Also: stored-energy locomotion. Fully-powered walking is expensive.
1. Run silently or near silently. They're generating electricity via redox reactions, not combusting.
2. Have effectively no moving parts. Again, no noise or vibration.
3. Product electricity directly. For powering electronics, this means no secondary generation required.
4. Utilise extremely expensive catalysts. The reason you don't see fuel-cell automobiles (excluding very small numbers of test vehicles) is that the engines cost, literally, on the order of $1 million, as opposed to a few hundred for a typical ICE. This price premium has proven difficult to overcome.
5. Operate better delivering fairly steady-state power, from what I understand. A tremendous benefit of ICEs is that they can scale output in a second or few seconds, with very little throttle lag. Yes, straight-up electric motors are even better at this, but straight-up batteries tend to not store much power.
A fuel cell is essentially a battery whose electrolytes you fill rather than recharge or replace. This offers the advantages of fuel-based systems (high energy capacity) and batteries (direct electrical output). Unfortunately, it introduces the disadvantages of fuel cells (cost, power delivery profile).
I was thinking of hydrocarbon fuel cells, to be honest.
But if you're trading an abundant, variable energy source (say, peak solar which is otherwise wasted) for a scarce but valuable and useful store, that's a net win.
Note that whether you're formulating H2 or hydrocarbons, the energy cost is about the same (the carbon sequestration from seawater mentioned above is low energy cost), though it requires fairly substantial capital investments.
One other alternative is the Li-Ion batteries that we already have.
In any case, I am just reacting to the hype we sometimes see about an `H2 energy future', as if hydrogen was a source of energy.
PS: As to fuel vs. energy costs. The vast majority of gas's costs has nothing to do with direct energy costs. Oil is already vastly more expensive than competing fuels so even a 2>1 energy loss could end up less expensive than current production methods.
Again: an ICE engine for a car is a few hundred dollars. A fuel cell for a car is about a million dollars. That's significant even to a physicist.
I root for electric propulsion and solar power (go Elon!). But I support all efforts in this fight.
I will read the references you gave. Edit: "Burning Buried Sunshine" is a great read! 86 m3 of ancient biomass for 1 gallon of fuel..
Carbon sequestration from seawater is a rather different animal from most CCS discussions. Though, in the world of strange bedfellows, it turns out that various coal industry organisations follow this information pretty closely and have some of the more complete compilations of research. Just ... beware biases.
Compared to external combustion engines (steam engines), ICEs have much quicker start-up and response times. Steam engines require building up a head of steam, and actually exhaust the working fluid (water) over time, which is why steam railroads had water towers every so often.
ICEs have been improved over more than 130 years, and scale from a few CCs of displacement to many cubic meters -- the smallest ICEs could fit in the palm of your hand, you could stand in the largest and not reach the sides or top of the cylinder.
Liquid hydrocarbon fuels are exceptionally energy dense by both weight and volume. This makes certain classes of use very difficult to substitute for: commercial passenger and freight aircraft, overland truck transport, and powered marine shipping really have few tractable alternatives. Aircraft would all but disappear without liquid hydrocarbons (gasoline for piston engines, kerosene for gas turbines), trucks would probably be replaced with electrified rail, and shipping would return to wind power. Optimists might suggest nuclear marine powerplants, but I find that unlikely; ships are lost at far higher rates than is commonly realised: about 200 every decade, and existing trials of both military and nonmilitary nuclear marine power have proven it expensive and nonviable for all but the most demanding instances -- aircraft carriers and submarines.
They're also quite stable in storage (proved over hundreds of millions of years), relatively safe to handle (no respiration or exceptional contact protection required), and their combustion products are mostly benign: CO2 (I'll get to this) and H20 with scant quantities of carbon monoxide, sulfer and nitrogen oxides, and other contaminants or partial combustion products, all of which can be greatly mitigated with combustion and exhaust controls and treatment.
The CO2 exhausted isn't a problem in itself but for the, um, slight problem that in the past 200 or so years humans have returned to the biosphere carbon sequestered over several hundreds of millions of years. Which turns out to be a rather considerable problem.
But it's only a problem where what you're burning are fossil fuels. There exist several options, though all much more expensive and/or constrained than present fossil fuels, for creating synthetic hydrocarbon-based liquid fuels. These also have challenges. Biofuels are intractable at scale given natural limits on plant production: what's called "HANNP" -- the human appropriation of net primary production -- or the photosynthetic ceiling. There's only so much plant growth which occurs and humans already consume much of it (40%, biofuel replacement of fossil fuels would consume another 20%, see Jeffrey S. Duke's "Burning Buried Sunshine" (2003), PDF available online, for more on this.
Another prospect: sequestering carbon from the biosphere, and combining it with hydrogen, electrolised from water. The US Navy and national energy labs (especially Brookhaven), as well as M.I.T., have researched this for the past 50 years. It's proven expensive and hasn't been scaled past very low production (a few litres), but does work. It raises costs of fuel from one unit of input energy per 20-40 units made available to two units per one provided -- that's a 40-80x increase in the real cost of fuel.
Not cheap, but it might still be our best option.