MX2011002452A

MX2011002452A - Perforated transparent glazing for heat recovery and solar air heating.

Info

Publication number: MX2011002452A
Application number: MX2011002452A
Authority: MX
Inventors: Christian Vachon
Original assignee: Solutions Energetiques Enerconcept Inc
Priority date: 2008-09-05
Filing date: 2008-09-05
Publication date: 2011-06-24
Also published as: AU2008361495A1; KR20110055712A; RU2011112928A; JP2012502241A; EP2326890A4; JP5389925B2; AU2008361495A8; BRPI0823056A2; EP2326890A1; RU2473848C2; CN102149986A; WO2010025537A1

Abstract

A heat collector comprises a transparent glazing (12) exposed to the ambient. The transparent glazing (12) is spaced from a back surface to define a plenum (16) therewith. A plurality of perforations is defined through the transparent glazing (12) for allowing outside air to flow through the transparent glazing (12) into the plenum (16) and substantially maintain the transparent glazing (12) at the ambient temperature, thereby providing for higher thermal efficiency.

Description

PERFORATED TRANSPARENT GLAZED FOR HEAT RECOVERY AND SOLAR AIR HEATING FIELD OF THE INVENTION The present application generally relates to a device positioned to preheat fresh outdoor air by means of free energy, such as solar energy and / or heat recovery.

BACKGROUND OF THE INVENTION " The design of traditional glazed solar air heaters generally comprises a transparent glass, polycarbonate or Lexan® cover placed in front of a dark solar absorber. The transparent front cover is provided to minimize heat losses from the top of the collector. Fresh air from outside is traditionally admitted at one end of the collector between the transparent front cover and the solar absorber. The air passes through the collector along fins and absorbs heat from the solar absorber as it travels along. Warm or warm air is discharged at the opposite end of the collector. As the air moves inside the collector, its temperature increases above the ambient. The higher the temperature in the collector, the higher the heat loss to the environment. Heat loss occurs through the bottom, edges and top (where the glaze is) of the collector. Typically, the edges and bottom are insulated, so that heat loss occurs mostly through the top, which is by convection between the absorber and the glaze and then by conduction through the glaze. When the glaze gets too hot, the collectors become less efficient.

Over the years, several non-glazed solar air heaters have been designed. The current designs of the transpired collectors are such that the solar absorption surface is located outside facing the sun, not protected by means of a glaze. The perforated absorber is coupled to a fan that creates a negative pressure between the building (or the bottom of the collector) and the absorber. When the fan is in operation, the air is carried through the absorber. The air that passes through the perforations in the outer opaque absorber breaks the warm air film that occurs naturally on the side facing outwards (the boundary layer) of the absorber. This method provides acceptable yields when the airflow per unit area exceeds 3 cfm per square foot (0.09 m2) of collector. However, for unit flow rates below 5 cfm per square foot, the amount of cold air that seeps into the perforated plate is insufficient to prevent the collector plate from heating up, thus adversely affecting the overall thermal efficiency of the system . The efficiencies at the speed of 2cfm per square foot fall to 30% or even less.

SUMMARY OF THE INVENTION Therefore, one objective is to correct the aforementioned problems.

Therefore, according to a general aspect of the present application, there is provided a heat sink comprising a transparent glaze exposed to the environment, the transparent glaze being separated from a rear surface to define an intake chamber together with it, a plurality of perforations defined through the transparent glaze in order to allow the outside air to flow through the transparent glaze into the intake chamber, the perforations are distributed over a surface area of the transparent glaze, the intake chamber has a outlet, and means of air movement to bring the heated air from said intake chamber through said outlet.

According to a general additional aspect, the rear surface includes a solar radiation absorption panel.

According to another general aspect, a device for heating air is provided, the device comprises a transparent perforated surface that allows solar radiation to pass through it., an absorption surface of solar radiation located behind the perforated transparent surface to absorb solar radiation, and an air space defined between the perforated transparent surface and the radiation absorption surface, the air flows in the space that absorbs heat from the radiation absorption surface while the fresh ambient air flowing through the perforations of the perforated transparent surface provides a minimum delta temperature through the transparent surface.

According to another general aspect still, a transparent and perforated surface exposed to the environment is provided. The perforated transparent surface is separated from a rear surface to define an air space or intake chamber therebetween. Fresh outside air is drawn into the intake chamber through the perforated transparent surface. The back surface can, for example, be provided in the form of a bottom of a solar collector, a building wall or roof, an outside surface of a greenhouse, a photovoltaic panel, the floor or any other non-porous surface. Between the perforated transparent surface and the rear surface, the air space is maintained under negative pressure due to mechanical or natural means. An outlet is provided to allow air flowing through the intake chamber to be brought into a conduit or channel, for use as supply air, ventilation, process or combustion to a device that consumes or needs thermal energy.

