Description:FORM 2
THE PATENT ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See section 10, rule 13)

TITLE: SOIL BASED TUBULAR HYDRO-VOLTAIC DEVICE

INVENTORS
LAL, Sujith Indian Citizen
Department of Science, Amrita School of Physical Sciences, Amrita Vishwa Vidyapeetham, Coimbatore, Tamil Nadu 641112, India.

BATABYAL, Sudip Indian Citizen
Department of Science, Amrita School of Physical Sciences, Amrita Vishwa Vidyapeetham, Coimbatore, Tamil Nadu 641112, India.

APPLICANT
Amrita Vishwa Vidyapeetham
Amrita School of Engineering,
Coimbatore, Tamil Nadu- 641112, India

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
SOIL BASED TUBULAR HYDRO-VOLTAIC DEVICE

CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a patent of addition of Indian Patent Application No. 202241065079 filed on November 14, 2022.
FIELD OF THE INVENTION
[0002] The present invention generally relates to electricity generating devices and more particularly relates to hydro-voltaic devices and methods thereof.
BACKGROUND OF THE RELATED ART
[0003] Recently, excessive exploitation and rapid population growth have posed several challenges. The climate crisis is worsening because of the unchecked use of fossil fuels and the rise in greenhouse gas levels, so there is still an urgent need to seek alternative clean energy sources and ways to generate electricity with the purpose of adjusting energy structures and solving environmental problems. Nowadays Hydrovoltaic generators (HGs) driven by water evaporation have emerged and exhibited an eco-friendly concept of electricity generation compared with traditional methods with the rise of nano science and nanomaterial.
[0004] In contrast to conventional technologies that harvest kinetic energy of water, hydrovoltaic (HV) technology generates electricity from the direct interaction of materials with water. In this approach, a specific form of an electric double layer (EDL) occurs between the liquid’s positive charge and the active material’s negative charge when water flows through the nanochannels. A gradient of EDL formation along the thickness, that causes an internal potential difference, leads to the formation of electric power. On the basis of the experimental observations, during the flow of water through carbon/ nanochannel, the formation of EDL causes a specific type of potential called streaming potential. Other mechanisms like ion flow induced (gradient of protons or ions) HV also has been reported (DOI:10.1063/1.3632990). Previous HV reports suggest that any kind of water such as moisture or water droplets may develop a considerable voltage. Hence, it provides the prospect of upgrading the mode of water energy use, constructing a renewable energy industry, and alleviating environmental issues without involving complex fabrication or impending toxic/expensive materials.
[0005] The major impact of HV efficiency depends on active material, which should be a high possibility of EDL formation. Plenty of materials have been reported with the HV effect, such as carbon nanotubes (CNT)(S. Ghosh, et al (Science (80-. )., 2003), Z. Luo, et al (Nano Energy, 2019), R. Kumar, et al (2022)), carbon black(S. Zhang, et al (J. Phys. Chem. C, 2021), S. Jiao, et al (Carbon N. Y., 2022)), activated carbon(S. Lal, et al (J. Power Sources, 2023), B. H. Kim, et al (Micro Nano Syst. Lett., 2015)), Al2O3(S. Chaurasia, et al (ACS Omega, 2022)), graphene, graphene oxide(S. Daripa, et al (ACS Omega, 2021), S. Jiao, et al (J. Mater. Chem. A, 2022)), perovskite(S. K. Sharma, et al (ACS Energy Lett., 2023))etc.
[0006] Researchers have developed various designs of hydro voltaic devices using soil as an active material which generate power wherein such devices provide voltage but the current produced is in the range of few µA. A Chinese patent application CN108988456A discloses adevice to generate electricity using soil that includes a soil battery pack, charge switch and electrolytic capacitor. It is connect by conducting wire with the two poles of the earth of soil battery pack after stating charge switch and electrolytic capacitor series connection. However, in this device voltage is being developed because of the bacterium present in the soil. Another Chinese application CN114665747A discloses a soil film and a moisture power generation device that can continuously utilize air moisture to generate 0-0.4V open-circuit voltage and 0-0.1 microampere short-circuit current. Hence, the power generation takes place byusing soil particles in a plane wherein the soil particle coated film has the property of absorbing moisture from the environment.
[0007] Furthermore, the above mentioned active material and devices are complex and not easy to fabricate. Accordingly, there is a need for easy to fabricate hydro voltaic device for power generation generating high voltage values and current values. A tubular structure containing soil based hydro voltaic device is disclosed that is capable of generating voltage and current.

