Hydropower generation by transpiration from microporous alumina

Advanced Energy Materials, 2020

The generation of renewable electricity is variable, leading to periodic oversupply. Excess power can be converted to hydrogen via water electrolysis, but the conversion cost is currently too high. One way to decrease the cost of electrolysis is to increase the maximum productivity of electrolyzers. This study investigated how nano-and microstructured porous electrodes could improve the productivity of hydrogen generation in a zero-gap, flow-through alkaline water electrolyzer. Three nickel electrodesfoam, microfiber felt, and nanowire felt-were studied to examine the tradeoff between surface area and pore structure on the performance of alkaline electrolyzers. Although the nanowire felt with the highest surface area initially provided the highest performance, this performance quickly decreased as gas bubbles were trapped within the electrode. The open structure of the foam facilitated bubble removal, but its small surface area limited its maximum performance. The microfiber felt exhibited the best performance because it balanced high surface area with the ability to remove bubbles. The microfiber felt maintained a maximum current density of 25,000 mA cm -2 over 100 hrs without degradation, which corresponds to a hydrogen production rate 12.5-and 50-times greater than conventional proton-exchange membrane and alkaline electrolyzers, respectively.

Nano Letters, 2019

Developing low-weight, frugal and sustainable power sources for resource-limited settings appears to be a challenging proposition for the advancement of next-generation sensing devices and beyond. Here, we report the use of centimeter-sized simple wet fabric pieces for electrical power generation, by deploying the interplay of a spontaneously induced ionic motion across fabric channels due to capillary action and simultaneous water evaporation by drawing thermal energy from the ambient. Unlike other reported devices with similar functionalities, our arrangement does not necessitate any input mechanical energy or complex topographical structures to be embedded in the substrate. A single device is capable of generating a sustainable open circuit potential up to ~700 mV. This suffices establishing an inherent capability of functionalizing self-power electronic devices, and also to be potentially harnessed for enhanced power generation with feasible upscaling.

with the addition of 8.5 GW of 4 h electricity storage, modeling showed curtailment remained at 8-10% in the ERCOT system. [4] Finding additional ways to utilize this excess generation is critical to maximizing the environmental and economic benefits of renewable power as its share of electricity generation increases. One strategy to utilize excess renewable electricity is to generate H 2 with water electrolysis, an approach that is also referred to as power-togas. [5-14] There are many potential uses of H 2 , including heating, ammonia production, metal refining, conversion into methane or liquid fuels, or use in fuel cell vehicles. [15] Very large amounts of H 2 can potentially be stored relatively cheaply in underground reservoirs to address the seasonal variability of renewable electricity generation. [10,16-18] The two most common water electrolysis systems are alkaline and proton exchange membrane (PEM). The alkaline electrolyzer is the most mature technology with a cost roughly half that of PEM electrolyzers. [5,19] On the other hand, PEM electrolyzers offer higher current densities (600-2000 mA cm −2) than alkaline electrolyzers (200-450 mA cm −2), enabling them to be more compact. [19,20] Without a tax on CO 2 emissions, techno-economic assessments of the feasibility of H 2 production via water electrolysis indicate that it is not cost-competitive with methane steam reforming under current market conditions. [12,21-23] Thus, commercial applications of electrolyzers are currently limited to small-scale, on-site hydrogen production for industrial applications, with a few larger-scale plants for ammonia fertilizer production in remote areas with excess electricity. [19] The opportunity to utilize low-cost, excess electricity from renewable generation will help to make water electrolysis cost competitive, but reductions in the cost of the electrolyzer plant will also be necessary. [24,25] One way to lower the electrolyzer cost and take advantage of periodically low electricity prices is to increase the amount of H 2 such plants can produce, i.e., their productivity, without degrading their lifetime. [19] The formation of gas bubbles currently limits the maximum current density, and thus productivity, of alkaline electrolyzers. [19,26] A variety of attempts have been made to address the bubble removal problem, including circulation of electrolytes across the surface of the electrode, [19,26-28] development of zero gap and other advanced electrolyzer architectures, [29-33]

Electrochimica Acta, 2003

The electrochemical fabrication of alumina membranes by anodizing of aluminium in phosphoric acid and oxalic acid solutions, in the temperature interval from (/1 to 16 8C, was investigated in order to study the influence of different parameters (initial treatment of aluminium surface, nature and composition of electrolyte, temperature) on the final characteristics of the membranes. Porous layers were grown using a linear potential scan at 0.2 V s (1 up to 160 V in H 3 PO 4 solution and 70 V in oxalic acid solution. The efficiency of porous layer formation was calculated by using Faraday's law and weight measurements. Pore size distribution and porosity of membranes prepared in 0.4 M H 3 PO 4 were found to be dependent on temperature, while in 0.04 M smaller pore size and lower porosity were obtained, independent of temperature. Highly ordered structures were formed by aluminium anodizing in 0.15 M oxalic acid solution at 70 V. A uniform pore diameter of about 90 nm was found, independent of temperature. A porosity value of about 26% was achieved and it was found to be independent of temperature for membranes prepared in oxalic acid. Porous layers grown either in H 3 PO 4 or oxalic acid solution crystallized at temperatures around 870 Á/890 8C. For membranes formed in oxalic acid the pyrolysis of oxalate anions also occurs. #

