FIGURE G-10 Sensitivity of the cost of hydrogen from distributed electrolysis to the price of input electricity.

electrolysis process produces little if any CO2 or other greenhouse gas emissions per se. Electrolyzers contain no combustion devices, and the only input to the process other than electricity is pure water.

However, there does exist a relationship between emissions and electrolysis. Any pollution associated with electricity consumed by the electrolyzer needs to be taken into account. As stated previously, one fundamental appeal of electrolysis is that it creates a path for converting renewable power into fuel. But the low capacity factors of renewables (other than geothermal and hydro power) make an all-renewables case very difficult on an economic basis. Electricity from nuclear plants is also non-emitting on a greenhouse gas emissions basis, but the outlook for additional nuclear plants is uncertain at best.

Power from the grid is assumed to derive from the grid’s average generating mix. With today’s grid mix, about 17.6 kg CO2 are emitted per kilogram of hydrogen. As the portfolio of energy resources utilized to supply electric power evolves, the amount of CO2 emitted to produce 1 kg H2 could either increase or decrease.

Electrolysis as an Early-Stage Transitional Hydrogen Fuel Source

Electrolysis may be particularly well suited to meeting the early-stage fueling needs of a fuel cell vehicle market. Electrolyzers scale down reasonably well; the efficiency of the electrolysis reaction is independent of the size of the cell or cell stacks involved. And the balance of plant costs in an electrolyzer are also fairly scalable.

The compact size of electrolyzers makes them suitable to be placed at or near existing fueling stations. And finally, electrolyzers can utilize existing water and electricity infrastructures to a considerable extent, obviating the need for a new pipeline or surface hydrogen transport infrastructure that would be required of larger, central station hydrogen production technologies.

Summary

Electrolytic hydrogen production is an existing technology that serves a high-value industrial chemicals-based mar-



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