CN107091963B

CN107091963B - Soil thermoelectric generation experimental apparatus

Info

Publication number: CN107091963B
Application number: CN201710553920.XA
Authority: CN
Inventors: 李文彬; 黄永胜; 徐道春; 陈臣; 王宁; 嘎拉泰
Original assignee: Beijing Forestry University
Current assignee: Beijing Forestry University
Priority date: 2017-07-09
Filing date: 2017-07-09
Publication date: 2023-08-04
Anticipated expiration: 2037-07-09
Also published as: CN107091963A

Abstract

The soil temperature difference power generation experimental device comprises a soil tank, a heating cable, a temperature controller, a temperature measuring probe, a heat absorption fin, a gravity heat pipe, a temperature difference power generation piece, a resistor, a thermocouple, a soil temperature and humidity sensor, a current transmitter and a data acquisition and transmission system; the heating cable can heat the soil and control the temperature of the soil by combining the temperature controller and the temperature measuring probe; the experimental device can collect data of temperature and humidity, temperature and current and voltage of soil and transmit the data to the platform of the Internet of things through a GPRS network, can promote related research of temperature difference power generation of the soil, and provides a basic experimental platform for power supply research of low-power devices working in special environments.

Description

Soil thermoelectric generation experimental apparatus

Technical Field

The invention relates to a soil thermoelectric generation experimental device which is suitable for soil thermoelectric generation experiments and research on a soil heat transfer mechanism. The soil temperature difference power generation experimental device can control experimental parameters such as temperature difference, humidity and resistance, perform soil temperature difference power generation experiments, and can also obtain real-time values of temperature, humidity, current and voltage, thereby providing a data base for the research of soil thermoelectric.

Background

The rapid development of the Internet of things technology enables the Internet of things technology to be widely applied in forestry, a large number of wireless sensors are arranged in the forest to collect various needed data, due to the particularity of the forest environment, the problem of power supply of the wireless sensors is more prominent, continuous and stable electric energy is difficult to obtain, the problem of difficult wire erection and high cost due to the adoption of line power supply is solved, the problem of difficult replacement, difficult timely replacement and pollution caused by improper treatment of old batteries due to the adoption of battery power supply is solved, and the application of the wireless sensors in the forest area is restricted. Therefore, an in-situ power supply mode adopting local materials becomes a necessary choice.

Relevant monitoring and research has shown that soil can be used to power forestry wireless sensors. The specific idea is as follows: the gravity heat pipe is buried in forest soil, heat energy in the soil is transmitted to the ground surface by utilizing the cyclic phase change of the working medium of the gravity heat pipe, then a semiconductor thermoelectric generation sheet is attached to the heat dissipation end of the gravity heat pipe, the other surface of the thermoelectric generation sheet is contacted with air, and the temperature difference at two sides is utilized for generating electricity for a sensor. According to the thought, the invention designs a set of soil thermoelectric generation experimental device.

Disclosure of Invention

Aiming at the problems, the invention designs a soil temperature difference power generation experimental device which comprises a wooden soil container, a soil temperature control system, a soil power generation system, a data acquisition and transmission system, a soil temperature and humidity sensor, a thermocouple and a current transmitter, wherein:

the wooden soil container is an experimental device foundation platform, the size is 50cm multiplied by 40cm, soil is placed in the soil container when the wooden soil container is used, and a soil power generation system and a sensor are buried in the soil. Different soil types can be replaced according to experimental requirements to study the heat transfer effect and the influence of the heat transfer effect on the electric energy output of the soil power generation system.

The soil temperature control system comprises a temperature controller, an external temperature measuring probe and a heating cable. The heating cable adopts S-shaped to arrange in wooden soil container bottom, and the simulation face heat source heats soil, and the heating cable passes through the temperature controller and supplies power. The external temperature measuring probe is arranged in the soil and is close to the heat absorption fins of the soil power generation system, and the temperature controller controls connection and disconnection of the heating cable power supply according to a temperature signal fed back by the external temperature measuring probe, so that the temperature is maintained at a set fixed value.

The soil power generation system consists of three parts, namely a heat absorption fin, a gravity heat pipe and 8 thermoelectric power generation pieces, wherein the heat absorption fin is arranged at the heat absorption end of the gravity heat pipe, so that the heat absorption efficiency of the gravity heat pipe is improved; the thermoelectric generation sheet is attached to the radiating end of the gravity assisted heat pipe through a sleeve; the circuit formed by connecting 8 thermoelectric generation sheets in series is connected with a resistor to form a current loop, and the resistance value of the resistor is 10Ω. In the experiment, the heat absorption fins and the lower half part of the gravity heat pipe are buried in the soil, and the thermoelectric generation sheets and the upper half part of the gravity heat pipe are exposed out of the soil surface.

