Hybrid TCUs?

Is there any interest at all in hybrid TCUs/reefers these days?

What kind of fuel savings would those of you pulling them hope to see? 30%? 45%?

What kind of ROI timeframe would you be willing to deal with for either the difference in cost of a factory unit or a bolt on sysytem and computer upgrade?

I understand there is zero tolerance for mechanical failure leading to load spoilage, so the solar and diesel systems would both power the cooling system as standalone units in case of the failure of the complimentary system, increasing reliability.

I've done some work with thin film photovoltaic cells as well as industrial motors, so I can't see the whole package exceeding 700lbs, the bulk of that being the battery pack/charge controller which could easily be installed on the belly of the trailer to keep the center of gravity low.

If there is enough interest I'm considering buying a wrecked late model reefer and starting field tests at 1k hour intervals. Just seeing what the O/Os have to say about it.