- Hydrogen is 0.082 kg/cu m.
- Hydrogen is MW 2 g/mol.
- Hydrogen is 11.2 cu m per kg at STP.
- Spicer generator batch - 0.3 kg/day production.
- Honda generator - 0.55 gal tank. 0.3 kg is about 0.3 gal fuel, so half a tank.
- Honda generator - runs 6.8 hrs at 225W output! . Thus, we have storage enough for 3.4 hours of 225W. That is about good for night power. 2x this is plenty, outside of space heating and cooking.
- Spicer generator can be built for $1k. Balance of system may be $1k. Tank is $3k. + Honda Generator clone at about $500.
- Overall cost of $5.5k for 765 Whr for hydrogen. $7k/kW
- Compare to Compressed Air, 100Whr per $300 tank with cheapo air engine - need $2400 in tanks for compressed air, unless use regular compressor for 100 psi, + Air engine. Propane Tank ia $2700 for 1000 gal, can go up to 14 bar, as opposed to 300 cu ft for cylinder. 1000 gal to cu ft is 134 cu ft, x14 atm is 1876 cu ft - or 6 cylinders. Cylinders cost $1800 for that amount, so actually lower cost and more portable. Here it pays to have a higher efficiency air engine - if 150 W/tank - need 5 tanks to match the hydrogen route - or $1500. Air engine - $500 let's say - and compressor $500. $2500 for 750 Whr - much better than hydrogen. at $3.3k/kW.
- For gravity storage - take a quick look at gravity storage, with 1/4 acre or 1000 sq meters, 2 m deep, or 1 meter usable. It is 1000 cubic meters of water, at 5 meter height (easy reach for most locations with hills) - we get MGH= 1000 cum * 1000kg/cum *10*5=50,000,000 Joules. 13kWhr! By far the cheapest. 20% friction loss and 90% pelton and 90% electrical gen gets you 8 kW from that system! So even an 1/8 acre pond could do it, for 4 kWhr of power. DIY with your own bulldozer, this system costs $1500 for pipe, $1k for turbine, and $200 for gen, for under $3k, for 8 kWhr, or $375/kWhr - but over lifetime - negligible as it pays back for itself at $1/day, so we get free electricity after 5 years payback. And better with 3D printed pipe.
- 1000ml/min - 1l/min - 60 l/hr - $2500 . If production price is $2500, we should be able to opensource this for DIY at 1/2 the cost at worst, 50% savings from labor. But likely, we can go down to $500 for materials at $1/lb + $10/lb for exotic materials.
Mr. Spicer Version
- In Iowa - http://www.hydrogenwindinc.com/. Went out of business in the 90s.
- See Solar Hydrogen Chronicles for more info on the Spicer system, which costs $200/cell for a 12 cell system, p66.
- Production rate - 1000W for 170 l/hr of hydrogen. Matches above electrolyzer pretty much exactly.
- 170*24=4080 l/day. 4 cubic meters per day. Volume of 1000 gal propane tank is 3.8 cu m. This fills one propane tank in one day!
- 4 cu m/11.2 = 0.36 kg hydrogen production per 24hr.
Solar Hydrogen Chronicles
See p. 44 for system overview of an electrolyzer from the Solar Hydrogen Chronicles
System cost for 0.36 kg hydrogen production per day is $7k raw, but $700 in the case of Production by the Masses:
- Alkaline electolyzer producer - 
- EBay - plates for $40 - 
- Alternative using hydrocarbon starting materials: Water-gas shift reaction using pyrolysis and hot steam