The data acquisition and transmission system comprises a data acquisition card and a GPRS data transmission module, wherein the data acquisition card can acquire signals such as temperature, humidity, loop current, loop voltage and the like, and the GPRS can send data to the data storage terminal of the Internet of things through a 2G network and a 3G network.

The soil temperature and humidity sensor is used for measuring the temperature and humidity of soil in the soil container, and is placed near the heat absorption fins when in use, and the signal line is connected to the data acquisition and transmission system.

The thermocouple is used for measuring temperatures of the heat absorption fin, the gravity heat pipe heat absorption end, the gravity heat pipe waist plate, the gravity heat pipe heat dissipation end and the cold end of the thermoelectric generation sheet, and is placed at the positions of the heat absorption fin near heat pipe end, the heat absorption fin far heat pipe end, the gravity heat pipe heat absorption end, the gravity heat pipe middle waist plate, the gravity heat pipe upper heat dissipation end and the cold end of the thermoelectric generation sheet respectively during use, corresponding measures for isolating soil or air temperature are taken, and the signal wire is connected to the data acquisition and transmission system.

The current transmitter is used for measuring the circuit loop current of the soil power generation system, is connected in series to the circuit loop of the soil power generation system when in use, and is connected to the data acquisition and transmission system. The experimental device is reasonable in structure, capable of changing the temperature and humidity of soil, capable of automatically measuring the temperature and humidity of the soil, the temperature difference at two ends of the temperature difference power generation piece and the current and voltage data, capable of sending the data to the platform of the Internet of things through GPRS, high in reliability and good in transmission stability, and has a great promoting effect for the research of the temperature difference power generation of the soil and the research of the soil heat transfer mechanism.

The purpose of the invention is that: based on the needs of forest soil temperature difference power generation research, the invention can control the soil temperature to be higher than the air temperature, so that experiments are not limited by seasons any more, and the research progress of soil temperature difference power generation is quickened. After the soil power generation system is removed, the research of a soil heat transfer mechanism can be carried out in a laboratory, and the defects of simulation research and the limitation of field test are overcome. Has extremely important significance for research on forest soil thermoelectric generation and research on power supply of low-power components in forest areas.

Drawings

FIG. 1: soil thermoelectric generation experimental apparatus overall design diagram

Fig. 2: schematic diagram for researching soil heat transfer mechanism

Fig. 3: schematic diagram of soil temperature control system

Fig. 4: schematic diagram for placing thermoelectric generation sheets

Fig. 5: schematic diagram of heat absorbing fin

Fig. 6: temperature difference power generation sheet connection schematic diagram

Reference numerals:

S1-S2, S4, S6-S8-thermocouple

S3-current transducer

S5-soil temperature and humidity sensor

1-resistance

2-data acquisition and transmission system

3-soil container

4-temperature probe

5-heating cable

6-temperature controller

7-Heat absorbing fins

8-gravity heat pipe

9-thermoelectric generation sheet

10-sleeve

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings, which illustrate embodiments of the invention. The same reference numbers in the drawings represent the same or similar elements, but the examples provided are not intended to limit the scope of the invention.

As shown in figure 1, the invention provides a soil thermoelectric generation experimental device which comprises a soil container (3), soil temperature control systems (4, 5 and 6), soil power generation systems (7, 8, 9 and 10), a data acquisition and transmission system (2), a resistor (1), a current transmitter (S3), thermocouples (S1-S2, S4 and S6-S8) and a soil temperature and humidity sensor (S5).

The wooden soil container (3) is a basic platform of the experimental device, the size of the wooden soil container is 50cm multiplied by 40cm, the soil collected in the forest is placed in the soil container, and the soil of different types can be replaced and the soil humidity can be changed according to experimental requirements. The length and width of the soil container are mainly determined according to the research requirement of the soil heat transfer mechanism, and the height is mainly established according to the research on the optimal size of the soil for longitudinal heat transfer and heat preservation. The soil temperature control system comprises a heating cable (5), a temperature controller (6) and an external temperature measuring probe (4), wherein the heating cable (5) is arranged at the bottom (figure 3) of a soil container (3) in an S shape, the heating cable is connected with a power supply through the temperature controller (6), the heating cable can be regarded as a surface heat source to heat soil, the soil temperature is higher than air, the limit of seasons on experiments is broken, the temperature controller external temperature measuring probe (4) is placed in the soil near the heat absorbing fins (7), a soil temperature signal is fed back to the temperature controller (6), the temperature controller (6) controls the connection and disconnection of the power supply of the heating cable (5) according to whether the fed-back temperature signal reaches a set temperature value, and the soil is heated to a set fixed temperature and then kept at a constant temperature.

