Solar precice dish for water splitting


Solar precise dish for water splitting.
USD 0.25/kgH2 or about 0.12 for southern regions, or 0.5 USA cents/kWh electricity
Judbarovski David, retired, systems engineering, principle inventor
Linkedin (eng), judbarovski@gmail.com, Israel
My personal professional sites: https://judbarovski.blogspot.com, since 2017
and https://judbarovski.livejournal.com, since 2006, archived

It is a small dimension system of about 1.0 m2 solar flux, and it comprises (1) precise thin wall planar mirror for redirecting solar beams on (2) precise thin wall dish concentrator, so its focal spot is motionless, (3) tiny motionless PV sensor between (1) and (2) and it can control the redirected solar beams to be parallel to the said dish axis, (4) two axis tracking control by micro servomotors, and (5)  pedestals for the said mirrors (1) and (2), and all of them have to be stable against a wind average velocity.

A small vessel supplied by water is placed in the said focal spot at about 2 meter from the said dish being 3 meter from a center of the said planar mirror. The dish and the planar mirror are Al and made with 0.5 mm thickness walls can be 0.2% dimensional accuracy (and it is a realistic accuracy!!!), and the last allows to reach 3000 K = 2700 C inside the said small vessel, so the water is split in hydrogen as a product and oxygen as a by-product or waste, and those mix of gases mixed with water vapor go through a thin tube at firth to a main tube for following pure hydrogen separation.

The controlled water supply stabilizes the said temperature 3000 K, when variable sun weather conditions. All other parameters can be calculated.
Let solar flux be 0.8 kW/m2 with 1500 kWh/m2/year, and about 0.7 kW/m2 can reach the said dish during 1200 hours of stable operation of the system, and all the said vessel walls are thermal insulated with an Al-foil as a reflector around that insulation. Let a solar concentrating window be 2 mm, so 0.03 cm2. So a heat loses W = 700 watt/20 + (k< 1.0) * 5.67 * 3.14 * 3 * 10 ^(-6) * 30^4 ~ = 70 watt, and 700-70 = 630 watt is a helpful heat.
So the said water feeding is 0.63 kW/ (240kJ /18g) =0.047 gram/s/m2 is split by 50%, producing 0.0026 g H2 /s/m2 at 1 atm,  so 12 kgH2 /year/m2, or 60.0 kgH2 in 5 years of CAPEX payback.
The CAPEX is about USD 15.0 being a sum of costs t of the system parts.
So it is ~=USD 0.25/kgH2, can be transformed by Fuel cells in 32 kWh electricity by 1.0 USA cents/kWh. It can satisfy any consuming schedule, because hydrogen can be stored and transported for distributed power generation and for export trade.
Annually it is 12.0 kgH2/m2 * 32 kWh/kg = 360 kWh/m2 = 300 W/m2, or 300/0.7 = 430 W/m2 of pick power vs.180 W/m2 for best PV solar panels being some times more expensive
If being 9 m2 land area for each system unit, so 360/9 = 40.0 kWh/m2 surface. For southern regions it can be 80 kWh/m2 or more.  
Such cheap electricity allows the world economics and human life totally to transform for feeding by electricity instead of all other energy sources.
A small share of Australian stony deserts can satisfy all mankind needs in energy. 

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