SUMMARY OF THE INVENTION
[0008] According to one embodiment of the present subject matter asoil based hydro-voltaic device for enhanced power generation is disclosed. The device includes a tubular structure having an open top end and an open bottom end. In various embodiments, the tubular structure is configured to hold soil and comprises a first electrode affixed to the top open end of the tubular structure. The structure further includes a perforated second electrode affixed to the bottom of the tubular structure, configured to immerse in an aqueous solution and allow entry inside the structure. In various embodiments, the first and second electrodes are connected along the length of the tubular structure. In various embodiments, the device includes a reservoir comprising the aqueous solution with the tubular structure in contact there within, wherein capillary action is configured to form an electric double layer formed at the soil - solution interfaces, thereby generating voltage and current flow between the first electrode and the second electrode. The device further includes a barrier attached to the bottom end, the barrier configured to control the inflow of the aqueous solution from the reservoir into the tubular structure. In various embodiments, the barrier includes a cotton ball. In various embodiments, the device has dimensions of length 30-80 mm X tubular diameter 8-15 mm X tube wall thickness of 1-2 mm.
[0009] In various embodiments, the device is configured to generate enhanced voltage on solar irradiation wherein the open top end is affixed with carbon cloth.In various embodiments, the device is configured to generate enhanced voltage on exposing the open top end to hot air. In various embodiments, the device generates a voltage in a range 0.6V to 1V.In various embodiments, the device generates a current in a range of 90- 95 µA.
[0010] According to another embodiment of the present subject matter, a method of fabricating a soil based hydro-voltaic device to generate voltage and current is disclosed. The method includes the step of providing filtered soil with a predetermined particle size. This is followed by the step of providing a tubular structure having electrodes at either end thereof and connected along the length. Next step is packing the soil along the length of the tubular structure followed with the step of placing the tubular structure in a reservoir comprising an aqueous solution. This is followed by allowing the water to flow through the tubular structure by capillary action. Final step includes forming an electric double layer at soil- aqueous solution interfaces, thereby generating voltage and causing flow of current across the ends of the tubular structure.
[0011] In various embodiments, the predetermined particle size of the soil is obtained by sieving with a filter having a mesh size of at least 0.6 mm. In various embodiments, the predetermined particle size of the soil comprises a particle diameter size is in a range 150- 200 µm and the gap between the soil grains in a range 60-90 µm. In various embodiments, the method includes a step of exposing the device to a light source and hot air to enhance the voltage generated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention has other advantages and features which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which:
[0013] FIG.1A: a schematic representation of a soil based tubular hydro-voltaic device.
[0014] FIG. 1B: a schematic representation of a modified SVH device with a hydrophilic cloth.
[0015] FIG. 2A: a schematic representation of a specific double layer formation occurring around the soil particles when water flows through it.
[0016] FIG. 2B: a photographic image showing morphology of silt soil using FE-SEM.
[0017] FIG. 3: a flow diagram of a method of fabricating a SHV device to generate voltage and current.
[0018] FIG. 4A: a graphical representation of voltage measured along the length of SHV(at Rt = 28°C and RH= 62-65 %).
[0019] FIG. 4B: a graphical representation of current generated from the SHV.
[0020] FIG. 4C: a graphical representation of power delivery of SHV.
[0021] FIG. 4D: a graphical representation of voltage generated by a modified SHV device when exposed to 1 sun illumination.
[0022] FIG. 4E: a graphical representation of cyclability of SHV.
[0023] FIG. 4F: a graphical representation of voltage measured along the length of SHV (at Rt = 28°C and RH= 62-65 %) for 35 days.
[0024] FIG. 5A: a graphical representation of X-Ray Diffraction (XRD) data of silt soil.
[0025] FIG. 5B: a graphical representation of Fourier Transform Infrared (FTIR) spectrum of silt soil.
[0026] FIG. 5C: a graphical representation of output current data of acid treated silt soil.
[0027] FIG. 5D: a graphical representation of comparison output voltage data of SHV device before and after autoclave treatment.
[0028] FIG. 5E: a graphical representation of confirmation experiment of voltage development along the thickness of SHV.
[0029] FIG. 6: FTIR spectrum of acid-washed slit soil SHV device.
