groove
12j : Plurality of Holes
12k : Bolt and Nut
121 : Eighth Hole
12m Eleventh Groove
12n : Ninth Hole
12o : Twelfth Groove
13 : Mounting arrangement
14a : First O ring
14b : Second 0 ring
14c : Third 0 ring
14d : Fourth O ring
The present invention mainly embodies an improved Heat Collection Element (1) for Linear Solar Collector which mainly comprises of: a helical coil (4);
a glass cover (6);
end covers (2a and 3a);
end seals (2d and 3d); • connection hose (2h and 3h);
• a secondary reflector (8);
• a clipping arrangement (9);
• a joining piece (12) and
• a mounting arrangement (13).
The said Heat Collection Element (1) has one end of it that acts as Inlet (2) for the Heat Transfer Fluid and the opposite end act as an Outlet (3).
A hollow Helical Coil (4) made of metal such as copper, with a selective coating is provided to enhance absorption of solar energy. The said Helical Coil (4) has Expansion Compensating Mechanism (5) on ends that have a spaced pitch between the helical turns wherein the suggested value of the said Expansion Compensating Mechanism (5) is between 0.1L to 0.2L on both the ends.
A Glass Cover (6) is provided to cover the said hollow Helical Coil (4) and thereby to avoid the energy loses from the said Helical Coil (4). The said Glass Cover (6) is provided with the Second Threaded Groove (2f) on Inlet (2) and Fourth Threaded Groove (3f).
End Covers (2a and 3a) are provided for closing the said Glass Cover (6) with the said hollow Helical Coil (4) inside where, an Inlet End Cover (2a) is provided at Inlet (2) end and Outlet End Cover (3a) is provided at the Outlet (3) end. The said Inlet End Cover (2a) consists of a First Threaded Groove (2c) for fixing the said Inlet End Cover (2a) with the Second Threaded Groove (2f) of the said Glass Cover (6). Further, the said Inlet End Cover (2a) consists of a First Hole (2b) to allow the traversing of the said Inlet Connection Hose (2h); a Second Groove (2j) for fixing the said Inlet End Seal (2d) and a First Extruded Part (2g) with a Third Groove (2k). The said Outlet End Cover (3a) is used to close the said Glass Cover (6) at Outlet (3) whereby the said Outlet End Cover (3a) consists of a Third Threaded Groove (3c) for fixing the Outlet End Cover (3a) with the Fourth Threaded Groove (3f) of the said Glass Cover (6). Further, the said Outlet End Cover (3a) consists of a Third Hole (3b) to allow the traversing of the said Outlet Connection Hose (3h); a Sixth Groove (3j) for fixing the Outlet End Seal (3d) and a Second extruded part (3g) with a Seventh Groove (3k).
A Space (7) between the said Glass Cover (6) and the said Helical Coil (4) is filled with heat conductive gases like argon.
Inlet End Seal (2d) and an Oxitlet End Seal (3d) are provided inside the said Inlet End Cover (2a) and Outlet End Cover (3a) respectively for : avoiding the leakage of said gases. The said . End Seals are of the material such as high temperature resistant rubber. ' The said Inlet End Seal (2d) is provided with a Second Hole (2e) for allowing the traversing of the said Inlet Connection Hose (2h) and a Fourth Groove (21) to fix on the said Second Groove (2j) of the said Inlet End Cover (2a) while the said Outlet End Seal (3d) is provided with a Fourth Hole (3e) to allow traversing of the said Outlet Connection Hose (3h) and a Eighth Groove (31) to fix with the Sixth .Groove . (3j) of the said Outlet End Cover (3a).
An Inlet Connection Hose (2h) traversing through, the First Hole (2b) and the Second Hole (2e) provided respectively in the said Inlet End Cover (2a) and said Inlet End Seal (2d) for the ingress of Heat Transfer Fluid, and an Outlet Connection Hose (3h) traversing through the Third Hole (3b) and Fourth Hole (3e) respectively provided in the said Outlet End Cover (3a) and Outlet End Seal (3d.) for the egress of the said Heat Transfer Fluid, whereby the said Inlet Connection Hose (2h) is welded with the said Helical Coil (4) at Inlet (2)and the said Outlet Connection Hose (3h) is welded with the said Helical Coil (4) at Outlet
(3) .
