H2O

Cost to generate H20

Here is an estimate of the cost to generate 1 liter of H2O (water) from electricity:

  • The chemical reaction for water electrolysis is:
    2H2O --> 2H2 + O2
  • This requires an input of 286 kJ of electricity per mole of water.
  • One mole of water = 18 grams = 18 mL of water
  • So to generate 1 liter of water (1000 mL) requires:
    1000 mL / 18 mL per mole = 55.6 moles
  • Electricity input required = 55.6 moles x 286 kJ per mole = 15,930 kJ
  • 15,930 kJ = 4.42 kWh of electricity
  • At an electricity price of $0.10 per kWh:
    Cost for 4.42 kWh = $0.44

So the estimated cost to produce 1 liter of H2O from water electrolysis powered by electricity is around $0.44, assuming an electricity rate of $0.10 per kWh.

This does not include the capital cost of the electrolyzer system. But in terms of just operating costs, the electricity required to split water into hydrogen and oxygen to generate 1 liter of H2O would be around $0.44 at current typical electricity prices.

to generate 1 liter of H2O from electricity via water electrolysis at an electricity rate of $0.15 per kWh:

  • The electricity input required to generate 1 liter of H2O is 4.42 kWh, based on the previous calculation.
  • At a cost of $0.15 per kWh:
  • Cost for 4.42 kWh at $0.15/kWh = 4.42 * $0.15 = $0.66

So with an electricity price of $0.15 per kWh, the estimated cost to produce 1 liter of H2O through electrolysis would be $0.66.

H20 Cost

For a large commercial electrolyzer:

  • Capacity: 500 liters H2O/hour
  • System cost around $400,000-$600,000
  • Utilizing proton-exchange membrane (PEM) electrolysis cells
  • Cell stack cost around $600 per kW
  • 500 liters/hr requires around 60 kW
  • Cell stack cost = 60 kW x $600 per kW = $36,000
  • Balance of system adds ~2X cost
  • Total system cost ~$400,000

Here is the cost estimate re-done for $0.15/kWh electricity and formatted more clearly:

Assumptions:

  • Electrolyzer efficiency: 70%
  • Electricity cost: $0.15/kWh
  • $400,000 electrolyzer capital cost
  • 10 year amortization
  • 5% interest
  • 50% capacity factor

To store 1 MWh electricity as H2O:

  • Electricity required: 1 MWh / 0.70 efficiency = 1.43 MWh
  • Electricity cost (@ $0.15/kWh): 1.43 MWh x $0.15/kWh = $214.50
  • H2O generated: 1.43 MWh x 278 g/MJ x 3600 MJ/MWh = 1,429 kg
  • Annual amortized capital cost: $48,763
  • Annual H2O production: 6,186 tonnes
  • Capital cost per tonne H2O: $48,763 / 6,186 tonnes = $7.88
  • Capital cost for 1.429 tonnes H2O: 1.429 tonnes x $7.88/tonne = $11.28

Total cost to store 1 MWh in H2O:

Electricity: $214.50 Capital: $11.28 Total: $225.78