Exactly how hard is it to electrolyze water into H and O2? Because I was thinking, wouldn’t it be far easier if all people had to do was fill their cars up with water and then plug it in to a power source to have some sort of electrolysis machine (either external or internal) convert it into O2 and H needed for portability?
Imagine, just fill your car up with water, and plug it in, overnight, your H and O2 tanks are full. Not only that, you could still have the option of filling up with Hydrogen and Oxygen externally as well.
Is there some real reason why this isn’t the best way to go about it? You get the benefits of grid-powered cars like a battery, but also the convenience to fill up on the road if necessary.
From what I understand the potential energy of a hydrogen oxygen reaction yields far more energy per weight than a battery alone can.
This is theoretically possible, but it’s impractical for several reasons. The big one is, it requires two tanks - a water tank and a H2 tank, which would reduce the amount of fuel storage by quite a bit. It would also require a compressor, and all of the electrolysis gear, that would be better of placed a a central location, rather than being lugged around with you.
First of all, carrying the oxygen is a complete waste of energy. The atmosphere is full of the stuff. If you carry the O2, you’re carrying about 32 times more fuel weight than you need to; it makes much more sense to discard the oxygen and just carry the hydrogen. Secondly, while you could conceivably do this, there is no net energy gain here. The energy you can potentially extract from burning hydrogen to produce water is just the same as the energy you used to electrolyze it in the first place, minus any inefficiencies (and there are always some) in the system. There are plenty of other problems with this sort of energy source, as no doubt others will be along to explain.
Why not have a home-based electrolysis machine that plugs into your water source and power source and pumps hydrogen into your car only? Then you’d have a great way to get the hyrdogen economy going without having to build the infrastructure. That’s what I’m trying to get at.
I am not concerned with the inefficiencies of electrolyzing and then combustion. But how does it compare to battery power? Say if you took two cars, one with batteries, and the other with the home electrolysis. Just how inefficient would it be?
I realize that hydrogen takes energy to create, I’m just thinking of this and comparing it with batteries. The problem with batteries is that they are heavy and you can’t go very far. Hydrogen seems to mitigate this to some degree (it is essentially just another type of battery), but we don’t have the infrastructure to produce it yet. Well, with my idea, you get the hydrogen with none of the infrastructure costs. Plus you could refill it when the infrastructure is around.
But I guess the crux of the matter is, is there any benefit to cracking water into H and O2 in a big centralized location and then shipping it around (like with gasoline). And if there is, is it enough to preclude home electrolysis?
ETA: Didn’t realize that Hydrogen Fuel Cell vehicles didn’t need to carry O2
Hydrogen is massively less energy dense than petrol. So now you have to spend yet more energy compressing it … and you have to carry round a heavy tank of highly compressed flammable gas in your car, reducing space, fuel efficiency and safety in it. All these may be able to be overcome but it’s not as easy as it looks.
Electrolysis is a very inefficient process to begin with, so there is a big energy loss there. As was mentioned, hydrogen has very little energy by volume so you need a pretty high tech system just to store it in any appreciable quantities. Just compressing it wont be enough to get you far.
Honda’s Home Energy Station is essentially designed to do exactly what the OP suggests except it produces hydrogen by refoming natural gas. Electrolysis just isn’t a good way to produce hydrogen.
Slight hijack, but wasn’t there a system for lysing water into H and O by running it through transparent tubes at the focus of big solar collecting mirrors, with some sort of a metal catalyst either built into the tubes or suspended in the water? Maybe 10 or 15 years ago, in the news?