On a weight basis, H2 is the most energy-rich fuel known and burns to give almost pure water. Thus, electricalenergy from the battery has been converted into chemical energy contained in the H2. These devices anticipate the imminent development of a renewable energy economy based on electricity and H2 fuel as complementary energy vectors. The reason for producing H2 from electricity, which of course consumes energy, is to create a form of energy storage useful for indefinite or long time-scales. As necessary storage time increases, the superior economy of chemical storage more than compensates for this energy expenditure.
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