Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S10/00—Solar heat collectors using working fluids
  • F24S10/50—Solar heat collectors using working fluids the working fluids being conveyed between plates
  • F24S10/506—Solar heat collectors using working fluids the working fluids being conveyed between plates having conduits formed by inflation of portions of a pair of joined sheets
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S10/00—Solar heat collectors using working fluids
  • F24S10/50—Solar heat collectors using working fluids the working fluids being conveyed between plates
  • F24S10/502—Solar heat collectors using working fluids the working fluids being conveyed between plates having conduits formed by paired plates and internal partition means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S10/00—Solar heat collectors using working fluids
  • F24S10/50—Solar heat collectors using working fluids the working fluids being conveyed between plates
  • F24S10/55—Solar heat collectors using working fluids the working fluids being conveyed between plates with enlarged surfaces, e.g. with protrusions or corrugations
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S80/00—Details, accessories or component parts of solar heat collectors not provided for in groups F24S10/00-F24S70/00
  • F24S2080/03—Arrangements for heat transfer optimization
  • F24S2080/05—Flow guiding means; Inserts inside conduits
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F2275/00—Fastening; Joining
  • F28F2275/06—Fastening; Joining by welding
  • F28F2275/067—Fastening; Joining by welding by laser welding
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/40—Solar thermal energy, e.g. solar towers
  • Y02E10/44—Heat exchange systems

Definitions

• Solar collectors are required to convert solar energy into heat.
• the solar energy can be stored in many ways. A much pplied method of storing the solar energy is by means of a solar boiler.
• a solar boiler is a tank in which water is stored which has been heated by the sun. The energy stored in the water can be transferred to for instance tap water by means of heat exchangers.
• the so-called solar collectors operate with liquids as medium.
• the efficiency is therefore low.
• the object of the present invention is to realize a solar collector with a high efficiency, i.e. one which converts a greater percentage of the energy received per surface area into energy absorbed by the medium.
• the present invention provides a solar collector, comprising: - a first plate for collecting solar energy,
• This device has the advantage that the medium is in direct contact with the whole surface area of the plate which comes into contact with the solar energy in the first instance. This is a great improvement relative to existing solutions because in existing solutions the medium flows through a pipe which is arranged against an energy-absorbing plate, wherein the greater part of the energy has to travel a longer distance in order to reach the medium and there is a much smaller surface area between the medium and the metal through which the medium flows in order to transfer the heat. These two factors result in a lower energy absorption and greater losses .
• a first embodiment of the invention comprises a framework for fixing the plates at a mutual distance along the edges thereof so as to seal the space between the plates and to create space between the plates which enclose the liquid.
• a second preferred embodiment provides ribs placed between the first and second plate in a manner such that, as seen from bottom to top, they substantially seal the space between the two plates, so that a zigzag- shaped throughflow channel for the liquid is created inside a space enclosed by the plates and the framework.
• Such a construction enables the liquid to flow through a narrower but longer channel through the absorption means. If a throughflow channel becomes too wide, the flow speed in the absorption means will not be the same everywhere, or will at least have a greater variation than in the case of narrower channels, whereby the heat- transfer efficiency will deteriorate.
• the slowly flowing parts of the medium will be situated in the absorption means for longer and thereby absorb less heat, since heat absorption depends on the temperature difference.
• a further preferred embodiment of the invention provides that the ribs are arranged substantially parallel on two parts of the framework placed opposite one another.
• This embodiment is brought about in practice by liquid channels which run perpendicularly in zigzag shape through the heat absorption means or a plurality of channels which run parallel to each other through the absorption means.
• liquid channels which run perpendicularly in zigzag shape through the heat absorption means or a plurality of channels which run parallel to each other through the absorption means.
• a further preferred embodiment of the present invention provides a solar collector wherein the first and the second plate are welded together along the edges with edge joints.
• This embodiment is preferably further provided with welded joints parallel to two parallel edges which extend from a side wall to a predetermined point situated at a distance from the opposite side of the collector as seen from the start of the welded joint.
• the plates are preferably also provided with weld points in a predetermined pattern for holding the plates together. The plates preferably move apart between the edge joints, welded joints and weld points. If two plates of stainless steel are welded together along the edges and subsequently provided with the welded joints and the weld points, it then becomes possible to cause the plates to move apart between the edge joints, welded joints and weld points.