ACS Applied Materials & Interfaces, 2017

The paper presents first experimental evidence of pronounced electrification effects upon reversible cycle of forced water intrusion-extrusion in nanoporous hydrophobic materials. Recorded generation of electricity combined with high-pressure calorimetric measurements improves energy balance of {nanoporous solid + non-wetting liquid} systems by compensating mechanical and thermal energy hysteresis in the cycle. Revealed phenomena provide a novel way of 'mechanical to electrical' and/or 'thermal to electrical' energy transformation with unprecedented efficiency and additionally open a perspective to increase the efficiency of numerous energy applications based on such systems taking advantage of electricity generation during operational cycle.

RSC Advances

Water in its various forms has been found to be one of the most abundant sources of energy on the planet after solar energy, and hydroelectric power plays a key role in renewable-energy supplies.

ACS Applied Electronic Materials, 2019

Experimental Section Growth and characterization of porous zinc oxide (ZnO) film : To grow a ZnO film having a porous characteristic, an aluminum oxide (Al 2 O 3) plate was used as a substrate. The Al 2 O 3 plates were washed with detergent, acetone, and isopropyl alcohol, sequentially for 10 min in each process. A solution of 0.1M zinc acetate (Zn(CH 3 COO) 2 ⸱2H 2 O, Sigma Aldrich) dissolved in methanol was prepared for a deposition of the porous ZnO film to the Al 2 O 3 plate. After the washing process, the plates was positioned in a bath containing the 0.1M zinc acetate solution. The bath was sealed in an autoclave and kept at 75℃ oven. In this condition, a layered basic zinc acetate (LBZA) was grown on the Al 2 O 3 plate through a solvothermal growth for 72 hours 31,32. The LBZA film was washed with a streamed methanol, and then sintered in a furnace with 500℃ air for 1 hour. A sintering condition over 350℃, various impurities including the acetate was removed and the LBZA film was transformed pyrolytically into the porous ZnO

Advanced Materials Letters, 2013

The basic concept of Gibbs standard state free energy predicts a favorable condition for both room and high temperature fabrication of nanoporous alumina in phosphoric acid electrolyte. The anodization of aluminum foil in acidic electrolytes is made possible by the well known process parameters that have been studied over the years. These parameters i.e. voltage, current density, type of electrolyte etc have been very effective when anodizing aluminum at freezing temperatures. When the operating temperature is raised above the freezing temperature, additional process parameters would be required to make the pore formation possible. The fabrication of the aluminum foil was carried out using phosphoric acid as the electrolyte source. The electrolyte pH was adjusted to 1, 3 and 5 in order to simulate different anodizing conditions. A potential of 50 V from a dc power supply was applied across the electrochemical cell, while a power regulating device with different power rating was attached to the electrochemical cell to provide the operating system with additional parameters that could influence the surface structure of the alumina. The micrographs obtained show that the propagation and growth of the pores at both room and high temperatures was made possible by the power regulating device attached to the cell.

International Journal of Advance Research and Innovative Ideas in Education, 2018

As increasing demand of electricity, there should be some alternative sources for generating electricity. Hydroelectric Cell (HEC) is an innovative alternative for producing green energy source by spitting of water. HEC has anode of Zinc plate and cathode of silver with Lithuim-substituted magnesium ferrite as electrolyte. When HEC is partially dipped in water, spontaneously hydroxide and hydronium ions are produced by water molecule dissociation. Hydronium ions trapped in nanopores develop enough electric field that further dissociates water molecules. This works shows the detail review of mechanism and thermodynamics of Hydroelectric Cell (HEC) working.

2009

Inspired by water transport in plants, we present a synthetic, microfabricated "leaf" that can scavenge electrical power from evaporative flow. Evaporation at the surface of the device produces flows with velocities up to 1.5 cm/s within etched microchannels. Gas-liquid interfaces within the channels move across an embedded capacitor at this velocity, generating 250 ms, 10-50 pF transient changes in capacitance. If connected to a rectified charge-pump circuit, each capacitive transient can increase the voltage in a 100 F storage capacitor by ϳ2-5 V. We provide estimates of power density, energy density, and scavenging efficiency.