High ultraviolet transmittance optical-thermal coupling utilization device and method

Abstract

The present invention relates to the technical field of solar energy, and disclosed are a high ultraviolet transmittance optical-thermal coupling utilization device and method. The device comprises: a reactor body, wherein a reaction chamber is provided in the reactor body; a light-transmitting assembly, comprising a window and a light-transmitting member, wherein the window is provided at the top end and the side wall of the reactor body, the portion of the window on the top end and the portion of the window on the side wall are communicated with each other, and the light-transmitting member is mounted at the window and the side wall for allowing ultraviolet light to pass into the reaction chamber; and an insulation layer, arranged on the reactor body, and used for insulating the reaction chamber. The present invention ensures that ultraviolet light in sunlight can enter the interior of the device to a maximum extent, provides a sufficient ultraviolet light source for subsequent photochemical reactions, and additionally, while maintaining high transmission of the ultraviolet light, achieves an efficient heat insulation effect.

Description

A device and method for high ultraviolet transmittance light-heat energy coupling utilization Technical Field

[0001] This invention relates to the field of solar energy technology, and in particular to a device and method for high ultraviolet transmittance light-heat energy coupling utilization. Background Technology

[0002] With the continuous growth of energy demand and the increasing severity of environmental pollution, the development and utilization of solar energy will reach new heights under the impetus of sustainable development strategies. The solar radiation wavelengths that reach the Earth's surface mainly include: ultraviolet light (250-400nm, 7% of energy), visible light (400-760nm, 50% of energy), and near-infrared light (760-2500nm, 43% of energy). Among these, ultraviolet light, due to its unique physical and chemical properties, demonstrates significant value in various fields such as environmental protection, sterilization, medicine, industry, and agriculture. Its utilization methods include photocatalytic water splitting for hydrogen production, photofermentation for hydrogen production, and photodegradation of pollutants. In recent years, it has also shown great potential and application value in the photodegradation of waste plastics.

[0003] Currently, most applications of ultraviolet (UV) light rely on artificial sources, such as gas discharge arc lamps like xenon and mercury lamps, UV lasers, and metal halide incandescent lamps. However, while these artificial sources provide powerful light sources, they also suffer from limited lifespan, high energy consumption, limited conversion efficiency, complex maintenance, and stringent environmental requirements. Therefore, efficiently utilizing the UV component of sunlight is crucial. However, current applications of UV light from sunlight suffer from low transmittance due to limitations in material properties, surface reflection, and equipment design. Furthermore, photothermal coupling catalysis technology is a hot topic in both industrial applications and academic research in energy conversion, pollutant treatment, organic synthesis, material preparation, and organic solid waste disposal. To achieve high transmittance and maximize solar energy absorption and conversion efficiency, devices often struggle to maintain effective heat insulation under high-temperature conditions. High transmittance requires thin, lightweight materials with excellent light transmission properties, but this usually sacrifices some thermal insulation performance, leading to excessive heat loss at high temperatures and impacting overall energy efficiency.

[0004] Therefore, there is an urgent need for a device and method for high ultraviolet transmittance light-heat energy coupling utilization to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a device and method for high ultraviolet transmittance light-heat energy coupling utilization, so as to solve the problems of low ultraviolet transmittance, insufficient spectrum utilization, and poor heat preservation effect in existing solar energy utilization devices.

[0006] To achieve the above objectives, the present invention provides the following solution: The present invention provides a high ultraviolet transmittance light-heat energy coupling and utilization device, comprising:

[0007] The reactor body has a reaction chamber inside it;

[0008] A light-transmitting component includes a viewing window and a light-transmitting element. The viewing window is opened at the top and side wall of the reactor body and the two are connected. The light-transmitting element is installed in the viewing window and the side wall to allow ultraviolet light to penetrate into the reaction chamber.

[0009] An insulation layer is provided on the reactor body to keep the reaction chamber warm.

[0010] According to the present invention, a high ultraviolet transmittance light-heat energy coupling utilization device is provided, wherein the light-transmitting element includes a light-transmitting plate, and the light-transmitting plate is fixedly connected to the window by bolts.

