Methanol for fuel cell as long-term storage in the house

Thank you - that sounds very plausible and please excuse my undifferentiated statement, which, as you rightly pointed out, was based on my lack of information. I will research again whether my accusation of [Grennwashing] is still justified. :) Then I just hope that the combination of battery and fuel cell will be promoted. :-D

For clean batteries (and for a play money investment) I recommend researching SALD batteries. Fraunhofer was involved in the development, a plant is currently being built in Eindhoven, unfortunately participations are not yet available for purchase in the typical private scope.

I stumbled upon a really convincing concept that can make my house independent from the electricity provider even in winter - it’s called methanology. The idea is simple and logical: In summer, you produce methanol with the photovoltaic surplus, which you store as long-term storage...

This roughly corresponds to the SynFuel concept as intended for aircraft engines.

The thing has a big catch regarding efficiency:

Methanol fuel cells have an efficiency of < 50% (calorific value -> electric),
i.e. from 1 kWh chemical heating energy from methanol, less than 500 Wh of electric energy comes out at the end, plus CO2 etc.

If you want to reverse the process, you first have to put in significantly more energy:
CO2 + air components (to obtain the H), to then get CH3OH (liquid methanol).
Additionally, energy must be spent to extract the CO2 from the air beforehand. Over the entire process chain, this will be (rounded) under 25% efficiency.
i.e. from 1 kWh of electrical input, later behind the fuel cell for propulsion about 0.25 kWh of useful energy remains.

This is always subtly "forgotten" in the presentations.
I don’t find anything about this even with the developer MY-technology.

The vision that electricity from solar cells doesn’t bring any additional environmental burden doesn’t help as long as there is not yet enough photovoltaic (or wind) electricity in surplus.
But even if there were enough surplus electricity, the additional CO2 pre-costs remain in the production chain of the additional solar panels.

In my opinion, this sounds too good to be true.

The vision that electricity from solar cells does not cause any additional environmental burden does not help as long as there is not enough photovoltaic power (or wind) in abundance.

This is about local solutions where enough electricity from solar cells can be provided and not about a patent for global world-saving. It is a functioning building block. If the solar power yield is sufficiently large, the efficiency from a climate protection perspective takes a back seat. An efficiency of 25% from almost CO2-neutral energy is certainly better than an efficiency of 80% from fossil fuels. Efficiency can no longer remain the holy benchmark when it comes to CO2 reduction, but rather the CO2 emission per kWh.

But even if there were enough electricity surplus, the additional CO2 pre-costs remain in the production chain of the additional solar panels

It is sufficiently proven that the CO2 balance of photovoltaic energy is very favorable even considering the production emissions. You don’t have to buy the cheapest modules from China that were manufactured with coal power. There are plenty of alternatives.