The air in the intake chamber is heated either by incident solar radiation on the surface of the rear panel, which acts as a solar absorber, and / or by heat escaping from the rear surface. The device can then act as a solar air heater and / or as a heat recovery unit. When used as a solar air heater, the rear surface may be of a dark color so that incident solar radiation passing through the perforated transparent surface is absorbed by the rear surface in the form of heat and is not reflected back to outer space. However, if the rear surface, for any aesthetic or other reason, should be light in color, solar thermal efficiency is still higher than other conventional non-glazed collector design. This is particularly true when the device is used as a heat recovery device, because the rear surface can be any color without influence on efficiency (this can even be transparent as in the case of a greenhouse), but while lower is the thermal resistance (insulation) of the posterior surface, the greater it is. the speed of heat recovery. The device can be used simultaneously for both solar heating and heat recovery functions.

If necessary, the preheated air leaving the device may have an auxiliary heating device located downstream (for example, a gas ignition system) to bring its temperature to a certain fixed point.

According to a further aspect, a method is provided for preheating exterior air for a building having a surface facing the sun, the method comprising: providing on the surface facing the building sun a perforated transparent surface that allows the solar radiation passes through it, an intake chamber is defined between the perforated transparent surface and the surface facing the sun, bring outside air through the perforated transparent surface towards the intake chamber, capture incident solar radiation which pass through the perforated transparent surface, heat the air in the intake chamber using captured solar radiation, and remove the heated air from the intake chamber.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a schematic side view of a solar collector including a perforated transparent surface according to an embodiment of the present invention; Figure 2 is a schematic side view of another embodiment of a solar collector having a perforated transparent glaze; Figures 3 and 4 are schematic side views of configurations mounted on the floor of solar collectors having transparent glaze perforated according to additional embodiments of the present invention; Fig. 5 is a schematic side view of a wall-mounted solar collector having a perforated transparent glaze; Fig. 6 is a schematic side view of a roof-mounted solar collector having a perforated transparent glaze; Figure 7 is a schematic view illustrating a perforated transparent glaze surrounding a greenhouse frame for preheating cold outside air before being taken to the greenhouse through a ventilation system; Y Fig. 8 is a graph comparing the efficiency of perforated glazed collectors against unglazed perforated collectors as a function of the amount of air flowing therethrough.

The term "glaze" herein is intended to refer broadly to any transparent surface that allows light to pass through it.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows a solar air heater 10 provided in the form of an elongated conduit type enclosure mounted on a base and including a perforated transparent glaze facing the sun 12 exposed to the environment and placed in front of a rear panel having a curved plate of solar radiation absorber 14 applied on an insulating layer 15. The back panel is generally provided in the form of a half-pipe wall covered with perforated transparent glaze 12. The absorber plate 14 may be of a dark color to maximize solar gain. The perforated glaze 12 can be provided in the form of a perforated plate resistant to transparent UV or polycarbonate. Other transparent polymers could also be used. The glaze 12 can be rigid or flexible. The perforations can be distributed over the entire surface of the glaze or only over a selected surface area thereof. The density of the perforations can be uniform or variable on the glazed surface.

The perforated glaze 12 and the solar radiation absorber plate 14 define an intake chamber 12 therebetween. A fan or other suitable means of air movement is operatively connected to an outlet 18 provided at one end of the rear panel to bring fresh outside air through the perforated glaze 12 into the intake chamber 16 before being directed to a ventilation system , such as a building ventilation system. The solar radiation that passes through the perforated transparent glaze 12 is absorbed by the absorber plate 14. The air in the intake chamber 16 collects the heat absorbed by the absorber plate 14 before being taken out of the intake chamber 16. As the air moves longitudinally along the intake chamber 16 between the absorber plate 14 and the perforated glaze 12, additional fresh outside air is carried through the perforated glaze 12. In this way, the glaze 12 remains at a temperature substantially equal to room temperature. Therefore, the temperature differential between the incoming air and the environment is equal to zero or close to zero, so that the thermal efficiency remains at the highest possible value. The heat losses through the glazed cover are then kept to a minimum.

