Marktm wrote: ↑
Sat Apr 24, 2021 11:44 am
Looked into several of the papers and presentations - most between 6 and 12 years old. Likely economics look a little better now with electrolyser improvements. I could not find any analysis of a stand-alone, totally renewable based project. As the amount of electricity is so high for production of dense phase hydrogen, using grid energy (IMO) as some predicted price/kWh is not realistic for mass adoption of the technology. Building a wind/solar plant specifically matched to the H2 production requirements might be quite an eye-opener as the on-stream factors and resultant size of the entire H2 production/compression/storage must match the highly variable renewables generation capabilities - without some significant energy storage (would be batteries or recycle low pressure H2 as turbine fuel?). My guess is that this dog chasing it's tail will show to be very costly - especially if life-cycle of all systems involved are carefully analyzed. If Matt Mccall's prediction of solid-state batteries come to fruition, all this will be mute
(Not holding my breath!)
Several of the articles on projects I've provided links to here are stand-alone.
The IRENA paper I mentioned said that one of the methods that will be used to deal with intermittency is modular electrolysers, bringing them on or taking them off-line as needed. I have no doubt they'll also make use of storage, - see below.
Renewable energy costs in good areas have gotten so low, at or below $0.02/kWh, that it doesn't seem to be a major issue. IIRR, Portuguese PV set a record last year at $13.1/MWh, i.e. 13.1¢/kWh. That's why countries like Chile, with excellent solar resources in the north (e g Atacama desert) and excellent wind approaching 50% CF in the south (Patagonia), as well as small populations, are looking to become major H2 exporters. Same goes for Australia.
The next most costly item is the electrolysers, and improvements in efficiency as well as increases in the operating hours and lifespan are expected to make green H2 competitive with fossil-fuels. I was kind of surprised at the relatively low operating hours now, but the amount required to make H2 cost-competitive is fairly low, only about 4,000 hours annually IIRR, an increase of about 1,000 hours annually.
The IRENA report says that aside from the electrolyser(s) there's
the balance of plant, which comprises power supply, water supply and purification, compression, possibly electricity and hydrogen buffers and hydrogen processing. Both components are important for the cost, since they have similar cost shares. The largest potential for near-term cost reduction is in this balance of plant, while RD&D is required to reduce stack cost and increase its performance and durability, as trade-offs among these are significant.
The flexibility of alkaline and PEM stacks is enough to follow fluctuations in wind and solar. The flexibility of the system is limited, however, by the balance of plant (e.g. the compressors) rather than the stack. Furthermore, flexibility in the very short term time scales involved (I e. sub-second) is not the key value proposition for electrolysers, as their key value system lies in bulk energy storage. This effectively decouples variability of generation from stability of hydrogen and power to X (PtX) demand through hydrogen storage in gas infrastructure (e.g. salt caverns, pipelines) and liquid e-fuels storage."
Page 26, if you're interested.