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
  • F24S10/70—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits
  • F24S10/73—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits the tubular conduits being of plastic material
• • 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
  • F24S10/70—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits
  • F24S10/72—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits the tubular conduits being integrated in a block; the tubular conduits touching each other
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S40/00—Safety or protection arrangements of solar heat collectors; Preventing malfunction of solar heat collectors
  • F24S40/70—Preventing freezing
• • 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
  • F24S80/50—Elements for transmitting incoming solar rays and preventing outgoing heat radiation; Transparent coverings
  • F24S80/52—Elements for transmitting incoming solar rays and preventing outgoing heat radiation; Transparent coverings characterised by the material
  • F24S80/525—Elements for transmitting incoming solar rays and preventing outgoing heat radiation; Transparent coverings characterised by the material made of plastics
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/40—Solar thermal energy, e.g. solar towers
  • Y02E10/44—Heat exchange systems

Definitions

• the field of the invention is related to renewable energy sources, specifically with the use of solar energy for water heating.
• the invention relates to a common problem in flat solar collectors Conventional used throughout the world, related to moisture in insulation, hard water use and sudden temperature changes (both low and high temperatures).
• the object of the invention is to prevent traditional solar collectors used in direct systems from being damaged due to: (a) being exposed to temperatures below the freezing point of water, water freezes and increases its volume, this in many cases it produces fractures of the pipes; (b) in regions where hard water is present (water with a high salt content), because the pipes in general of these collectors are of small diameters, salt deposits can occur inside the pipes that could along the length of the time to block them; (c) in general the thermal insulation used in these collectors to avoid heat losses to the environment are mineral wool, or materials such as polyurethane or polyisocyanurate which absorb moisture; since the flat collectors are in no case hermetically sealed, if there is moisture in the thermal insulation like those already mentioned, there is an evaporation of water in it and a condensation on the roof which causes the efficiency of the equipment to be reduced and that the insulation is degrading its thermal properties very quickly over time.
• a fairly common form used for freeze protection can be: (a) drain the liquid or part of it from the absorbers; (b) the use of water solutions with glycols (antifreeze mixtures that reduce the freezing point of the mixture used); (c) by heating or replacing the liquid found in the absorber.
• These well-known methods work with the principle of avoiding freezing but have some disadvantages.
• the common antifreeze formed by water solutions with ethylene glycol and propylene glycol are toxic and in brand safety codes, which being so requires the use of at least two interface metals between the toxic fluid and drinking water, which increases the cost of system.
• Glycols degrade during the life of a solar absorber and therefore require replacement.
• Another method used for freeze protection in systems where drinking water is used is to pump hot water from the thermo tank to the absorber when necessary to prevent it from freeze This method has the disadvantage that the thermal losses of the system are significantly increased and requires additional electronic control to perform this function when a certain temperature (generally close to the freezing point) is reached in the absorber. If there is an electrical failure, normally this equipment could not prevent freezing in the system.
• Another commonly used method is to drain the absorber liquid or part of it through an antifreeze valve placed at the bottom of the system that opens mechanically once a certain setpoint temperature is reached (usually between 4 and 7 ° C), when draining part of the water it is occupied by water coming from the tank at a higher temperature which prevents it from freezing.
• This antifreeze valve has mainly two disadvantages: (a) it can be opened a large number of times in conditions of extreme temperatures, which results in a significant loss of wasted system water:. (.
• US Patent 4044754 is an anti-freeze protection system for solar absorbers with sensors inside the absorber that monitor the temperature of the water and when it approaches the freezing temperature, the sensor operates a valve to drain the water from the absorber.
• US patent 4557252 is An antifreeze system for solar systems with forced convection (uses a pump), consists of a sensor that records the temperature of the water inside the absorber and a valve to drain the water from the absorber when its temperature decreases from a predetermined value.
• US 4557252 While it is drained, the pump injects liquid from the tank at a higher temperature to the absorber, our model has no electronic actuators or moving parts that can fail over time and works without electricity, in addition to the Previously, US 4557252 has the disadvantage that the thermal losses of the system are increased by pumping water already heated to the absorber where it will be cooled.
