- Jul 18, 2021 5:10 am GMT
The linked article appears in PV Magazine, reporting on an MIT study published in Applied Energy. It's a straightforward and -- so far as I can tell -- an accurate report on the conclusions of the study. I have major reservations about the study itself. If it weren't for the MIT brand and the study's relevance to a critically important issue, I wouldn't be sharing this link. The published study is behind a pay wall. I haven't read it. However, I found a poster session for the study here. It gives more detail than the abstract published at Elsevier's Science Direct, but not enough to resolve my reservations about the study. A sampling:
- The study is supposed to deal with seasonal storage, but has lithium-ion batteries and hydrogen-fired gas turbines coming out as close competitors. From my own calculations, along with everything else I've read on the matter, lithium-ion batteries are not even remotely competitive for seasonal storage -- in California or almost anywhere else. It would take a 500-fold reduction in specific cost of energy storage to change that.
- Their calculations for the cost of green hydrogen presume that RE will be extensively available for powering electrolyzers at a price of only $10 per MWh. That's an absurdly low figure. Sure, wholesale electricity prices do get that low or lower, in periods when surplus RE is being curtailed. But one can't support commercial production of green hydrogen from the occasional periods when RE is available at such low prices. Simply in terms of total energy, there wouldn't be enough MWh available to support a market. But worse, it would require a huge capital expenditure for electrolysis equipment that would only be used for a few hours a week.
- The study apparently assumes that hydrogen combustion turbines would be the choice for generating RES backing power from hydrogen. It ignores the likelihood that fuel cells would be a better choice. Trends suggest that high temperature SOFCs feeding CO2 Brayton cycle bottoming engines will soon be able to deliver higher efficiency with lower capital cost.
If anyone with a subscription to Applied Energy reads the full article and finds I'm wrong, please leave a comment.
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