Engines that use some external source of heat, and heat water to steam, to drive either a turbine or a closed-cycle piston arrangement to provide rotary output, were also tried early in the development of self-propelled vehicles.
If there is no reclamation of the exhaust steam, through a condensing system that recycles the spent steam as hot water, then the system is just too wasteful of the water, and is subject to having an adequate resupply of water, which for steam purposes, has to be free of virtually all minerals and most other contaminants. But back in the 1920’s a fellow Abner Doble, made just such a steam-powered automobile. It was vastly superior in almost every way to the leading steam powered car of that time, the Stanley Steamer, but the Stanley brothers thought they knew everything there was to know about steam automobiles. Doble could not get adequate financing for his projects, and he fell into the mistake of building virtually every example as a custom design, never settling on one design that could be mass produced. But as innovative engineering goes, they were marvels. Jay Leno rebuilt one using some more modern materials and technological advances, and it performed most magnificently. It is QUIET, with astonishing acceleration for such a heavy vehicle, and able to cruise with modern day traffic.
What is needed to provide an adequate heat source, may come from propane, or compressed natural gas, or even have a very small version of a thorium-fueled molten salt nuclear reactor, which can be scaled down to fit aboard an automotive platform. Minimal to no emissions, relative rapid start-up, and economical of fuel resources.
But of course the star-gazing engineers will continue to putz around with batteries and battery charging systems, and smaller, lighter “more efficient” battery arrays, of which, most designs are either impractical, or have some really sensitive issues concerning reliability.