CN1716642B - Hybrid photoelectric photo-thermal collector - Google Patents

Abstract

A hybrid photovoltaic/thermal solar collector includes a photovoltaic cell layer laminated on a surface of a heat collector absorber plate. The heat collector comprises a box structure (e.g., extruded box structure aluminum) having a plurality of longitudinally extending adjacent channels interconnected by a pair of transverse headers at either end of each longitudinal channel.

Description

Hybrid Photoelectric Photothermal Collector

technical field

The invention relates to a hybrid photoelectric/thermal collector, which can convert solar energy into electric energy by using photovoltaic cells, and can also convert solar energy into thermal energy by using a thermal energy collector.

Background technique

Solar energy can be used to provide energy in domestic and industrial applications in two basic ways. First, thermal collectors can be used to convert solar energy into heat. Typically, for example, a heat collector may comprise metal plates capable of absorbing as much solar energy as possible and transferring this energy as heat to water flowing in pipes that are in contact with the metal plates. The water here is then heated and can be used directly as a hot water source, or to drive heating or cooling systems, for example by means of a heat exchange device.

Another way to harness solar energy is to use photovoltaic cells (commonly known as "solar cells") to convert solar energy into electricity. Photovoltaic cells are well known, usually made of a semiconductor material such as single crystal silicon, which convert incident solar radiation into electrical energy.

While both techniques are fairly well recognized and used in many practical applications, neither technique is particularly efficient. For example, the daily average thermal efficiency of heat collectors is about 50%, while for photovoltaic cells this efficiency is even lower. For monocrystalline photovoltaic cells, the maximum conversion efficiency is about 24%, but in practical applications, due to various reasons, this efficiency is as low as 13%-15%. In other words, as much as 85%-87% of the solar energy incident on the photovoltaic cell is either reflected or absorbed as heat.

For this reason, it is known to provide combined hybrid photovoltaic/thermal collectors which combine the use of photovoltaic cells to generate electrical energy and the use of conventional thermal collectors to generate thermal energy.

In known hybrid photovoltaic/thermal collectors there are plates for photovoltaic cells positioned such that solar energy is incident on them. A thermal collector is arranged below the solar panel, which receives thermal energy from the solar panel. In other words, at least a portion of the incident solar energy that is not converted to electricity but is absorbed as heat by the thermal collector is then transferred from the solar panel to the thermal collector where it can be used to heat water. In this way, at least a portion of the incident energy that is not converted into electrical energy is not wasted but can be used to heat the water. Hybrid photovoltaic/thermal collectors also have the advantage of being able to generate both electricity and hot water in a single unit.

However, to increase the efficiency of the heat collector, it is important to have good heat transfer between the photovoltaic panel and the heat collector. The design of the heat collector and the method of gluing or otherwise attaching the heat collector to the photovoltaic panel are very important design factors. Although many designs of hybrid photoelectric/thermal collectors have been proposed, none have been fully successful so far.

Contents of the invention

According to an embodiment of the present invention, there is provided a hybrid photovoltaic/thermal solar collector comprising a layer of photovoltaic cells laminated on the surface of a thermal collector heat absorbing plate, wherein the thermal collector comprises a box structure having A plurality of longitudinally extending adjacent channels interconnected by a pair of transverse headers located at both ends of each longitudinal channel.

Preferably, the box structure comprises a number of mortise and tenon modules. In a preferred embodiment, each module contains a number of longitudinal channels and is formed with connections for connection to adjacent like modules. For example, each of said modules comprises a longitudinally extending female connector formed on one side of the module parallel to the longitudinal channel and a longitudinally extending male connector formed on the other side of the module. on one side and parallel to the longitudinal channel. Preferably, each said module comprises three longitudinal channels.

The box structure is made of aluminum alloy.

