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

TITLE: CARBONIZED POTATO BASED HYDRO-VOLTAIC DEVICE AND METHOD THEREOF

INVENTORS

LAL, Sujith, Indian Citizen
Department of Sciences, Amrita School of Physical Sciences, Coimbatore, Amrita Vishwa Vidyapeetham, India

BATABYAL, Sudip, Indian Citizen
Amrita Centre for Industrial Research & Innovation (ACIRI), Amrita School of Engineering, Coimbatore, Amrita Vishwa Vidyapeetham, 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

CARBONIZED POTATO BASED HYDRO-VOLTAIC DEVICE AND METHOD THEREOF

CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a patent of addition of Indian Patent Application No. 202141052771 filed on November 17, 2021.
FIELD OF THE INVENTION
[0002] The present invention generally relates to electricitygenerating deviceand more particularly relates to hydro-voltaic devices and methods thereof.
BACKGROUND OF THE RELATED ART
[0003] Currently, 80% of the world's electricity is supplied by fossil fuels such as oil, natural gas, and coal. The increasing consumption rate of these finite resources is a significant factor contributing to climate change and its catastrophic impacts. Hydro-voltaic (HV) is a recently developed technique to generate electricity using water flow inside charged porous medium induced by water evaporation.HV has the potential to produce electricity when water flows across a highly functional groups attached surface,whetherin the form of humidity, flowing water from rain, wetting a surface, by capillary action or evaporation. Hence, HV devices might generate a streaming potential and current that can be retrieved as power.
[0004] Water molecules are solvated when they come in contact with a nanomaterial's polarizable surface. As water moves over the material's surface, opposing charges to the induced dipole is drawn into and transported through nanochannels parallel to the water's flow. The flow of charges that results from the net charge motion is known as a streaming current, and the potential that results from it is known as a streaming potential. Evaporation from the nanomaterial's surface allows continuous power generation. Overall, the kinetic energy produced by water flow and attracted ions is continuously converted into electrical energy. Choosing an environmentally friendly, low-cost, highly stable HV device might boost practical application usage and limit power shortage. On the other side, solar energy-based water purifications are very much popularized due to easily available incoming solar energy. Further, solar thermal evaporation (STE) is a newly developed method to convert impure water into freshwater under the influence of sunlight by evaporationwithout any high-cost consumption. The exact mechanism of STE is a solar absorber with a floating substrate that can float in water. The solar absorber should be an excellent light absorber which can directly convert light to heat. The substrate is a well-porous medium with low thermal conductivity used to uplift the water to the top of the solar absorber and reduce the heat conduction to the water simultaneously. Therefore, merging STE with HV might provide an excellent approach to collect the freshwater and power generation simultaneously.
[0005] Further, there is no previously reported work on power generation with STE combined with HVusing acarbonized potato substrate. The charges present on the carbonized potato substrate plays an important role in power generation activities. However, energy harvesting by using the surface properties of carbonized potato substrate are not at all explored. Accordingly, there is a need for easy to fabricate hydro-voltaic device integrated with STE for power generation generating high voltage values and current values. A carbonized potato substratebased hydro-voltaic device is disclosed that is capable of generating voltage and current.
SUMMARY OF THE INVENTION
[0006] According to one embodiment of the present subject matter, a carbonized potato based hydro-voltaic device with enhanced wicking and evaporation capacity is disclosed. The device includes a porous substrate formed of carbonised potato having a photon absorbing 3-D structure with an upper surface and a lower surface. In various embodiments, the substrate configured to imbibe and wick an aqueous solution. In various embodiments, the device includes a first electrode affixed to the upper surface of the substrate. In various embodiments, the device also includes a second electrode affixed to the bottom surface of the substrate configured to immerse in the aqueous solution. In various embodiments, the first or the second electrode is made of aluminum, copper or carbon fiber. In various embodiments, the device further includes an open-top reservoir configured to hold the aqueous solution with the substrate in contact therewithin, wherein capillary action is configured to form an electric double layer formed at the substrate pores- aqueous solution interfaces, thereby generating voltage and current flow between the first electrode and the second electrode.
[0007] In various embodiments, the device generates voltage in the range of 0.2 to 0.5 V.In various embodiments, the device is configured to generate current in the range of 4 to 5 µA/ device.In various embodiments, the device generates power of at least 3µW/sq.cm.In various embodiments, the device provides evaporation rate of 2.8 Kg m-2 h-1 or more under one-sun illumination.In various embodiments, the device generates enhanced voltage on exposing the upper surface to hot air or on solar irradiation.In various embodiments, the device has a working life of at least 12 months.
