Reuse CO2 to reduce emissions.

Estorageguy said:
' So you are effectively getting more energy for a given amount of CO2 released.'

Perhaps you would explain why this is a bad thing, except in some fantasy world of power from unicorn farts?

QUOTE: "the application will take excess electricity from intermittent renewable energy sources"

There is no "excess electricity". The problem is that the coal-based power plants are given priority to sell their polluted electricity, rather than giving priority to the windmills. The windmills are then designated as "excess". This is pure balderdash, of course.

The correct solution is to dial down the coal plants, not to use some massively lossy process to convert the windpower electricity to methanol.

Jus7me:
You are clearly unfamiliar with how the power market works in Germany.
Renewables are prioritised over fossil fuels.

However as little as a nominal 10% of the grid average from wind results in more than 100% of the grid in very windy conditions, as it is hugely variable.

Similarly a low average from solar still results in more than 100% of the grid on a summer's day.

The difficulty in electrolysing this surplus is that it results in poor capacity utilisation for the electrolysers, even with buffering.

There are indeed sometimes surpluses from renewables though.

You can't dial down plants that are "must run" further than the level where they can supply their essential services, even if the plants burn coal.  The grid needs reserves, reactive power and load-following, and the negative-load characteristic of wind and PV means more such capacity is required, not less.  Skimp, and you get failures (frequency excursions, over/undervoltage, and blackouts).

Schedulable loads (like these electrolyzers) are one way of dealing with un-schedulable generation.  However, the cost of the product is going to be astronomical.  At Germany's wind capacity factor of less than 20%, those electrolyzers are going to be working at perhaps 12% of full capacity.  To put this in financial terms, the capital (and thus interest) cost will be 8.3 times as much as if the system just ran 24/7.

Then you have the cost of power.  Unless the feed-in tariff isn't paid for excess generation, that power should be priced at the FIT.  As of 2012, that was € 0.0893/kWh.  At an energy/gas ratio of perhaps 60 kWh/kg, the power to generate one kg of hydrogen costs €5.36.  It takes 3 moles of hydrogen to generate 1 mole of MeOH from CO2 (3H2 + CO2 -> CH3OH + H2O), so 1 kg of hydrogen will generate 166.7 moles of MeOH or about 5.33 kg worth (6.74 liters).  At about half the energy density of gasoline, this contains the energy of about 3.3 liters of petrol, for a cost of power of about €1.60 per petrol-liter-equivalent (CO2, electrolyzers and the methanol plant not included).  Since the juice alone costs well in excess of typical European pump prices with all taxes included, we can dismiss power-to-methanol as a toy of the wealthy.

Perhaps I should add that although many think that I am an advocate of fuel cells and hydrogen, what I dislike is the grounds on which they are often dismissed.

If you are going to use loads of renewables, the only way we know which may work is to use loads of hydrogen and its derivatives, such as methane.

Otherwise the storage is impossible, and even with hydrogen the economics are difficult.

Personally I would simply build loads of nuclear reactors, which have much less need of hydrogen storage, but if lots of renewables are the choice, then the reality is that that means hydrogen.

A Plan:
If you have natural gas; switch your coal plants over;
Build out your hydro, wind and solar...other renewables; and buffer the demand with storage batteries and water storage, etc., dropping out gas plants as you build out. Buffer with a nuclear plant or two if needed; but, be aware an investment in nuclear means it will be around for a long time because they are an expensive investment.
Stay away from all the complication and complexity of changing forms of energy from one to another. These schemes are less efficient by their very nature and usually include continuing with hydrocarbons. Try not to create CO2 and pollution in the first place.

The whole idea is to stop mining and burning hydrocarbons, period.
Any modifications to the plan to make it cleaner?, have at it!

This is a rich country 'solution' that is really beside the point. In the Third World, which is where the big growth in energy production is happening, this would be much too expensive. There they are building coal plants for electrification--cheapest energy available (externalities excluded, if course). We need even cheaper nuclear that can be deployed across the developing world.