• US 4237862 and US 4269167 are for closed and pressurized solar systems where water is drained from the absorber without the need for a sensor or valve (does not contain moving parts), it only requires a circulation system with a pump. The tank where the water is received is filled only up to_cier.to-level-qu
• US 4308856 is an antifreeze device consisting of an eight-shaped tube welded to the absorber fin that has a steel bar on its two sides and both bars are joined by a U-shaped steel profile. so that when the volume of the inner fluid of the tube is increased in the form of eight, an elastic deformation of the tube and the U-shaped steel profile will occur, said deformation will return to its original shape once the ice has been undone thanks to the U-profile with which the tube is attached in the form of eight, our system does not require special geometries to be made for pipes or of additional profiles (which increases its cost) to be able to counteract the effect of water expansion when it is frozen, our system can be placed in virtually any normal configuration of the absorbers that exist in the market without appreciably increasing the cost of system.
• GB 2117110 uses a system of different energy dissipation means associated with each absorber duct; These means are eyelashes or fins, which the author says is that the freezing occurs progressively from one point of the tube (stringer) to the other end and the expansion occurs outside these stringers, which can cause the expansion to be absorbed into the absorber heads where there is a greater area designed to absorb this dilation; In addition to the above because it is more difficult for the heads to freeze because they have a much greater volume than the stringers (risers), our system can be placed in virtually any configuration of the .
• the conical shape of the stringers is effective to avoid the rupture of the pipe since it starts freezing and hence the expansion of the water in a region of the stringer located in its central part where there is the minimum cross section of the conical section and successively It extends towards the ends of the stringers, where, because the head is insulated, the freezing is not reached in this area or is much slower, causing the expansion produced by the water in the stringers, our system does not require that the heads be isolated (which decreases the area of solar collection) or that special conical pipes are manufactured with their minimum cross-section in the center of the crossbar so that this effect can occur (these special stringers make the absorber more expensive since they are not commercially available in the market).
• the reversible flat solar collector, object of this invention is encapsulated in a rectangular box with the face exposed to the sun covered by some transparent material for example: cellular polycarbonate, while the four sides are made of metallic or plastic foil, for example foil pintro or aluminum and the backrest is also a cover of some cellular polycarbonate material equal to that used as a cover.
• an absorbent plate for example of plastic materials such as polypropylene.
• the absorber plate is composed of a large number of flexible ducts (for example plastic) attached to the inlet and outlet heads through which a heat transfer fluid flows (generally water, although glycol, or a mixture of both, can be used).
• the absorber plate is made of a material that does not degrade with ultraviolet rays and acts as a selective surface (dark colored finish) thereby increasing the heat absorption of the sun's rays.
• the object of the invention is to provide a reversible flat solar collector with protection against freeze damage, scale and problems related to insulation that deteriorates with moisture, which can be coupled to a direct system (thermosiphon systems or forced convection systems, where the agiia that will be used later passes through its ducts).
• a direct system thermosiphon systems or forced convection systems, where the agiia that will be used later passes through its ducts.
• the materials and manufacturing processes used in this sensor can be inexpensive to promote its massive use and not have moving parts that can be damaged during its useful life that must be at least 10 years.
• FIG. 1 shows the components of the reversible flat solar collector consisting of a plastic absorber (1) protected by a rectangular box with the face exposed to the sun formed by a cellular polycarbonate cover (2), while the four sides are made of pintro, aluminum or plastic sheet (3) with some grooves or vents (4) to avoid that very high temperatures are reached inside and the backrest (5) also of cellular polycarbonate equal to that used as a cover.
• Inside the absorber heads is the device to prevent damage of the absorber in case of freezing of water (6), which is detailed in Figure 2.
• an absorber plate is placed (of plastic materials such as polypropylene).
• the absorber plate is made of a material that does not degrade with ultraviolet rays and that can act as a selective surface (finished in black or dark color) thereby increasing the heat absorption of the sun's rays.
• FIG 2 shows one of the important devices of the model to prevent the absorber from suffering fractures during the process of freezing the water inside its pipes (Fig. 1 6).
