MAILBOX: 23 Years Using Solar-Powered Hydrogen

Intermediate

In the summer of 2012, a rebuild—or “resurrection” as we like to call it—of a hydrogen and oxygen production plant was conducted. In 1994, this hydrogen plant, which uses PV energy to electrolyze water, was featured in HP39. After 16 years of reliable PV-powered hydrogen and oxygen production, in 2010 we shut down our home-sized hydrogen plant. The plant was offline for about two years, due to operational problems with high cell voltage and cross-contamination of the hydrogen and oxygen output, which made them unsuitable for storage.

We wanted to get the plant back in service so we could have hydrogen available for cooking and oxygen for welding and cutting, our main applications. As a summer intern at H-Ion Solar, Nathan Miller took on the challenge of overhauling the hydrogen plant.

The first step was diagnosing the problem. We measured the voltage across each cell while the plant had been off for a considerable amount of time. Additional voltage measurements were taken once the plant was fired up. The cathodes were in excellent shape, but the separator boxes had cracked and split, and the anodes were severely corroded.

We installed replacement Spicer cell-packs into the cell containers. These second-generation packs improve on the previous model. The new model features an envelope around each electrode—one collects anode gas (oxygen) and one collects cathode gas (hydrogen). The cells received a new paint job, new Teflon O-rings, new gaskets (for the removable end-plate), and new stainless steel bolts. After replacing the electrodes and separators in four bad cells, and replacing the gas purifier catalysts, this plant is now in “standby” service, and can be used to generate oxygen and hydrogen.

The hydrogen plant requires a technically educated operator who can perform regular maintenance and day-to-day operational supervision. The plant has complex purification systems, for both hydrogen and oxygen output. The double-bubbler scrubbers have to be checked, filled with water, and drained. The water-removal filters have to be drained manually several times a week. And water must be added once or twice a week. Purity of produced gasses must be checked to assure storage safety.

New options are available for hydrogen production by electrolysis. We are now using our new Proton-OnSite PEM-electrolyzer, one of several gas chromatography H2 carrier gas vendors. This type of electrolyzer is simpler to install and operate. Our new H2 generator contains a palladium purification filter that is smaller and simpler than our old H2 -O2  plant with H2  and O2  catalytic-purifier trains.

We are also doing a type of hydrogen net-metering using the PEM electrolyzer. When a hydrogen tank refill is needed, the small 300 cubic centimeter per minute PEM electrolyzer is started until the tank is full. This may take several days, and our storage can provide several days’ worth of H2 for cooking and oxygen for welding.

We have used the hydrogen and oxygen for 23 years for: barbecuing, heating, welding and oxy-cutting, and briefly for making electricity in a fuel cell. We are unable to run the hydrogen heaters, except occasionally, due to inadequate seasonal storage.

Nathan Miller & Walt Pyle • MIT and H-Ion Solar

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