Figure 2 shows a second embodiment in which similar reference characters refer to similar components. The solar air heater 10a shown in Figure 2 essentially differs from the solar air heater 10 shown in Figure 1 in that the solar air heater 10a has a flat configuration characterized by the transparent glaze and the rear panel separated and parallel. The back panel is provided in the form of a flat absorber plate 14a applied on a flat layer of insulating material 15a. The absorber plate 14a could be corrugated. Side walls or supports 19a are provided along the perimeter of the rear panel and the perforated transparent glaze 12a in order to create a uniform air gap 16a therebetween. The perforated glaze 12a and the back panel are preferably co-extensive. The rear panel 14a can be provided in the form of photovoltaic (PV) panels to provide the dual function of heating air and cooling PV panels, which produce more electricity when its surface is kept at cold temperatures. As shown in Figures 1 and 2, the perforated transparent glaze 12a is preferably supported at an inclination equal to the latitude of a given location, and facing the equator, depending on usage. However, it is understood that the transparent glaze could be oriented and tilted in another way. For example, Figure 4 shows a horizontally oriented perforated transparent glaze, while Figure 5 shows a vertically oriented glaze.

As shown in Figures 3 and 4, the solar air heater can be mounted directly on the floor, the floor surface forming the rear panel of the device. In the embodiment of Figure 3, where similar reference characters refer to similar components, the intake chamber 16b is formed by the perforated transparent glaze 12b, a building wall 20b and the floor G. The fresh outdoor air brought to the the intake chamber 16b is heated by the solar radiation absorbed by the floor G as well as by the heat escaping from the building through the wall 20b. The fresh outside air flowing through the perforations defined in the transparent glaze 12b maintains the delta temperature through the glaze close to zero, thus ensuring a high thermal efficiency. The heated air is removed from the intake chamber 16b and circulated in building B through the building ventilation system (not shown). As shown in Figure 4, where similar reference characters once again refer to similar components, the solar air heater can also be provided in the form of an enclosure having a perimeter wall 19c, a bottom end closed formed by the ground, and an upper end covered by the perforated transparent glaze 12c. An outlet 18c is provided connected to suitable air moving means for removing the heated air from the intake chamber 16c.

As shown in figures 5 and 6, the perforated transparent glaze 12d and 12e can be mounted in opposite relation to a building wall 20d or the roof 22e of a building. In the embodiment of Figure 5, the intake chamber 16d is formed between the exterior surface of the building wall 20d and the vertically oriented vertically perforated transparent glaze 12d. In the embodiment of figure 6, the intake chamber I6e is formed by the outer surface of the roof of the building 22e and the perforated transparent glaze 12e. In both embodiments, the heat escaping from the envelope of the building through the wall 20d or the roof 22e is recovered to heat the air in the intake chamber 16d and 16e. The roof 22e and the wall of the building 20d act as absorbers of solar radiation to further heat the ambient air carried to the intake chambers 16d and 16e. The solar radiation passes through the perforated transparent glaze and is absorbed by the underlying wall of the building or roof surfaces and the air in the intake chamber absorbs heat from the wall or roof of the building. In contrast to solar walls or conventional solar roofs where solar radiation is directly absorbed by dark panels covering the wall or ceiling of buildings, the transparent glaze does not adversely alter the appearance (ie does not change the color of the wall or building roof) of the building. Unlike the prior art, the performance of the system is not influenced or restricted by the color of the perforated panels installed on the wall or ceiling of the building. The perforated glaze 12d and 12e are transparent and, therefore, do not change the color of the building wall or ceiling. Nothing is compromised for aesthetic reasons.

Figure 7 shows a further potential application of the present invention. More particularly, Figure 7 illustrates a greenhouse B 'having a structure covered with a transparent film or membrane 25f, as is known in the art. A glaze. perforated transparent 12f is mounted to the wall and roof of the greenhouse to define a double-walled structure including an air gap 16f defined between the perforated transparent glaze 12f and the inner transparent film 25f. In this embodiment, the perforated transparent glaze 12f acts as a second insulating layer for the greenhouse B '. The heat escaping from the greenhouse through the inner film 25f is recovered in the air space 16f. A fan or the like can be provided to bring heated air from the air space back to the greenhouse B '. The perforated transparent glaze 12f maintains the transparency required for the growth of the plants.

