Ultra-low cost Alkaline electrolyzers using commercial-off the shelf (COTS) cost reduction methodology

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Alkaline electrolyzer technology is ripe for dramatic cost reduction. Current alkaline electrolyzer technology is excessively expensive beyond what material costs would predict, mainly due to very small production volumes, a noncompetitive market with a small number of big players, and relatively little use of COTS (commercial off the shelf) methodology of cost reduction.

Pochari Technologies research has thus applied this methodology to bring to market affordable hydrogen generators fabricated from readily available high-quality components, raw materials, and equipment procured on Alibaba.com.

An alkaline cell is a relatively simple system, consisting of three major components. The electrode (a woven wire mesh), a gasket (made of cheap synthetic rubbers, EPDM etc), and a material for fabricating the diaphragm membrane for separating and oxygen and hydrogen while permitting sufficient ionic conductivity (usually polypropylene sulphide or Polytetrafluoroethylene

(TEFLON). The fourth component are the “end plates” which consist of heavy-duty metallic or composite flat sheets which hold a series of rods tightly pressing the stacks to maintaining sufficient pressure within the stack sandwich.

Unlike batteries, noble mineral intensity is alkaline technology is relatively small, with nickel mesh loading of under 500 grams/m2 of active electrode surface area needed to achieve anode life of 5 or more years assuming a corrosion rate of below 0.25 MPY. With current densities of 500 miliamp/cm2 at 1.7-2 volts being achievable at 25-30% KOH concentration, power densities of nearly 10 kW/m2 is realizable. This means a one megawatt electrolyzer at an efficiency of 75% (45 kWh/kg-H2 LHV) would use 118 square meters of active electrode surface area. Assuming a surface/density ratio of a standard 80×80 mesh, 400 grams of nickel is used per square meter of total exposed area of the mesh wires. Thus, a total of 2.25 kg of nickel is needed to produce 1 kg of hydrogen per hour. For a 1 megawatt, the nickel would cost only $1000 assuming $20/kg.

For a lower corrosion rate of 1 um/yr, a total mass loss of 7% per year will occur with a surface/mass ratio of 140 grams/m2-exposed area, the nickel requirement is only $350 or 17.5 kg for one megawatt! Although this number is achievable, higher corrosion rates will likely be enounctered. To insure sufficient electrode reserve, a nickel loading of

Power density of 6.8 kW/m2 electrode area.

For the diaphragm separators using a half a milimeter thick sheet of Polytetrafluoroethylene, around 88 grams is used per kilowatt, at a typical cost of PTFE of $9/kg, around $0.79/kilowatt can be expected assuming an electrode power density of 6.8 kW/m2 (400 miliamps at 1.7 volts)

Gasket costs are virtually negligible, with only 4.8 grams of rubber needed per kilowatt.

For 30% NaOH at 117 C, a corrosion rate of 0.0063 millimeter per year (0.248 MPY) is observed for an optimal nickel concentration of 80%. This means 55 grams of Ni is lost for one square meter, if we choose 10% per year as an acceptable weight loss, we return to 550 grams per square meter as the most realistic target nickel loading, with much lower loading achievable with reduced corrosion rates. A lower concentration of KOH/NaOH and lower operating temperature can be utilized as a trade-off between corrosion and power density.

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