Originally posted by Megalodon
Your kidding right? I can make hydrogen with 2 copper rods and a 9V bat and a cup of water.
Exactly. That's the point. You have to expend energy to MAKE hydrogen. So energy has to be bottled up *somewhere*, sent to you, where you once again convert it from it's original form to yet another form.
That is inefficient. It's also why solar cells don't "make" electricity quite yet - it takes so much energy to make a solar cell to begin with, that it takes one heck of a long time to get as much energy back as it took to make the thing in the first place.
What that means is in effect, hydrogen and solar cells are no better than another form of battery - they take energy actually produced in one place, and let you expend it elsewhere. That's great if you're located somewhere that makes it very difficult to transport original-source electricity (in space or so far out of town that they won't run power lines to your shack, or in an area experiencing energy utilization that exceeds distribution capacity), but it's not so efficient for other things like driving a car around town. That's why there is such a great economic case to be made for hybrid gas-electric cars - they still run on original-source energy (petrochemicals) but they use batteries to use that source more efficiently.
It's also why pure plug-in electric cars aren't such a good idea yet. Making efficient batteries and lugging them around still uses so much energy that it isn't practical or more efficient than other hybrid designs for anything except very short-haul conditions. Making and then hauling around enough batteries to go very far is just not efficient enough. Plug-in cars are great for golf carts and utility use anywhere that is near enough to a socket so you don't need tons of batteries (such as electric tow vehicles at airports and factory vehicles) but for anything other than that, battery technology hasn't gone forward enough to make it more efficient overall than other concepts.
Of course, I am 100% in favor of forwarding multiple lines of research and development that can change the equation to make it so some of these other ways to grab, convert, store, transport, and use energy, but every one of those alternative energy "sources" must go through at least one full cycle, and any "source" that goes through two cycles is almost inherently doomed to be less efficient.
Capture the energy source from somewhere (mine coal, suck up oil, put up a wind turbine, make a river dam)
Convert the energy to something useful - Refine the oil, turn mechanical wind or water energy into electricity, etc.
Transport the energy - power lines, gas pipelines and fuel trucks, or shipping solar cells somewhere
Store the energy - You won't be using all that energy at once, so you must be able to store it cheaply and without degredation. Gas is relatively easy, alcohol (for example) sucks up water and hydrogen requires high pressure containment.
Use it efficiently - Burning stuff produces emissions and waste heat, electricity is fairly easy but certain items like consumer-grade motors suitable for vehicle use are still expensive.
You gotta go through the whole cycle and measure the cost and efficiency from start to finish. That is why hydrogen is such a bad idea right now - you gotta go through the capture - convert - transport - store cycle at least TWICE to get hydrogen to the user, since there is no such thing as a hydrogen well. You have to first capture-convert-transport-store-use some other energy source before you can even begin making hydrogen. That is not inherently efficient, even though the last step of using hydrogen is attractive even at the consumer level. But for it to get there, you gotta go through the whole cycle twice if not three times (gas to electricity to hydrogen). And that makes hydrogen a lot less useful.