In a preferred embodiment, the first transverse header is formed at one end with a cold water inlet and a plug behind the first longitudinal channel, whereby the cold water flowing into the tube is forced by natural circulation down through the first longitudinal channel to the second water collecting pipe. The hot water outlet may be arranged at the end of the first water collecting pipe opposite to the cold water inlet.

Preferably, a layer of thermally insulating material is secured to the surface of the aluminum box structure opposite the photovoltaic cells.

Preferably, said photovoltaic cells are laminated to the surface of the heat collector heat absorbing plate with a layer of electrically insulating material. A layer of electrically insulating material is also laminated on the surface of the photovoltaic cell opposite the heat collector.

According to another aspect of the present invention, there is also provided a method of manufacturing a hybrid photovoltaic/thermal solar collector, comprising the steps of: (a) forming a thermal collector absorber plate with a flat surface, (b) using a single-step The vacuum lamination process laminates the layers of photovoltaic cells on the plane with a layer of electrically insulating material in between.

In a preferred embodiment of the method, said use of a single-step vacuum lamination process further includes laminating a layer of electrically insulating material on the surface of the photovoltaic cell layer opposite the heat collector absorber plate. Preferably, said step (a) comprises mortise-jointing a plurality of modules, wherein each module is formed by an extrusion process.

Description of drawings

Some embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

Fig. 1 shows the overall schematic diagram of the hybrid photoelectric/thermal collector according to the embodiment of the present invention,

Fig. 2 represents the thermal collector of the embodiment of the present invention in plan view form,

Fig. 3 represents the thermal collector of the embodiment of the present invention in the form of sectional view, and it illustrates the module structure,

Figure 4 shows a hybrid collector arrangement whereby photovoltaic cells are laminated on top of the heat collector,

Figures 5a-5c show details of assembling the heat collector components of the box structure.

Detailed ways

Figure 1 shows an overall schematic diagram of a hybrid photovoltaic/thermal (PV/T) collector according to an embodiment of the present invention. The PV/T collector contains a heat absorbing panel 1 for receiving incident solar radiation. In Fig. 1, the heat absorbing plate 1 is square, but it is understood that it could be rectangular or other possible shapes. The specific structure of the plate (heat absorbing plate) 1 will be described in more detail below, but in general the plate 1 is formed with a flat aluminum top surface on which the photovoltaic cell array is bonded using vacuum extrusion technology.

The flat aluminum top surface is also within the top surface of the heat absorbing plate of the aluminum flat top box heat collector unit (described further below) with channels for water to flow therein. These channels form a water flow circuit, which includes a recirculation pipe 2 , a water storage tank 3 , a hot water outlet 4 , an exhaust pipe 5 and a drain valve 6 . Simply put, the water flowing through the loop by natural circulation is continuously heated and thus can be used in many applications. It will be appreciated that this circulation of water can be suitably controlled at a fixed design flow rate or a variable flow rate, optionally through the use of a circulating pump.

As mentioned above, the top surface of the panel 1 is provided with a plurality of photovoltaic cells on which the sun's rays are incident. These photovoltaic cells generate electrical energy in a conventional manner which, via a converter 14 , can be used to drive an electrical load 15 or to charge an accumulator 13 . The hybrid collector arrangement is provided with a front glass cover 11 (Fig. 4) and an intermediate air layer, which improves the thermal performance of the collector.

