How efficient is the process of creating CH4 from excess green energy?

[mcgarry_J]

Creating CH4 from H2 + CO2
This was a topic raised before.
However a point that should have been made and wasn't is as follows.
The problem with electricity is that it cannot be stored.
Wind energy often has to be dumped at times of low demand (night, holiday periods, weekends). The amount and frequency of excess energy availability will increase as more and more wind generation is installed. The "storage" of electricity in one form or another is the key issue. Batteries and Fuel cells are other options, but both are still basically chemical reactions.
If excess green energy is the source for the CH4 reaction then the question is:-
1) What is the cycle efficiency of a CH4 reaction.
The cycle being a) create CH4 using CO2 + H2, b) store CH4 c) Use CH4 burning Gas Turbine Electricity Generator at high demand times
2)What would the capital cost of the CH4 plant.
3)Storage might not be an issue, if the gas can be pumped into an already existing gas network.
Cost may be too high now, but the break even point is a function of the cost of Oil/Gas or Coal.
All the above questions could be asked of batteries and fuel cells and there are associated capital costs.
The Gas Turbine will already be built so there is no captital cost associated with it.

 

[Borek]

And your point is?

 

[mcgarry_J]

My point is that storing Electricity is, indirectly, the biggest single problem facing the planet.
Awareness of this is very low. Discussion of the possible solutions is also very low and even rough cost comparisons of the options are to my knowledge either non-existent or incomplete. I think that the problem of Electricity storage is an inconvenient fact that is being ignored by both commercial and particularly political interests, in their hype about greening the planet.

 

[DrStupid]

Awareness of this is very low. Discussion of the possible solutions is also very low and even rough cost comparisons of the options are to my knowledge either non-existent or incomplete.

There is awareness and there are discussions. There are even projects (e.g. http://www.newenergy.info/fileadmin/newE/dokumente/NEW_04_11_Windgas_Seite_48.pdf )

 

[Ryan_m_b]

This sounds very similar to various approaches to artificial photosynthesis a field with huge potential to create carbon-neutral fuel.

 

[Dr_Morbius]

If I am correct converting H2 and CO2 to CH4 is endothermic. There's no point in doing it. Makes more sense to electrolyze water to H2.

 

[Ryan_m_b]

If I am correct converting H2 and CO2 to CH4 is endothermic. There's no point in doing it. Makes more sense to electrolyze water to H2.

That depends, if you check the link above for artificial photosynthesis you'll see that the energy will come from sunlight. Creating methane is one step, many efforts hope to the same method to create longer chains of hydrocarbons to produce oil. This has several advantages over H2 if the aim is fuel production the biggest of which is that we don't have to rebuild the existing oil storage/using infrastructure. It will also provide a way of making carbon-neutral oil but could also be used as a carbon capture technique (although regarding the latter planting trees is a nicer approach IMO)