• This embodiment has the particular advantage that it can be manufactured inexpensively.
• -A further preferred embodiment of the present invention provides inlet and outlet means to allow liquids to flow in and out of the solar collector.
• the medium can be supplied in cold state and be discharged in hot state after heat absorption.
• the throughflow speed can be adjusted. Depending on the quantity of energy which can be absorbed per unit of time and the throughflow speed, it is possible to regulate how great the difference in temperature ⁇ t must become .
• a subsequent preferred embodiment of the present invention has the provision that the first plate consists of a non-transparent material with high i at- conducting properties.
• all solar energy is first collected by the plate and transferred to the medium.
• the medium does not therefore receive any direct solar energy. This is nevertheless efficient, for instance in the light of the durability of the installation.
• this first plate is provided with means which improve the absorbing properties of the plate.
• This can be a coating, and this coating can be provided with black colouring agents.
• An object of such a coating is to increase the absorption coefficient of the absorption surface .
• Another object of the coating is to reduce the emission coefficient of the absorption surface. Owing to good absorbing properties and a high coefficient of heat conduction, the heat is absorbed efficiently by the first plate and fed through to the medium, thereby increasing the efficiency of the collector.
• An example of the choice of material for the first plate is stainless steel, since stainless steel is a cost- effective, inexpensive material.
• a further preferred embodiment of the present invention has the provision that a cover plate is mounted above the first plate for limiting heat losses, for instance due to convection. Since the first plate becomes hot under the influence of the solar energy, there will be a higher temperature than the medium, no matter how efficient the heat transfer to the medium may be. This temperature difference is necessary, since without temperature difference there is no heat transfer. This higher temperature is probably also higher than the ambient temperature. This temperature higher than the ambient temperature will ensure that a part of the absorbed heat is lost.
• the first way is to prevent radiation energy from the first plate by means of reflection.
• the second way is to stop heat flow by means of air which is heated at the surface of the first plate. Retention of this hot air increases the temperature of the air between the first plate and the cover plate and thereby prevents new air repeatedly being heated on the first plate.
• cover plate can also block solar energy
• a further preferred embodiment of this invention is that the cover plate is provided with a reflection-reducing surface.
• a treatment for preventing energy losses on the underside of the cover plate is also provided.
• a further embodiment of the present invention has the provision that the solar collector and the cover plate are contained in a housing.
• This housing serves on the one hand to enable positioning of the components relative to each other and on the other to insulate these components and the space between these components.
• These insulating means are then situated on the inside of the housing and serve to reduce heat flows on the sides and underside of the device.
• a further preferred embodiment of the present invention provides a second plate with the lowest possible coefficient of heat conduction. This has the advantage that the heat losses to the rear side of the solar collector are reduced.
• a further preferred embodiment of the present invention has the provision that the invention is disposed in a position wherein the a ⁇ age angle relative to the solar radiation is as perpendicular as possible. The reflection of the solar radiation by the cover plate and the first plate will then be as low as possible. This increases the efficiency of the device.
• a further preferred embodiment of the present invention provides a rotatably disposed device so that it is positioned as perpendicularly as possible relative to the solar radiation. This method comprises the following steps of:
• Fig. 1 is an exploded view of an embodiment of the present invention in perspective, wherein the upper plate is shown as transparent;
• Fig. 2 is an exploded view of another embodiment of the invention;
• Fig. 3a and 3b show respective partly cut-away views of details III of figure 1 and figure 2;
• Fig. 4 is a cross-section of a part of the collector
• Fig. 5 is a cross-section of the collector in a housing
• Fig. 6 shows a graph of the heat absorption of a collector over a period of a number of hours.
• Fig. 1 shows the first plate 2 which is drawn at a distance above the rest of the embodiment. Also shown is the framework consisting of parts 4, 5, 6 and 7 which together form a rectangle. Parts 4 and 5 respectively 6 and 7 are herein situated parallel to each other. Relative to first plate 2 the second plate 3 is situated on the other side of the framework consisting of parts 4, 5, 6 and 7. The first plate, parts 4, 5, 6 and 7 and the second plate together form a basic embodiment of the present invention.
• Liquid openings 13 and 14 serve as inlet and outlet for the medium, for instance water or glycol or any other liquid.
• This medium flows through the heat- absorbing means, also referred to as collector.
• the heat- absorbing means also referred to as collector.
