Whether you&#x27;re looking at hydrogen or hydrocarbons, you need some chemical energy carrier mechanism.  In the long run, either will have to be formulated, and yes, there&#x27;s about a 50% efficiency hit straight off the top in elecrolysing hydrogen.<p>But if you&#x27;re trading an abundant, variable energy source (say, peak solar which is otherwise wasted) for a scarce but valuable and useful <i>store</i>, that&#x27;s a net win.<p>Note that whether you&#x27;re formulating H2 or hydrocarbons, the energy cost is about the same (the carbon sequestration from seawater mentioned above is low energy cost), though it requires fairly substantial capital investments.