I showed you guys the portable turbines they are coming out with. Here is a micro turbine on a chip for even smaller uses. They will be real cheap because they are made from sand. We have plenty of that.
It looks to me the future will have pop in power supplies just like the battery packs we use now on power tools. They will be batteries with a turbine and fuel supply in it. So you would open a cap on each one and add some fuel to it and it would power up to keep the battery charged. A car could have a bank of them like they do with lithium batteries now.
The concept is simple. A large engine in a car rarely needs all it's power. When sitting at a light you waste fuel. When on a highway you waste fuel because the engine is idling along but having to rotate 8 pistons with all that friction. The only time you need all the power is on take off.
The idea is to use the battery and electic motor to get you going. Then when your on the highway the turbine recharges the juice you used to get going in each battery. It may take a while to recharge it because the turbines will be tiny. But it would be enough to power the car during highway travel and a little more to recharge the juice you used to get up to highway speed.
The capacitor will be a key to make this happen because it holds a huge charge for the first few feet to get a car rolling. Then the battery kicks in drawing more power until your at highway speed. The turbine will be helping power it all along and when you hit highway speed will be able to replace all the power you used. The size can be small because it will run all the time charging a little bit at a time.
Capstone should be designing 2,000k units that can be dropped into a car with a battery pack and electric motor.