As a caveat, flow through batteries (liquid, non-atmosphere dependent "fuel" cells) do have some interesting advantages, in that the bulk of their mass is a flowing liquid, and thus their tank could be emptied/refilled quickly in a service-station like infrastructure, but there are some aspects of this that bear consideration.
1. Their peak power output is limited compared to conventional batteriesof the same total system mass, as only a small fraction of the electrolyte is active at any given time, necessitating a small rechargeable one or two stage (e.g. High peak power LiFePo or LiFePo plus ultra cap) additional battery to provide for peaking power (accelerating) and regenerative braking, which increases system mass
2. The materials used for the flowing electrolyte must have toxicity/volatility/danger less than or equal to conventional fuels otherwise the protections will further increase system mass
3. The need to both fill and drain when refueling requires more complex infrastructure, and the need to measure the drained fluid to determine how much to charge the customer (since the guild continuously flows, you deplete it as a whole, and then recharge to 100% capacity, regardless of actual amount "used"), increasing infrastructure cost
6. The infrastructure must add charging equipment for the electrolyte at each facility, increasing cost
7. The energy densities are still much less than combustion fuels
8. It still depends where the energy comes from--if its combustion on the other end, it's a net energy loser, as the round trip charge/discharge efficiency combinedwith generation/transmission efficiency makes it worse than just burning the fuel in a vehicle (this is why intracity buses, which have short routes, regular depot stops, and access to concentrated infrastructure (they always refuel at the depot) seem like ideal use cases for modern electrics, but use natural gas economically--it's more efficient than paying for natural gas generated electricity, and the capital costs of the infrastructure and per-bus equipment (batteries vs conventional engines) outweigh any benefits
Conventional fuel cells (liquid reformed hydrocarbon or hydrogen plus air) are a unique possibility, but still have major problems:
1. The storage density, and energy required to do so of hydrogen is low (density) and high (cost of compression/liquification)
2. While a fuel-cell/electric motor may be double the efficiency of a combustion engine, the efficiency cost of electrolyzers and power transmission make the overall system only marginally more efficient than combustion (provided the electricity comes from combustion plants)--and making hydrogen from natural gas is a net energy loser in this math. If the power comes from nuclear, then the round trip efficiency can be better, more on that later.
3. Methanol reforming fuel cells (which can use methanol as a fuel, eliminating the need for expensive and energy costly, low density hydrogen storage) are incapable of long life and are low power density devices, and have lower efficiencies, thus making them unsuitable for vehicle applications without highly sought after cell membrane technologies that are heavily invested in, but progress is elusive.
4. While it is possible to generate hydrogen with nuclear power, and use fuel cells to extract the highest possible round trip efficiency from the fuel, and the overall round trip efficiency may be higher
Fuel cell: 33% plant * 90% transmission * 75% electrolysis * 90% storage (10% energy lost to store) * 80% fuel-cell plus motor equals 16% total. Vs
My methanl strategy: 33% plant * 75% synthetic methanol process * 33% engine equals 9% total
So the fuel cell has nearly double the round trip efficiency, but requires not only all the vehicles be converted to fuel-cell electric, but all the service stations converted to hydrogen pumps and storage and large scale electrolyzers at enormous infrastructure cost vs no costly changes to any of the vehicles or infrastructure, except for refinery-like (large scale, but few in number) chemical plants at the large power plants--which already have the large land area due to exclusion zones.
With the reduced capital cost, it's far easier to "switch" to my strategy, and since methanol storage is far easier in vast quantities than hydrogen, plants can run at 100% all the time, and use excess energy to make the fuel (hell, even unreliable (wind) power could be used as the conversion process could be throttled rapidly to allow any amount of generation to be used), and large scale storage (just like gasoline and petroleum) allows for smooth (inelastic) supply rates at widely varying levels of demand and generation.
You can see why I like my idea--it gives consumers everything they like about normal vehicles (can fill up anywhere, long range, more than enough power), while minimizing infrastructure changes and costs, while resulting in a carbon-neutral fuel cycle--true, you use more uranium or thorium, but the fuel cost isn't a big driver for plants, especially if it allows for large base load plants to run at 100% throttle all the time when they are most efficient, and the electrically driven synthesis process is used as a load-leveler: plants could be sized for peak electrical only load, and the surplus capacity (about 50% on average average to peak loading) used to generate the transportation fuels.