A Secondary Reflector (8) is fixed on outer side on the Glass Cover (6) of the said Heat Collection Element "( 1) and is provided for facilitating the capturing of the reflected rays that bypasses the said Helical Coil
(4) of the said Heat Collection Element ( 1) and focusing it back to the said Heat Collection Element (1). The said Secondary Reflector (8) is a Reflective sheet curved in compound parabolic shape.
A Clipping Arrangement (9) is provided for fixing the said a Secondary Reflector (8). The said Clipping Arrangement (9) is preferably made of non-corrosive metal having weather proof Coating to protect it from climatic variation. ί
A Joining Piece ( 12) is provided to facilitate interconnection of two'
ii units of said Heat Collection Element ( 1) when arranged in plurality in a series. The said Joining piece ( 12) has an Upper section ( 12a), a Lower section (12b) and a Third extruded part ( 12c). The said Upper section ( 12a) and the said Lower section ( 12b) are joined together with bolt and nut ( 12k) at Fifth Hole ( 12d) and the said lower section ( 12b) and the said Third extruded part ( 12c) are permanently attached. The said Joining Piece (12) has an Outlet Facing Side ( 12A) that faces the Outlet (3) of a Heat Collection Element ( 1) in a series and an Inlet Facing Side ( 12B) that faces the Inlet (2) of adjacent Heat Collection Element ( 1) in a series. The said Joining Piece ( 12) is provided with a Sixth Hole ( 12e), on the said Outlet Facing Side ( 12A) which fixes with the Outlet Connection Hose (3h) of one unit of the said Heat Collection Element ( 1) whereby the proper fixing of the said Sixth Hole ( 12e) and the said Outlet Connection Hose (3h) is facilitated by a First O ring (14a) between a ninth groove (12f) at the said Sixth Hole (12e) and a Fifth Groove (3i) at the Outlet Connection Hose (3h). An Eighth Hole (121) is provided on the said Inlet Facing Side (12B) of the said Joining Piece (12) which fixes with the Inlet Connection Hose (2h) of adjacent unit of Heat Collection Element (1) and the proper fixing of the said Eighth Hole (121) and the said Inlet Connection Hose (2h) is facilitated by a Second O ring (14b) between a eleventh groove (12m) at the said Eighth Hole (121) and First Groove (2i) of the said Inlet Connection Hose (2h). A Seventh Hole (12g) is provided on the said Outlet Facing Side (12A) for fixing the said Outlet End Cover (3a) of one unit of the said Heat Collection Element (1) whereby the proper fixing of the said Seventh Hole (12g) the said Outlet End Cover (3a) is facilitated by a Third O ring (14c) between a tenth groove (12i) at the said Seventh Hole (12g) and a Third Groove (2k) at the Outlet End Cover (3a). A Ninth Hole (12n) is provided on the said Inlet Facing Side (12B) for fixing the said Inlet End Cover (2a) of adjacent unit of Heat Collection Element (1) whereby the proper fixing of the said Ninth Hole (12n) and the said Inlet End Cover (2a) is facilitated by a Fourth O ring (14d) between a Twelfth Groove (12o) at the said Ninth Hole (12n) and a; Seventh Groove (3k) at the said Inlet End Cover (2a). The said Third Extruded Part (12c) consists of Plurality of Holes (12j) for fixing the said Joining Piece (12) with a Mounting Arrangement (13).
Another embodiment of the present invention is to provide multi pass
Helical Coil (4) to be used when a high mass flow rate is required. The said multi-pass Helical Coil (4) is made by bending plurality hollow metal pipe. Thus said multi-pass Helical Coil (4) has plurality of turns and plurality of starting points. The bending of plurality of pipes (two or more) is done along the parallel axis with respect to each other. The ends of the said Helical Coil (4) are welded respectively with Inlet Connection Hose (2h) and Outlet Connection Hose (3h) for the ingress and egress of the Heat Transfer Fluid.
DETAIL DESCRIPTION OF THE INVENTION
The features, nature and advantages of the disclosed subject matter will become more apparent from the detail description set forth below when taken in conjunction with the drawings in which like reference numerals identify correspondingly throughout.
The present invention embodies an improved Heat Collection Element (1) for Linear Solar Collector to achieve medium operation range with high efficiency at low cost.