According to another embodiment of the present subject matter,a method of fabricating a carbonized potato based hydro-voltaic device for enhanced evaporation to generate voltage and current. The method includes the steps of slicing potato in a pre-determined dimensional range. In various embodiments, the pre-determined dimensional range is a thickness of at least 1.5 cm and diameter of at least 4 cm. This is followed by dehydrating the sliced potato in an alcoholic solution for 48 hrs. Next step is carbonizing the dehydrated potato by heating to 280-290°C in muffle furnace for 180 min to form the carbonized potato substrate with irregular surface. This is followed by polishing the surface of the substrate to form final substrate. Further, the method includes attaching electrodes along the thickness of the substrate surface to form a hydro-voltaic (CHV) device. In various embodiments, the electrodes are attached by wrapping a parafilm or an elastic band along the edges of the substrate. Next step is placing the CHV device in an open-top reservoir comprising an aqueous solution under predetermined conditions. In various embodiments, the predetermined conditions for the operation include relative humidity of 55-60% and a temperature ranging from 25-28°C.This is followed by allowing the aqueous solution to flow through the CHV device by capillary action. Finally, the method includes the step of forming an electric double layer at the substrate pores - aqueous solution interfaces, thereby generating voltage and causing flow of current across the ends of the CHV device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] 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:
[0009] FIG.1: a schematic illustration of a potato based carbonized hydrovoltaic (CHV)device and EDL formation when water flows through the vertical pores.
[0010] FIG. 2: a flow diagram of a method of fabricating a CHV device to generate voltage and current.
[0011] FIG. 3A: FESEM image of carbonized potato sample without ethanol treatment.
[0012] FIG. 3B: FESEM image of ethanol-treated carbonized potato slice.
[0013] FIG. 4A: a graphical representation of obtained voltage with a CHV device, using aluminium electrodes with DI water as bulk, under ambient conditions (room temperature at 25 °C and RH at 58.5 %) without any external light irradiance.
[0014] FIG. 4B: a graphical representation of obtained current with a CHV device, using aluminium electrodes with DI water as bulk, under ambient conditions (room temperature at 25 °C and RH at 58.5 %) without any external light irradiance.
[0015] FIG. 4C: confirming the HV effect from the fabricated device to minimize the galvanic effect by connecting two copper electrodes.
[0016] FIG. 4D: confirming the HV effect from the fabricated device to minimize the galvanic effect by connecting two carbon fiber electrodes.
[0017] FIG. 5: a graphical representation of voltage enhancement of a single CHV device, using aluminium electrodes with DI water as bulk, during the light ON condition (room temperature at 25 °C and RH at 58-60 %) under one sun illumination.
[0018] FIG. 6A: a graphical representation of observed voltage enhancement from 150 mV to 200 mV when the airflow in the air-liquid interface changes from 0 m s-1 to 5.5 m s-1 without light ON condition.
[0019] FIG. 6B: a graphical representation of observed voltage increase during the hot wind flow changes from 0 m s-1 to 5.5 m s-1 without light ON condition.
[0020] FIG. 7A: a graphical representation of observed voltage change under different temperatures of bulk water.
[0021] FIG. 7B: a graphical representation of observed voltage change by varying water wicking through CHV by changing the RH of the environment.
[0022] FIG. 8A and 8B showCHV device before (FIG. 8A) and after (FIG. 8B) surface modification for better charge collection.
[0023] FIG. 9: a graphical representationshowing relative comparison TGA data of bare, ethanol-treated and ethanol-treated carbonized potato.
[0024] FIG.10: showing Fourier Transform Infrared Spectroscopic study of carbonized potato substrate.
[0025] FIG.11: showing hydrophilic test of the CHV device to ensure high water wicking.
[0026] FIG.12: a graphical representationof altering the generated voltage by vacuum and open state CHV device
[0027] FIG.13: a graphical representationshowing analysis of the device performance by changing the pH value of bulk water. Understanding the mechanism by passing different H+ concentration ions through CHV device.
[0028] FIG. 14: represents statistical data of 6 fabricated CHV device’s output voltage and current performance.
[0029] FIG. 15: a graphical representationshowing practicability test using CHV device with obtained data of evaporation rate and power generation from a single device simultaneously under 1 sun illumination.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0030] 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.
[0031] 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.
