Siemens study on grid integration

Interesting.

I do think they're really missing something if they aren't thinking of battery as a norm, especially given methanation efficiency of 60%. (I believe it could go a bit higher if you're using combined heat). Consumer PV+battery seems like a natural destination.

However:
- methane is already heavily used
- methane will remain desirable for some other uses
- there's significant potential biomethane generation
- methane has its own distribution network, which could be easier for long-distance re-distribution of energy
- large supplies of methane would allow for back-up generation in case of sustained grid failure
- in case of methane surplus you could convert excess hydrogen or methane to liquid hydrocarbons for easier storage

I foresee the global economy shifting to renewable electricity and methane. Batteries will particularly help with small scale, distributed generation and demand smoothing, while methane generation will be used along with some biomethane to meet methane demand and provide large-scale energy distribution.

That's a very interesting article. It really points out the need for massive energy storage systems to make all this work and begs the question of why we aren't investing a whole lot more on energy storage research. Batteries for power storage are still pretty expensive for any significant capacity.

It would be interesting to see what the levelized cost of such a system would be, wind plus pretty much 100% fast reacting gas generators plus methane plants. I'd think there would have to be a significant amount of excess peak wind capacity to generate enough methane for the low times. Of course, Siemens does want to sell hardware so may not view capital costs as a major problem.

Keep in mind that's for Germany, which is far smaller than the US.

Based on this Stanford study, if you interconnect wind farms across a large enough area you can count on about a third to a half of total output as baseload generation with availability similar to that of baseload coal.

http://web.stanford.edu/group/efmh/winds/aj07_jamc.pdf

I imagine as the area was larger, the amount that could be relied on as baseload would grow. The same likely applies to other solar/wind combos when being used as load following generators in regions that have daily peaks.

Here's a paper that discusses meeting all demand with renewable energy. There's a very interesting graph on page 1172 the shows a mix of renewables meeting 100% of California's electricity requirements with a backup generation provided by natural gas.

http://web.stanford.edu/group/efmh/jacobson/Articles/I/DJEnPolicyPt2.pdf

On this page there's a graph showing houring renewable generation in CA.

http://www.caiso.com/outlook/outlook.html

The combined renewable output from today actually looks pretty close to what baseload would be. Wind is high in the evening, when solar isn't generating, and as solar ramps up wind dies down. All other renewable generators are flat and provide normal baseload.

To get to 100% we'll need to install enough to account for the amount of energy generated by thermal+imports in this pdf.

http://content.caiso.com/green/renewrpt/DailyRenewablesWatch.pdf

It's difficult, since we'll need to install ~8x existing capacity of wind/PV/solar thermal, but not impossible. Technically we may even be able to only replace a fraction of imported energy since a lot of that is likely hydro from the PNW.

The larger the area, the easier it tends to be to integrate distributed renewables and provide power when people use it.

The main flaw is the assumption about electrolysis. AFAIK there is no affordable commercial process to do this. It's easy to do a little lab experiment. I did it 40 years ago as a kid. Commercially it's still all very small scale and expensive. Combining the hydrogen with carbon dioxide to form methane is doable and a good idea, rather than trying to work with hydrogen.

If it were easy to crack water with surplus electricity and just make methane with it we would have had decent grid storage options a long time ago.

It would work much more straightforwardly to supply the grid with nuclear generated electric and use process heat to crack water and make methane for vehicles. Trying to use solar and wind to entirely power Germany might be incompatible with being an advanced industrial economy.

Ludus said:

The main flaw is the assumption about electrolysis. AFAIK there is no affordable commercial process to do this. It's easy to do a little lab experiment. I did it 40 years ago as a kid. Commercially it's still all very small scale and expensive. Combining the hydrogen with carbon dioxide to form methane is doable and a good idea, rather than trying to work with hydrogen.

If it were easy to crack water with surplus electricity and just make methane with it we would have had decent grid storage options a long time ago.

It would work much more straightforwardly to supply the grid with nuclear generated electric and use process heat to crack water and make methane for vehicles. Trying to use solar and wind to entirely power Germany might be incompatible with being an advanced industrial economy.

Click to expand...

It's not been done before, because there's no motivation to do it unless you have intermittant renewables and it's not affordable unless they're cheap. Since they're cheaper than ever and Germany is willing to use its wealth to green they're very interested in doing it.