[andrew*debbie]

25kW motor. The generator output will be slightly less.

I've posted this before somewhere. -- There are some rotary engine generators out there that are very compact for the power output. Not sure if it is possible to buy one.

 

[andrew*debbie]

Google Rotary engine genset -- There a few but maybe none for sale.

If you are willing to DIY, there are some very compact rotary motors available.

For example the 26kW Wolfe XF50 weighs only 18.7kg.

http://www.woelfle-engineering.com/Produkte/produkte_XFXH40rotaryengines_en.html

 

[andrew*debbie]

Modifying the car also voids many insurance polices.

 

[andrew*debbie]

Cubewano has built a one off:

http://cubewano.com/products/range-extenders/


Their main products are rotary engines and compact APUs for UAVs. The range extender probably is a repackaged APU. I doubt they sell to the public, and if they do the prices won't be low.