[0030] FIG. 7A: a graphical representation of voltage measured along the length of SHV with carbon electrodes to ensure the power-generating performance from soil rather than electrodes.
[0031] FIG. 7B: a graphical representation of output current data with carbon electrodes to ensure the power-generating performance from soil rather than electrodes.
[0032] FIG. 7C: a graphical representation of voltage measured along the length of SHV with identical aluminium electrodes to ensure the power-generating performance from soil rather than electrodes.
[0033] FIG. 7D: a graphical representation of output current data with identical aluminium electrodes to ensure the power-generating performance from soil rather than electrodes.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0034] While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.
[0035] Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of "a", "an", and "the" include plural references. The meaning of "in" includes "in" and "on." Referring to the drawings, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein.
[0036] The present subject matter discloses a soil based hydro-voltaic device (SHV) that is capable of enhanced power generation, as further disclosed with reference to the drawings. In various embodiments, a method of fabricating a soil based hydro-voltaic device to generate voltage and current is disclosed.
[0037] A schematic representation of a soil based tubular hydro-voltaic device is illustrated in FIG. 1A, according to one embodiment of the present subject matter. The soil based hydro-voltaic device 100 includes a tubular structure 101, a reservoir 115 and a barrier 117. In various embodiments, the SHV device 100 is primarily configured to hold soil.
[0038] In various embodiments, soil based hydro- voltaic device 100 includes the tubular structure 101 with an open end and an open bottom end. In various embodiments, the tubular structure 101 is configured to hold soil 105. In various embodiments, the tubular structure 101 includes a first electrode 111 affixed to the top end. In various embodiments, the tubular structure 101 includes a perforated second electrode 113 affixed to the bottom end. In various embodiments, the perforated second electrode 113 is configured to immerse in an aqueous solution 109 to allow entry inside the structure 101. In various embodiments, the first and second electrodes 111, 113 are connected along the length of the tubular structure 101.
[0039] In various embodiments, the tubular structure is immersed in a reservoir 115 comprising the aqueous solution 109 with the tubular structure 101 in contact there within. In various embodiments, the device 100 produces high voltage and high current under ambient temperature without any external energy such as light, heat, or wind, between the electrodes 111 and 113. In various embodiments, immersing the tubular SHV 100 in the reservoir of aqueous solution 109 allows capillary flow of the aqueous solution 109 and hence the interaction of aqueous solution 109 with the soil 105 inside the tubular structure101 and evaporation and phase change are believed to cause a potential across the tubular structure.
[0040] In various embodiments, the aqueous solution 109 may be water or other polar fluid. In various embodiments, the bottom end of the tubular structure 101 is attached with the barrier 117. In various embodiments, the barrier 117 is configured to control the inflow of the aqueous solution 109 from the reservoir 115 into the tubular structure 101. In one embodiment, the barrier may be a cotton ball.
[0041] In various embodiments, the tubular structure 101 has a predetermined diameter and length. The capillary flow of aqueous solution and hence the potential is configured to vary with the thickness of the tubular structure 101.
[0042] In various embodiments, an electrical double layer (EDL) is formed due to interaction of soil with aqueous solution, at the soil- aqueous solution interfaces as illustrated in FIG. 2A. The soil has one or more functional groups, especially carboxylic, hydroxyl and oxygen-rich functional groups. In various embodiments, the one or more functional groups attach with H+ in aqueous solution, and create the EDL layer, thereby generating voltage and current flow between the first electrode 111 and the second electrode 113.The EDL layer and the movement of charges are illustrated in FIG. 2Aillustrating a specific double layer formation occurring around soil particles 105 when aqueous solution 109 flows through it. In one embodiment, the gradient of the functional group along the direction of the solution flow generates the voltage across the device.
[0043] In various embodiments, the soil- aqueous solution interaction and thereby the voltage of the soil based hydro-voltaic device 100 is proportional to the quantity of soil 105 present in the tubular structure 101, up to an optimum value. This means as the quantity of soil 105 decreases from this optimum value, the soil- aqueous solution interaction reduces, thereby leading to reduction in the output voltage.
