CN103225898B - Low-cost intelligent anti-overheating plastic panel solar thermal collector - Google Patents

Abstract

The invention discloses a low-cost intelligent anti-overheating plastic flat-plate solar heat collector, which is characterized in that a high-temperature-resistant heat-conducting plastic substrate with pipes integrated with a heat-collecting plate and a water pipe replaces the metal substrate and the heat-conducting plastic substrate used in the traditional flat-plate heat collector. The metal pipe not only reduces the cost and weight of the heat collector, but also increases the contact area between the heat-absorbing plate core and the working medium fluid. At the same time, the plastic has good stretchability, and there are no problems such as tube explosion in summer and freezing cracks in winter, which improves the safety factor of the collector. More importantly, the heat collector of the present invention adopts a hollow design between the transparent cover plate and the heat-absorbing plate core, which can realize intelligent evacuation or inflation, and can significantly reduce the heat loss on the upper surface of the heat collector during vacuuming, improving Heat collection efficiency: when inflating, the temperature of the heat collector can be quickly lowered to prevent damage or even damage caused by the sudden water stoppage of the heat collector. This function can be realized by setting the operating temperature range, which plays the role of intelligent adjustment and automatic protection .

Description

A low-cost intelligent anti-overheating plastic flat panel solar collector

technical field

The invention relates to a flat-plate solar heat collector, specifically a low-cost, light-weight plastic flat-plate solar heat collector that can be intelligently adjusted, refrigerated, and prevented from being damaged by overheating in the air, and belongs to the technical field of solar energy.

Background technique

As we all know, the energy problem is one of the most prominent problems facing the world today, and solar energy is an inexhaustible clean energy. Solar heat conversion is the most popular and main form of solar energy utilization in the world, and the most representative one is solar water heater. my country has become the country that produces the most solar water heaters in the world, and also has the world's largest solar water heater market.

The solar collectors that have been widely used mainly include vacuum tube solar collectors and flat plate solar collectors. Among them, vacuum tube solar collectors still account for more than 85% of the domestic collector market, while in foreign countries, the opposite is true. , flat plate collectors have accounted for more than 90% of the collector market share. The main reason is that the cost of domestic flat plate collectors is still too high. Compared with the mature vacuum tube solar collectors, there is a big disadvantage in price, so it is not as good as low-cost solar collectors in the domestic market. Tube collectors are more popular.

However, with the acceleration of domestic urbanization, the rise of villas, high-rises and small high-rises leaves less and less opportunities for vacuum tube collectors, and the continuous development of hot water projects also requires the popularization of flat-panel solar energy. Drawing lessons from foreign experience, to effectively solve the problem of solar energy and building integration, flat-panel solar energy should be the first choice. Moreover, the daily average efficiency of the flat-plate solar collector is higher than that of the vacuum tube solar collector, and at the same time, it has a strong pressure-bearing capacity and a large heat-absorbing area. Since the flat-panel solar water heater is separated from the water storage tank, it is more flexible and perfect to be combined with the building, and it is easy to realize integration with the building, replacing roof panels, wall panels, etc., and at the same time saving the cost of corresponding building materials. Therefore, the flat-panel solar collector is used in Large-scale projects have more advantages. Therefore, from the perspective of the development trend of solar collectors, flat-panel solar water heaters have great potential for development.

The main reason for the high cost of flat-plate collectors is that most of the current flat-plate collectors use expensive copper or aluminum plates, and most of them need to use ultrasonic spot welding or high-frequency welding to weld metal water pipes to the collector plates. resulting in further cost increases.

In addition, the current flat collector cover glass and the absorbing plate core are directly connected to the atmosphere, so convection heat conduction is unavoidable, thereby dissipating heat over a large area on the entire cover plate, and the thermal insulation performance is poor, causing the collector Decrease in heat collection efficiency. At the same time, unlike vacuum tube collectors, the current common flat-plate collectors do not have the antifreeze function. When used in severe cold winter, the water in the collector may freeze, which not only affects the normal operation of the collector, but also once Icing in the water pipe can easily lead to the expansion and cracking of the heat collecting pipe.

