A nanofluid trough solar concentrator

Abstract

The application provides a nanofluid groove type solar concentrator and relates to the technical field of concentrators.The solar concentrator comprises a protective cover, a mounting seat is fixedly connected to the inner wall of the middle position of the bottom of the protective cover, a reflecting mirror is arranged in the mounting seat, and a nanofluid is arranged in a heat collecting pipe.The nanofluid comprises the following raw materials: multi-walled carbon nanotubes, glycerol and betaine.The nanofluid is prepared by compounding nanoparticles and a base fluid, is filled into the heat collecting pipe to perform heat absorption and heat conduction, the multi-walled carbon nanotubes have excellent heat conduction performance, the heat collecting pipe adopting the nanofluid has high efficiency in heat transfer, and due to the good stability of the nanofluid and the high refractive index of the nanoparticles, the nanofluid does not have the phenomena of precipitation and stratification in long-term use, and the heat collecting pipe has high heat transfer and heat conduction efficiency.

Description

Technical Field

[0001] This invention relates to the field of concentrator technology, specifically to a nanofluidic trough type solar concentrator. Background Technology

[0002] Solar energy is the most abundant and cleanest renewable energy source on Earth. Efficient, safe, and low-cost utilization of solar energy can effectively solve global energy problems. The focus of solar thermal utilization is converting solar energy into heat energy for applications such as thermal power generation, thermochemical conversion, heating, and cooling. Based on the concentrating and collecting method, solar thermal systems can be divided into trough, dish, and tower systems. Among these, trough solar thermal systems are the most widely used and mature in commercial operation, suitable for applications in the medium to low temperature range.

[0003] Traditional trough concentrators concentrate sunlight onto collector tubes via parabolic mirrors, with the heat absorbed by the working fluid inside the tubes. However, most traditional concentrators use pure basic fluids as their working fluid, which generally have low thermal conductivity and stability. Over time, this can lead to stratification or sedimentation, affecting heat transfer efficiency. Furthermore, in extreme weather events such as hail, traditional concentrators lack protection for the mirrors, causing changes in the curvature of the mirror's inner surface and consequently impacting the concentrating effect. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a nanofluidic trough solar concentrator that solves the problems of generally low thermal conductivity of pure basic fluids and the lack of protection for reflectors.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a nanofluidic trough solar concentrator, comprising a protective cover, end caps fixedly connected to the inner diameter of both sides of the protective cover, the protective cover being semi-circular in shape and the end caps being circular in shape; expansion grooves penetrating and provided within the wall thickness of both ends of the protective cover; a first arc-shaped plate slidably connected within each expansion groove of the protective cover, the first arc-shaped plate being a quarter-circle arc in shape; expansion grooves penetrating and provided within the wall thickness of each first arc-shaped plate; a second arc-shaped plate slidably connected within each expansion groove of the first arc-shaped plate, the second arc-shaped plate being a quarter-circle arc in shape; a mounting base fixedly connected to the inner wall of the bottom center of the protective cover, the mounting base having a cross-section approximately U-shaped; a reflector disposed inside the mounting base; clamps disposed on both sides of the bottom of the reflector; and a heat collection tube disposed between the two clamps.

[0006] Preferably, feet are fixedly connected to the outer walls on both sides of the bottom of the protective cover, and servo motors are fixedly connected to the center of the opposite side of the end cap. The output ends of the servo motors are fixedly connected to U-shaped rods, and one end of the U-shaped rods is fixedly connected to the end point of the arc-shaped end face of the second arc plate.

[0007] Preferably, the two sides of the reflector are slidably connected to the end cap.

[0008] Preferably, both ends of the heat collection tube are threaded with sealing caps, and the heat collection tube is filled with nanofluid.

[0009] Preferably, pressure sensors are uniformly distributed and fixedly connected to the inner wall of the mounting base, and each pressure sensor is fixedly connected to a spring at its top.

[0010] Preferably, the nanofluid comprises the following raw materials: multi-walled carbon nanotubes, glycerol, and betaine, wherein the mass ratio of glycerol to betaine is 12:1.