Referring to Fig.1 shows cross section view of the present Heat Collection Element (1) according to present invention from Front (Fig 1A) and from Side (Fig IB). The said Heat Collection Element (1) has a construction of component parts as described hereinafter. One end of the said Heat Collection Element (1) acts as Inlet (2) for the Heat Transfer Fluid and the opposite end act as an Outlet (3). A hollow Helical Coil (4) made by helically bending a hollow metal pipe which includes a copper pipe is inserted in to a Glass Cover (6). Bending the said metal pipe into the Helical Coil (4) increases the surface area and thereby the Heat Transfer Area for the Heat Transfer Fluid. The helical turns of the said Helical Coil (4) have a higher pitch on the ends to provide an Expansion Compensating Mechanism (5) as described in Fig 4. The said Helical Coil (4) has a selective coating to enhance absorption of solar energy. The said Glass Cover (6) with the said Helical Coil (4) inside has an Inlet End Cover (2a) at Inlet (2) end and Outlet End Cover (3a)' at the Outlet (3) end. Gases including Argon, which facilitate heat transfer from Glass Cover (6) to the Helical Coil (4), are filled in the Space (7) between the said Glass Cover (6) and the said Helical Coil (4). An Inlet End Seal (2d) and an Outlet End Seal (3d) of the material such as high temperature resistant rubber is fixed inside the said Inlet End Cover (2a) and Outlet End Cover (3a) respectively for avoiding the leakage of said gases. Further, the said Helical Coil (4) is attached with an Inlet Connection Hose (2h) which in turn traverses through the First Hole (2 b) and the Second Hole (2e) provided respectively in the said Inlet End Cover (2a) and said Inlet End Seal (2d). The said Inlet Connection Hose (2h) is provided for ingress of the Heat Transfer Fluid into the said Helical Coil (4). Also, an Outlet Connection Hose (3h) is attached to the said Helical Coil (4) at the opposite end and traverses through the Third Hole (3b) and Fourth Hole (3e) respectively provided in the said Outlet End Cover (3a) and Outlet End Seal (3d). The said Outlet Connection Hose (3h) is provided for the egress of the said Heat Transfer Fluid. A Secondary Reflector (8) is fixed on outer side on the Glass Cover (6) of the said Heat Collection Element (1) using Clipping Arrangement (9). Fig. 1C shows the fragmented view of the present Heat Collection Element (1) according to present invention.
Referring to Fig. 2 shows the typical solar collection arrangement of linear concentric type profile. The existing Receiver (1 1) is generally provided with a Receiver Metal Tube (11a) and a Receiver Glass Cover (l ib), fixed at the focal length of Primary Reflector ( 10) using a mounting arrangement. The said Receiver Glass Cover (l ib) is provided to reduce the convective losses due to wind. Further, the said Primary Reflector (10) has Reflecting Sheet such as Mirror fixed on the Profiled Structure. Fig 2B shows the relative positioning of the Secondary Reflector (8) according to the present invention with the primary reflector (10) Referring to Fig. 3 shows the various linear concentric type profiles of parabolic troughs of the collector. Fig. 3A shows parabolic troughs with a parabolic shape whose focal point is outside the parabola whereas Fig. 3B and 3C is a compound parabolic trough with a focal point inside the geometrical shape of the said parabolic trough type of collector. Variations in the shape of the troughs results in different concentrate type profiles of the collectors. Such variations in the profile increase aperture area for same reflector size and focus the reflected rays at focal line.
Referring to Fig. 4 shows Helical Coil (4) of Heat Collection Element (1). The said Helical Coil (4) is made by helically bending a hollow metal pipe. Plurality of such hollow metal pipes is bent to form multi start helical structure. The selection for the said Helical Coil (4) to have single or multi turns depends upon the requirement of mass flow rate and temperature range. Fig. 4A shows a single pass Helical Coil (4) with single turn; and the said Helical Coil (4) has a singular starting point. For the purpose of flow of Heat Transfer Fluid into and out of the said Helical Coil (4); the said Helical Coil (4) is welded at the ends respectively with Inlet Connection Hose (2h) and Outlet Connection Hose (3h). Fig. 4B shows a multi-pass Helical Coil (4) with has dual turns and two starting points. For the purpose of the said multi pass Helical Coil (4), bending of plurality of pipes (two or more) is done along the parallel axis with respect to each other and has multiple starting points. The ends of the said Helical Coil (4) are welded respectively with Inlet Connection Hose (2h) and Outlet Connection Hose (3h) for the ingress and egress of the Heat Transfer Fluid. Further, The Helical Coil (4) has Expansion Compensating Mechanism (5) on both the ends. For compensating expansion, it is preferred in the present invention to take spaced pitch between the helical turns of the said Helical Coil (4). Further, the suggested value of such Expansion Compensating Mechanism (5) shall be between 0.1L to 0.2L on both the ends for the purpose of the present invention. The said Expansion Compensating Mechanism (5) also facilitates absorption of thermal shocks. The said Inlet Connection Hose (2h) and Outlet Connection Hose (3h) also has a First Groove (2i) and a Fifth Groove (3i) respectively for enabling connections with other unit of the Heat Collection Element (1). Fig. 4C shows the Cross Section of various possible Helical Coils.