[0011] According to the present invention, a high ultraviolet transmittance light-heat energy coupling utilization device is provided, wherein the heat insulation layer includes an inner sidewall layer, a middle sidewall layer and an outer sidewall layer arranged sequentially from the inside to the outside, and the middle sidewall layer is made of aerogel material.

[0012] According to the present invention, a high ultraviolet transmittance light-heat energy coupling utilization device is provided, wherein the light-transmitting plate, the inner layer of the sidewall, and the outer layer of the sidewall are all quartz glass.

[0013] According to the present invention, a high ultraviolet transmittance light-heat energy coupling utilization device is provided, wherein the thickness of the quartz glass is 5mm-50mm, the transmittance of the quartz glass in the ultraviolet band 185nm-400nm is 90.8%-99.8%, and the transmittance of the quartz glass in the ultraviolet band 250nm-400nm is 70%-100%.

[0014] According to the present invention, a high ultraviolet transmittance light-heat energy coupling utilization device is provided, wherein a feeding device is provided on the reaction vessel body, the feeding device is connected to the reaction chamber, and a cover plate and a sliding module are provided on the feeding device.

[0015] According to the present invention, a high ultraviolet transmittance light-heat energy coupling utilization device is provided, wherein a material trough and a sand plate are provided at the bottom of the reaction chamber.

[0016] According to the present invention, a high ultraviolet transmittance light-heat energy coupling utilization device is provided at the bottom of the reaction vessel body, a liquid outlet is provided at the bottom of the liquid outlet, a condensing device is installed on the liquid outlet, the condensing device is connected to an external cooling source, a gas outlet is connected to the liquid outlet, the gas outlet is connected to an external gas detection device, and a gas inlet is installed on the reaction vessel body, the gas inlet is connected to the reaction chamber.

[0017] According to the present invention, a high ultraviolet transmittance light-heat energy coupling utilization device is provided, wherein a photothermal detection device is installed on the reaction vessel body, and the detection end of the photothermal detection device extends into the reaction chamber.

[0018] A method of using a high ultraviolet transmittance light-heat energy coupling utilization device includes the following steps:

[0019] The material is placed in the reaction chamber, and a reaction gas or carrier gas is introduced into the reaction chamber.

[0020] The device is placed outdoors, and light enters the reaction chamber through a light-transmitting component.

[0021] During use, the reaction chamber is kept warm by the insulation layer.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] This invention provides a high ultraviolet transmittance light-heat energy coupling utilization device and method. The reaction chamber is used to place materials. Ultraviolet light is allowed to penetrate into the reaction chamber through a light-transmitting element. The heat insulation layer reduces heat conduction and convection heat transfer, ensuring that ultraviolet rays from sunlight can enter the device to the maximum extent, providing a sufficient ultraviolet light source for subsequent photochemical reactions. At the same time, while maintaining high ultraviolet light transmittance, it achieves efficient heat insulation effect. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 is a side view of the present invention;

[0027] Figure 3 is a top view of the present invention;

[0028] Figure 4 is a schematic diagram of the fixture structure of the present invention;

[0029] Figure 5 is a schematic diagram of Embodiment 2 of the present invention;

[0030] Figure 6 is a structural schematic diagram of Embodiment 3 of the present invention;

[0031] The components are as follows: 1. Air inlet; 2. Transparent plate; 3. Bolt; 4. Reactor body; 5. Inner side wall layer; 6. Middle side wall layer; 7. Outer side wall layer; 8. Feeding device; 9. Material trough; 10. Sand plate; 11. Condensation device; 12. Air outlet; 13. Liquid outlet; 14. Photothermal detection device; 15. Cover plate; 16. Sliding module; 17. Support groove; 18. Storage groove; 19. Rotating shaft; 20. Scraper; 21. Support ring; 22. Half gear; 23. Limiting block. Detailed Implementation

[0032] 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.