[0011] Preferably, the preparation process of the nanofluid includes the following steps:

[0012] S1. Basic Fluid Preparation

[0013] Add betaine and glycerin to a magnetic stirrer according to the mass ratio and stir continuously at 300-500 r / min for 1 hour until a stable basic fluid is formed after uniform mixing.

[0014] S2. Final Mixing

[0015] The base fluid obtained from S1 and the multi-walled carbon nanotubes were then placed together in an ultrasonic oscillator for homogenization and dispersion until the nanoparticles were dispersed to a concentration of 50 ppm, thus obtaining a uniformly distributed nanofluid.

[0016] Working principle: The concentrator can be fixed to the ground through the mounting holes and fixing bolts at the bottom of the base. The heat collection tube is fixed to the inner wall of the bottom of the reflector by clamps. Then, the installed reflector is slid down along the end cap onto the mounting base, so that the bottom of the reflector rests smoothly on the spring. The concentrator is now installed. When the concentrator is working, sunlight shines on the inner wall of the reflector and is reflected onto the heat collection tube, heating the heat transfer medium inside the heat collection tube. In case of extreme weather, the control servo motors are activated. The two servo motors drive the U-shaped rods to rotate relative to each other. The U-shaped rods drive the second arc-shaped plate, which is fixed at one end, to rotate around the servo motors. The second arc-shaped plate rotates from the first arc-shaped plate... The plate unfolds from the telescopic groove inside, while the first arc-shaped plate rotates and unfolds from the telescopic groove of the protective cover. After the U-shaped rod rotates 90°, the two second arc-shaped plates close together, forming a relatively enclosed space with the protective cover, end cap, first arc-shaped plate, and second arc-shaped plate. This prevents damage to the reflector and heat collection tube inside the protective cover from hard objects such as hail. Conversely, the first and second arc-shaped plates can be retracted, and the heat collection tube can operate normally. If the unfolding process is not timely, hard objects such as hail may hit the reflector. The pressure sensor at the bottom of the spring can monitor abnormal pressure changes, quickly detect pressure changes, and trigger an alarm, allowing staff to replace the reflector in a timely manner. In addition, the nanofluid inside the heat collection tube has high heat transfer and thermal conductivity efficiency.

[0017] This invention provides a nanofluidic trough type solar concentrator. It has the following beneficial effects:

[0018] 1. This invention utilizes a nanofluid, prepared by combining nanoparticles and a basic fluid, to fill a heat collection tube for heat absorption and conduction. Due to the excellent thermal conductivity of multi-walled carbon nanotubes, the heat collection tube employing the nanofluid exhibits high heat transfer efficiency. Furthermore, the good stability of the nanofluid and the high refractive index of the nanoparticles prevent precipitation and stratification during long-term use, ensuring the heat collection tube maintains high heat transfer and conduction efficiency.

[0019] 2. This invention uses a servo motor to drive the U-shaped rod to rotate, with a maximum rotation angle of 90°. This, in turn, causes the first and second arc-shaped plates to rotate around the servo motor. The first and second arc-shaped plates slide out from the telescopic groove, and the two arc-shaped plates combine to form a closed space, thus preventing the reflector inside the protective cover from being damaged or dented by hail. Furthermore, a spring and pressure sensor at the bottom of the reflector support it. When the reflector is hit by a hard object, the pressure sensor can quickly detect the pressure change and trigger an alarm, ensuring that the reflector's focusing effect is not affected. Attached Figure Description

[0020] Figure 1 This is a closed schematic diagram of the present invention;

[0021] Figure 2 This is a schematic diagram of the unfolded state of the present invention;

[0022] Figure 3 This is a structural diagram of the mounting base of the present invention;

[0023] Figure 4 This is an exploded view of the mounting base of the present invention;

[0024] Figure 5 This is an exploded view of the protective cover of the present invention;

[0025] Figure 6 This is a SEM image of the multi-walled carbon nanotubes of the present invention;

[0026] Figure 7 The UVeViseNIR spectra of nanofluids with different concentrations of base liquid in this invention are shown below.