Fig. 5 and 6 refer to End Covers where Fig 5 shows cross section of front view of End Cover (2a and 3a) and Fig. 6 shows the isometric view with cross section of End Covers (2a and 3a). the said Inlet End Cover (2a) is used to close the said Glass Cover (6) at Inlet (2) whereby the said Inlet End Cover (2a) consists of a First Threaded Groove (2c) for fixing the said Inlet End Cover (2a) with the Second Threaded Groove (2f) of the said Glass Cover (6) and the said Outlet End Cover (3a) is used to close the said Glass Cover (6) at' Outlet (3) whereby the said Outlet End Cover (3a) consists of a Third Threaded Groove (3c) for fixing the Outlet End Cover (3a) with the Fourth Threaded Groove (3f) of the said Glass Cover (6). Further, the said Inlet End Cover (2a) consists of a First Hole (2b) to allow the traversing of the said Inlet Connection Hose (2h); a Second Groove (2j) for fixing the said Inlet End Seal (2d) and a First Extruded Part (2g) with a Third Groove (2k) while the said Outlet End Cover (3a) consists of a Third Hole (3b) to allow the traversing of the said Outlet Connection Hose (3h); a Sixth Groove (3j) for fixing the Outlet End Seal (3d) and a Second Extruded Part (3g) with a Seventh Groove (3k). The said Third Groove (2k) and the said Seventh Groove (3k) are provided to fix an O ring. The said O ring (14) ensures proper fixing different units of said Heat Collection Element (1) as described later. Referring to Fig. 7 shows view of the End Seals (2d and 3d). The said Inlet End Seal (2d) is provided with a Second Hole (2e) for allowing the traversing of the said Inlet Connection Hose (2h) and a Fourth Groove (21) to fix on the said Second Groove (2j) of the said Inlet End Cover (2a). Also, the Outlet End Seal (3d) is provided with a Fourth Hole (3e) to allow traversing of the said Outlet Connection Hose (3h) and a Eighth Groove (31) to fix with the Sixth Groove (3j) of the said Outlet End Cover (3a).
Referring to Fig. 8 shows the Secondary Reflector (8) with Clipping Arrangement (9). The said Secondary Reflector (8) is a Reflective sheet curved in compound parabolic shape and facilitates capturing of the reflected rays that bypasses the said Helical Coil (4) of the said Heat Collection Element (1) and focuses it back to the said Heat Collection Element (1). Fig. 8 A shows the front view of Secondary Reflector (8) with a Clipping Arrangement (9). The said Clipping Arrangement (9) is permanently attached to the said Secondary Reflector (8). Fig. 8B shows side view of the Secondary Reflector (8) with the said Clipping Arrangement (9). The said Clipping Arrangement (9) mentioned hereinabove is preferably made of noncorrosive metal having weather proof Coating to protect it from climatic variation. Further, Fig. 8C shows the isometric view of the Secondary Reflector (8) with a Clipping Arrangement (9).