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Example

[0034] Referring to Figures 1-4, the present invention provides a high ultraviolet transmittance light-heat energy coupling and utilization device, comprising:

[0035] The reaction vessel body 4 has a reaction chamber inside it;

[0036] The light-transmitting component includes a viewing window and a light-transmitting element. The viewing window is opened at the top and side wall of the reactor body 4 and the two are connected. The light-transmitting element is installed in the viewing window and side wall to allow ultraviolet rays to penetrate into the reaction chamber.

[0037] The insulation layer is installed on the reactor body 4 and is used to keep the reaction chamber warm.

[0038] Specifically, the reaction chamber is used to hold materials. Ultraviolet light is allowed to penetrate the chamber through a light-transmitting element, while an insulation layer reduces heat conduction and convection, ensuring that ultraviolet rays from sunlight can enter the device to the maximum extent possible, providing a sufficient ultraviolet light source for subsequent photochemical reactions. Simultaneously, while maintaining high ultraviolet light transmittance, efficient heat insulation is achieved.

[0039] As an optional implementation, the light-transmitting component includes a light-transmitting plate 2, which is fixedly connected to the viewing window by bolts 3.

[0040] In one embodiment of the present invention, ultraviolet light is transmitted into the reaction chamber through a light-transmitting plate 2.

[0041] As an optional implementation, the insulation layer includes an inner sidewall layer 5, a middle sidewall layer 6, and an outer sidewall layer 7 arranged sequentially from the inside to the outside, wherein the middle sidewall layer 6 is made of aerogel material.

[0042] In one embodiment of the present invention, the middle layer of the sidewall is made of a high-transmittance aerogel vacuum composite thermal insulation material with a thickness of 10mm, so as to achieve thermal insulation of the reaction chamber.

[0043] As an optional implementation, the light-transmitting plate 2, the inner sidewall layer 5, and the outer sidewall layer 7 are all made of quartz glass.

[0044] In one embodiment of this application, the top is made of quartz glass to ensure high ultraviolet transmittance and the transfer of solar energy heat to the interior of the reaction chamber, and the sidewalls are made of a special optically transparent material as the outer layer, which has high transmittance to ultraviolet light.

[0045] Specifically, a layer of highly transparent and heat-insulating aerogel material is tightly bonded to the inner side of the outer layer. Inside the aerogel layer, a fine microporous support structure is used to maintain the shape stability of the aerogel and prevent it from collapsing in a vacuum environment. A high-vacuum layer is formed between the support structures to further reduce heat conduction and convective heat transfer. The vacuum layer maintains a long-term high-vacuum state through sealing technology and getters, ensuring that ultraviolet rays from sunlight can enter the device to the maximum extent, providing sufficient ultraviolet light source for subsequent photochemical reactions. At the same time, while maintaining high ultraviolet light transmittance, it achieves efficient heat insulation.

[0046] As an optional implementation, the thickness of the quartz glass is 5mm-50mm, the transmittance of the quartz glass in the ultraviolet band 185nm-400nm is 90.8%-99.8%, and the transmittance of the quartz glass in the ultraviolet band 250nm-400nm is 70%-100%.

[0047] In one embodiment of the present invention, the quartz glass allows ultraviolet light to pass through, and a quartz glass resistant to high temperatures of 1000°C is selected.

[0048] As an optional implementation, the reactor body 4 is provided with a feeding device 8, which is connected to the reaction chamber. The feeding device 8 is provided with a cover plate 15 and a sliding module 16.

[0049] In one embodiment of the present invention, referring to FIG1, the feeding device 8 is specially designed to meet the need for rapid heating to the reaction temperature in rapid pyrolysis, non-in-situ catalytic pyrolysis or gasification. When the temperature reaches the reaction temperature, the sample is put into the reaction vessel from the opening of the feeding device 8. The feeding device 8 is provided with a cover plate 15 and a sliding module 16 to achieve high-temperature uniform feeding.

[0050] The specific sliding module 16 is a slider. The sample is placed in the middle of the reaction vessel by pushing the slider by hand. After the sample is placed, it is pulled back to the side wall.