[0027] Figure 8 The graph shows the thermal conversion efficiency of multi-walled carbon nanotubes of different concentrations according to the present invention.

[0028] Figure 9 This is a comparison chart of the stability of nanofluids at different concentrations according to the present invention;

[0029] Figure 10 This is a comparison diagram of the stability of different base liquids in this invention.

[0030] The components are: 1. Protective cover; 2. End cap; 3. Foot; 4. First arc plate; 5. Second arc plate; 6. Servo motor; 7. Mounting base; 8. Reflector; 9. Clamp; 10. Heat collection tube; 11. Spring; 12. Pressure sensor; 13. U-shaped rod; 14. Telescopic groove; 15. Sealing cover. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1:

[0033] like Figure 1-5As shown, this embodiment of the invention provides a nanofluidic trough type solar concentrator, including a protective cover 1. End caps 2 are fixedly connected to the inner diameter of both sides of the protective cover 1, and the protective cover 1 is semi-circular in shape. The end caps 2 are circular in shape. Telescopic grooves 14 are provided through the wall thickness of both the front and rear ends of the protective cover 1. A first arc-shaped plate 4, shaped like a quarter circle, is slidably connected within each telescopic groove 14 on the protective cover 1. A second arc-shaped plate 5, also shaped like a quarter circle, is slidably connected within each telescopic groove 14 on the first arc-shaped plate 4. In extreme weather conditions, control servo motors 6 are activated. The two servo motors 6 respectively drive U-shaped rods 13 to rotate relative to each other. The U-shaped rods 13 drive the second arc-shaped plate 5, fixed at one end, to rotate... The servo motor 6 rotates in a circle, and the second arc plate 5 rotates and unfolds from the telescopic groove 14 inside the first arc plate 4. The first arc plate 4 rotates and unfolds from the telescopic groove 14 inside the protective cover 1. After the U-shaped rod 13 rotates 90°, the two second arc plates 5 close together, so that the protective cover 1, end cap 2, first arc plate 4 and second arc plate 5 form a relatively closed space, which prevents the reflector 8 and heat collection tube 10 inside the protective cover 1 from being damaged by hard objects such as hail. Conversely, the first arc plate 4 and second arc plate 5 can be stored, and the heat collection tube 10 can work normally. A mounting base 7 is fixedly connected to the inner wall at the middle position of the bottom of the protective cover 1, and the cross section of the mounting base 7 is approximately U-shaped. A reflector 8 is set inside the mounting base 7. Clamps 9 are set on both sides of the bottom of the reflector 8. The heat collection tube 10 is set between the two clamps 9.

[0034] Foot bases 3 are fixedly connected to the outer walls on both sides of the bottom of the protective cover 1. Servo motors 6 are fixedly connected to the center of the opposite side of the end cover 2. The output end of the servo motor 6 is fixedly connected to a U-shaped rod 13, and one end of the U-shaped rod 13 is fixedly connected to the end point of the arc-shaped end face of the second arc plate 5. The concentrator can be fixedly installed on the ground through the mounting holes and fixing bolts at the bottom of the foot base 3. The heat collection tube 10 is fixedly installed on the inner wall of the bottom of the reflector 8 through the clamp 9. Then, the installed reflector 8 is slid down along the end cover 2 onto the mounting base 7, and the bottom of the reflector 8 is placed stably on the spring 11. The concentrator is then installed. When the concentrator is working, sunlight shines on the inner wall of the reflector 8 and is reflected onto the heat collection tube 10 to heat the heat transfer medium in the heat collection tube 10.

[0035] The two sides of the reflector 8 are slidably connected to the end cap 2. The reflector 8 can be replaced by sliding the reflector 8 with the mounting base 7 and the end cap 2.

[0036] Both ends of the heat collection tube 10 are threaded with sealing caps 15. The heat collection tube 10 contains nanofluid, which can be replaced through the sealing caps 15.