Since the flat plate collector itself does not have the characteristics of intelligent antifreeze and overheating, the current solar energy system of the flat plate collector usually uses a vacuum solenoid valve to evacuate the water delivery pipeline, a constant temperature circulating pump to fix the temperature of the circulating pipe box water source, or an anti-backflow emptying device, etc. Antifreeze insulation measures. In northern my country and other countries and regions with relatively cold winters, in order to ensure the normal use of water heaters when the temperature is below 0°C, it is usually adopted to equip the water pipeline with electric heating and heat preservation, install a vacuum solenoid valve to evacuate the water pipeline, and adopt The water source of the constant-temperature circulation pump and the constant-temperature circulation pipe box or the anti-freezing and heat preservation measures such as anti-backflow emptying device are adopted, otherwise the solar water heater will "hibernate" and cannot be used. These use of external force to "antifreeze" the water pipeline has become an indispensable auxiliary configuration for flat-panel solar water heaters at this stage, but on the one hand, this has caused the complexity of the system and the difficulty of maintenance, and on the other hand, more importantly, it has caused costs. further increase. In the hot summer, if the current flat plate collector structure encounters a water cut-off, the collector will be in an empty state, resulting in overheating of the collector system, damage to some parts, and a serious shortening of the heat collection performance. service life of the device.

Contents of the invention

Aiming at the deficiencies of the existing flat-panel solar heat collector technology and products, the invention discloses a low-cost intelligent anti-overheating plastic flat-panel solar heat collector. Low heat loss due to the controlled hollow structure, low cost, lightweight plastic flat panel solar collectors that prevent overheating of the system due to air drying.

In order to improve the efficiency of solar collectors, an effective way is to minimize convective and radiative heat loss while maintaining maximum solar energy collection. When the system is overheated due to air drying, in order to reduce the system temperature, an effective way is to increase the heat convection between the system and the external environment.

Therefore, the present invention proposes a high-temperature-resistant heat-conducting plastic substrate with pipes that integrates heat collecting plates and water pipes to replace the metal substrates and metal pipes used in traditional flat-plate heat collectors, which not only reduces the cost of heat collectors, but also reduces the The weight also increases the contact area between the heat absorbing plate core and the working medium fluid. At the same time, the plastic has good stretchability, and there are no problems such as tube explosion in summer and freezing cracks in winter, which improves the safety factor of the collector. More importantly, the heat collector of the present invention adopts a hollow design between the transparent cover plate and the heat-absorbing plate core, which can realize intelligent evacuation or inflation, and can significantly reduce the heat loss on the upper surface of the heat collector during vacuuming, improving Heat collection efficiency: when inflating, the temperature of the heat collector can be quickly lowered to prevent damage or even damage caused by the sudden water stoppage of the heat collector. This function can be realized by setting the operating temperature range, which plays the role of intelligent adjustment and automatic protection .

The specific structure of the flat solar heat collector of the present invention is shown in accompanying drawing 1.

The uppermost layer is a transparent cover plate 1, which is made of transparent glass or transparent plastic, which can be tempered glass, float glass, insulating glass, bulletproof glass, glass reinforced plastic (FRP), and organic glass (PMMA) with a light transmittance of 92%. And polycarbonate (PC), the thickness is 2 ~ 20mm;

Use transparent glue to glue a layer of transparent glass beads 2 on the lower surface of the transparent cover plate as the spacer support for the hollow layer between the glass cover plate and the core of the heat-absorbing plate. The diameter of the transparent glass beads is 0.5 mm to 2 mm;

Sealing strips 6 are used to seal the frames at both ends of the hollow layer. The sealing strips are made of elastic materials to prevent air leakage from the hollow layer due to the difference in coefficient of thermal expansion between the glass and the plastic on both sides of the hollow layer;