Fig. 9 and 10 refers to the Joining Piece (12); Fig. 9 shows the isometric view of Joining Piece (12); where Fig. 9A shows the isometric view of Joining Piece (12) from the right hand side illustrating the Outlet Facing Side (12A) of the said Joining Piece (12) and Fig. 9B shows the isometric view of Joining Piece (12) from the left hand side illustrating the Inlet Facing Side (12B) of the said Joining Piece (12). Fig. 10 shows the cross section front view (Fig. 10A) and cross section side view (Fig. 10B) of interconnection of two Heat Collection Element (1) using a Joining Piece (12). A Joining piece (12) is provided to facilitate interconnection of two adjacent units of the said Heat Collection Element (1). The said Joining Piece has an Upper section (12a), a Lower section (12b) and a Third extruded part (12c). The said Upper section (12a) and the said Lower section (12b) are joined together with bolt and nut (12k) at Fifth Hole (12d) the said lower section (12b) and the said Third extruded part (12c) are permanently attached. The said Joining Piece (12) has an Outlet Facing Side (12A) that faces the Outlet (3) of a Heat Collection Element (1) in a series and an Inlet Facing Side (12B) that faces the Inlet (2) of adjacent Heat Collection Element (1) in a series as clearly depicted in Fig. 10A. The said Joining Piece (12) is provided with a Sixth Hole (12e), on the said Outlet Facing Side (12A) which fixes with the Outlet Connection Hose (3h) of one unit of the said Heat Collection Element (1). The proper fixing of the said Sixth Hole (12e) and the said Outlet Connection Hose (3h) is facilitated by a First O ring (14a) between a ninth groove (12f) at the said Sixth Hole (12e) and a Fifth Groove (3i) at the Outlet Connection Hose (3h). In the same manner, an Eighth Hole (121) is provided on the said Inlet Facing Side (12B) of the said joining piece (12) which fixes with the Inlet Connection Hose (2h) of adjacent unit of Heat Collection Element (1). And the proper fixing of the said Eighth Hole (121) and the said Inlet Connection Hose (2h) is facilitated by a Second O ring (14b) between a eleventh groove (12m) at the said Eighth Hole (121) and First Groove (2i) of the said Inlet Connection Hose (2h). Further, a Seventh Hole (12g) is provided on the said Outlet Facing Side (12A) for fixing the said Outlet End Cover (3a) of one unit of the said Heat Collection Element (1). The proper fixing of the said Seventh Hole (12g) the said Outlet End Cover (3a) is facilitated by a Third O ring (14c) between a tenth groove (12i) at the said Seventh Hole (12g) and a Third groove (2k) at the Outlet End Cover (3a). In the same manner, a Ninth Hole (12n) is provided on the said Inlet Facing Side (12B) for fixing the said Inlet End Cover (2a) of adjacent unit of Heat Collection Element (1). The proper fixing of the said Ninth Hole (12n) and the said Inlet End Cover (2a) is facilitated by a Fourth O ring
(14d) between a Twelfth Groove (12o) at the said Ninth Hole (12n) and a Seventh Groove (3k) at the said Inlet End Cover (2a). The said Third Extruded Part (12c) consists of Plurality of Holes (12j) for fixing the said Joining Piece (12) with a Mounting Arrangement (13) as depicted in Fig. 1 1
Referring to Fig. 11 shows the Inter Connection of Heat Collection Element (1) in plurality, arranged in series using Joining Piece (12) and it's mounting using mounting arrangement (13).
Referring to Fig. 12 shows the front view and the side view of the O Ring.
Further, hereinbefore disclosed is the preferred embodiment of the said improved Heat Collection Element (1) with reference to accompanying drawings. Here, it is to be noted that the present invention is not limited thereto. Furthermore, the component parts described are not meant there to limit its operating, and any rearrangement of the component parts for achieving the same functionality is still within the spirit and scope of the present invention. It is to be understood that the drawings are not drawn to scale and are only for illustration purposes. WORKING OF THE INVENTION
For the purpose of the present invention, the Heat Collection Element (1) for Linear Solar Collector disclosed hereinabove is fixed at a focal point of a linear collector. Plurality of such Heat Collection Element (1) is interconnected in a series using Joining Piece (12) and is mounted using mounting arrangement (13). The Heat Transfer Fluid enters in to the said Heat Collection Element (1) from the said Input Connection Hose (2h) and passes through the said Helical Coil (4) which is a single pass or a multi pass coil. The said Helical Coil (4) gets heated as the rays get reflected from the collector and concentrate on it. The reflected rays that circumvent due to the pitch distance gets collected by Secondary Reflector (8) and are focused back to the Heat Collection Element (1) thereby ensuring energy collection from complete set of rays available for efficient heating. Further, the resultant heated Heat Transfer Fluid moves out of the said Heat Collection Element (1) through Outlet Connection Hose (3h). Where the said collectors are in series; the said Heat Transfer Fluid moves out from Outlet Connection Hose (3h) of one Heat Collection Element (1) of the said collectors in series and enters in to the Inlet Connection Hose (2h) of another Heat Collection Element (1) of the collector adjacently attached to it. In the same manner, the said Heat Transfer Fluid moves from First Heat Collection Element (1) to the adjacent and then to the next till the last unit in the series and the Heat Transfer Fluid gets heated attaining higher temperature from each of the said units of the Heat Collection Element (1) than the temperature attained in the previous unit. The number of units of the Heat Collection Element (1) to be used depends on the requirement of temperature range and the volume. The said Heat Collection Element (1) as described herein above works efficiently in the temperature range of 50-350°C as per the analysis shown below in the Graph 1.