[0037] Pressure sensors 12 are evenly distributed and fixedly connected to the inner wall of the mounting base 7. Each pressure sensor 12 has a spring 11 fixedly connected to its top. If the unfolding process is not timely, hard objects such as hail may hit the reflector 8. The pressure sensors 12 at the bottom of the springs 11 can monitor abnormal pressure changes, quickly detect pressure changes, and trigger an alarm, allowing staff to replace the reflector 8 promptly. Additionally, the nanofluid inside the heat collection tube 10 has high heat transfer and thermal conductivity efficiency.

[0038] Example 2:

[0039] This invention provides a nanofluid comprising the following raw materials: multi-walled carbon nanotubes, glycerol, and betaine, wherein the mass ratio of glycerol to betaine is 12:1.

[0040] The preparation process of nanofluids includes the following steps:

[0041] S1. Basic Fluid Preparation

[0042] Add betaine and glycerol to a magnetic stirrer according to the mass ratio and stir continuously at 500 r / min for 1 hour until a stable basic fluid is formed after uniform mixing.

[0043] S2. Final Mixing

[0044] The base fluid obtained from S1 and the multi-walled carbon nanotubes were then placed together in an ultrasonic oscillator for homogenization and dispersion until the nanoparticles were dispersed to a concentration of 50 ppm, thus obtaining a uniformly distributed nanofluid.

[0045] Nanofluids, prepared by combining nanoparticles and a basic fluid, are incorporated into a heat collector tube for heat absorption and conduction. Due to the excellent thermal conductivity of multi-walled carbon nanotubes, the heat collector tube using nanofluids exhibits high heat transfer efficiency. Furthermore, the good stability of the nanofluids and the high refractive index of the nanoparticles prevent precipitation and stratification during long-term use, ensuring the heat collector tube maintains high heat transfer and conduction efficiency.

[0046] Furthermore, betaine and glycerol in this invention constitute a natural deep eutectic solvent. This combination can also be replaced with other common natural deep eutectic solvents, including but not limited to water + ammonia eutectic, water + sulfuric acid, paraffin + organic acid, etc. Meanwhile, the multi-walled carbon nanotubes in this invention are nanostructures composed of multiple concentrically arranged carbon layers, and can also be replaced by single-walled carbon nanotubes, graphene, carbon nanoparticles, nanofibers, etc.; other black light-absorbing materials can also be used, such as carbon black, metal nanoparticles, and organic dyes.

[0047] Example 3:

[0048] This invention provides a nanofluid comprising the following raw materials: multi-walled carbon nanotubes, glycerol, and betaine, wherein the mass ratio of glycerol to betaine is 12:1.

[0049] The preparation process of nanofluids includes the following steps:

[0050] S1. Basic Fluid Preparation

[0051] Add betaine and glycerol to a magnetic stirrer according to the mass ratio and stir continuously at 300 r / min for 1 hour until a stable basic fluid is formed after uniform mixing.

[0052] S2. Final Mixing

[0053] The base fluid obtained from S1 and the multi-walled carbon nanotubes were then placed together in an ultrasonic oscillator for homogenization and dispersion until the nanoparticles were dispersed to a concentration of 50 ppm, thus obtaining a uniformly distributed nanofluid.

[0054] Nanofluids, prepared by combining nanoparticles and a basic fluid, are incorporated into a heat collector tube for heat absorption and conduction. Due to the excellent thermal conductivity of multi-walled carbon nanotubes, the heat collector tube using nanofluids exhibits high heat transfer efficiency. Furthermore, the good stability of the nanofluids and the high refractive index of the nanoparticles prevent precipitation and stratification during long-term use, ensuring the heat collector tube maintains high heat transfer and conduction efficiency.

[0055] Furthermore, betaine and glycerol in this invention constitute a natural deep eutectic solvent. This combination can also be replaced with other common natural deep eutectic solvents, including but not limited to water + ammonia eutectic, water + sulfuric acid, paraffin + organic acid, etc. Meanwhile, the multi-walled carbon nanotubes in this invention are nanostructures composed of multiple concentrically arranged carbon layers, and can also be replaced by single-walled carbon nanotubes, graphene, carbon nanoparticles, nanofibers, etc.; other black light-absorbing materials can also be used, such as carbon black, metal nanoparticles, and organic dyes.