At both ends of the hollow layer 3, a low-cost suction membrane pump 4 and an air pump 5 are respectively used. These two pumps are equipped with automatic controllers, and are connected to the temperature sensor of the water pump 11, and the automatic controller is controlled by the temperature sensor. , to control the on-off of the pump. Wherein, the hollow layer is evacuated by a membrane pump, and the hollow layer is inflated by an air pump. For small-area heat collectors, micro-film pumps and air pumps can be used. For large-area collectors, such as roofs or wall panels, only one membrane pump and one air pump are needed uniformly, so maintenance is simple and convenient, and the cost can still be kept low;

The lower layer of the hollow layer is a high-temperature-resistant heat-conducting plastic substrate 8 with pipes coated with a solar selective absorption coating 7. In the middle of the board is a hollow pipe. Among them, high-temperature-resistant and thermally conductive plastics are 40-50% lighter than aluminum materials, and their thermal conductivity ranges from 1W/(m·K) ^-1 to over 20W/(m·K) ^-1 , and some grades can reach 100W/(m·K) ) ^-1 or more, almost close to metal, even better than the thermal conductivity of borosilicate glass 3.3 used in glass vacuum tube solar collectors 1.2W/(m·K) ^-1 . Since plastic modification is relatively easy and the cost is low, PPA (polyphthalamide) and PA high thermal conductivity composite plastics (thermal conductivity: 5~15W/(m·K) ^-1 ) that can withstand continuous high temperature of 200°C can be used. , PPS substrate modified plastics that can be used for a long time at 200-240°C, liquid crystal polymer LCP, Teflon with an operating temperature of -196°C to 300°C, polyimide (PI) with an operating temperature above 350°C ) and other engineering plastics; in the plastic plate, it is a hollow pipe made directly with a mold. Compared with the traditional flat plate collector that uses ultrasonic spot welding of copper tubes and heat-absorbing plate cores, the working medium and heat-absorbing plate in this method The thermal conduction contact area between the cores is larger and more sufficient, and the cost is greatly reduced. At the same time, due to the good creep resistance, high hardness, high wear resistance and good chemical corrosion resistance of plastic under load, it is very suitable for pipelines;

The pipeline of the high-temperature-resistant heat-conducting plastic substrate 8 is filled with a working medium 9, and the working medium 9 is a heat-conducting fluid, which can be water, antifreeze or oil;

The upper surface of the plastic substrate is plated with a solar selective absorbing coating 7, and its material is composed of a bottom metal film and an absorbing film. Among them, the metal film is a material with high infrared reflectivity, such as copper, aluminum, silver, nickel; the absorbing film has a high absorption of sunlight, such as black chromium (CrO _x ), black nickel (NiS-ZnS), black cobalt (CoO _x ), black copper (CuO _x ), NiCrN, NiO _x , CrN _x O _y , TiN _x O _y , AlN _x O _y , AlCuFe, AlN-A, TiAlN, TiAlN _x O _y , TiSiN or Fe ₃ O ₄ . The absorptivity of the solar selective absorbing coating can reach more than 96%, the emissivity is lower than 4%, and the utilization rate of light and heat is high;

Below the plastic plate is the insulation layer 10, which is made of materials with low thermal conductivity, not easily deformed or volatilized, and does not produce toxic gases. Usually, the thermal conductivity is required to be no greater than 0.06W/(m·K) ^-1 . Available materials are: rock wool, glass wool, polyurethane, polystyrene, aerogel or phenolic foam. Appropriate insulation materials can be selected according to the working temperature.

The water pump 11 is connected with the heat collector pipeline, has a temperature sensor and an automatic controller, and is connected with the automatic controller of the suction film pump 4 and the air pump 5 to control the flow rate and temperature of the working medium in the heat collector.

The whole heat collector is fixed as a whole by frame 12, and frame material can be selected aluminum alloy, also can adopt high-strength engineering plastics, as, PBT adds glass fiber, nylon adds glass fiber, PPS adds glass fiber, PPO adds glass fiber etc.

