WHAT ABOUT green hydrogen, made from renewable energy sources, as a source of fuel?
The most convenient way to produce green hydrogen is by electrolysis of water. It can be done anywhere there is water and electricity. However, this consumes a lot more energy than steam reforming methane into hydrogen.
2 H2O → 2 H2 + O2 (lots of electrical energy required)
Thus, it is practical to produce green hydrogen only if there is a readily available cheap source of electricity.
Although it’s uneconomical as an original source of energy, hydrogen from renewable energy sources may have a use as a carrier of energy. Electricity is a more common energy carrier, but human societies consume it at varied rates throughout a 24-hour period. For example, if more air conditioners are used during the hot daytime, then obviously more electricity is used during daytime than in nighttime. Note however that many geothermal and hydroelectric, and even nuclear plants produce electricity at a more or less uniform rate throughout the day and night, as explained above. What to do with the extra electricity during times when there is extra electricity because of low consumption rates? One can transform it into the chemical energy of batteries.
Or one can transform it into the chemical energy of hydrogen, by electrolyzing water. Hydrogen can be stored. During times when electricity is lacking, the stored H2 can be converted into electricity in fuel cells. Hydrogen can also be transported by pipelines to stations that can sell it to hydrogen vehicles.
In countries with an abundance of renewable energy sources, namely geothermal and hydroelectric, this can be economically done. Here is an ideal situation:
Excess electricity from geothermal power plants electrolyzes H2O into hydrogen and oxygen. Unused hydrogen is stored and used gradually. Most of this hydrogen eventually gets fed into fuel cells during times of increased electricity demand. There it is electrochemically reacted to atmospheric oxygen and converted back into water and electricity. This ensures a constant electric supply to the power grids. The rest of the hydrogen is pumped into pipelines that go into gas stations, dwellings, and industries, for more local electric production via fuel cells. Some of it is directly combusted in hydrogen vehicles and industries that need fuel. A significant amount of the hydrogen also goes into various factories, where it is used to make hydrocarbons, plastics, hydrochloric acid, ammonia and fertilizers, other chemicals, and as a reducing agent for oxides, and so on. As for the oxygen, it can be routed into other pipelines, and into chemical factories, welding works, hospitals and clinics, and just all sorts of industries that need oxygen.
Thus, green hydrogen may be used as a form of energy storage, and energy carrier, under appropriate conditions.
How about natural hydrogen (also known as white hydrogen or gold hydrogen), generated by natural process, can we use it as an economical energy source?
If there is an appropriate minable concentration of it, we certainly can.
White hydrogen is continuously formed in the ground by various processes such as serpentinization, reduction of water in reducing environments, decomposition of hydroxyl ions in certain minerals, water radiolysis, fermentation and nitrogen fixation by various organisms in the biosphere.
The catch is that concentrations of underground hydrogen that can be commercially exploited is rare. There is a report of a locality in Mali where white hydrogen is emitted out of the ground, and is concentrated enough to be used as fuel by the local community. But unfortunately, this seems to be the exception rather than the rule. Unless in the future, large concentrations of hydrogen deposits are found. (Send comments and suggestions to mabuhibisaya2017@gmail.com)/PN