[0044] In various embodiments, the voltage in the soil based hydro-voltaic device 100 is dependent on the length of the tubular structure 101, the diameter of the tubular structure 101, the tubular diameter of the structure or the quantity of soil 105 held in the structure. In various embodiments, the SHV device has dimensions of length 30-80 mm X tubular diameter 8-15 mm X tube wall thickness of 1-2 mm. In various embodiments, the SHV device 100 is configured to produce voltages in the range of 0.6V to 1V. In various embodiments, the SHV device 100 is configured to generate currents in a range of 90- 95 µA at a given voltage.
[0045] In one embodiment, the SHV device 100 is configured to generate enhanced voltage on solar irradiation. A carbon cloth 119 is affixed to the open top end of the tubular structure 101.FIG. 1B illustrates a schematic representation of a modified SHV device with a hydrophilic cloth. The power generated by the modified device has a slightly enhanced effect during light ON condition. In one embodiment, the SHV device 100 is configured to generate enhanced voltage on exposing the open top end of the tubular structure 101 to hot air. In various embodiments, two or more SHV devices 100 are connected in series and parallel arrangements to get a combined output voltage.
[0046] In another embodiment, a method 200 of fabricating a soil based hydro-voltaic device to generate voltage and current is disclosed. A flow diagram of a method of fabricating a soil based hydro-voltaic device to generate voltage and current is illustrated in FIG. 3, according to one embodiment of the present subject matter. The method in step 201 includes providing filtered soil of a predetermined particle size. Step 203 includes providing a tubular structure having electrodes at either end thereof and connected along the length. In various embodiments, step 205 includes packing the soil along the length of the tubular structure. This is followed by step 207 of placing the tubular structure in a reservoir comprising an aqueous solution. In step 209, the aqueous solution is allowed to flow through the tubular structure by capillary action. Finally, the method includes step 211 of forming an electric double layer (EDL) at soil- aqueous solution interfaces, thereby generating voltage and causing flow of current across the ends of the tubular structure. The EDL is formed by attachment of functional groups in soil, especially oxygen rich functional groups, carboxylic and hydroxyl groups, with H+ in the aqueous solution. This leads to the generation of voltage and causing flow of current across the ends of the tubular structure. In some embodiments, the method may include an additional step of exposing a carbon cloth affixed top end of the tubular structure to light to enhance the voltage generated. In some embodiments, the method may include additional step of exposing the top end of the tubular structure of the SHV device to hot air, thereby enhancing the voltage and current drawn from the device.
[0047] In various embodiments, the predetermined particle size of the soil is obtained by sieving with a filter having a mesh size of at least 0.6 mm. In various embodiments, the predetermined particle size of the soil comprises a particle diameter size is in a range 150- 200 µm and the gap between the soil grains in a range 60-90 µm. In various embodiments, the soil may include sandy clay soil or loamy soil or silt soil of any particle size.
[0048] The SHV device 100 and the method 200 of the present invention provide a tubular three dimensional (3D) device with a higher output than a conventional flat two- dimensional device (2D). The SHV device 100 may generate power in a simple, efficient way with negligible external energy support. The method 200 brings in use the soil as an active material, hence improving the practical usage of readily available natural resource. The SHV device and method of the present invention may have application in navy or defence to generate power during emergency condition. The method 200 has been experimentally validated and has demonstrated production of an extremely low cost SHV device. Thus the device of the present invention is configured to be lightweight and cost efficient. Besides, the SHV device of the present invention is an eco-friendly alternative to disposable energy generating devices that are of complex design, expensive to manufacture and thus may have higher environmental impact. Also, the SHV device generates current and voltage irrespective of the position of the light source and anytime of the day. Moreover, the SHV device and method of the present invention is of low cost, chemical free, recyclable and of compact nature.
[0049] Although the detailed description contains many specifics, these should not be construed as limiting the scope of the invention but merely as illustrating different examples and aspects of the invention. It should be appreciated that the scope of the invention includes other embodiments not discussed herein. Various other modifications, changes and variations which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the system and method of the present invention disclosed herein without departing from the scope of the invention as described here and as set forth in the claims attached herewith.