The working principle of the low-cost, intelligent, low heat loss plastic flat panel solar collector that can prevent the system from overheating caused by air drying is as follows:

According to the actual use requirements of the collector, the operating temperature of the collector can be set by yourself. Under ordinary sunlight and low temperature in winter, when the temperature of the working medium in the collector is lower than the operating temperature, the temperature sensor attached to the water pump will send a signal to the automatic controller of the suction membrane pump to make it start automatically, and the hollow layer It is vacuumed to reduce convective heat loss, improve heat collection efficiency, and thus increase temperature; at the same time, in the cold winter, the vacuum hollow layer also isolates the heat convection between the heat collector and the outside world, preventing the low temperature outside from cooling the water in the heat collector. Freeze, so that the flat plate collector itself has the antifreeze function. In addition, when the flat plate collector is integrated with the building and used as roof and wall panels, the hollow layer is evacuated, and the collector also has the effect of noise insulation.

Under the high temperature and hot sun in summer, if there is no water supply, the collector will be in an empty state. At this time, when the temperature of the heat collector is higher than the operating temperature, the temperature sensor of the water pump will send a signal to the automatic controller of the suction membrane pump and the air pump, and the two pumps will be automatically started at the same time, so that the hollow layer becomes air circulation. This greatly increases the heat convection on the upper surface of the heat-absorbing plate core and dissipates the heat, thereby reducing the temperature of the collector system and greatly extending the service life of the collector.

In this way, the flat plate heat collector of the present invention has the function of intelligent control.

The flat plate collector of the present invention has the following advantages:

1. The plastic substrate integrated with the heat collecting plate and the water pipe is adopted, which greatly reduces the cost of the heat collector and also reduces the weight of the heat collector;

2. The hollow structure that can be vacuumed intelligently reduces the heat loss of the system, and at the same time, it can also prevent freezing in winter; when it is integrated with the building and used as roof and wall panels, it also has the effect of noise insulation;

3. The hollow structure that can be intelligently inflated is used to increase convective heat conduction, which can prevent the system from being overheated and damaged when the collector is empty in summer when the water is cut off;

4. The plastic has good stretchability, there is no problem of tube explosion in summer, freezing and cracking in winter, etc., and the safety is high;

5. The system has long service life and low maintenance cost.

Description of drawings

Accompanying drawing 1 is a schematic structural diagram of a low-cost intelligent anti-overheating plastic flat solar collector disclosed by the present invention; the labels in the accompanying drawing 1 are: 1, transparent cover plate; 2, transparent glass beads; 3, hollow layer; 4, Membrane suction pump; 5. Inflatable pump; 6. Sealing strip; 7. Selective absorption coating; 8. High temperature resistant heat-conducting plastic; 9. Working medium; 10. Insulation layer; 11. Water pump;

Accompanying drawing 2 is the top view of the transparent cover plate and glass beads of the hollow layer; the labels in the accompanying drawing 2 are: 1, transparent cover plate; 2, transparent glass beads.

Detailed ways

In order to make the content, technical solutions and advantages of the present invention clearer, the present invention will be further described below in conjunction with specific examples. These examples are only used to illustrate the present invention, but the present invention is not limited to the following examples. The specific embodiment of the present invention is described in detail below in conjunction with accompanying drawing:

Example 1: Low-cost plastic flat panel solar collector with all-plastic intelligence to prevent overheating

The specific structure of the flat solar heat collector of the present embodiment is shown in accompanying drawing 1.