[0032] The present subject matter discloses a carbonised potato based hydro-voltaic (CHV) device with enhanced wicking and evaporation capacity, as further disclosed with reference to the drawings. In various embodiments, a method of fabricating a carbonized potato based hydro-voltaic device for enhanced evaporation to generate voltage and current is disclosed.
[0033] A schematic representation of a carbonized potato based hydro-voltaic device is illustrated in FIG. 1, according to one embodiment of the present subject matter. The carbonized potato based hydro-voltaic (CHV) device 100 includes a porous substrate 101, a first electrode 105, a second electrode 106 and an open-top reservoir 107. In various embodiments, the CHV device 100 is primarily configured to imbibe and wick an aqueous solution 104.
[0034] In various embodiments, the porous substrate 101 may be a porous material formed of ethanol modified carbonised potato, forming a photon absorbing three-dimensional structure. In various embodiments, the substrate 101 includes an upper surface 102 and a lower surface 103. In various embodiments, the porous substrate 101 may be placed on the top of the aqueous solution 104 in the open-top reservoir 107such that it imbibes and wicks the solution as shown in FIG. 1.In various embodiments, the substrate may absorb solar energy for vaporization leading to evaporation of the aqueous solution 104. In various embodiments, the substrate 101 increases the rate of evaporation of the aqueous solution 104.
[0035] In various embodiments, the device 100includes the first electrode 105 affixed to the upper surface 102and the second electrode 106 affixed to the lowersurface103 of the substrate 101. In various embodiments, the second electrode106 is configured to be immersed in the aqueous solution104heldin the reservoir 107. In one embodiment, the electrodes are attached to the substrate by simply holding the electrodes in mechanical contact with the porous substrate. The electrodes may be held in contact with the substrate using any method, including spring-loaded clamps, wrapping a parafilm or an elastic band along the edges of the substrate, or other known means.
[0036] In various embodiments, the carbonised potato substrate 101 is immersed in the reservoir 107 comprising the aqueous solution 104 with the substrate in contact therewithin. In various embodiments, the reservoir 107 may have a conventional three dimensional shape with a volumetric capacity to hold the aqueous solution 104 to be imbibed and wicked by the substrate 101. The reservoir 107may be a hollow storage space and may be configured to carry the substrate 101. In an embodiment, the reservoir 107may be composed of a leak proof and water-resistant material such as polyethylene or any water resistant material with an ability to resist corrosion.
[0037] In various embodiments, the aqueous solution 104 may include any fluid with a viscosity equivalent to that of water or any fluid which may have similar chemical properties as that of water and may include salt water, waste water or impure water. In various embodiments, the aqueous solution 104 may be water or other polar fluid. The aqueous solution 104 may be heated through the substrate to provide raised voltage of 0.5V when exposed to one sun illumination (1 kW m2).
[0038] In various embodiments, the device 100 produces high voltage and high current between the electrodes 105 and 106, under ambient temperature and relative humidity. In various embodiments, immersing the CHV device 100 in the reservoir 107 of aqueous solution 104 allows capillary flow of the aqueous solution 104. In various embodiments, the interaction of aqueous solution 104 with the porous substrate 101 with evaporation and phase changes are believed to cause a potential across the substrate 101. In various embodiments, an electrical double layer (EDL) is formed due to interaction of the porous substrate 101 with the aqueous solution 104, at the substrate pores-aqueous solution interfaces as illustrated in FIG. 1.In various embodiments, the EDL is formed by attachment of functional groups in the porous carbonized potato substrate, especially surface hydroxyl and oxygen rich functional group with H+ in the aqueous solution. In various embodiments, a gradient of water molecule is formed along the thickness and pore diameter of the CHV, leading to formation of a potential difference. As shown in FIG. 1, the water flows through the vertical pathway, H+ ions in water and the functional groups on surface of the substrate to form an EDL layer. In various embodiments, the flow of water generates a streaming potential leading to power generation along the thickness of the device.
[0039] In various embodiments, the CHV device 100 is configured to produce voltages in the range of 0.2V to 0.5V. In various embodiments, the CHV device100 is configured to generate currents in a range of 4- 5µA/sq.cm from single CHV device 100. In various embodiments, the CHV device 100 is configured to generate power of at least 3µW/sq.cm. In various embodiments, power generation capacity of the CHV varies with type of electrode used. In various embodiments, the electrodes may include aluminium, copper or carbon fiber electrodes.