The soil power generation system consists of three parts, namely a heat absorption fin 7 (figure 5) at the bottom of a gravity heat pipe (8), a gravity heat pipe (8) in the middle and thermoelectric generation sheets (9) with the upper part 8 connected in series. The gravity heat pipe has excellent heat conductivity which is incomparable with common metal, the gravity heat pipe is divided into a heat absorption end, a heat insulation waist plate and a heat dissipation end, a working medium which is easy to generate phase change is arranged in the heat pipe, a liquid working medium absorbs heat and evaporates at the heat absorption end, a gaseous working medium rises to the heat dissipation end to release heat, and the gaseous working medium flows back to the evaporation end after being condensed into liquid drops, and the heat energy is automatically transferred after repeated circulation. The invention adopts a normal temperature gravity heat pipe with the length of 2m and the outer diameter of 40mm, the pipe shell, the end cover and the waist plate of the gravity heat pipe are made of stainless steel, the liquid absorption core is made of porous material, and the working medium is inorganic salt. The heat absorption fin is a section copper pipe, 6 copper sheets are fixed on the outer vertical surface, the inner vertical surface is attached to the heat absorption end of the gravity heat pipe for heat transfer, the copper sheets are contacted with soil for heat absorption, the inner diameter of the copper pipe is 40mm, the length of the copper sheets is 250mm, and the thickness of the copper sheets is 1 mm. The principle of the thermoelectric generation sheet is Seebeck effect, which is taken as a theoretical basis of a thermoelectric energy conversion technology, and indicates that in a loop formed by two metals A and B, if the temperatures at the connection positions of the two metals are different, current can be generated in the loop, and corresponding electromotive force, namely thermoelectric force, is induced. The Seebeck effect of the semiconductor material in the existing materials is most obvious, so the current thermoelectric generation sheets are all made of the semiconductor material. The invention uses a TG12-6-02 type thermoelectric generation sheet manufactured by the company Marlow Industries of the United states, the length is 44mm, the width is 40mm, and the thickness is 3.3mm. The thermoelectric generation sheet (9) and the gravity heat pipe (8) are jointed by a sleeve (10) (figure 4) to realize the transition from a cylindrical surface to a plane, the sleeve is a copper or silver cube, a through hole is arranged between the upper surface and the lower surface and is assembled with the gravity heat pipe, and the other four surfaces are jointed with the thermoelectric generation sheet; and heat conduction silica gel is smeared between the assembling surface of the gravity heat pipe and the sleeve, the joint surface of the sleeve and the thermoelectric generation sheet and the joint surface of the gravity heat pipe and the heat absorption fin, so that the heat transfer efficiency is improved. The thermoelectric generation sheet is attached to the outer surface of the heat dissipation end of the heat pipe, and generates electricity by utilizing the temperature difference between the heat dissipation end and air. 8 thermoelectric generation pieces are connected in series to form a current loop, and a resistor (1) and a current transducer (S3) are connected in the circuit (figure 6).

In order to reduce heat loss, except for a heat absorption end and a heat dissipation end, the rest parts of the gravity heat pipe in the soil power generation system are wound with asbestos belts for heat preservation.

[ example 1 ]

As shown in fig. 1, the soil power generation system (7, 8, 9, 10) is placed in the soil container (3), the heat absorption ends of the heat absorption fins (7) and the gravity heat pipes (8) are embedded into soil, the heat dissipation ends of the thermoelectric generation sheets (9), the sleeves (10) and the gravity heat pipes (8) are exposed out of the soil surface, the soil layer thickness between the heat absorption fins (7) and the heating cables (5) is 5cm, the soil power generation system and the heat source, namely the heating cables (5), are completely isolated, and the heat transmitted by the heat pipes is ensured to be absorbed from the soil instead of being directly absorbed from the heat source. The experiment device is provided with the sensors, thermocouples are arranged on the fins at positions far away from the heat pipe (S6), near the heat pipe (S7) and on the gravity heat pipe heat absorption end (S8), so that temperature change data of the key positions can be obtained, data support is provided for optimization of a soil power generation system, heat insulation treatment is carried out between the thermocouples and soil by using a heat insulation adhesive tape, and the obtained temperature data is ensured to be the temperature of measured metal, but not the soil temperature. Because the soil humidity has a great influence on the heat transfer of the soil and is an important parameter affecting the heat transfer of the soil and the power generation of the system, a soil temperature and humidity sensor (S5) is further arranged in the soil with the same height to obtain the change condition of the soil temperature and the humidity of the layer. In order to evaluate the heat transfer efficiency of the heat pipe, the adiabatic effect of the waist plate portion was examined, and a thermocouple (S4) was also disposed in the middle of the heat pipe, wound with an asbestos tape to isolate the air temperature. Finally, thermocouples are respectively arranged at the radiating end (S2) of the heat pipe and the cold end (S1) of the thermoelectric generation sheet for temperature monitoring, and heat insulation adhesive tapes are also attached to the thermocouples to isolate the air temperature.

