I think “e-fuels” is the keyword you want for this subject.
Efficiency isn’t great. To start with, burning fuels already has bad efficiency. We usually don’t care because we’re exploiting millions of years of energy storage in nature. When we’re asked to handle the full cycle, suddenly the costs are less appealing. We try to find more efficient cycles, such as fuel cells.
Other than efficiency, there are also trace byproducts like CO, CH4, NO, and NO2. So e-fuels aren’t fully non-toxic or neutral for global warming. But they’re an improvement.
Aside: If you look up “CO2 batteries”, what you’ll find is air compression based energy storage. This is actually surprisingly efficient, and CO2 has some nice properties in this role (related to heat capacity). But the capital and maintenance costs are not (yet?) competitive with various chemical batteries.
Latest Answers