Figure imgf000031_0001
0 100 200 300 400 500 600
Temperature (°C)
Graph 1: Comparision of Efficiency of the present improved Heat Collection Element (1) with the existing collectors and receiver.
The Graph 1 represents the temperature on its horizontal axis and the efficiency on vertical axis. The curve representing the Flat Plate Collector, which is generally used for temperature range of 50°C - 80°C shows that its efficiency suitable for temperature below 100°C, which decreases drastically with increase in temperature and mass flow rate. Another curve representing the Evacuated Tube Collector, which has lower thermal losses, is efficient for temperature range of 60°C-150°C. Further, the curve representing Parabolic Trough Collector with Existing Receiver shows that it is suitable for higher temperature range. Furthermore, the line representing the Parabolic
Trough Collector with the present improved Heat Collection Element (1) shows its broad coverage range from temperatures from 50°C- 350°C that is the present improved Heat Collection Element (1) provides an advantage over Flat Plate Collectors, Evacuated Tube Collectors as well as Parabolic Trough Collector with Existing Receiver. Additionally, the said curve for Parabolic Trough Collector with the present improved Heat Collection Element (1) represents higher efficiency as compared to the Parabolic Trough Collector with Existing Receiver in the medium temperature range proving it to be more efficient and suitable for medium temperature operation range for linear collectors including parabolic troughs. Also, the present improved Heat Collection Element (1) covers a lower working temperature range due to the coil type arrangement and presence of highly conductive gases respectively. This makes it suitable for collectors including roof-top type collectors required for the medium temperature range of 50°C-350°C and medium mass flow rate.
ADVANTAGES OF THE INVENTION
1. The proposed invention is highly efficient and feasible for medium temperature operation range i.e. for 50°C-350°C temperatures.
2. The coiled shape of the Heat Collection Element of the present invention provides maximum surface area to the Heating Transfer Fluid increasing its efficiency.
3. The Heat Collection Element of the present invention is narrow and hence circulates lesser volume of heating fluid at a time and hence the startup time is less for the system.
4. The helical coil of the present invention can be single start or multi start, which helps to adjust the range of flow rate as well as the range of temperature of the Heat Transfer Fluid according to the requirement. The helical coil of the present invention has spaced pitch at its end, helping to overcome the expansion of coil during heating at higher temperature.
Smaller size and medium operation range makes the present invention feasible for roof top type collectors.
Small size of the present invention also facilitates easy manufacture, mounting, installation and transportation.
The end covers of the Heat Collection Element in the present invention itself has fitting and mounting arrangement which helps for easy mounting of the Heat Collection Element on collector using joining piece.
The helical coil of the present invention itself has connection arrangements facilitating connection with other units.
It is possible to assemble and repair the present system on site. In case of requirement of replacement, the unit to be replaced is easily detachable as the interconnection is not a permanent type. No special welding is involved requiring skill and adding up the cost.
The secondary reflector of the present invention redirects deflected rays to the Heat Collection Element that initially did not reach or hit the said Heat Collection Element.
The present invention has a lower manufacturing cost.