EXAMPLES:
[0050] Example- 1: Fabrication of Soil Hydro-voltaic device: A tubular soil based hydro-voltaic device (SHV)with a length of 5 cm was fabricated to analyse the significance of water and functional group incorporated substrate. The tubular SHV was fabricated using approximately 2 grams of silt soil wherein the soil was collected and sieved through a filter of 0.6 mm mesh. FIG. 1A illustrates the SHV devicefabricated to carry out further experiments. The filtered silt soil with uniform particle size was packed in a plastic tube with two electrodes along the length. The working electrode and counter electrode were aluminium metal foil and copper foil respectively. The bottom electrode was made with holes using bell pins for a better pathway for water wick. A cotton piece was attached to the bottom of the device to retain moisture inside the device and to control the flow of water to the top of device. FIG. 2A shows the photograph of the cross-section view of the device without electrodes. The image shows the amount of soil arranged in a packed manner. This can amplify the interaction between functional groups and water, which leads to high chance of EDL than in the 2D system.
[0051] FIG. 2Aindicates that when water flows through the soil particles, huge, abundant negative functional groups of soil grains can attract the positive charges in water, creating a specific EDL. During water flow, the strength of EDL is high when soil particles are nearby and decreases as the distance between the particles increases. This created a specific voltage in the horizontal view between the individual soil grains. Furthermore, along the length of the device, an overall EDL variation occurs (along the vertical view) due to liquid flow between the bottom and top. This also creates a resultant potential when water molecules are pumped through soil grains. During water flow, the movement of H+ ions creates a potential called streaming potential. The flow of electrons through the external circuit creates a specific type of current called streaming current. This mechanism was well convinced with experimental observations. The significance of soil voltage generation was confirmed with many experimental observations and material characteristics data.
STRUCTURAL AND FUNCTIONAL GROUP CHARACTERIZATION: To confirm the EDL formation by soil, structural and functional group analysis of the soil was performed to further use in a practical application.
[0052] Field Emission Scanning Electron Microscope (FE-SEM) Analysis: To understand the surface texture of the soil, Field Emission Scanning Electron Microscope (FE-SEM) was taken. FIG. 2B indicates the FE-SEM image depicting the high-grain-like structures of the soil; this indicates the high chance of EDL formation between the soil and water during water wicking. The average diameter of the soil particle is 150-200 µm, and the gap between the grains is 60-90 µm. However, the gaps can vary depending on the packing inside the tube. FIG. 2Ashows that the water flowing between the soil particles creates an EDL layer near the contact surface of soil and water. The forming EDL creates a difference in potential along the length.
[0053] X-Ray Diffraction (XRD) Analysis:X-Ray Diffraction (XRD) technique was used to understand structural properties of the soil. The obtained data is shown in FIG. 5A. It was observed that all obtained peaks were sharp indicating highly crystalline structure. The most predominant peak at 29º and 58º were due to the presence of Kaolinite in silt soil. The second majority peaks at 26.5º, 28.7º, 50.8º, and 60º were due to the presence of SiO2 in the soil. The diffraction peak at 16º was due to the gibbsite found in soil.
[0054] Fourier-transform Infrared Spectroscopy (FTIR) Analysis:
[1]It was observed that the presence of functional groups played a crucial role in EDL phenomena for better interaction of positive and negative ions. The presence of oxygen-rich functional groups played a key role in developing streaming potential. The existence of a functional group was confirmed with the FTIR spectrum, and it is shown in FIG. 5B. The obtained highly intense peak at the wave number 1003 cm-1 indicates the vibrations of SiO2 due to soil. The peak at 1241.31 cm-1 is due to the vibrations of COO carboxylic group. The peak at 1641 cm-1 is due to the stretching vibration of carbon and oxygen, whereas the peaks at 3617 cm-1 and 3689 cm-1 indicated the vibrations of hydroxyl groups. The presence of these oxygen-rich functional groups might enhance the EDL formation that leads to generating power.
[2] Evaluation of Functional Charges of Soil:To confirm that the functional charges of the soil could be a valid reason for the voltage generation, acid treatment was done with the collected soil to remove the functional groups in the soil. Bare soil was treated with concentrated sulfuric acid for three days and washed with deionised (DI) water to eliminate the functional groups of the soil. To further confirm the functional groups presence of acid treated soil, FTIR was taken and shown in FIG. 6. The FTIR spectrum of acid-treated soil clearly explained that the oxygen functional groups and hydroxyl groups were lowered and shown nearly a flat spectrum.
