"He foresees a greater variety of hybridizations combining oil, natural gas, electric batteries, hydrogen fuel cells and maybe some as yet undeveloped alternati

"He foresees a greater variety of hybridizations combining oil, natural gas, electric batteries, hydrogen fuel cells and maybe some as yet undeveloped alternative fuel options." Surely engines that combine multiple energy sources are more expensive and less efficient than engines that use a single source? My understanding of the current hybrids is that they exist because one energy source (petrol) can be quickly and easily replaced, whereas the other (electric battery) takes time to replace and isn't as easily available. Best I can tell, that makes hybrids a temporary solution to the lack of widely available better energy sources. Once most cars have settled on a non-petrol energy source, I can't see why hybrids would continue to exist.