Hydrogen: Energy Carrier or Energy Source?

There is no question in my mind that we’re heading for a hydrogen economy, and that that’s a very good thing. But as readers of this blog will have recognized, I’m a stickler for getting the words right. In the lofty chambers of policymakers who will only ever have a vague understanding of science and technology, ill-chosen words lead to ill-begotten policies. On the great catastrophe surface of public opinion, misleading words lead to a duped populace.

In order for anything to be an energy source, it has to be produced and delivered using less energy that it provides at the point of consumption. Otherwise it is an energy carrier.

General Motors has provided a set of lesson plans (grades five through eight) on “Hydrogen: Tomorrow’s Energy Source”. The point they want to make that “petroleum can no longer be the main source of energy in the United States”, but that does not entail that hydrogen is an energy source that can replace petroleum without needing any other energy sources to produce the hydrogen. So this usage is misleading at best.

Can we expect hydrogen to become an energy source that provides more energy to a fuel cell, catalytic heater or other device than it takes to produce it? Or will hydrogen only ever be an energy carrier that must be produced as efficiently as can be managed using a renewable, distributed energy source such as wind, photovoltaic solar, geothermal or hydro? Hydrogen can and often is produced by reforming natural gas, after all, and that is not where we want to be heading in a hydrogen economy.

So how much energy does it take to produce hydrogen?

If you use electricity to hydrolyze water and then convert the hydrogen back to electricity in a fuel cell, you’ll get less energy out than you put in (because each step in the process is less than 100% efficient) and hydrogen is just a carrier. This remains true when the hydrogen is converted into work by other means than a fuel cell.

So hydrogen production by reformation of methane is just another way of processing a non-renewable fossil fuel, and electrolytic hydrogen is just a carrier. Is there no way to break out of this apparent thermodynamic trap and produce hydrogen with less energy input than we can take out at the point of consumption?

There is.

Living organisms produce more than they take in as a matter of course, by using part of their energy to self-organize, thus reducing entropy. This is possible in the galactic short-run because our planet is an open system, exchanging energy and entropy with the sun and surrounding space.

So it should come as no surprise that it is living organisms that can help us beat the thermodynamic trap and produce hydrogen with less energy than we take out. Specifically, I’m talking about the production of biohydrogen in an algae reactor.

It was discovered less than 10 years ago that if you deprive algae of sulfur, their process of photosynthesis starts producing hydrogen instead of oxygen. Just last year, it was discovered that they’ll also switch from oxygen to hydrogen if you add copper to their nutrient mix.

Algae reactors (and the algae farms we’ll see in the future) do require some energy to operate, but nothing like the input required for electrolytic hydrogen and certainly requiring no input of fossil fuels.

Photosynthetic hydrogen? Now that’s what I call solar energy!

Further Reading


One Response to “Hydrogen: Energy Carrier or Energy Source?”

  1. […] See the original post: Hydrogen: Energy Carrier or Energy Source? […]

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