[0055] Energy-dispersive X-ray (EDX) spectroscopy analysis: Assuming that the reduction in functional groups may slow down voltage generation also, EDX spectroscopy was performed. EDX data and the current output performance of acid treated soil as SHV was measured and shown in FIG. 5Crespectively.This was further confirmed with EDX of bare and acid-treated soil. It was observed that the oxygen content was high in bare soil and totally reduced after acid treatment. This highly signified the reduction of functional groups after acid treatment. The HV effect was measured with acid-treated soil, as shown in FIG. 5C. The picture shown that the generated current with acid soil is very less in the 3-4 µA. This implied that the power was developed during the interaction of water with the functional groups in soil. Therefore, the natural soil was enough to generate electricity without resource replenishment and damage.
PERFORMANCE ASSESSMENT OF SHV DEVICE IN VARIOUS CONDITIONS:
[0056] Evaluation of Voltage and Current Generated By SHV: On the basis of this understanding and previous reports, the voltage along the length of the device was measured, which is shown in FIG. 4A. The device obtained a maximum voltage of 0.75 V under ambient conditions (room temperature, Rt = 28 ºC and room humidity, RH= 62-65 %) and it lasted for a long duration without any reduction/change.
[0057] In the same environment, the current generated from the device was measured, as shown in FIG. 4B. A single 3D SHV can generate a current in the range of 95 µA. This observed current is high when compared to other HV-based reports. This enhancement is due to the high surface area interaction between soil and water due to 3D packing. FIG. 4C shows the power delivery from the device for a long time. Nearly 73 µW of electric power can generate from a single device. It was noted from FIG. 4Cthat the device's power was constantly providing for more than 800 min without any change. Remarkably, it was found that power was generated after only water passed through the soil, indicating that water wicking is a crucial factor for voltage generation. Varying the capillary flow through the device is a solution to alter the EDL formation to observe the voltage change. For that, an SHV connected with a source meter was kept under ambient conditions (room temperature, Rt = 28 ºC and room humidity, RH=62-65 %) and the output voltage was measured. The device gave an output voltage of 0.77 V under the ambient condition as shown in FIG. 4D. By supplying one sun illumination artificial solar light (1 kW m-2) into the top surface, the voltage was changed to 0.8 V. This increment in the voltage was due to the increase in water wicking. However, this is not a substantial change because of the less light-exposed area due to the tubular device structure.
[0058] Modified Soil Based Hydro-voltaic Device And Performance Analysis: To overcome the issue of less light-exposed area, a hydrophilic black colour cloth was attached to the top of the fabricated SHV device. When exposed to 1 sun illumination, this modified device shows a voltage enhancement from 0.8 V to 0.9 V. This indicated a better understanding of the mechanism of the SHV device. The observed data is shown in FIG. 4D.
[0059] Effect of Wind Flow on Performance of SHV device: The variation in output voltage of fabricated SHV was observed by changing the wind flow over the device. The wind flow altered the water wicking capacity of the SHV, thereby affecting the voltage output. During the ambient condition, the output voltage of SHV shown a voltage output of 0.72 V. This voltage output increased to 0.92 V when hot air was passed on the top of SHV. The cyclability of this test is shown in FIG. 4E.From this it was concluded that the generated voltage was due to the interaction between the water and the substrate (soil) during the water wicking process.
[0060] Stability Assessment Of SHV Device: Stable electric power output is much needed to demonstrate a practical approach with SHV. Therefore, the evaluation was done with a single device for over 35 days by keeping the device in water. After 35 days of experimentation, it was noticed that the device shown the same voltage without any change under ambient conditions. This suggested that the fabricated soil based HV device can act as an electric source to light up for the long term without any change in power.
PERFORMANCE ANALYSIS OF THE FABRICATED SHV: To confirm the practical application of SHV, SHV devices were connected in series to add up the voltage to use it in a practical application. Therefore, several attempts were made to show the usage of the SHV device.
