With a few home-job, warranty-voiding hybrid-hacks out there already, some say one of the next frontiers for hybrid electric vehicles could be the coupling of grid-connected recharging. But how about going off-grid for that electric recharging?An article at Green Car Congress details how a Canadian engineer named Steve Lapp has created his own version of a prototype Photovoltaic Prius. The car is a 2001 Prius modified with roof-top solar panels and an additional battery system to supplement the charge in the original equipment NiMH batteries. The car is still a rough prototype — a demonstration of concept — but even with the limitations of the systems, he says he has achieved an initial 10 percent fuel efficiency improvement from 4.5 l/100km (52 mpg US) to 4.0 l/100km (59 mpg US). For the full article at Green Car Congress, see the following link.