The biggest hope is moving away from heat engines and the inherent ineffiencies of the Carnot cycle.
What energy source do you envision?
Most electrical power is generated from a thermal power plant?
That is true.
The trouble in doing this are the costs involved in possible replacements. When we look at possible replacements, we realize that:
1. The internal combustion engine sucks...
2. But everything else sucks at least as hard, if not harder. So far.