The top layer is a polycarbonate (PC) cover plate with a thickness of 3mm;

Use transparent glue to stick a layer of transparent glass beads on the lower surface of the cover plate as a spacer for the hollow layer between the glass cover plate and the heat-absorbing plate core. The diameter of the glass beads is 2mm;

The lower layer of the hollow layer is the heat-absorbing plate core, and its substrate material is Teflon with a working temperature of -196 degrees to 300 degrees, and the thickness is 40mm;

The upper surface of the plastic substrate is coated with a solar selective absorption coating composed of a metal copper film and a TiAlN absorption film, the absorption rate is greater than 96%, and the emissivity is lower than 3%;

In the middle of the plastic plate is a hollow water pipe made directly with a mold. Compared with the traditional flat plate collector that uses ultrasonic spot welding of copper tubes and heat-absorbing plate cores, the heat conduction contact between water and heat-absorbing plate cores in this method The area is larger and more adequate, and the cost is greatly reduced. At the same time, due to the good creep resistance, high hardness, high wear resistance and good chemical corrosion resistance of plastic under load, it is very suitable for fluid pipelines.

Use butyl rubber as the sealing strip to seal the frames at both ends of the hollow layer.

At both ends of the hollow layer, low-cost suction membrane pumps and air pumps are used respectively. These two pumps are equipped with automatic controllers and connected to the temperature sensor of the water pump. The automatic controller is controlled by the temperature sensor to control the pump. on and off. Wherein, the hollow layer is evacuated by a membrane pump, and the hollow layer is inflated by an air pump. For small-area heat collectors, micro-film pumps and air pumps can be used. For large-area collectors, such as roof or wall panels, only one membrane pump and one air pump are needed, so the cost is still low.

Outside the collector, there is a water pump with a temperature sensor and an automatic controller connected to the plastic pipe to control the flow rate and temperature of the working medium in the collector.

Below the plastic board is the thermal insulation layer, which uses phenolic foam with low thermal conductivity, not easy to deform or volatilize, and does not produce toxic gas.

The whole heat collector is fixed by a frame, and the material of the frame is machinable high-strength engineering plastic nylon plus glass fiber.

The feature of this embodiment is that it adopts all plastic materials, which is lightweight, durable and low in cost.

Embodiment 2: A low-cost intelligent anti-overheating plastic flat solar collector with a glass cover plate and an aluminum alloy frame.

The specific structure of the flat solar heat collector of the present embodiment is shown in accompanying drawing 1.

The top layer is a tempered glass cover with a thickness of 5mm;

Use transparent glue to stick a layer of transparent glass beads on the lower surface of the glass cover plate as the spacer between the glass cover plate and the hollow layer of the heat-absorbing plate core. The diameter of the glass beads is 1mm;

The lower layer of the hollow layer is a heat-absorbing plate core, and its substrate material is a PPS base material modified high-temperature-resistant heat-conducting plastic that can be used for a long time at 200-240°C, with a thermal conductivity of 5W/(m·K) ^-1 and a thickness of 50mm ;

The upper surface of the plastic substrate is plated with a solar selective absorption coating composed of a metal copper film and a TiN _x O _y absorption film, with an absorption rate of 96% and an emissivity of 4%;

In the middle of the plastic plate is a hollow water pipe made directly with a mold. Compared with the traditional flat plate collector that uses ultrasonic spot welding of copper tubes and heat-absorbing plate cores, the heat conduction contact between water and heat-absorbing plate cores in this method The area is larger and more adequate, and the cost is greatly reduced. At the same time, due to the good creep resistance, high hardness, high wear resistance and good chemical corrosion resistance of plastic under load, it is very suitable for fluid pipelines.

Use butyl rubber as the sealing strip to seal the frames at both ends of the hollow layer.

At both ends of the hollow layer, low-cost suction membrane pumps and air pumps are used respectively. These two pumps are equipped with automatic controllers and connected to the temperature sensor of the water pump. The automatic controller is controlled by the temperature sensor to control the pump. on and off. Wherein, the hollow layer is evacuated by a membrane pump, and the hollow layer is inflated by an air pump. For small-area heat collectors, micro-film pumps and air pumps can be used. For large-area collectors, such as roof or wall panels, only one membrane pump and one air pump are needed, so the cost is still low.

Outside the collector, there is a water pump with a temperature sensor and an automatic controller connected to the plastic pipe to control the flow rate and temperature of the working medium in the collector.