The circuit formed by connecting 8 thermoelectric generation sheets in series is connected with a 10 omega resistor (1) to form a current loop, a current transducer (S3) is connected into the current loop to collect current data (figure 6), the output power of the soil power generation system is obtained by combining the voltage measurement function of the data acquisition card, and the performance of the soil power generation system is evaluated according to the power and temperature data. All sensors are connected to a data acquisition card (2) and then transmit data to an Internet of things data storage terminal through a GPRS wireless network.

The power supply of the temperature controller (6) is connected, the fixed temperature is set, the heating cable (5) starts to heat soil, the soil temperature starts to rise, the heat absorbing fins (7) absorb heat from the soil and transmit the heat to the heat absorbing end of the gravity heat pipe (8), the gravity heat pipe (8) transmits the heat to the heat dissipating end, the heat is transmitted to the hot end of the thermoelectric generation sheet (9) through the sleeve (10), a temperature difference is formed between the heat dissipating end and the cold end of the thermoelectric generation sheet (9), electric energy is generated in the thermoelectric generation sheet (9), and a current loop is formed through the resistor (1) and the current transmitter (S3); when the temperature at the temperature measuring probe (4) reaches a preset temperature value, the temperature controller (6) cuts off the power supply of the heating cable, the heating of the soil is stopped, and when the temperature at the temperature measuring probe is lower than the preset temperature, the temperature controller (6) is connected with the power supply of the heating cable again, the soil is circularly heated, and the soil temperature is maintained at a preset fixed value; finally, the power supply of the temperature controller is disconnected, and the temperature of the soil is reduced to the room temperature; the thermocouple (S1-S2, S4, S6-S8), the soil temperature and humidity sensor (S5) and the current transmitter (S3) monitor the data change of each position in real time in the whole process, and acquire, transmit and store the data through the data acquisition and transmission system (2). And the later stage can analyze the relation between the generated energy and the temperature difference of the two ends of the temperature difference generating piece.

[ example 2 ]

As shown in fig. 2. The soil power generation system is removed, soil is placed in a soil container, soil temperature and humidity sensors S5-1, S5-2 and S5-3 on the symmetrical planes of the soil container are arranged at the same height, the distances from the bottom of the soil container to the soil container are 10cm, S5-4, S5-5 and S5-6 are respectively located right above the soil temperature and humidity sensors, the distances from the bottom of the soil container to the soil container are 20cm, and S5-7, S5-8 and S5-9 are located right above the soil temperature and humidity sensors and are located 30cm from the bottom of the soil container to the bottom of the soil container. All soil temperature and humidity sensors are connected to the data acquisition and transmission system.

And (3) starting an experiment by opening the temperature controller (6) and a monitoring system power supply, heating to a stable state, keeping the temperature at each position for a period of time after the temperature is not changed, closing the power supply of the temperature controller (6), cooling to the room temperature to obtain data of the whole heating-heat preservation-cooling process, and analyzing the data of each temperature and humidity sensor to obtain the heat transmission rule of the soil. In the experiments, different groups of experiments can set different temperatures on the temperature controller (6) and control different humidity of soil.

In summary, the above embodiments are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Technical effects

According to the invention, the heating cable is used for heating the soil, and the temperature of the soil can be controlled at different set values by the temperature controller and the temperature measuring probe. The experimental device has a multi-signal acquisition function, and can acquire soil temperature and humidity, metal temperature, current and voltage signals at the same time; the GPRS wireless network is used for sending data to the data storage terminal of the Internet of things, so that the data can be checked in a networking manner at any place, and the method is reliable and convenient. In the soil container, the research on the soil heat transfer rule in the soil temperature difference power generation can be carried out indoors by changing the soil type, changing the soil moisture content and the like. The invention can also study the influence of the factors on the power generation effect by changing the length of the heat pipe, the soil heating temperature and the number of thermoelectric generation sheets.