• This damping device consists of a flexible plastic pipe (eg polyethylene), which has been sealed by means of heat in one of its two versions: (a) at the ends of this flexible pipe; (b) or a series of additional intermediate seals are made to those of the ends. In both cases, air is trapped inside that absorbs the pressure exerted by the water when it solidifies and presents volumetric expansion.
• a flexible plastic pipe eg polyethylene
• Figure 3 shows the plastic absorber (polypropylene) and a detail of a cross section formed by a large number of flexible stringers (7) of black or dark plastic (to increase the absorption of solar radiation) attached to the heads (8) In these pipes circulates the fluid to be heated.
• the plastic damping device (9) shown in Fig. 3 is inserted along the length of both heads. This device acts as follows: the absorber used (Fig. 3) either in direct systems of forced convection (where a water pump is used to circulate the water through the collector) or of natural circulation (as is the case of systems terrn £ siphonLC.os_ampliamen ⁇
• freeze protection device has no moving parts therefore it does not require maintenance, nor does it use electricity to operate (it is a passive system) and unlike some that exist in the market it is not necessary to drain the water from the absorber (with its consequent waste in most cases) or that the absorber's water is replaced with water from the tank produce which causes the thermal losses of the system to be significantly increased, by pumping already heated water to the absorber where it will cool.
• Another very important advantage of this system is its low cost compared to the cost of implementing antifreeze valves or electronic control systems, or in other cases that of making special pipe geometries or adding additional fins to dissipate energy, which obviously It makes them have to be sent to make special pipes that would greatly increase the cost of the absorber.
• This device additionally produces that the absorber _y_eLsist.ema_in_the_that-is-installed- can also dampen sudden increases in pressure such as those that can be caused by water hammers or in the initial filling of the system.
• Another serious problem is the use of flat solar collectors in direct hard water systems (with high salt contents) which in general because flat solar collectors are formed by few metal stringers (risers, typically 6 to 14) in diameters smaller than an inch in diameter where it circulates, in the case of thermosyphonic systems water at low speeds and sometimes at high temperatures, it can eventually produce deposits of these salts that can sometimes block the duct leaving the duct unusable system.
• the collector is formed by a large number of ducts (7) so that the flow of water is divided into a large number of branches which makes it more difficult that all of these can be sealed;
• the plastic material used polypropylene or similar
• the plastic material used has a greater resistance to the adhesion of salts compared to metal pipes.
• the collector is insulated at its front and rear (where there is the largest area of losses compared to the lateral sides) with an area of air trapped in cellular polycarbonate; which, being in a steady state, has a thermal conductivity similar to polyurethane close to 0.024 W / mK, this advantage allows this insulator not to degrade as the insulation materials commonly used in flat solar collectors such as mineral wool or polyurethanes which absorb a large amount of moisture and easily degrade over time upon contact with water.
• a cellular polycarbonate plate (2 and 5) has been used that has air trapped inside (low conductivity) acting as insulation; In addition to the above, it gives the collector stiffness.
• This system allows as an additional advantage that if the cover (2) for some reason deteriorates over time, the collector can turn and continue to operate in the same way as when it was initially installed.
• Another additional advantage of the sensor given the materials with which it is built: in general plastics, pintrq or aluminum foil_is_that_all-materials-are not-degraded by being in direct contact with environmental conditions of temperature, humidity, ultraviolet rays, etc. which extends the system life. Additionally, it allows the collector to not be completely airtight and can have vents (4) to prevent the absorber from reaching high temperatures, such as those produced in conditions of stagnation in flat collectors, which can cause the absorber plastic to degrade over time. and do not reach the planned useful life or avoid using more expensive plastics to prevent degradation due to exposure to high temperatures.
• This invention therefore extends the life of the collector because it cannot reach excessively high temperatures that degrade the materials from which the collector is made; the inside of the collector cannot reach excessive temperatures due to the vents (4) that have been designed in the frame of the collector so that by means of natural convection, hot air is removed from them inside and replaced by temperature air environment considerably reducing the maximum temperatures that can be reached inside it.
• Figure 2 Damping device formed by a flexible plastic pipe sealed at its ends (a) or all along it (b).

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

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Publications (1)

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Citations (6)

• 2012
  • 2012-07-23 MX MX2012009644A patent/MX2012009644A/es unknown
• 2013
  • 2013-07-17 WO PCT/MX2013/000089 patent/WO2014017896A1/fr not_active Ceased

Patent Citations (6)

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