[0056] Example 4:

[0057] like Figure 6-10 As shown, this embodiment of the invention provides a comparative experiment of different heat transfer media inside the heat collection tube. The specific experiment is as follows:

[0058] Experiment 1: Scanning Electron Microscopy Analysis of Multi-walled Carbon Nanotubes

[0059] SEM images of multi-walled carbon nanotubes are as follows Figure 6As shown, a series of slender tubular structures arranged side by side can be observed. These tubular structures exhibit a clear hierarchical structure, i.e., layers of inner and outer tubes. Each tubular structure has a small diameter, typically ranging from a few nanometers to tens of nanometers. The distance between the inner and outer tubes is visible, forming a nested structure. The surface of MWNTs is smooth and uniform, appearing black or gray overall. The tubular structures are generally highly linear, without obvious bends or twists. In the SEM images, the ends of the tubular structures can sometimes be seen to be slightly flared or exhibit some open morphology.

[0060] Furthermore, interactions between MWNTs can also be observed in SEM images. Sometimes, multiple tubular structures intersect or intertwine with each other, forming complex network structures. This interaction results in a highly interconnected network among MWNTs, increasing the stability and mechanical strength of the structure.

[0061] Experiment 2: Verifying the Influence of Optical Properties on Photothermal Absorption

[0062] The UVeViseNIR spectra of nanofluids with different concentrations of base liquid were measured. Figure 7 A shows the transmission spectra of multi-walled carbon nanotube nanofluids with different mass fractions. Pure NADES exhibits high transmittance in the visible light wavelength range, while the multi-walled carbon nanotube nanofluids show lower transmittance in the 200-1400 nm wavelength range. The transmittance of the multi-walled carbon nanotube nanofluids decreases with increasing multi-walled carbon nanotube mass fraction, indicating that multi-walled carbon nanotubes can improve the light absorption performance of the nanofluids, and this performance increases with increasing multi-walled carbon nanotube content.

[0063] Figure 7 b shows the extinction coefficients of nanofluids with different masses of multi-walled carbon nanotubes. The extinction coefficient of the 150 ppm multi-walled carbon nanotube nanofluid is the highest at 1200 nm, while that of pure NADES is the lowest at the same wavelength. It can be seen that the extinction coefficient of the nanofluid increases with increasing mass of multi-walled carbon nanotubes.

[0064] The reflectivity of nanofluids with different concentrations of multi-walled carbon nanotubes, such as Figure 7 As shown in c. The higher the concentration, the lower the reflectivity of the nanofluid.

[0065] Figure 7 Figure d shows the absorbance of multi-walled carbon nanotube nanofluids at different concentrations. Consistent with the above results, the absorbance increases with increasing nanofluid concentration. However, the increase in absorbance gradually weakens when the concentration reaches a certain value. This phenomenon provides evidence for determining the optimal photothermal conversion concentration.

[0066] Solar spectral irradiance of nanofluids, such as Figure 7 As shown in e, the spectral irradiance increases with the increase of nanofluid concentration.

[0067] Figure 7 f shows the solar energy weighted absorptivity of nanofluids at different concentrations. The absorptivity is absorbed by the liquid in the solar spectrum. Pure DES has the lowest absorptivity (Am), indicating that multi-walled carbon nanotube nanofluids have a higher absorption capacity than the base liquid.

[0068] Experiment 3: Verifying experimental data of different concentrations of multi-walled carbon nanotubes under sunlight.

[0069] like Figure 8 As shown in Figure a, the temperature rise rate is fastest at 50 ppm. Figure 8 b shows its thermal image at the highest temperature. Both the heating process and the highest temperature indicate that 50 ppm is the optimal concentration. Figure 8 As shown in c, the photothermal conversion efficiency is also highest at 50 ppm, verifying the above selection.