[0040] In one embodiment, the CHV device 100 is configured to generate enhanced voltage onexposing the device to hot air or on solar irradiation. In various embodiments,the CHV device 100 provides an evaporation rate of 2.8 Kg m-2 h-1 or more under one-sun illumination.In various embodiments, two or more CHV devices 100 are connected in series and parallel arrangements to get a combined output voltage. In various embodiments,the CHV device 100has a working life of at least 12 months with no change in performance output.
[0041] A flow diagram showing a method200 of fabricating a potato based carbonized hydro-voltaic (CHV) device to generate voltage and current is shown in FIG. 2. The method includes slicing of potato in pre-determined dimension range in step 201. In various embodiments, the predetermined dimensional range is a thickness of at least 1.5 cm and diameter of at least 4 cm.In step 202 the sliced potato is dehydrated in an alcoholic solution for around 48 hours. In one embodiment, ethanol may be used as a dehydrating agent. Carbonizing the dehydrated potato in step 203 takes place in muffle furnace. The dehydrated potato slices are heated at 280-290ºC for 120-180 min, to get the substrate with irregular surface. This is followed by step 204 of polishing the substrate surface to form final substrate. In step 205, electrodes are attached along the thickness of the polished substrate surface to form a CHV device.In various embodiments, the electrodes are attached by wrapping a parafilm or an elastic band along the edges of the substrate. Step 206 includes placing the CHV device in an open-top reservoir comprising an aqueous solution under pre-determined conditions. In various embodiments, the predetermined conditions for the operation include relative humidity of 55-60% and a temperature ranging from 25-28°C. This is followed by step 207 wherein the aqueous solution is allowed to flow through the CHV device by capillary action. Finally, the method includes step 208 of forming an EDL between carbonized potato substrate pores- aqueous solution interfaces, thereby generating voltage and causing flow of current across the ends of the CHV device.
[0042] In various embodiments, dehydrating sliced potato in alcoholic solution in step 202 may remove the carbohydrate and fibers in the sliced potato and generate a plurality of microchannels. The generated microchannels may impart porosity, light weight substrate for enhancing its floating property on the aqueous solution without any support or assistance and helps in imbibing and wicking of the solution. In various embodiments, the carbonizing of the dehydrated substrate in step 203 may enhance light- absorbing property of the porous substrate and increases the rate of evaporation of the solution when exposed to the solar irradiation. In various embodiments, the method may include additional step of exposing the fabricate CHV device to hot air or solar irradiation, thereby enhancing the voltage and current drawn from the device.
[0043] The CHV device 100of the present invention may generate power in a simple and efficient way. The method 200 brings in use the carbonized potato substrate as an active material, hence improving the practical usage of readily available natural resource. The method 200 has been experimentally validated and has demonstrated production of an extremely low cost CHV device. The crisscross porous nature and floating ability of the carbonized potato substrate are believed to be responsible for this performance.Thus the device of the present invention is configured to be lightweight and cost efficient. Besides, the CHV 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.Moreover, the CHV device and method of the present inventionare of chemical free nature and provide a substrate with excellent floatation and transport capabilities in water. The device is compact, portable and has a minimal operation cost with no complex instrumentation involved.Further, by harvesting dual-energy the device may help to solve energy and water crisis.
[0044] 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:
[0045] EXAMPLE 1: FABRICATION OF CARBONIZED POTATO CAKE BASED HYDROVOLTAIC (CHV) DEVICE:
[0046] Material:To prepare ethanol modified carbonised potato or porous substrate, potato was purchased from nearby market. The ethanol (product no. 1.00990) was purchased from Sigma-Aldrich Chemicals Private Limited. For the terminals of the hydrovoltaic (HV) device, aluminium, carbon fiber and copper foil were used as electrodes. Hydrochloric acid (HCl) was used to change the pH level of water.
[0047] Fabrication Of CHV Device:To fabricate carbonized ethanol-treated potato cake as a hydrovoltaic (CHV) device a potato was sliced into round shape with a diameter of 4 cm and thickness of 1.5 cm. The sliced potato was washed with deionized water (DI) and allowed to soak in ethanol for two days. After two days of ethanol treatment, the thickness of the slice was slightly reduced, and the colour of the ethanol was changed. The ethanol-treated potato slice was allowed to carbonize at the temperature of 280-290 °C using a muffle furnace for 3 hours. The obtained ethanol treated potato slice shown an irregular surface, making it complicated to connect the electrode for hydrovoltaic measurement. Hence, the surfaces of dehydrated potato were polished or smoothened using a polishing machine to create a flat surface on both sides. The flat surface before and after surface modification using the polishing machine is shown in FIG. 8A and 8B, respectively. Two aluminium electrodes were connected along the thickness of two ends of the smooth surface and wrapped with parafilm or elastic band only at the edges of dehydrated potato slice. The as-fabricated CHV device was connected to the sourcemeter to measure the power generation performance.
