Two moderate size nuclear plants would take 12 to 16 years to build?

H2 is an excellent energy storage media.

Electrolysers can produce clean H2 with exccess/surplus REs. FCs can produce clean electricity in mobile units (cars-trucks-locomotives-ships etc) and at fixed plants for the power grids.

There are no practical limits to how much clean H2 can be produced, stored and used to supply clean energy for transportation, industries, agriculture and many other uses to progressively replace all bio and fossil polluting fuels to reduce pollution and GHG.

I expect there won't be much hydrogen generation from renewables until renewable generation exceeds demand. Otherwise you are choosing to supply either the grid or the electolyzer with fossil generated electricity. It might make more sense to shut the fossil generator down and pay them for the electricity they might have generate.

Electricity demand and supply are not always or seldom matched.

Electrolysers could be used outside peak demand periods, i.e. about 70% to 80% of the time and by intermittent (Solar-Wind) energy sources.

Some of the clean H2 produced could be used to feed large FCs and produce clean electriity to cover some of the demand during peak periods and remove more old CPPs to reduce pollution and GHG.

The bulk of the clean H2 produced, with clean excess-surplus e-energy, could be stored and distributed for use by FCEVs of all sizes.

Hydrogen is the most common element in the universe. It is free and present in great/huge quantities on Earth (in water) and can be cleanly extracted with free excess Solar and Wind e-energy.

Secondly, clean H2 can be stored for future uses, in fixed FCs to produce clean electricity to handle peak demands and in FCEVs of all sizes to reduce pollution and GHGs.

Clean H2 is much cheaper to extract-store and use than Nuclear-Coal-NG power plants. Mass produced electrolyzers + compressors can fit into standard transportable containers and install in many thousand places very quickly.

Solar energy is also free and plentiful but batteries are still limited and too costly for extended range heavy vehicles.

HarveyD

I used the example of 2 nuclear power units to indicate the amount of power involved. Use 5 large gas turbine units if you prefer.

Anyway, this whole concept does not make much sense to me. In the United States, the amount of renewable energy is about 8.4 % not counting hydro which can be controlled or stored. So the best thing is to just put the power in the grid and burn less coal or gas.

Using the best numbers that I could find, the efficiency of an electrolizer is from 43 to 67 %, the efficiency of a fuel cell is about 40 to 60 % and it takes about 10 % of the available energy to compress the hydrogen. So using the high range, you only get back 36 % of what you put in (0.67 x 0.60 x 0.90 = 0.36). Using the middle of the range, you only get back 25 %.

So while, hydrogen is the most common element, getting it out of water is really expensive. The best way is probably high temperature electrolysis using nuclear power if we only had a surplus of nuclear power.

I wouldn't rule out the possibility that at some point in the future renewable generation capacity is so inexpensive that generators will overbuild rather that include storage. In that event there will be surplus renewable energy that can be used to produce hydrogen and the the hydrogen would be useful as a long-term backup.

SOEC are 70% SOFC with output turbo are 70%, allowing 5% for compression that would make 45% round trip. Sell the oxygen to offset costs.

With solar panels efficiency approaching 40% to 50% and direct drive slow turning wind turbines, on very high towers, approaching 10 MW, those two sources of REs will soon produce enormous amount of clean electricity.

Being intermittent sources, matching supply and demand, will require major adjustments in most grids. Two ways currenly available are:

1) more efficient, very expensive limited batteries pathway.

2) more affordable but less efficent, almost unlimited H2 avenue.

In practice, both ways are possible and will probably be used together with extended range BEVs, FCEVs and e-planes.

CPPs and then NGPPs and ICEVs will progressively be phased out

Batteries are a lot more expensive but they also make a lot more financial sense as sort term grid storage. They are financially viable now. In Q1 2017 California alone installed over 200 megawatt hours of battery grid storage. California basically is the US market at this point but that represents a 50 fold increase YOY. GTM projects that this market will grow 10 fold between now and 2022. With battery prices in $/kWh expected to drop in half by 2021 and battery life expected to double in that time (effectively a 4 fold increase in ROI) I would think that 10 X increase would be conservative. The limiting factor is likely to be production capacity rather than demand.

I would expect that in the future we will see intelligence added to the grid and what we'll see is discretionary consumption incented to shift to match production. On a larger scale intermittent production is more predictable.

While FCs may prove to be financially viable for some electricity production needs I doubt that H2 will be the choice. I would expect that priority would be given to carbon positive processes which use electricity to produce fuel suitable for seasonal storage.

I see it as AND not OR when it comes to EV/FCV.