[0070] Experiment 4: Verifying the stability of nanofluids at different concentrations

[0071] Figure 9 a represents a newly prepared nanofluid of the same concentration. Figure 9 From left to right in image b, the nanofluids represent 0, 10, 30, and 50 cycles, respectively. Figure 9 c is the cyclic projection diagram of the nanofluid. Figure 9 a and Figure 9 By comparison with b, it can be seen that even after multiple cycles, no obvious deposition or aggregation occurred at the bottom of the nanofluid, indicating that NADES has good stability. Subsequently, its transmittance was tested, according to... Figure 9 As can be seen from c, although the transmittance decreases significantly with the increase of the number of cycles, the transmittance also gradually increases with the increase of the number of cycles, and then reaches a relatively balanced position.

[0072] Experiment 5: Verifying the stability of different base solutions

[0073] Figure 10 From left to right in image a are the newly prepared glycerol + betaine-based, ethylene glycol-based, and deionized water-based nanofluids, while the nanoparticles are all multi-walled carbon nanotubes. Figure 10b shows the fluid condition after seven days of settling. After seven days of observation, both ethylene glycol-based and water-based fluids showed varying degrees of deposition and aggregation, especially the ethylene glycol-based fluids, which exhibited significant aggregation. Therefore, using glycerol + betaine as the base fluid for the nanofluid and multi-walled carbon nanotubes as the nanoparticles demonstrated good stability and maintained excellent thermal stability even under repeated cycling conditions. Glycerol and betaine provided the nanofluid with stability and suitable flowability.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A nanofluidic trough type solar concentrator, comprising a protective cover (1), characterized in that: The protective cover (1) has end caps (2) fixedly connected to its inner diameter on both sides. The protective cover (1) is semi-circular in shape, and the end caps (2) are circular in shape. Expansion grooves (14) are provided through the wall thickness of both the front and rear ends of the protective cover (1). First arc-shaped plates (4) are slidably connected within the expansion grooves (14) on the protective cover (1). The first arc-shaped plates (4) are quarter-circular in shape. Expansion grooves (14) are provided through the wall thickness of the first arc-shaped plates (4). The first arc plate (4) has a second arc plate (5) slidably connected in the expansion groove (14), and the second arc plate (5) is a quarter circle arc. The protective cover (1) has a mounting base (7) fixedly connected to the inner wall at the bottom middle position, and the cross section of the mounting base (7) is approximately U-shaped. The mounting base (7) has a reflector (8) inside, and the reflector (8) has clamps (9) on both sides of the bottom of the bottom. The heat collection tube (10) is arranged between the two clamps (9). The protective cover (1) has feet (3) fixedly connected to the outer walls on both sides of the bottom. The end cover (2) has a servo motor (6) fixedly connected to the center of the opposite side. The output end of the servo motor (6) is fixedly connected to a U-shaped rod (13), and one end of the U-shaped rod (13) is fixedly connected to the end point of the arc-shaped end face of the second arc plate (5). Both ends of the heat collection tube (10) are threaded with sealing caps (15), and the heat collection tube (10) is filled with nanofluid; Pressure sensors (12) are uniformly distributed and fixedly connected to the inner wall of the mounting base (7). Each pressure sensor (12) is fixedly connected to a spring (11) at its top. The nanofluid comprises the following raw materials: multi-walled carbon nanotubes, glycerol, and betaine, wherein the mass ratio of glycerol to betaine is 12:

1.

2. The nanofluidic trough solar concentrator according to claim 1, characterized in that: The two sides of the reflector (8) are slidably connected to the end cap (2).

3. The nanofluidic trough solar concentrator according to claim 1, characterized in that: The preparation process of the nanofluid includes the following steps: S1. Basic Fluid Preparation Add betaine and glycerin to a magnetic stirrer according to the mass ratio and stir continuously at 300-500 r / min for 1 hour until a stable basic fluid is formed after uniform mixing. S2. Final Mixing The base fluid obtained from S1 and the multi-walled carbon nanotubes were then placed together in an ultrasonic oscillator for homogenization and dispersion until the nanoparticles were dispersed to a concentration of 50 ppm, thus obtaining a uniformly distributed nanofluid.

Images