[0048] EXAMPLE 2: STRUCTURAL AND FUNCTIONAL GROUP CHARACTERIZATION: To confirm the EDL formation, structural and functional group analysis of the carbonized carbon was performed to further use in a practical application.
[0049] Morphological Characterization of Fabricated Device: The CHV device was synthesized simply by soaking the sliced potato in ethanol to generate pores by removing the starch for high water pumping. Mostly, formed interconnected pore structure enhances the surface area, which results in a high chance of interaction between the surface of the carbonized potato and water molecules during capillary action. The significance of ethanol treatment and carbonization generated the pores by throwing away the starch, a suitable remedy for high carbon water interaction.
[0050] The surface morphology of the material before and after ethanol/carbonization treatment was analysed. Scanning Electron Microscopy (SEM) was used to examine the morphology and microstructure of the device using a Carl Zeiss system running at 5 kV. The FESEM image of the potato slice before ethanol and carbonization treatment is shown in FIG. 3A and FIG. 3B. It signifies the abundance of starch present in the potato. After ethanol treatment without carbonisation, the pores were developed, but not thoroughly, depicting that the air-solid interface loosely bounded starches was removed. However, the starches inside the potato slice were very hard to remove. Therefore, the ethanol-treated potato slices were allowed to carbonise at 280-290 °C, and its SEM image is shown in FIG. 3B. This clearly indicated that high pores were formed after ethanol treatment and suggested that almost all starches were removed creating crisscross interconnected pores. These interlinked pathways are critical to boosting the interaction of the liquid with its surface when the liquid flows.
[0051] The FESEM image of the carbonised sample without an ethanol treatment is shown in FIG. 3A. It was found that the sudden decomposition of whole starch collapses the entiresystem, which would not be recommended for a crisscross porous structure for better water pumping.
[0052] Confirmation OfStarch Removal: (1) Iodine Test: The advantage of ethanol treatment for removing the loosely bound starch was confirmed by a simple starch test using an iodine solution experiment. The change in iodine solution to bluish black indicated the presence of starch in the bare potato slice after a few minutes. In contrast, the formation of bluish black was reduced, and the iodine solution was clear in ethanol-treated potato slices.
[0053] (2) Thermo-gravimetric Analysis: Furthermore, thermo-gravimetric analysis (TGA) was performed to analyse the comparison percentages of starch present in the bare, ethanol-treated carbonized and ethanol-carbonized potato samples. It was found that starch was relatively higher in bare than in ethanol-treated devices. After ethanol-carbonized treatment, the relative weight loss was significantly less than the other two samples. From this, it was confirmed that after ethanol treatment, the loosely bounded starch was excreted out, making a path for interior starch to eject during carbonization.
[0054] Evaluation Of Hydrophilic Nature Of Fabricated CHV:The adhesive force between solid and liquid surfaces depends on the hydrophilic nature of the solid surface; therefore, to confirm the hydrophilic nature of CHV, FTIR analysis and contact angle measurements were performed.
[0055] (1)Functional Group Analysis Of Fabricated Device:The functional groups were confirmed using Fourier Transform Infrared (FTIR) spectra for better water wicking by the FTIR Spectrometer (Thermo-Fisher Scientific-USA). The obtained FTIR spectrum is shown in FIG. 10. The FTIR spectrum of CHV shows the peak at 508 cm-1 corresponds to the interaction between carbon and nitrogen (C-N-C) due to the nitrogen presence in potato, the peak at 749 cm-1 indicating the out-of-plane bending vibrations of carbon-hydrogen (C-H), the peaks at 1139 cm-1 belongs to single bond vibration between carbon to oxygen molecules, peak at 1231 cm-1 indicating the carbon to nitrogen bond (C-C-N) and a peak obtained at 1363 cm-1 assigned as the in-plane CH bending. A high, sharp, intense peak was obtained in the region at 1592 cm-1, and 1703 cm-1 belongs to the stretching vibrations double bonded carbon-oxygen molecules.
[0056] (2) Contact Angle Measurement: Additional confirmation on hydrophilicity was studied using contact angle measurement. A drop of water was dropped on the surface of carbonized potato substrate. The angle of contact is changed to 8° from 147° within 0.5 s, indicating the super hydrophilicity and the existence of a highly porous structure, is shown in FIG. 11.
[0057] EXAMPLE 3: PERFORMANCE ANALYSIS OF THE FABRICATED CHV:
[0058] The hydro-voltaic measurement was carried out using a Keithley source meter (Model No: 2450). Aluminium, carbon cloth fibre, and copper tape were used as electrodes to measure the generated current and voltage. All experiments were carried out using double distilled deionized water (DI) as a bulk liquid. The ambient relative humidity (RH) is measured using the Thermopro hygrometer.
