My Turn: There is no ‘free hydrogen’

For the Monitor
Published: 1/13/2020 6:01:12 AM
Modified: 1/13/2020 6:00:27 AM

The Jan. 4 Monitor article “N.H. a good fit for new hydrogen plant tech” was nice to read in that it shows our great state is working hard to blend new with old and advance us to a new energy future.

While it is the most abundant element in the universe, on our planet hydrogen is tightly bound with other elements such as oxygen and carbon, and it takes a lot of energy to separate it from them. Hydrogen is thus not an energy source but rather means of storing energy.

We can get “free” hydrogen only from chemical reactions powered by energy from an external source. For example, using electricity to split water into hydrogen and oxygen (“electrolysis”) or heat to dissociate a mixture of methane and steam to produce hydrogen and carbon monoxide (“steam reforming”). Once you produce clean hydrogen, you have to compress and store it until it is needed. To generate electricity from the stored hydrogen, you can use fuel cells that combine it with oxygen (air) to produce electrons directly, or you can burn it in an engine and drive a generator to produce electrons.

What does the efficiency – the ratio between the energy used (e.g. electricity in our homes) and the energy consumed (wind, sunlight, chemical energy in fossil fuels) – look like for a power-to-hydrogen-to-power system: electrolyzer (to split water) efficiency is about 70%; hydrogen compressor efficiency about 89%; Polymer Electrolyte Membrane Fuel Cell efficiency about 47%. Thus the overall net system efficiency is about 29%.

If instead of a fuel cell a gas turbine is used to burn the hydrogen, its efficiency might be 35% to yield overall efficiency of about 22%.

So why would any company buy more electricity than it can sell? So they can buy low (e.g., at night), store it and then sell high (e.g., at dinnertime). If all our power came from clean sources, like wind or solar, this might be okay, but there is still a lot of power from coal or gas-fired power plants where it is cheaper to keep the plant running and sell the electricity at very low cost than to start and stop the plant according to demand.

However, this dumps a lot more CO2 into the atmosphere. And yes, in addition to all this talk about energy efficiency is fine, but people need good jobs and good health.

I am sure folks in Groveton and the investors have thought carefully about these issues, but if they require government subsidies to be profitable we all need to study renewable energy options carefully before giving our blessing to ideas that may sound too good to be true.

The greatest hope we can have for our future is for us all to research, read and think through things carefully, and then decide what is best for us, our communities, our country and our planet.

(Alexander Slocum lives in Bow.)




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