Not all solar energy incident on a photovoltaic cell is converted into electricity. Some of the solar energy may be reflected, but most will be converted to heat in the photovoltaic cells. This heat will reduce the efficiency of the photovoltaic cell, and unless it can be used, it will appear as a waste of energy. A heat collector heat absorber plate is therefore placed under the photovoltaic cells to remove this part of the heat energy from the photovoltaic cells and make this part of the energy available for heating water. In a preferred embodiment of the present invention the photovoltaic cells are laminated on top of the aluminum flat top heat absorber panels in order to provide a very good heat transfer from the photovoltaic cells to the absorber. A laminator has two chambers, an upper chamber and a lower chamber, in which heat absorbing plates, photovoltaic cells, etc. are placed. The sequence of layers in a laminate is illustrated in FIG. 4 . Specifically, in order to bond the photovoltaic cell to the heat absorbing plate, the planar top surface of the absorber is first cleaned, and then a layer of opaque electrical insulating material 40 is bonded to said surface with silicone glue 41, the electrical insulating material 40 is For example Tedlar-Polyester-Tedlar (TPT). Then coat both sides of the photocell 42 with ethylene acetic acid (EVA) 43 and fix it on the TPT layer 40, and then lay a transparent TPT layer 44 on the top surface of the photocell. Photocells are then laminated on top of the absorber using a vacuum lamination process. The overall thickness of TPT, EVA and photovoltaic cells is only about 2mm.

This device was constructed by placing all the constituent layers of the PV/T device (except the cover glass) in a vacuum laminator between two fiber cloths. Heat is then applied to raise the temperature of the air in the laminate to about 110°C, at which point the EVA will begin to melt. The vacuum pump is then run for 6-10 minutes to eliminate the air in the upper and lower chambers. The constituent layers are tightly stacked together. Air is then sent back to the upper chamber through an inflation process of about 30 seconds, so that the upper chamber is brought back to atmospheric pressure while the lower chamber remains at a vacuum. This is followed by the lamination process, which lasts 16-20 minutes at 140°C. The heat was then turned off to allow the PV/T system to fix on the inside of the laminate and allow the EVA to set. Then move the PV/T system to a constant temperature room, where the structure of the PV/T system can be stabilized.

As noted above, Figure 2 is a plan view of a heat collector according to an embodiment of the present invention comprising an aluminum flat top box absorber structure and consisting of a number of interconnected tenon modules each formed as a single body extrusions. Figure 2 shows the heat sink structure in plan view, while Figure 3 is a cross-sectional view showing a particular module and its connection to adjacent modules. Each module 20 comprises an upper plane 21, a lower plane 22 and a vertical (as shown in FIG. 3 ) beam 23 which divides the module 20 into three longitudinal channels 24 through which water can flow, as described hereinafter. aisle. Along one edge of the modules 20 (shown as the right edge in Figure 3), each module is provided with a longitudinal male connector 25, while along the opposite longitudinal edge (shown as the left edge in Figure 3), each The modules are formed with corresponding female connectors 26 . It will be appreciated that the male connector 25 of one module can be received within the female connector 26 of an adjacent module 20 whereby two such modules can be connected together. In this manner, many identical modules 20 can be connected together to form a large unit of any desired size. It will also be understood that when many such modules 20 are joined together in this manner, their upper planes 21 together form the plane (heat absorber) 1 for holding the photovoltaic cells.

Referring now to FIG. 2, two aluminum pipes 27, 28 serving as transverse headers are connected to both ends of the channel 24 so as to interconnect the longitudinal channels and allow water to flow from the end of the longitudinal channel 24 into another such longitudinal channel. . However, an aluminum tube 27 is provided with a plug 29 after the first longitudinal passage from one end of the tube 27, which forms the cold water inlet 30 for the absorber. Specifically, cold water enters the absorber through inlet 30 and is forced to flow down through first longitudinal channel 24 due to plug 29 until it reaches aluminum tube 28 on the opposite side of the absorber. The cold water then flows through the aluminum tube 28 and up through all remaining longitudinal channels (at a reduced flow rate), during which time the water is heated by the thermal energy passed from the photovoltaic cells into the heat absorber, and the warm/hot water is collected in The first aluminum pipe 27 on the other side of the plug 29, and the warm water can be discharged through the hot water outlet 31.

During the assembly process, as shown in Figures 5a-5c, the header and the longitudinal channels were fitted together using a silicone pad 100 under a pressure of 7 kg. At the same time, connect them firmly with rivets on the grooved part of the collector tube. Fill all gaps, if any, with silicone.