As can be seen from the previous modalities, the device can be used in several applications including: • solar thermal air heaters • solar fresh air preheater mounted on walls or roofs of buildings • Hybrid solar air / water heating systems • pre-heating of air-to-air and air-to-water heat pumps • transparent energy recovery device for greenhouses · Cooling of photovoltaic panels • low cost, residential solar preheater Various devices may also be provided downstream of the device for additional air processing. For example, the device could be attached to the following units: • supply air unit powered by gas • air-based heat pump (air-to-air or air-to-water) · Heat pump for pool • combustion chamber • heat recovery unit The perforated or transpirated glaze described above offers numerous benefits. The inlet air is admitted through the glazed surface, either in a large proportion of its surface or over the entire surface. Accordingly, the glazed surface remains cool so that the heat loss from the upper part of the collector is substantially prevented. In addition, the temperature of the air inside the collector remains relatively cold, decreasing heat losses through the bottom and edges. The proposed perforated transparent glaze design provides solar efficiencies at least as good as that provided by the perforated plate design at high flow rates. However, for lower flow rates, the solar efficiency is still high and far exceeds that of the opaque perforated collectors, and even exceeds that of the glazed collectors, for less than half the cost. This can easily be seen from figure 8. More particularly, it can be seen that for flow velocity between 2 and 6 cfm per square foot of perforated surface, the efficiency of a perforated glaze with a black back surface is much higher than that of a conventional metal perforated sheet metal solar collector. The difference in performance is even more noticeable for light-colored or white solar collectors. The perforated glaze with a white back surface is up to 100% more efficient than a metal perforated white sheet collector. It can also be seen that the difference in performance between the conventional non-glazed perforated collectors and the perforated glazed designs described is even more significant at low flow rates of, for example, 3 or 4 cfm per square foot.

It will be apparent to those skilled in the art that modifications can be made to the illustrated embodiments without departing from the spirit and scope of the invention, as defined in the following claims.

Claims

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following is claimed as a priority: CLAIMS

1. - A heat sink comprising a transparent glaze exposed to the environment, the transparent glaze is separated from a rear surface to define an intake chamber together with it, a plurality of perforations defined through the transparent glaze to allow outside air to flow through the transparent glaze towards the intake chamber, the perforations are distributed over a surface area of the transparent glaze, the intake chamber has an outlet and means for moving air to bring heated air from said intake chamber through said chamber. departure.

2. - The heat collector according to claim 1, characterized in that the rear surface includes a solar radiation absorption panel.

3. - The heat sink according to claim 2, characterized in that said solar radiation absorption panel is superimposed on a layer of insulating material.

4. - The heat collector according to claim 2, characterized in that said solar radiation absorption panel is curved.

5. - The heat collector according to claim 1, characterized in that the rear surface comprises at least one photovoltaic panel.

6. - The heat collector according to claim 1, characterized in that the rear surface is a light color.

7. - The heat collector according to claim 2, characterized in that the solar radiation absorption panel is corrugated.

8. - The heat collector according to claim 1, characterized in that the rear surface has an elongated tube-like configuration with the perforated glaze running longitudinally along one side thereof.

9. - The heat sink according to claim 1, characterized in that the intake chamber is at least partially delimited by a building wall.

10. - The heat collector according to claim 1, characterized in that the rear surface includes a transparent membrane that forms part of a building envelope of a greenhouse.

11. - The heat collector according to claim 1, characterized in that the rear surface is at least partially defined by a floor surface.

12. - A device for heating air comprising a perforated transparent surface that allows solar radiation to pass through it, a solar radiation absorption surface located behind said transparent perforated surface to absorb solar radiation, and a space of defined air between said transparent perforated surface and said radiation absorption surface, the air flows in the space that absorbs heat from the radiation absorption surface while the fresh ambient air flowing through the perforations of the perforated transparent surface provides a minimum delta temperature through the transparent surface.

13. - The device according to claim 12, characterized in that the means that move air are provided to maintain said space under negative pressure.

14. - The device according to claim 13, characterized in that the perforated transparent surface is mounted to a building surface, the air space is defined between the perforated transparent surface and the building surface.

15. - The device according to claim 14, characterized in that the building surface is a transparent membrane that extends over a greenhouse structure.

16. - The device according to claim 14, characterized in that the surface of the building forms part of the solar radiation absorption surface and is of a light color.

17. - The device according to claim 12, characterized in that the solar radiation absorption surface comprises a collector panel mounted to a building surface, the perforated transparent surface separates the collector panel from the environment.

18. - A method to preheat outside air for a building that has a surface facing the sun, the method comprises: provide on the surface facing the building sun a transparent perforated surface that allows solar radiation to pass through it, an intake chamber is defined between the perforated transparent surface and the surface facing the sun, bring outside air through the perforated transparent surface towards the intake chamber, capture incident solar radiation that passes through the perforated transparent surface, heating the air in the intake chamber using the captured solar radiation, and Remove the heated air from the intake chamber.

19. - The method according to claim 18, characterized in that incident solar radiation is captured by the wall facing the building sun.

20. - The method according to claim 18, characterized in that the capture of incident solar radiation comprises mounting a collector panel on the wall of the building at a distance from the perforated transparent surface, the intake chamber is defined between the perforated transparent surface and the collector panel.