solar driven hydrogen generator [geek.com]

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vernes
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solar driven hydrogen generator [geek.com]

Post by vernes »


RobL
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Post by RobL »

Bad idea because of the high temp required. Practical limit for economic solar concentrating mirrors is about 2500x solar concentration. With solar insolation of normally 0.4-0.9kW/m² that means you get about 1000-2300kW/m² solar input to your receiver. But with a 1700°C receiver temperature you are radiating about 900kW/m² away. That means that your receiver is only about 10-65% efficient, wasting a huge amount of solar energy.

Far better to use the lower temperature (850°C) Sulphur-Iodine cycle for creating hydrogen that will have receiver efficiencies >90%.

jnaujok
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Not financially sound

Post by jnaujok »

From their own paper, the say that producing 120,000kg of hydrogen a day will require a $750M plant in the Mojave desert.

And that only produces Hydrogen at $5+ per kilogram. And given that hydrogen has a lower energy density than gasoline, that would take less than 10,000 cars off hydrocarbons.

Are we really willing to spend $75,000 per car to produce a fuel more expensive even than current gasoline?

KitemanSA
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Post by KitemanSA »

And you are surprised why???

Everyone knows that solar today is not an energy harvesting method but a subsidy harvesting method.

Not so much as wind, but...

Tom Ligon
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Post by Tom Ligon »

Zinc oxide used to make molten zinc? I'd hardly go that way.

Decades ago they found you can reduce the power needed for electrolysis of water to hydrogen by using titanium dioxide electrodes. That plus conventional PV should work.

http://www.pnas.org/content/72/4/1518.abstract

Ultraviolet irradiation (351, 364 nm) of the n-type semiconductor TiO2 as the single crystal electrode of an aqueous electrochemical cell evolves O2 at the TiO2 electrode and H2 at the Pt electrode. The gases are typically evolved in a two: one (H2:O2) volume ratio. The photoassisted reaction seems to require applied voltages, but values as low as 0.25 V do allow the photoassisted electrolysis to proceed. Prolonged irradiation in either acid or base evolves the gaseous products in amounts which clearly demonstrate that the reaction is catalytic with respect to the TiO2. The wavelength response of the TiO2 and the correlation of product yield and current are reported. The results support the claim that TiO2 is a true photoassistance agent for the electrolysis of water. Minimum optical storage efficiencies of the order of 1% can be achieved by the production of H2.

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