[0059] Performance ofFabricated CHVDevice: Two aluminium electrodes were used to make contact between the thickness of CHV. A stretchable band is used to hold the electrodes with the surface of CHV to collect more charges. The device was allowed to float on the DI water, and the two ends of the electrodes were connected to the Keithley sourcemeter. A voltage has been generated along the thickness within 2 minutes when the water is wicked to the top. Simultaneously, the induced current also was measured. The generated voltage and its corresponding electric current are shown in FIG. 4A and FIG. 4B. FIG. 4A indicates that the CHV gives a constant voltage of 220 mV over a long range. To confirm the potential developed through the material, the same device was analysed with other identical electrodes to ignore the galvanic effect of the device. The flow of H+ ions through the thickness can deliver the maximum electric current up to 4.5 µA to 5 µA continuously during water pumping from a single device, is shown in FIG. 4B, and its corresponding power was calculated, and it shows nearly 3 µW.
[0060] The electrodes, such as carbon fibre and copper, were used, and the obtained voltage is shown in FIG.4C and FIG. 4D. In both, the obtained voltage is nearly 220 mV, the same as aluminium electrodes. This further depicts the voltage developed only with the help of CHV (room temperature 25 °C and RH= 58%).
[0061] Evaluation Of Water-Functional Group Interaction: To understand the mechanism more clearly, several experiments were conducted to show the voltage generated only when water flows through the porous substrate pathway. To proceed with further proof, the only way to enhance the water-functional groups' interactions (W-FG). For that, water flows through the porous structure varied by increasing its evaporation. A single device was allowed to float on water, and the electrodes were connected to a source meter. The solar simulator provides a broad spectrum of artificial solar light with one sun (1 kWm-2) intensity to the top of the floating CHV device. It was found that, during light ON situations, the device provided excellent evaporation, enhancing the water flow rate through the pores, confirming the increase in voltage during light ON. The enhancement in voltage indicated that more water is wicked,more is the interaction between the H+ of water and the functional groups of substrates (W-FG interactions). A voltage of 0.2 V was obtained, as shown in FIG. 4A and FIG. 4B, underambient condition.
[0062] Effect Of Sun Illumination On Performance Of Fabricated CHV Device: Furthermore, the voltage is increased when applying one sun illumination. It is clear that the Voltage was shifted from 0.2 V to 0.5 V, as shown in FIG. 5 ensuring theincrease in Voltage due to the external light, which further increased the W-FG interactions.
[0063] Effect ofEvaporationonPerformance ofFabricated CHVDevice:Wind flow is a crucial factor in boosting the evaporation rate of the device. Therefore, different wind flows were provided to the device to study the voltage change. Two step analysis was performed to ensure the voltage change. Ambient temperature with different air flow rates was provided, and measured the output voltage. Additionally, hot air was supplied with varying flow rates to measure the voltage change and is schematically illustrated in FIG. 6A. FIG. 6A shows the graphical representation of voltage generated with corresponding flow rates under ambient temperature. The airflow rate is directly proportional to the evaporation rate. Thus, the effect of evaporation enhancement resulted in voltage enhancement. FIG. 6B shownthe effect of supplying different flow rates of hot wind to the CHV on the voltage generation. During the hot wind, flow varied from 0 m s-1 to 5.5 m s-1, and the corresponding generated Voltage was shifted from 220 mV to 330 mV, indicating the voltage increment during hot air pass-by. The voltage was generated when water molecules pump through the interconnected porous membrane. It was found that the device constantly provides more than 200 mV in ambient conditions and improves when external factors come.
[0064] The above experiments confirmed that water plays a vital role in the power generation in the CHV. It was observed that the voltage along the thickness between two electrodes was 6 mV, whereas the voltage was suddenly increased when DI water was added to the container. This shown the source of potential is due to the interaction of water with the CHV device.The maximum obtained voltage was found after 15 minutes. This Voltage was higher than voltage shown in FIG. 4A due to use of different electrodes.
[0065] Effect ofWater Flow Rate OnPerformance Of CHV Device: Furthermore, to alter the water pumping rate of the CHV device, bulk water was provided and thetemperature was varied, and the corresponding voltage was measured. The voltage output was measured with the different bulk water temperatures at 12 °C, 30 °C, and 62 °C. It is well-known that hot water molecules can quickly move faster than cold water. During high temperatures, the water molecules get high kinetic energy, which possesses faster movement than in cold conditions. From the observation, the high-temperature bulk water has shown double the times voltage of the water at cold temperatures because of the high flow rate of water molecules. The observed data is shown in FIG. 7A. This indicated that the voltage has been enhanced during the flow rate increases. Therefore, EDL formation may be enhanced between the flowing water molecules and the functional groups of the solid surface.