It should be noted that the bottom surface of the heat collector (ie the side opposite the photovoltaic cells) is fitted with a thermal insulation plate to prevent thermal energy from escaping from the flat top box collector, thereby maximizing the efficiency of the heat collector. On the other hand, the solar panel does not have to cover the entire top surface of the thermal collector so that part of the incident solar energy can be directly absorbed by the thermal collector. It should also be understood that the one-step vacuum lamination assembly technique described above can also be used for conventional finned tube heat collectors and box structures. However, a box structure for the heat collector is advantageous because it provides better heat conduction and solar cells can be more easily laminated on the surface of the box structure. Also in a conventional process, vacuum lamination is applied to PV devices without heat collectors. In the latter case, the solar panel is connected to the heat collector by using a thermally conductive adhesive (such as silica gel or alumina epoxy, etc.) under room conditions, so that the air trapped in the adhesive layer may cause Lower heat transfer rate between solar panel and heat collector.

Claims (13)

1. A hybrid photovoltaic/thermal solar collector comprising a layer of photovoltaic cells laminated on the surface of a thermal collector heat absorbing plate, wherein said thermal collector comprises a box structure whose upper surface constitutes a heat absorbing plate slab, the box-like structure consists of a number of interconnected mortise-and-mortise modules, each module comprising an upper plane, a lower plane, and vertical beams that divide the modules into a number of longitudinally extending adjacent channels, the longitudinal channels Interconnected by a pair of transverse water collecting tubes provided at both ends of each of said longitudinal channels, with a layer of electrically insulating material between the photovoltaic cell and the heat collector heat absorbing plate. 2. The hybrid collector of claim 1, wherein each of said modules comprises a longitudinally extending female connector and a longitudinally extending male connector, the female connector being formed on one side of the module parallel to With respect to the longitudinal channel, a male connector is formed on the other side of the module parallel to the longitudinal channel. 3. The hybrid collector of claim 1, wherein each of said modules contains three longitudinal channels. 4. The hybrid collector of claim 1 wherein said box structure is constructed of aluminum alloy. 5. A hybrid collector as claimed in claim 1 , wherein the first header of said tubes is formed at one end with a cold water inlet and a plug behind the first longitudinal channel, whereby cold water flowing into the tube is forced to flow downwards Through the first longitudinal channel to the second water collection pipe. 6. The hybrid collector as claimed in claim 5, wherein the hot water outlet is provided at the end of the first water collecting pipe opposite to the cold water inlet. 7. The hybrid collector of claim 5, wherein the flow of water in the channels is designed for natural circulation. 8. The hybrid collector of claim 1, wherein a layer of thermally insulating material is affixed to the box structure on the surface opposite the photovoltaic cells. 9. The hybrid collector of claim 1, wherein the electrically insulating material is Tedera-polyester-Tedera. 10. The hybrid collector of claim 1, further comprising a layer of electrically insulating material laminated to the surface of the photovoltaic cell opposite said thermal collector. 11. A method of making a hybrid photovoltaic/thermal solar collector comprising the steps of: (a) forming a heat collector absorber plate with a flat surface, said heat collector comprising a box structure consisting of a number of interconnected mortise and tenon modules, each module comprising an upper plane, a lower plane and a vertical beams, the vertical beams separating the modules into a number of longitudinally extending adjacent channels, and (b) Laminating the photovoltaic cell layer on the plane of the heat absorbing plate using a single-step vacuum lamination process with a layer of electrically insulating material between the photovoltaic cell layer and the plane. 12. The method of claim 11, wherein the single step vacuum lamination process further comprises laminating a layer of electrically insulating material on the surface of the photovoltaic cell layer opposite the heat collector absorber plate. 13. The method of claim 11, wherein step (a) comprises mortising together a plurality of modules, wherein each module is formed by an extrusion process.

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