[0051] As an optional implementation, a material trough 9 and a sand plate 10 are provided at the bottom of the inside of the reaction chamber.

[0052] In one embodiment of the present invention, specifically to ensure that the material storage tank 9 and the sand plate 10 are removed from the reaction vessel for weighing after the reaction, a clamp is also included. By clamping them at a certain angle and extending them into the reaction vessel, the clamp is fixed to the edge of the material storage tank 9, so that the material storage tank 9 and the sand plate 10 can be removed.

[0053] As an optional implementation, the bottom end of the reactor body 4 is provided with a liquid outlet 13, a condensing device 11 is installed on the liquid outlet 13, the condensing device 11 is connected to an external cooling source, a gas outlet 12 is connected to the liquid outlet 13, the gas outlet 12 is connected to an external gas detection device, and a gas inlet 1 is installed on the reactor body 4, the gas inlet 1 is connected to the reaction chamber.

[0054] In one embodiment of the present invention, referring to FIG1, the condensing device 11 is connected to a low-temperature water bath or a cold water pump, the gas outlet 12 is connected to a gas detection device through a pipeline, and the liquid outlet 13 is connected to a round-bottom flask for liquid collection.

[0055] As an optional implementation, a photothermal detection device 14 is installed on the reactor body 4, and the detection end of the photothermal detection device 14 extends into the reaction chamber.

[0056] In one embodiment of the present invention, referring to FIG1, the temperature inside the reaction chamber is detected by a photothermal detection device 14.

[0057] A method of using a high ultraviolet transmittance light-heat energy coupling utilization device includes the following steps:

[0058] The material is placed in the reaction chamber, and a reaction gas or carrier gas is introduced into the reaction chamber.

[0059] The device is placed outdoors, and light enters the reaction chamber through a light-transmitting component.

[0060] During use, the insulation layer is used to keep the reaction chamber warm.

[0061] Specifically, during use, the device of the present invention is placed outdoors, the experimental sample to be tested is placed in the reaction chamber, a concentrator is used to focus sunlight onto the light-transmitting plate and into the reaction chamber, and the photothermal detection device 14 is used to detect the light power density and temperature inside the chamber in real time. During the experiment, the device is kept sealed. The inlet 1 is connected to the carrier gas or the reaction gas, the condenser 11 is connected to the low temperature water bath or the cold water pump, the outlet 12 is connected to the gas detection device through a pipeline, and the liquid outlet 13 is connected to the round bottom flask for liquid collection.

[0062] Specifically, quartz glass with a thickness of 5mm was selected, which can achieve 100% transmittance in the ultraviolet band of 250nm-400nm and can withstand high temperatures of 1000℃. The middle layer of the sidewall is made of high-transmittance aerogel vacuum composite thermal insulation material with a thickness of 10mm. The experimental results show that the pollutant degradation rate is 100% and the pyrolysis oil yield is 80%.

[0063] The inner layer is made of quartz glass with a thickness of 10mm. It has a transmittance of 97% in the ultraviolet band of 250nm-400nm and can withstand a high temperature of 1000℃. The middle layer of the side wall is made of high-transmittance aerogel vacuum composite thermal insulation material with a thickness of 10mm. It has a pollutant degradation rate of 93% and a pyrolysis oil yield of 76%.

[0064] The top and sidewall outer and inner layers are made of quartz glass with a thickness of 15mm. It has a transmittance of 94% in the ultraviolet band of 250nm-400nm and can withstand a high temperature of 1000℃. The middle layer of the sidewall uses a high-transmittance aerogel vacuum composite thermal insulation material with a thickness of 10mm, a pollutant degradation rate of 80%, and a pyrolysis oil yield of 70%.

[0065] The top and sidewall outer and inner layers are made of quartz glass with a thickness of 20mm. It has a transmittance of 91% in the ultraviolet band of 250nm-400nm and can withstand a high temperature of 1000℃. The middle layer of the sidewall uses a high-transmittance aerogel vacuum composite thermal insulation material with a thickness of 10mm, a pollutant degradation rate of 50%, and a pyrolysis oil yield of 59%.