Claims

1. An improved Heat Collection Element (1) for Linear Solar Collector mainly comprises of: a hollow Helical Coil (4) made of metal such as copper, with a selective coating to enhance absorption of solar energy; a Glass Cover (6) to cover the said hollow Helical Coil (4); an Inlet End Cover (2a) at Inlet (2) end and Outlet End Cover (3a) at the Outlet (3) end for closing the said Glass Cover (6) with the said hollow Helical Coil (4) inside; a Space (7) between the said Glass Cover (6) and the said Helical Coil (4) filled with heat conductive gases like argon; an Inlet End Seal (2d) and an Outlet End Seal (3d) of the material such as high temperature resistant rubber fixed inside the said Inlet End Cover (2 a) and Outlet End Cover (3a) respectively for avoiding the leakage of said gases; an Inlet Connection Hose (2h) traversing through the First Hole (2b) and the Second Hole (2e) provided respectively in the said Inlet End Cover (2a) and said Inlet End Seal (2d) for the ingress of Heat Transfer Fluid, and an Outlet Connection Hose (3h) traversing through the Third Hole (3b) and Fourth Hole (3e) respectively provided in the said Outlet End Cover (3a) and Outlet End Seal (3d) for the egress of the said Heat Transfer Fluid, whereby the said Inlet Connection Hose (2h) is welded with the said Helical Coil (4) at Inlet (2) and the said Outlet Connection Hose (3h) is welded with the said Helical Coil (4) at Outlet (3); a Secondary Reflector (8) is fixed on outer side on the Glass Cover (6) of the said Heat Collection Element (1) for facilitating the capturing of the reflected rays that bypasses the said Helical Coil (4) of the said Heat Collection Element (1) and focusing it back to the said Heat Collection Element (1); a Clipping Arrangement (9) for fixing the said Secondary Reflector (8) on said Glass cover (6); and a Joining Piece (12) to facilitate interconnection of two units of said Heat Collection Element (1) when arranged in plurality in a series.
2. An improved Heat Collection Element (1) for Linear Solar Collector as claimed in claim 1; wherein the said Helical Coil (4) is single pass or multi pass.
3. An improved Heat Collection Element (1) as claimed in claim 1; wherein Helical Coil (4) has Expansion Compensating Mechanism (5) on both the ends.
4. An improved Heat Collection Element (1) for Linear Solar Collector as claimed in claim 3 has an Expansion Compensating Mechanism (5) that further has a spaced pitch between the helical turns of the said Helical Coil (4).
5. An improved Heat Collection Element (1) for Linear Solar Collector as claimed in claim 3 and claim 4, wherein the value of the said Expansion Compensating Mechanism (5) is between 0.1L to 0.2L on both the ends.
6. An improved Heat Collection Element (1) for Linear Solar Collector as claimed in claim 1 wherein the said Inlet End Cover (2a) is used to close the said Glass Cover (6) at Inlet (2) whereby the said Inlet End Cover (2a) consists of a First Threaded Groove (2c) for fixing the said Inlet End Cover (2a) with the Second Threaded Groove (2f) of the said Glass cover (6) and the said Outlet End Cover (3a) is used to close the said Glass Cover (6) at Outlet (3) whereby the said Outlet End Cover (3a) consists of a Third Threaded Groove (3c) for fixing the Outlet End Cover (3a) with the Fourth Threaded Groove (3f) of the said Glass cover (6).
7. An improved Heat Collection Element (1) for Linear Solar Collector as claimed in claim 1 wherein the said Inlet End Cover (2 a) consists of a First Hole (2b) to allow the traversing of the said Inlet Connection Hose (2h); a Second Groove (2j) for fixing the said Inlet End Seal (2d) and a First Extruded Part (2g) with a Third Groove (2k) while the said Outlet End Cover (3a) consists of a Third Hole (3b) to allow the traversing of the said Outlet Connection Hose (3h); a Sixth Groove (3j) for fixing the Outlet End Seal (3d) and a Second Extruded Part (3g) with a Seventh Groove (3k).
8. An improved Heat Collection Element (1) for Linear Solar Collector as claimed in claim 1 wherein the said Inlet End Seal (2d) is provided with a Second Hdle (2e) for allowing the traversing of the said Inlet Connection Hose (2h) and a Fourth Groove (21) to fix on the said Second Groove (2j) of the said Inlet End Cover (2a) while the said Outlet End Seal (3d) is provided with a Fourth Hole (3e) to allow traversing of the said Outlet Connection Hose (3h) and a Eighth Groove (31) to fix with the Sixth Groove (3j) of the said Outlet End Cover (3a).
9. An improved Heat Collection Element (1) for Linear Solar Collector as claimed in claim 1 wherein the said Secondary Reflector (8) is a
Reflective sheet curved in compound parabolic shape.
10. An improved Heat Collection Element (1) for Linear Solar Collector as claimed in claim 1 wherein the said Clipping Arrangement (9) is preferably made of non-corrosive metal having weather proof coating to protect it from climatic variations.