Below the plastic board is a thermal insulation layer, which uses polystyrene with low thermal conductivity and low cost.

The entire heat collector is fixed as a whole by a frame, and the material of the frame is aluminum alloy.

Claims (8)

1. low cost intelligent prevents an overheated plastic board solar thermal collector, it is characterized in that: be made up of transparent cover plate (1), clear glass pearl (2), hollow layer (3), membrane pump of bleeding (4), inflator pump (5), sealing joint strip (6), solar selectively absorbing coating (7), the thermostable heat-conductive plastic base (8) of band pipeline, working media (9), heat-insulation layer (10), water pump (11), frame (12) successively to bottom from top layer; Transparent cover plate (1) and be coated with solar selectively absorbing coating (7) band pipeline thermostable heat-conductive plastic base (8) between form hollow layer (3); Clear glass pearl (2) scatters the support attached to as hollow layer (3) on transparent cover plate (1) with transparent glue, its diameter is 0.5mm ~ 20mm; The thickness of described hollow layer (3) is adjusted by the diameter of clear glass pearl (2), and its scope is at 0.5mm ~ 20mm, and hollow layer two ends bezel seal gets up by sealing joint strip (6); Bleeding, to be positioned at hollow layer (3) two ends be that hollow layer vacuumizes and inflates for membrane pump (4) and inflator pump (5); Water pump (11) is connected with heat collector pipeline, with temperature sensor and automatic controller, and be connected with the automatic controller of membrane pump of bleeding (4) with inflator pump (5), the pipeline communication of the thermostable heat-conductive plastic base (8) of water pump (11) and band pipeline, to control the flow velocity of working media in pipeline (9); Whole heat collector is fixed as one by the frame (12) of aluminium alloy or high-strength engineering plastic.

2. a kind of low cost intelligent according to claim 1 prevents overheated plastic board solar thermal collector, it is characterized in that: described transparent cover plate (1) is clear glass or transparent plastic, and thickness is 2 ~ 20mm.

3. a kind of low cost intelligent according to claim 1 prevents overheated plastic board solar thermal collector, it is characterized in that: described membrane pump of bleeding (4) is connected to hollow layer one end, with automatic controller to control its break-make, and with water pump (11) with temperature sensor be connected.

4. a kind of low cost intelligent according to claim 1 prevents overheated plastic board solar thermal collector, it is characterized in that: described inflator pump (5) is connected to the hollow layer other end, with automatic controller to control its break-make, and with water pump (11) with temperature sensor be connected.

5. a kind of low cost intelligent according to claim 1 prevents overheated plastic board solar thermal collector, it is characterized in that: the described solar selectively absorbing coating (7) being coated on the upper surface of the thermostable heat-conductive plastic base (8) of band pipeline is made up of underlying metal film and absorbing membrane, wherein metallic film is copper, aluminium, silver or nickel has the material of infrared high reflectance, and absorbing membrane is CrO _x, NiS-ZnS, CoO _x, CuO _x, NiCrN, NiO _x, CrN _xo _y, TiN _xo _y, AlN _xo _y, AlCuFe, AlN-Al, TiAlN, TiAlN _xo _y, TiSiN or Fe ₃o ₄to the material of sunshine high-selenium corn.

6. a kind of low cost intelligent according to claim 1 prevents overheated plastic board solar thermal collector, it is characterized in that: thermostable heat-conductive plastic base (8) material of described band pipeline is thermostable heat-conductive plastics, coating for selective absorption (7) is coated with, with hollow pipeline in the middle of plastic base at the upper surface of plastic base.

7. a kind of low cost intelligent according to claim 1 prevents overheated plastic board solar thermal collector, it is characterized in that: described working media (9) is water, anti-icing fluid or oils heat-conducting fluid.

8. a kind of low cost intelligent according to claim 1 prevents overheated plastic board solar thermal collector, it is characterized in that: described heat-insulation layer (10) material is one or more in rock wool, mineral wool, polyurethane, polystyrene, aeroge or phenol formaldehyde foam.