[0066] Effect ofRelative Humidity onPerformance ofCHVDevice: The water-wicking rate depends on how many water molecules are in the atmosphere. If the atmosphere has less water molecules (less relative humidity, RH), the water flow rate through the system will increase. Therefore, different atmospheric humidity is also a key idea to vary the water flow rate from bulk to the interface of CHV through the pores. Thus, the study was done for voltage generation with different atmospheric relative humidity. It is depicted in FIG. 7B that the voltage suddenly dropped from 200 mV to 140 mV when the RH changed from 58% to 66%; further reduction in voltage was observed when the RH increased to 72%. In the range of 88% RH, the device shows a voltage of nearly 70 mV. This also evidently indicates the water flow is the primary reason for the voltage development.
[0067] Performance Analysis ofCHV DeviceinVacuum Desiccator:To slow the evaporation further, single CHV device connected with aluminium electrodes was kept with water in a container inside a vacuum desiccator and allowed to alter the vacuum/release(open) condition. The two electrodes were connected with a multimeter kept inside the desiccator itself. During open conditions, the output voltage was measured in the range of 190-175 mV and started to vacuumize. Under vacuum conditions, the device exhibits a voltage in the range of 10-20 mV. The repetition of open-vacuum conditions was done, and the obtained altering output voltage is shown in FIG. 12. This show under a vacuum, the kinetic energy of the water molecules through the porous pathway might be minimal along the thickness, leading to overall voltage drops. The obtained voltage under the vacuum-open method is less as compared to FIG. 4A due to the short duration of the experiment (50 seconds).
[0068] All the above experiments confirm the voltage has been generated when water plays with the porous substrate during wicking. Therefore, the assumption was made to change the EDL formation during wicking. For that, the H+ ions concentration of bulk water was varied to ensure the EDL change inside the water-substrate interface. The concentration of H+ ions is changed by adding the hydrochloric acid drops to the bulk water and measured its corresponding pH value. The observed voltage is shown in FIG. 13. This clearly explained the enhancement in voltage due to the interaction of more H+ ions with the functional groups of substrate and gave an indication to the HV mechanism that the interaction of opposite charges along its length can generate a potential difference.
[0069] Performance Analysis With Multiple CHV Devices:
[0070] (1)To target the daily usage of the CHV device, five CHV devices were connected in series to boost up the voltage to show a real purpose. Five CHV devices connected with different electrodes (aluminium and copper foil) were used along the thickness. The resultant voltage of 3.5 V was obtained with a series connection. A red LED bulb was used to light up when connected to the device. The five CHVs connected in series with electrodes, and the obtained resultant voltage of nearly 3.5 V. A red colour LED is connected to two ends of the series circuit, and it immediately glows up and continues for three days. After 3rd day of the experiment, the LED turned OFF due to the lack of bulk water (whole bulk water gets dried due to evaporation). After adding water to the bulk container, the LED again started to glow. This shows the device can generate power continuously, even under ambient conditions. The shelf-life ability was analysed for the device ability for practical application after one year of usage. A newly fabricated CHV device was tested in February 2022. It generated an output voltage of 0.25 V and was enhanced to 0.52 V during light ON.
[0071] (2) For the systematic data, six CHVs were analysed and their corresponding output voltage and current were measured. Specifically, all CHV devices provided the voltage in the range of ~200-250 mV, and 5 µA, respectively, as shown in FIG. 14. Moreover, experimental measurements were carried out to show the power generation and evaporation cam occurred simultaneously to observe the practicability, and the obtained data is shown in FIG. 15. The figure clearly shows the evaporation rate is showing more than 2.8 Kg m-2h-1 and obtained the voltage of nearly 0.5 V under one sun illumination. The negligible reduction in evaporation rate is due to the attachment of electrodes on the interface layer of the CHV. The electrodes act as a negligible barrier to incoming solar light. However, this reduction is not much less from 3.14 Kg m-2h-1. This experiment conveyed the practicability of the device for future energy harvesting.
[0072] Evaluation Of Durability Of CHV:The same device was tested after one year, and obtained same output voltage. The one-year-old CHV device giving a voltage of 0.247 V and enhanced to 0.54 V during a light applied on it.

