This is a conversation that I have a lot. Usually with smart, curious people that are interested in our eternal “energy dilemma”. There are A LOT of fundamental misconceptions in our public energy debate, most of them perpetuated by interested parties.
One glaring example is the promise of the so-called hydrogen economy. Let’s cut to the chase. One very easy and convenient way of obtaining usable energy is to just burn stuff. It can be oil, coal, wood, natural gas, hydrogen. A lot of stuff burns nicely. You can convert that energy into mechanical movement and use it directly, or transform that movement into electricity.
We need energy in many different places and for different purposes. In some cases, it’s more convenient to transport the stuff-to-burn and in other cases it’s better to transport the electricity.
This duality is a source of confusion: yes, electricity and chemical fuels are form of transporting energy. BUT chemical (fossil) fuels are also a source of energy. To transport electricity we first need to turn some other form of energy into electricity. To transport oil we just need to pump it from the ground.
So, what about hydrogen again? It’s an abundant element, it burns nicely (producing water and heat as outputs). But there’s a (fatal) catch. The form of hydrogen we need is molecular hydrogen (H2) and there’s NONE of it floating around. Hydrogen is easily captured by other elements and most of what we have is in water, hydrocarbons, etc.
Wait a second, isn’t that actually a good thing? We take water, take the hydrogen out of it, use it for our energy needs (burning it) and we get water again! It’s a closed, endless process! Alas, no. For that sad negative we have to thank the 2nd law of thermodynamics, the greatest killjoy in all of science. Really, if there is a God somewhere*, I will never forgive him for imposing the 2nd law of thermodynamics on us. What this law means, in lay terms, is that you can not get back to the starting point without losing some energy in the process. So the hydrogen scheme looks like this, more or less:
You have a solar panel and produce electricity with it. Efficiency (I’ll be generous): 20% (You could use some other more efficient energy than solar, but I want to be hipster-eco-conscious here)
You take the electricity and use it to breakdown water and produce Hydrogen. Efficiency: 40%
Now you can do two things:
a) Store it in tanks (which is VERY difficult) so that you can use it wherever you want (like in a car, ship, etc.). You will burn it in your car. Efficiency: 40%.
b) You transport it (with pipes) so that it can be used in other places by burning it in, let’s say, a modern turbine or fuel cell. Efficiency: 55%.
Total process efficiency with either alternative is depressingly low (4%). And in the end, we’re using the hydrogen ONLY as a way of transporting energy that we already had converted into electricity. What is the freaking point of that!?
Transporting electricity is not a very efficient process (line loses are about 20%) but transporting hydrogen is HELL. Hydrogen molecules are very small and tend to diffuse into almost all metal alloys. So you lay a crazy expensive pipe network for transporting H2 and you have to scrap the whole infrastructure in less than a decade because all the pipes have become brittle from the hydrogen diffusion. You DO NOT want brittle pipes transporting an extremely flammable gas.
I understand the search: we want to be able to use primary energy sources other than fossil fuels but we lack the convenience that fossil fuels provide for storing energy. Fossil fuels are easy to move, have very high energy densities and burn nicely.
We have many good ideas for replacing these fuels with other sources (like the Sun, the wind, nukes, geothermal, tides, whatever…) but we don’t have many good ones for the role of fossil fuels as easily manipulated energy storage.
Hydrogen could conceivably be one such storage&transport medium. But it is NOT one today. There are huge engineering problems to be solved. And it will always be a process that requires huge over-capacity in generation because producing H2 is just stupidly costly (in energy terms).
Other alternative is using hydrocarbons but only as a storage medium, not as a primary source: bio-fuels. With bio-fuels, the theory goes, we have a renewable source (the sun will make the grass/soy/corn/sugar cane grow again) and we’re using the methanol/ethanol only as an energy storage medium. OF COURSE this produces CO2 (it doesn’t matter much if you simply burn the fuels or if you feed them to a fancy fuel cell, you will get CO2 as an output), but supposedly the same CO2 will be captured by the plants when they grow up again.
One last point about the misinformation: Regarding fuel cells, if they use anything different than pure H2, like methanol, ethanol, natural gas, gasoline, etc. they DO produce CO2. It’s just a little less than burning because they are (usually) more efficient, but they’re based in an oxidation of the fuel and there’s no way to do that without producing CO2. In the case of natural gas, modern turbines can be as efficient as any fuel cell on the market. They’re just less fashionable (and cheaper).
* There isn’t.