[0061] Experiment-1:In first experiment, six SHV devices were connected in series and allowed to stand in water to sum up the overall voltage. Three different colours (red, blue, green) LEDs (light emitting diodes) were connected individually to the two terminals of the series circuit. It was noted that the LEDs kept ON for three days, and slightly the intensities were slowed down due to the lack of bulk water. After the addition of water, the LEDs started to glow with high intensities. This clearly shows that the performance of SHV gives a major to generate electricity which can be utilised in daily life applications.
[0062] Experiment 2:In second experiment, devices were constructed and connected as series and parallel to increase the overall power (7 SHV series and 4 resultant series voltage as parallel). LEDs were arranged as letter A and connected with the circuit. By adding water to the container, all LEDs were started to glow and gives continuous output after third of experiments without any external energy support. After the fifth day of the experiment, the amount of water was reduced due to evaporation, so whole LEDs were glowing with very less intensities. Similarly, after the addition of water, the intensity of light started to increase. The output voltage from 6 SHV series connected devices operated the scientific calculator without a battery. The calculator's battery was removed and the solar panel was sealed with an opaque adhesive tape to ensure the SHV source could only be a source for the calculator to work.
[0063] Experiment 3: In third experiment, 32 devices were connected as series and parallel combinations (8 series X 4 parallel) with a switch and capacitor. The capacitors were allowedto store the charge for 20s with open circuit with LEDs. During closing the circuit with light, the LEDs started to glow with high intensity. Again, switch OFF the LED circuit to start the capacitor to charge for the next 20 s. Again closing the circuit, the LEDs started to glow. The experiments were repeated for several cycles. This depicts that the continuous output of SHV could be useful for long-term applications without any interruption. For utilizing this free source energy to daily applications, a combination of series and parallel of several SHVs with 6 capacitors were allowed to charge an android mobile phone. The capacitors were charged for nearly 5 min, and connected with android mobile. The mobile started to charge immediately using the source from SHV. Notably, after 10 s, the mobile phone charging stopped due to total discharge of capacitors.
[0064] Performance analysis of fabricated 2D vs 3D SHV devices:2D and 3D devices were fabricated (the electrode distance is 5cm) without packing the soil and were dipped in the nearby ground. The observed voltage with 2D devices was nearly 1.39 V, and with 3D devices, it was 2.57 V, signifying the 3D devices developing the voltage when placed in the ground soil. Further, FIG. 5E provides confirmation on voltage development along the thickness of SHV. This indicated that the 3D SHV device could be a possible initiation to high power production in a simple and efficient way without using any external active materials other than soil.
[0065] Comparison Of Electrochemical Performance of Electrodes Using SHV: Surface charges of microalgae create electricity during the water flow through the device (https://doi.org/10.1016/j.jpowsour.2023.232951). The article disclosed that green alive algae's surface charges interact with water forming a voltage. Dead algae show a negligible voltage effect, indicating less interaction of surface charge with water. Therefore, to examine the source of power generation in the SHV same scheme was used for the fabricated SHV wherein the live microorganism surface charges were reduced by using autoclave treatment. Autoclave treatment was done with soil and measured its HV effect. The obtained voltage before and after autoclave treatment is shown in FIG. 5D. It was clearly visible that the effect of microorganism surface charges was less in SHV. Only 0.1 V was reduced after the autoclave treatment. This indicated that the generation of voltage mostly depended on surface functional groups of soil rather than surface charges of micro-organism. The voltage verification along the length was verified by connecting the two terminals of the source meter on one side and different sides.
[0066] Performance Analysis Of SHV Using Non-Active Electrodes: To emphasize the presence of soil gives the voltage rather than electrodes, the non-active electrodes such as carbon or identical aluminium were connected on both sides and measured the performance of SHV. The observed data is shown in FIG. 7. By connecting the carbon electrodes on both sides, the SHV device showed an output voltage of nearly 0.26 V under ambient conditions (light OFF) and kept on increasing and the current was shown in FIG. 7A and FIG. 7B. For further evidence, aluminium electrodes were used as top and bottom electrodes. FIG. 7B graphically represents the voltage and current output which was nearly the same as carbon electrodes. This indicated the generation of electricity from soil during water pumping through capillary action.