Claims

1. The utility model provides a soil thermoelectric generation experimental apparatus, includes soil container (3), soil temperature control system, soil power generation system, data acquisition and transmitting system (2), resistance (1), current transmitter (S3), thermocouple and soil temperature and humidity sensor (S5), its characterized in that:

soil is placed in the soil container (3); the soil temperature control system comprises a heating cable (5), a temperature controller (6) and an external temperature measuring probe (4), wherein the heating cable (5) is arranged at the bottom of a soil container (3) in an S shape, the heating cable is connected with a power supply through the temperature controller (6), and the external temperature measuring probe (4) is arranged near a heat absorbing fin (7); the heat absorption fin (7), the gravity heat pipe (8), the thermoelectric generation piece (9) and the sleeve (10) form a soil power generation system, the heat absorption fin (7) is matched with the heat absorption end of the gravity heat pipe (8), the thermoelectric generation piece (9) is attached to the heat dissipation end of the gravity heat pipe (8) through the sleeve (10), 8 thermoelectric generation pieces (9) are connected in series to form a current loop, a resistor (1) and a current transmitter (S3) are connected in the loop, the heat absorption fin (7) and the heat absorption end of the gravity heat pipe (8) are buried in soil in the soil container (3), the distance between the heat absorption fin and the heating cable (5) is 5cm, and the heat dissipation ends of the thermoelectric generation piece (9) and the gravity heat pipe (8) are exposed out of the soil surface; the first thermocouple (S1) is attached to the cold end of the thermoelectric generation sheet (9), the second thermocouple (S2) is attached to the radiating end of the gravity heat pipe (8), the third thermocouple (S4) is attached to the middle part of the gravity heat pipe (8), the fourth thermocouple (S6) is attached to the position, far away from the gravity heat pipe, of the heat absorption fin (7), and the fifth thermocouple (S7) is attached to the position, close to the gravity heat pipe, of the heat absorption fin (7); the soil temperature and humidity sensor (S5) is placed in the soil where the heat absorption fins (7) are located; the thermocouple, the soil temperature and humidity sensor (S5) and the current transmitter (S3) are connected to the data acquisition and emission system (2);

the temperature controller (6) is connected, a fixed temperature is set, the heating cable (5) starts to heat soil, the soil temperature rises, the heat absorbing fins (7) absorb heat from the soil and transmit the heat to the heat absorbing end of the gravity heat pipe (8), the gravity heat pipe transmits the heat, the heat is transmitted to the heat end of the thermoelectric generation sheet (9) through the sleeve (10), a temperature difference is formed between the heat and the cold end of the thermoelectric generation sheet (9), electric energy is generated in the thermoelectric generation sheet (9), and a current loop is formed through the resistor (1) and the current transmitter (S3); when the temperature at the temperature measuring probe (4) reaches a set temperature value, the temperature controller (6) cuts off the power supply of the heating cable, the heating of the soil is stopped, when the temperature at the temperature measuring probe (4) is lower than the set temperature, the temperature controller (6) is connected with the power supply of the heating cable again, the soil is circularly heated, the soil temperature is maintained at a set fixed value, and the soil temperature is controlled to be higher than the air temperature; finally, the power supply of the temperature controller (6) is disconnected, and the soil temperature is reduced to the room temperature; in the whole process, each thermocouple, a soil temperature and humidity sensor (S5) and a current transducer (S3) continuously monitor the humidity, temperature, current and voltage data change of each position, and a data acquisition and transmission system (2) acquires the soil temperature and humidity, metal temperature, loop current and loop voltage data in real time and sends the data to an Internet of things data storage terminal for storage through a GPRS wireless communication network.

2. The soil thermoelectric generation experimental device according to claim 1, wherein the thermoelectric generation experiment can be performed under the condition that the soil temperature is lower than the air temperature.

3. The soil thermoelectric power generation experimental device according to claim 1, characterized in that the heat absorbing end of the gravity assisted heat pipe (8) is provided with heat absorbing fins (7), and the heat absorbing fins (7) are of rectangular sheet-shaped structures and extend linearly from the center to the periphery.

4. The soil thermoelectric generation experimental device according to claim 1, characterized in that a sleeve (10) is adopted between the heat dissipation end of the gravity assisted heat pipe (8) and the thermoelectric generation sheet (9), and the sleeve material is silver or copper.