Hydrogen Production
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Basics
- This page explores various methods of hydrogen production
- 39.4 kWh of electricity and 8.9 liters (l) of water at normal conditions (25 C and 1 atm) to make 1 kg of hydrogen [1]
- Electrolyzers (alkaline and PEM) are 50-80% efficient [2]
Cost
- This article states that hydrogen cannot be produced cheaply. [3] However, if we use OSE's 1 cent/kWhr cost of electricity as documented in the Seed Eco-Home PV System, with alkaline electrolyzers (see Hydrogen Production, the cost of returning that electricity through solar hydrogen is 5 cents per kWhr. See Round-Trip Electricity from Hydrogen.
- Alkaline electrolyzer generation cost is -
- Hydrogen applience - $7.60/kg hydrogen - [4]
- Hydrogen generator - 6kWhr/cu m. 1 cu m is 45 moles, or 90 grams of hydrogen. [5] This system would thus cost 12 cents (conservative) per 90 grams using the OSE PV system. This is $1.32/kg of hydrogen. The GGE is thus $1.32/gallon equivalent cost of gasoline. The 6kWhr/cu m is reasonable, in that it reflects a 66 kWhr cost of electricity per kg of hydrogen - the standard value for an alkaline electrolyzer implying 60% efficiency.
- $3.33/kg cost for power plant storage - [6]
- From steam reforming of methane - $1.25/kg - [7]
- Extreme existing cost reduction case - Based on Seed Eco-Home PV System, we go with 50 cent/kW cost of panels with large shipping orders (40 cents for a contaner - in which container shipping is $500, compared to full trailer load). Then we reduce system cost 30% by feeding electrolyzers directly instead of using inverters, chargers, and storage. Then we go from 2 cents to 1.4 cents with this 30% reduction - to 1 cent by 40 year lifetime instead of 25 year lifetime of panels. So we go down to 66 cents per GGE.
- Paper showing $5/kg production, at 1000 kg/day scale. Most of the cost is electricity. [8]. Assumes 5c/kwhr cost. Thus, right there we have <$2.5/kg cost of hydrogen if electricity cost were negligible compared to 5c/kwhr.
- $3.2Euro/kg - [9]
- Capital costs of $1k/kw_e cost for 1kW electric input- [10]
- Electrolyzer is $1k/kw and 75000 hours life for alkaline electrolyzers - [11]
- Capital costs of generation: 66 hours per kg equivalent. Electrolyzer can make 1000 gallons of gasoline - per $1000. So capital costs are $1 per gallon. This reflects the industry, where capex of electrolyzer is comparable to electricity costs of producing hydrogen.
Electrolyzer Design
- From Solar Hydrogen Chronicles, we have $100 cells which use stainless steel and take 100W each (24v made of 2v cells, running up to 40A).
- Ultimately, we are talking about stainless steel electrodes, a separator, and potassium hydroxide.
- The cost of materials requires is low - these are all COTS materials. This indicates that based on stainless steel costs of around $1 (see Commodity Prices), the electrolyzer cost should be significantly less than $100/10lb - and more like a dollar a pound of dry weight.
- If it costs $1000/kW hydrogen production to get $1/kg capex for hydrogen - then corresponding reduction in capex gives corresponding reduction per kg cost - based on a simple $1000 capex to $1/kg hydrogen costs.
- Note that a minor portion of cost goes to gas conditioning - so the stack cost is the dominant factor -
(from [12]). Thus, the cost limit for electrolyzers is the cost of stainless. - From Wikipedia [13], hot dip galvanized nickel is a good and cheap electrode - [14]
Research
Energy Requirements
- about 50kWhr [15] to produce one kg of hydrogen. At electrical costs of 10 cents per kWhr, that is $5 per kilo, equivalent to a $5/gal of gasoline cost for the Energy Density.
- For the Seed Eco-Home built in 2016 - the total installed marginal cost of 3kW is $2000 in 2017 - See Seed Eco-Home PV Cost. This could produce 1 kg of hydrogen in 3 days. Perfect. Annual cost of fuel at $3/gal is $1200 - 400 gallons at 25 mpg - for 10k average miles. So we would get free fuel after 2 years of use.
- If cost over lifetime is considered - 20 years at 3kW of production yields 20*365*6*3 kWhrs = 131,400 kWhrs. This yields an energy cost of 1.5 cents per kilowatt hour. Or equivalent to 80 cent per gallon gasoline cost.
- This makes a great case for the Seed Eco-Home + Hydrogen Filling Station + Open Source Hydrogen Car + Microfactory + Aquaponic Greenhouse as a productive unit for civilization with automated food harvest and passive electricity and fuels production.
Electrolysis Of Water
Wind Hydrogen
See $6k concept design of 20 kw wind turbine - Deka-kW_VAWT_Wind_Turbine. If the think lives for 20 years, and has a median capaity factor of 40% - [16] - then we are getting 5 kW of power for $6k. Compared to 3kW for $2k, but with 1/2 the capacity factor of wind - the solar option translates to 3kW for $4k compared to wind. Thus, the wind power option is approximately similar to PV. Except the wind can be self-manufactured, but probably has higher maintenance costs. However, if the wind turbine lasts 100 years, then we have a significant advantage. Further, if we could get a larger system than 20kW for wind - then we could be at an advantage in cost performance.
H from Aluminum
One way to generate hydrogen is by reacting aluminum with base such as NaOH.
This company promises $2000 home scale units for producing hydrogen at $1 per Kg
Steam Reforming of Hydrocarbons
- This breaks down hydrocarbons into hydrogen and other byproducts (Usually carbon dioxide or carbon monoxide, althugh not always)
- This is usually done with fossil fuels, but it could use renewable biofuels such as biodigester gas (either impure, or purified to pure methane)
- Wikipedia Page on Steam Reforming
Artificial Photosynthesis (Also Called Photocatalytic Production)
- This uses catalysts that replicate some of the partial processes of photosynthesis to produce water from water and sunlight, or carbon dioxide and sunlight
- Wikipedia Page on Artificial Photosynthesis
- Wikipedia Page on Photocatalytic Water Splitting
- Wikipedia on Photochemical Carbon Dioxide Reduction
Biohydrogen
- This uses genetically modified microrganisms to produce hydrogen, either by modified photosynthesis, or by modified fermentation of sugar
- Wikipedia Page on Biohydrogen