[0066] The top and sidewall outer and inner layers are made of quartz glass with a thickness of 5mm. It has a transmittance of 100% in the ultraviolet band of 250nm-400nm and can withstand a high temperature of 1000℃. The middle layer of the sidewall uses a high-transmittance aerogel vacuum composite thermal insulation material with a thickness of 10mm, a pollutant degradation rate of 96%, and a pyrolysis oil yield of 80%. Example

[0067] Referring to Figure 5, light-transmitting elements of different thicknesses have different transmittance. For experiments that require precise photochemical reaction conditions, since different light power densities exist under different light irradiation bands, obtaining the corresponding reaction conditions by adjusting the thickness of the light-transmitting element step by step requires a large number of experiments, which is very difficult and troublesome.

[0068] By using machine learning algorithms to train on a large amount of existing data, with reaction parameters as input and the thickness of the light-transmitting component as output, the thickness of the light-transmitting component can be quickly and effectively adjusted according to reaction requirements.

[0069] Specifically, it includes the following processes:

[0070] Data collection: Collect pollutant degradation rates and liquid product yields obtained under different experimental conditions, including but not limited to light irradiation bands and light power density.

[0071] Data preprocessing includes data cleaning, handling missing values, and handling outliers.

[0072] Feature selection: Selecting and constructing features needed for model training, which may include feature selection, feature extraction, feature transformation, etc.

[0073] Model design, taking artificial neural networks as an example: design the structure of the neural network, including the number of layers, the number of neurons, activation functions, etc. The ratio of the training set to the test set is 3:1 or 4:1.

[0074] Model training: Training the model using the training dataset.

[0075] Model validation: Evaluate the model's performance using a validation dataset.

[0076] The model performance is satisfactory: using R 2 Alternatively, RMSE can be used to assess whether the model's performance meets expectations.

[0077] Model Deployment: If the model performance is satisfactory, deploy the model to the production environment.

[0078] Model tuning: If the model performance is unsatisfactory, model tuning may be performed, which may include adjusting the model structure, optimizing hyperparameters, etc.

[0079] Model prediction: Using a trained model to predict new data.

[0080] Result evaluation: Evaluate the results of the model's predictions.

[0081] Results met expectations: Assess whether the predicted results met expectations.

[0082] End: If the result meets expectations, the process ends; otherwise, return to the model tuning step. Example

[0083] Referring to Figure 6, the reactor body 4 is also provided with a support groove 17. A receiving groove 18 is rotatably connected in the support groove 17. Several rotating shafts 19 are rotatably connected in the receiving groove 18 along the circumferential direction. A scraper 20 is fixedly connected to the rotating shaft 19. A support ring 21 is rotatably connected in the receiving groove 18 through a bearing. A toothed groove is provided on the support ring 21 along the axial direction. A half gear 22 is fixedly connected to the rotating shaft 19. The half gear 22 meshes with the toothed groove.

[0084] Furthermore, the support ring 21 is also provided with a limiting block 23, which is used to contact the storage groove 18 and push the storage groove 18 to rotate.

[0085] Furthermore, the scraper 20 has an arc-shaped structure.

[0086] In this embodiment, the scraper 20 is initially stored in the storage groove 18. When it is necessary to clean the top light-transmitting plate 2, the support ring 21 rotates, driving the half gear 22 to rotate, so that the scraper 20 extends onto the light-transmitting plate 2. As the support ring 21 rotates, the storage groove 18 rotates, and the extended scrapers 20 clean the light-transmitting plate 2. During the cleaning process, guided by the arc-shaped structure, dust and impurities are deflected away from the center. Subsequently, the support ring 21 is rotated in the opposite direction to reset the scraper 20, collecting the dust and impurities into the storage groove 18, thereby cleaning the light-transmitting plate 2 and preventing dust residue on the light-transmitting plate 2 after cleaning, ensuring the light transmission effect of the light-transmitting plate 2. Example

[0087] In this embodiment, an annular slide rail is fixedly connected to the top of the inside of the reactor body 4. A sliding block is provided on the annular slide rail, and a telescopic scraper is fixedly connected to the bottom of the sliding block. The telescopic scraper is in contact with the inner sidewall of the reactor body 4.

