Comment by jgable

Wrightspeed did this a while (10 years?) ago. It looks like they have since pivoted to fully electric powertrains for buses, but when they first started they were doing range-extending hybrid powertrains for heavy trucks. I found an article the describes the system at the time:

  https://www.e-hike.net/tr/content/wrightspeed-unveils-new-turbine-range-extender-medium-and-heavy-duty-electric-powertrains-30

With a range-extender hybrid system, you can keep the turbine closer to its peak-efficiency operating point, since it only has to handle steady-state load while the battery takes up the spikes. Not sure how it would do up a long grade, but I imagine they designed for that.