@lad:
I am not quite sure what you mean by buffering with nuclear, particularly if you are talking in terms of 'a plant or two'.

What nuclear is great at is baseload, and you want to run it all the time to amortise the build cost.

That is why solar in Germany is not a help of any description, as it takes away all baseload in the days in the summer, slap bang when it is not needed in Germany.

In the States it is a different matter, as there is a considerable excess of peak summer demand over peak winter demand, so nuclear could provide baseload without solar getting in the way too much if used for the summer peak.

A nuclear fuel cycle is most economic and effective if you have at least a couple of dozen plants, and you do not increase such risk as there is which has in any case been grossly and wilfully exaggerated by having more plants proportionately to their number.

It is not ten times more risky to have twenty nuclear plants than two.

Solar in Germany has a large negative worth.
It ruins the economics of any sensible way of generating power, and provides power when it is of the very least use.

If you live in cold climate, how are you going to heat your house in winters if you don't use fossil fuel, or use hydrogen made from RE collected from other seasons?In winters, RE output is not any higher than other seasons, yet the energy consumption due to heating demand will be several folds higher!

In a word: Insulation. The Europeans have for many years been building houses to a much higher level of energy efficiency than can be got by stuffing fiberglass between 2X4 studs as we do in North America. And since the 1990s they've gone so far as to start building homes, and other building, to Passivhaus standards. Such buildings are designed to have an annual heating and cooling demand, as calculated with the Passivhaus Planning Package, of not more than 15 kWh/m² per year (4746 btu/ft² per year) in heating and 15 kWh/m² per year cooling energy OR to be designed with a peak heat load of 10W/m². Basically, you can heat these houses just from the waste heat of the normal activities of living in them. No furnace needed.

Electrolysis is shown here (pg 12) at 77% efficient:
https://www.iea.org/media/workshops/2013/hydrogenroadmap/Session4.4DecourtSBCEnergyInstitute.pdf

that is fair enough, as although Norsk Hydro hits 80% in some of their installations, a lot will be short of that.

They give the mid term likely efficiency (10 years?) as 84%, and show underground storage, presumably in salt caverns as that is what the German's are looking at, at 95% efficiency.

I don't know why they list fuel cells as only 30% efficient,as that is a lot less than the Kyocera home fuel cell gets, at 46.5% and 90% including the thermal heat capture for water heating:
http://fuelcellsworks.com/news/2012/03/15/kyocera-osaka-gas-aisin-chofu-and-toyota-announce-completion-of-world-class-efficiency-residential-use-solid-oxide-fuel-cell-sofc-cogeneration-system-co-development-and-commercialization-of-ene/

It is also a lot less than fuel cells get in cars, or the miles per kg of H2 would be impossible.

So putting the numbers together:
0.84*0.95*0.9 where use of the heat is possible:
72% round trip.

Where heat capture is not possible, perhaps in a car:
0.84*0.95*0.465 = 37%, around the same as the very best gasoline engines.

Not all losses are accounted for their, so adding compression at 0.95% efficiency (target, DOE) then around 35% efficiency is obtainable in cars.

Pipeline losses might amount to 3%, so 0.97, then you end up with 34%.

That is in the right area to be practical, although of course when the electricity can be used more directly that is always more energetically efficient.

Those numbers work fine for VW's FCEV PHEVs though.

Hmm, there have been additions on the thread I just quoted since I last looked at it.

They are regarding higher heating value versus lower heating value, really issues for for engineers than the rest of us, but I prefer the more conservative figure of 77% for electrolysis, rather than the 90% or even 84% I used above.

So:
0.77*0.95*0.9 where heat use is possible = 66%
0.77*0.95*0.465 where it is not = 34%

Allow an additional around 3% for pipeline losses.

That is still perfectly workable.

@SJC:
Fair enough.
I simply beat a hasty retreat when the engineering gets abstruse and above my pay grade.