• ribs 8, 9, 10,- 11 and 12. These together form on the one hand a longer path for the liquid through the collector and on the other a narrower path through the collector than if these ribs were not present.
• the embodiment in fig. 2 substantially differs from the embodiment of fig. 1 in that the inlet holes and outlet holes 14 and 16 are not arranged in the second plate, but in the side parts 4 and 5 of the framework. This has structural advantages when it is difficult to arrange conduits on the rear side of the collector. This may be the case for instance if the device as a whole must be rather flat.
• FIG. 3 is a cross-section of a part of collector 1. Shown are the first plate 2 provided with a coating 2a and second plate 3 with which the hollow space H is bound. The liquid serving as medium in the heat transfer runs through this hollow space H.
• a collector which is contained in a housing.
• the collector is shown here by first plate 2 and second plate 3 and hollow space H.
• the collector is enclosed close-fittingly by side walls 25 and 26 of the housing.
• Situated directly below and above the collector are air compartments in LI and L2.
• Under LI is situated an insulation layer 21 which is in turn placed on bottom plate 24 of the housing.
• Above L2 the housing is sealed by cover plate 23.
• This cover plate 23 is intended for the purpose of reducing heat losses from the collector. Heat losses from a collector can take place in two ways, viz. by radiation and convection.
• the coating on the first plate preferably has a very low energy coefficient, i.e. the radiation losses are negligible. The losses due to convection are however not negligible.
• the cover plate thus ensures that energy which would be lost through convection is to a great extent retained.
• a cover plate reflects solar radiation. However, with a correct coating radiation losses through reflection are relatively small compared to the gain achieved by preventing energy losses from the collector due to convection. A heated collector will also lose energy on the unders i de.
• a lay---- 21 of insulating material is provided. Insulation can optionally also be arranged (not shown) on the sides between the collector and walls 25 and 26.
• the thickness of air layers Ll and L2 influences the magnitude of the energy losses.
• the thickness of insulating layer 21 likewise affects the magnitude of the energy losses.
• the graph (fig. 6) shows the heat production of a typical collector according to the present invention wherein the collector is manufactured from a metal.
• the choice of material has little influence on the yield, i.e. in the order of magnitude of several percent.
• the application of a cover plate is of greater importance, in the order of magnitude of 10-15%.
• a further embodiment 70 (fig. 7) consists of two stainless steel plates 71, 72. These two plates are welded together along edges 73, 74, 75, 76 by means of laser welding, wherein a liquid supply 81 is arranged in a recess 80. Welded joints 77, 78, 79 are then arranged, which designate the boundaries of a liquid throughflow channel. Weld points 82 are subsequently arranged. These weld points serve to hold plates 71, 72 together. In this embodiment the welding operations take place by means of a laser-welding process.
• the plates are pressed apart by supplying a liquid through opening 81 under high pressure.
• the collector can further be provided with liquid inlet and outlet holes 83, 84.
• These and other embodiments can for instance be embodied in sheet steel with a thickness from 0.3 mm. Although thicknesses of 0.8 or 1.2 to 1.5 mm can also be envisaged, the thickness is not limited in respect of its upper limit.
• This material can for instance be supplied and processed in standard sizes, such as on a roll of 2.5 metres x 40 metres, whereby solar collectors of very large size are possible such as 2.5 metres x 8 metres, as well as smaller sizes in an order of magnitude of for instance l x l metre.
• This embodiment can be provided with a black coating such as for instance soot or blackboard paint.
• the throughflow rate area of the liquid for heating is preferably about 7 litres per square metre of collector surface area. This can however be adjusted depending on the desired energy absorption and liquid properties. It has been found that an ideal distance for a rib or welded joint spacing is 15 to 20 cm.
• the present invention is not limited to the above described preferred embodiments; the rights sought are defined by the following claims.

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• Life Sciences & Earth Sciences (AREA)
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• 2001
  • 2001-04-10 EP EP01922139A patent/EP1272800A1/de not_active Withdrawn
  • 2001-04-10 AU AU2001248917A patent/AU2001248917A1/en not_active Abandoned
  • 2001-04-10 US US10/257,552 patent/US20040025864A1/en not_active Abandoned
  • 2001-04-10 WO PCT/NL2001/000285 patent/WO2001077590A1/en not_active Application Discontinuation
• 2005
  • 2005-01-21 US US11/040,474 patent/US20050205082A1/en not_active Abandoned

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