Any dirty, carbon-emitting IC engine can be easily adapted to burn Hydrogen, which is "clean"-- it burns with water H2O-- as its byproduct. The "problem" with hydrogen as a fuel is that separating it from something (water, for example) always involved energy in some "dirty" form.
Now comes the idea of "storing" wind and solar excess energy (when the wind is blowing or the sun is shining) by using that energy to split water into oxygen and hydrogen. Of course, hydrogen is clean-burning, when the energy is later needed. One could even adapt our existing (natural and LP) gas-handling technologies (pipelines and tank trucks, etc) to handle H=hydrogen, to create the "time and place utilities" needed for things like automobiles or generating electricity in situ for small electric loads.
H=hydrogen handling is a bit "harder" -- more volatile and needing tighter seals, etc. but still absolutely do-able in a technical sense. This technology (splitting water as an energy storing technique) competes with electric batteries and pumped hydro, et al. I am unsure of the "competitive edge or deficit" it may have against other techniques at scale... (I will get and add "engineering numbers" here if I can) but in any case the "friction loss" of splitting water and burning hydrogen back to water must be competitive or better than batteries, and certainly at least as clean.
<quote from https://www.everycrsreport.com/reports/R42455.html>
...Conceptually, hydrogen is a simple storage technology, produced by splitting water using electricity (among other options), storing hydrogen on board the vehicle, and then converting it to electricity to drive an electric motor via a fuel cell. (Internal combustion engines could also be used, but the low efficiency of that process is less attractive.) The challenges of a hydrogen-based transportation system include the development of an entirely new fueling infrastructure including hydrogen delivery systems and filling stations, with needed safety standards and protocols. The low volumetric energy density of hydrogen makes storage challenging without extremely high-pressure tanks, or advanced chemical storage still in the early research phase. Finally, fuel cells for vehicles remain expensive, with limited lifetimes. There have been demonstration fuel cell vehicle programs by several major auto manufacturers, with announced plans for commercial deployment as soon as 2015. However, substantial research efforts will be needed to reduce costs and improve performance for many of the technologies needed for large-scale hydrogen based transportation. There are other electricity-to-fuel pathways under consideration, but with limited research and development efforts in the United States. They face similar challenges of requiring new fuel infrastructure and currently face much higher costs than fossil fuel alternatives. </quote>