, Claims:We claim:
1. A soil based hydro-voltaic device (100) for enhanced power generation, comprising:
a tubular structure (101) having an open top end and an open bottom end, the structure configured to hold soil (105) wherein the tubular structure comprises:
a first electrode (111) affixed to the top open end of the tubular structure; and
a perforated second electrode (113) affixed to the bottom of the tubular structure, configured to immerse in an aqueous solution (109) and allow entry inside the structure (101);
a reservoir (115) comprising the aqueous solution (109) with the tubular structure (101) in contact there within, wherein capillary action is configured to form an electric double layer formed at the soil - aqueous solution interfaces, thereby generating voltage and current flow between the first electrode (111) and the second electrode (113); and
a barrier (117) attached to the bottom end, the barrier configured to control the inflow of the aqueous solution from the reservoir into the tubular structure.

2. The hydro-voltaic device as claimed in claim 1, wherein the device has dimensions of length 30-80 mm X tubular diameter 8-15 mm X tube wall thickness of 1-2 mm.

3. The hydro-voltaic device as claimed in claim 1, wherein the first and second electrodes (111, 113) are connected along the length of the tubular structure (101).

4. The hydro-voltaic device as claimed in claim 1, wherein the barrier (117) includes a cotton ball.

5. The hydro-voltaic device as claimed in claim 1, wherein the device is configured to generate enhanced voltage on solar irradiation wherein the open top end is affixed with carbon cloth (119).

6. The hydro-voltaic device as claimed in claim 1, wherein the device is configured to generate enhanced voltage on exposing the open top end to hot air.

7. The hydro-voltaic device as claimed in claim 1, wherein the generated voltage is in a range 0.6V to 1V.

8. The hydro-voltaic device as claimed in claim 1, wherein the device (100) generates current in a range of 90- 95 µA.

9. A method (200) of fabricating a soil based hydro-voltaic device to generate voltage and current, the method comprising the steps of:
providing filtered soil (201) with a predetermined particle size;
providing a tubular structure (203) having electrodes at either end thereof and connected along the length;
packing the soil (205) along the length of the tubular structure;
placing the tubular structure in a reservoir (207) comprising an aqueous solution;
allowing the water to flow through the tubular structure (209) by capillary action; and
forming an electric double layer (211) at soil- aqueous solution interfaces, thereby generating voltage and causing flow of current across the ends of the tubular structure.

10. The method as claimed in claim 7, wherein the predetermined particle size of the soil is obtained by sieving with a filter having a mesh size of at least 0.6 mm.

11. The method as claimed in claim 7, wherein the predetermined particle size of the soil comprises a particle diameter size is in a range 150- 200 µm and the gap between the soil grains in a range 60-90 µm.

12. The method as claimed in claim 7, comprising the step of exposing the device to a light source to enhance the voltage generated.

13. The method as claimed in claim 7, comprising the step of exposing the device to hot air to enhance the voltage generated.

Dr V. SHANKAR
IN/PA-1733
For and on behalf of the Applicants