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The German natural gas infrastructure can in fact store several hundreds of TWh.
by cygx 7y ago
The German natural gas infrastructure can in fact store several hundreds of TWh.
- manfredo 7y agoWhat do you mean natural gas infrastructure? Pneumatic storage?
- cygx 7y agoLots of German households and industries use natural gas for heating, hence we've got something like 400,000 km of pipeline as well as storage facilities sitting around. Instead of buying natural gas from Russia, we could fill them with synthetically produced methane and/or hydrogen, generated during off-peak hours.
- manfredo 7y agoSynthetic methane production has a theoretical maximum efficiency of 30-40%. So we'd need to build 3x as much power and is actually needed, and a bunch of electrolysis and Sabatier reaction plants on top of that. Or we can just follow France's example and build nuclear plants.
- cygx 7y agoThose numbers are outdated. Round-trip efficiencies of up to 80% have been claimed: https://www.sciencedirect.com/science/article/pii/S0360544218320693 https://www.sciencedirect.com/science/article/pii/S036054421... If that's legit and can be made cost-effective, the case for nuclear is largely gone...
- manfredo 7y agoEfficiencies of over 100% have been claimed. Over 50% of the US patent office's applications are for entropy-reversing devices. Come back to me once these claimed figures are actually implemented.
- cygx 7y agoReverse fuel cells aren't magic, though. I agree that 80% seems rather ambitous...
- 08-15 7y ago...in the form of methane. How do you store wind and solar? Uhm, well, electrolysis and Sabatier reaction, and then you clean it up and compress it or something. Unfortunately, you need a source of carbon dioxide (no, not air, extracting a trace gas is rather impractical), and then the whole process has a round trip efficiency of certainly no better than 20%. Looks like we need a 4x or so overbuild of unrealiables so that methanation can keep the lights on in winter. What confuses me is that there are much more practical chemical storage methods nobody talks about. Ammonia comes to mind. It's easier to make and easier to store. I can't help but think that the whole methanation idea is a PR stunt by the gas industry, intended to positively associate renewables with fossil gas in the minds of the unwashed masses.
- cygx 7y agoGerman Wikipedia lists round-tip efficiencies of 30-38%, and 43–54% if you cogenerate heat. I've already linked a paper which makes promises of efficiencies of up to 80% using reverse fuel cells. Here's an older one that promises 'only' 70% efficiency, using caverns for CO2 and CH4 storage: https://pubs.rsc.org/en/content/articlelanding/2015/EE/C5EE01485A https://pubs.rsc.org/en/content/articlelanding/2015/EE/C5EE0... Not sure how much of these claims will survive after contact with reality...
- manfredo 7y agoHeat cogeneration doesn't really improve efficiency of the methane generation process itself. Cogeneration refers to using the waste heat of a thermal plant to assist in some other facility. Using the waste heat of a gas plant to heat water in desalination is an example of cogeneration. So it does improve overall energy efficiency, but it assumes that there's a convenient source of heat next door. Wind and photovoltaics don't generate any significant amount of heat though, so there's no opportunity for cogeneration.
- cygx 7y agoCogeneration happens at the gas-to-power side of things. Doesn't help you with electricity generation, but that's ok as the goal is reduction of emissions across all sectors.