[0088] The sliding block drives the moving wheel to rotate on the annular slide rail via a separate drive motor. When in use, it controls the telescopic scraper to extend and contact the inner wall of the reactor body 4. The sliding block moves the telescopic scraper to move on the inner wall of the reactor body 4, thus cleaning the inner wall of the reactor body 4. Conversely, when not in use, the telescopic scraper is in a retracted state to avoid blocking the light.

[0089] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0090] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A high ultraviolet transmittance light-heat energy coupling and utilization device, characterized in that, include: The reactor body (4) is provided with a reaction chamber inside the reactor body (4); The light-transmitting component includes a viewing window and a light-transmitting element. The viewing window is opened at the top and side wall of the reactor body (4) and communicates with both. The light-transmitting element is installed on the viewing window and side wall to allow ultraviolet light to penetrate into the reaction chamber. An insulation layer is provided on the reactor body (4) to keep the reaction chamber warm.

2. The high ultraviolet transmittance light-heat energy coupling and utilization device according to claim 1, characterized in that: The light-transmitting component includes a light-transmitting plate (2), which is fixedly connected to the window by bolts (3).

3. The high ultraviolet transmittance light-heat energy coupling and utilization device according to claim 2, characterized in that: The insulation layer includes an inner sidewall layer (5), a middle sidewall layer (6), and an outer sidewall layer (7) arranged sequentially from the inside to the outside. The middle sidewall layer (6) is made of aerogel material.

4. The high ultraviolet transmittance light-heat energy coupling and utilization device according to claim 3, characterized in that: The light-transmitting plate (2), the inner layer (5) of the side wall, and the outer layer (7) of the side wall are all made of quartz glass.

5. The high ultraviolet transmittance light-heat energy coupling and utilization device according to claim 4, characterized in that: The thickness of the quartz glass is 5mm-50mm, the transmittance of the quartz glass in the ultraviolet band 185nm-400nm is 90.8%-99.8%, and the transmittance of the quartz glass in the ultraviolet band 250nm-400nm is 70%-100%.

6. The high ultraviolet transmittance light-heat energy coupling and utilization device according to claim 1, characterized in that: The reactor body (4) is provided with a feeding device (8), which is connected to the reaction chamber. The feeding device (8) is provided with a cover plate (15) and a sliding module (16).

7. The high ultraviolet transmittance light-heat energy coupling and utilization device according to claim 1, characterized in that: The bottom of the reaction chamber is provided with a material trough (9) and a sand plate (10).

8. The high ultraviolet transmittance light-heat energy coupling and utilization device according to claim 1, characterized in that: The bottom end of the reactor body (4) is provided with a liquid outlet (13), a condenser (11) is installed on the liquid outlet (13), the condenser (11) is connected to an external cooling source, a gas outlet (12) is connected to the liquid outlet (13), the gas outlet (12) is connected to an external gas detection device, and a gas inlet (1) is installed on the reactor body (4), the gas inlet (1) is connected to the reaction chamber.

9. The high ultraviolet transmittance light-heat energy coupling and utilization device according to claim 1, characterized in that: A photothermal detection device (14) is installed on the reactor body (4), and the detection end of the photothermal detection device (14) extends into the reaction chamber.

10. A method of using a high ultraviolet transmittance light-heat energy coupling and utilization device, applicable to the high ultraviolet transmittance light-heat energy coupling and utilization device as described in claim 1, characterized in that, Includes the following steps: The material is placed in the reaction chamber, and a reaction gas or carrier gas is introduced into the reaction chamber. The device is placed outdoors, and light enters the reaction chamber through a light-transmitting component. During use, the reaction chamber is kept warm by the insulation layer.

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