11. An improved Heat Collection Element (1) for Linear Solar Collector as claimed in claim 1 wherein the said Joining Piece (12) has an Upper section (12a), a Lower section (12b) and a Third extruded part (12c).
12. An improved Heat Collection Element (1) for Linear Solar Collector with a Joining piece (12) as claimed in claim 11 whereby said Upper section (12a) and the said Lower section (12b) are joined together with bolt and nut (12k) at Fifth Hole (12d) and the said lower section (12b) and the said Third extruded part (12c) are permanently attached.
13. An improved Heat Collection Element (1) for Linear Solar Collector with a Joining piece (12) as claimed in claim 11 and 12 wherein the said Joining Piece (12) has an Outlet Facing Side (12A) that faces the Outlet (3) of a Heat Collection Element (1) in a series and an Inlet Facing Side (12B) that faces the Inlet (2) of adjacent Heat Collection Element (1) in a series.
14. An improved Heat Collection Element (1) for Linear Solar Collector with a Joining piece (12) as claimed in claim 11, 12 and 13, wherein the said Joining Piece (12) is provided with a Sixth Hole (12e), on the said Outlet Facing Side (12A) which fixes with the Outlet Connection Hose (3h) of one unit of the said Heat Collection Element (1) whereby the proper fixing of the said Sixth Hole (12e) and the said Outlet Connection Hose (3h) is facilitated by a First O ring (14a) between a ninth groove (12f) at the said Sixth Hole (12e) and a Fifth Groove (3i) at the Outlet connection hose (3h).
15. An improved Heat Collection Element (1) for Linear Solar Collector with a Joining piece (12) as claimed in claim 11, 12, 13 and 14, wherein an Eighth Hole (121) is provided on the said Inlet Facing Side (12B) of the said joining piece (12) which fixes with the Inlet Connection Hose (2h) of adjacent unit of Heat Collection Element (1) and the proper fixing of the said Eighth Hole (121) and the said Inlet Connection Hose (2h) is facilitated by a Second O ring (14b) between a eleventh groove (12m) at the said Eighth Hole (121) and First Groove (2i) of the said Inlet Connection Hose (2h).
16. An improved Heat Collection Element (1) for Linear Solar Collector with a Joining piece (12) as claimed in claim 11, 12, 13, 14 and 15, wherein a Seventh Hole (12g) is provided on the said Outlet Facing Side (12A) for fixing the said Outlet End Cover (3a) of one unit of the said Heat Collection Element (1) whereby the proper fixing of the said Seventh Hole (12g) the said Outlet End Cover (3a) is facilitated by a Third O ring (14c) between a tenth groove (12i) at the said Seventh Hole (12g) and a Third Groove (2k) at the Outlet End Cover (3a).
17. An improved Heat Collection Element (1) for Linear Solar Collector with a Joining piece (12) as claimed in claim 1 1, 12, 13, 14, 15 and 16 wherein a Ninth Hole (12n) is provided on the said Inlet Facing Side (12B) for fixing the said Inlet End Cover (2a) of adjacent unit of Heat Collection Element (1) whereby the proper fixing of the said Ninth Hole (12n) and the said Inlet End Cover (2a) is facilitated by a Fourth O ring (14d) between a Twelfth Groove (12o) at the said Ninth Hole (12n) and a Seventh Groove (3k) at the said Inlet End Cover (2 a).
18. An improved Heat Collection Element (1) for Linear Solar Collector with a Joining piece (12) as claimed in claim 11 wherein the said Third Extruded Part (12c) consists of Plurality of Holes (12j) for fixing the said Joining Piece (12) with a Mounting Arrangement (13).
PCT/IN2013/000357 2012-06-07 2013-06-05 An improved heat collection element for linear collector WO2013183067A2 (en)

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CN108088098A (en) * 2018-02-08 2018-05-29 广州聚能太阳能科技有限公司 A kind of fluid delivery structure for straight-through type solar energy heat collector
CN108151333A (en) * 2018-02-08 2018-06-12 广州聚能太阳能科技有限公司 A kind of straight-through type solar energy collecting system
CN114739018A (en) * 2022-04-08 2022-07-12 北京立可尔新能源科技有限公司 High-heat-conduction W-shaped vacuum heat-collecting tube solar heat-collecting system
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