New (Flow) Battery Design Could Help Solar and Wind Energy Power the Grid

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33. Pressurization may not be the challenge you imagine

http://world.honda.com/FuelCell/SolarHydrogenStation/

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[font size=5]Honda begins experimental operation of next-generation Solar Hydrogen Station for household use.[/font]

[font size=3]With the goal of replacing fossil fuels, reducing emissions and combating climate change, Honda has worked proactively to development of fuel cell electric vehicles, which it views as the ultimate clean mobility of the future. Also believing it crucial to eliminate CO[font size=1]₂[/font] emissions that result from the production, storage and supply of hydrogen fuel, Honda is engaged in the research and development of advanced H[font size=1]₂[/font] infrastructure technologies.

Since 2001, Honda has operated an experimental solar-powered water electrolyzing hydrogen station in Los Angeles, California. In January 2010 in the same location, Honda began experimental operation of a next-generation Solar Hydrogen Station that is small enough to fit in a typical household garage. To produce high-pressure hydrogen, the previous station required not only an electrolyzer but also a separate compressor unit. For the next-generation Solar Hydrogen Station, Honda developed a new high-differential pressure electrolyzer that combines electrolysis and compression functions in a single unit.Since a separate compressor is no longer necessary, the Solar Hydrogen Station is more compact, quieter and lower in cost, making home hydrogen supply a more realistic option going forward.

In March 2012, Honda installed at the Saitama Prefectural Office Japan's first solar hydrogen station that emits zero CO[font size=1]₂[/font] through the entire process of producing, storing, and supplying hydrogen. This project, conducted in a public-private partnership with Saitama Prefecture and Iwatani Corporation, was commissioned by Japan's Ministry of the Environment and seeks to verify new technologies for realizing the low-carbon society of the future.

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By operating next-generation Solar Hydrogen Stations, Honda seeks to enhance the efficiency of sustainable energy supply technologies while identifying and solving any issues that may stand in the way of full commercialization of hydrogen production and supply stations.

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http://www.hydrogen.energy.gov/pdfs/progress11/ii_e_3_dunn_2011.pdf

[font face=Serif][font size=5]II.E.3 High-Capacity, High Pressure Electrolysis System with Renewable Power Sources[/font]

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[font size=4]Results[/font]

[font size=3]Avãlence has existing technology that is globally unique in its ability to deliver hydrogen directly at storage-ready pressures of 2,500 and 6,500 psi without a separate compressor. Using an alkaline electrolyte process, the Avãlence Hydrofiller systems integrate the production and compression processes by operating the electrolytic cells at the desired delivery pressure. The systems can interface directly with renewable electricity supplies and have been shown in previous work (DOE Small Business Innovation Research project completed in April 2005) that the electrolyzer operates through the full range of voltages output from the connected photovoltaic (PV) array without using any power conditioning equipment. These characteristics result in a renewable hydrogen production and delivery system that is significantly more efficient and reliable, and substantially less expensive than existing commercially available electrolyzer and compressor system sets. The smaller scale Hydrofillers are based on a single cathode/anode tubular cell design with production capability of about 0.1 kg/day per cell. A revolutionary design approach to this high-pressure cell core is needed for an order-of-magnitude capacity scale up of the individual electrolyzer modules.

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[font size=4]Introduction[/font]

Initial test work on nested components, with passive circulation, was conducted during the first quarter of FY 2011. The test results from one nested set did demonstrate substantial recirculation (driven only passively at this point). The recirculation had a very positive effect in that purity of hydrogen (before the catalyst) increased from 98.5% typical at 2,200 psig to >99.5% at 2,200 psig. The recirculation resulted in less dwell time inside the cells for the gas bubbles and therefore less opportunity to diffuse or leak by whatever minute paths exist. This is an indication that Avãlence should be able to return to high pressure operation (6,000 psig) with no compressor, and stay below the required safety limit of 2% impurity before the catalysts. The test cell, with five nested electrodes, will use active circulation, which should further reduce dwell time, so even better results are anticipated. In support of the multi electrode testing, Avãlence has selected circulation pumps for testing of the five nested electrodes.

Based on the tests conducted during the first quarter of FY 2011 and additional analysis, there is a problem of excessive voltage drop associated with axial electrical conductivity in the nested set of 316 stainless steel electrodes. As a result, additional design work was undertaken to decrease electrical resistance within the cells and associated with pass through (sealed) conductors. This is focusing on the selection and construction of the anodes and cathodes that provide the axial conductivity and electrical pass through, and which are also of acceptable cost. The test cell design is limited to 3’ height due to concern over voltage loss axially. This means that the pilot plant cells at 6’ will require that electrical connections are made at both ends of the electrodes or another solution is devised in order to improve the conductivity. For example, it is possible to solve this problem with a change in material (to nickel for example), but this is costly. Avãlence is working on other concepts such as layering (cladding) the electrodes to deliver both the conductivity required and to manage the cost.

Lastly, design work focused on how to align the plurality of electrodes and membranes top and bottom for better manufacturability. This is being addressed by securing the membranes and inner electrodes to a top alignment mount made of PVC that will be glued to the upper gas manifold (also made of PVC). The relatively thin membranes will be reinforced at the bottom with a PVC guide ring glued to the membranes. The membranes and electrodes are attached to a PVC bottom alignment guide, and the entire assembly can then be inserted into an outer anode and flange assembly. Avãlence is researching the manufacture and supply of stiff tubular membranes made by casting a membrane material onto a rigid ceramic, extruded PVC, or other support.

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