, Claims:We claim:
1. A carbonized potato based hydro-voltaic device (100) with enhanced wicking and evaporation capacity, comprising:
a porous substrate (101) formed of carbonised potato having a photon absorbing 3-D structure with an upper surface (102) and a lower surface (103), the substrate (101) configured to imbibe and wick an aqueous solution (104);
a first electrode (105) affixed to the upper surface (102) of the substrate (101);
a second electrode (106) affixed to the bottom surface (103) of the substrate (101), configured to immerse in the aqueous solution (104); and
an open-top reservoir (107) configured to hold the aqueous solution (104) with the substrate (101) in contact therewithin, wherein capillary action is configured to form an electric double layer formed at the substrate pores- aqueous solution interfaces, thereby generating voltage and current flow between the first electrode (105) and the second electrode (106).

2. The device (100) as claimed in claim 1, wherein the generated voltage is in the range of 0.2 to 0.5 V.

3. The device (100) as claimed in claim 1, wherein device (100) is configured to generate current in the range of 4 to 5 µA/ sq. cm.

4. The device (100) as claimed in claim 1, wherein the device (100) generates power of at least 3µW/sq.cm.

5. The device (100) as claimed in claim 1, wherein the device (100) provides evaporation rate of 2.8 Kg m-2 h-1 or more under one-sun illumination.

6. The device (100) as claimed in claim 1, wherein the device (100) generates enhanced voltage on exposing the upper surface to hot air or on solar irradiation.

7. The device (100) as claimed in claim 1, wherein the device (100) has a working life of at least 12 months.

8. The device (100) as claimed in claim 1, wherein the first or the second electrode (105, 106) is made of aluminum, copper or carbon fiber.

9. A method (200) of fabricating a carbonized potato based hydro-voltaic device for enhanced evaporation to generate voltage and current, the method comprising the steps of:
slicing (201) potato in a pre-determined dimensional range;
dehydrating (202) the sliced potato in an alcoholic solution for 48 hrs;
carbonizing (203) the dehydrated potato by heating to 280-290°C in muffle furnace for 180 min to form the carbonized potato substrate with irregular surface;
polishing (204) the surface of the substrate to form final substrate;
attaching electrodes (205) along the thickness of the substrate surface to form a hydro-voltaic (CHV) device;
placing the CHV device in an open-top reservoir (206) comprising an aqueous solution under predetermined conditions;
allowing the aqueous solution to flow through the CHV device (207) by capillary action; and
forming an electric double layer (208) at the substrate pores - aqueous solution interfaces, thereby generating voltage and causing flow of current across the ends of the CHV device.

10. The method (200) as claimed in claim 9, wherein the predetermined dimensional range is a thickness of at least 1.5 cm and diameter of at least 4 cm.

11. The method (200) as claimed in claim 10, wherein the electrodes are attached by wrapping a parafilm or an elastic band along the edges of the substrate.

12. The method (200) as claimed in claim 10, wherein the predetermined conditions for the operation in step (206) include relative humidity of 55-60% and a temperature ranging from 25-28°C.

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