Steve Lapp, a Canadian engineer created a prototype Prius fitted with a number of roof-mounted photovoltaic cells, an extra battery to supplement the car's OEM batteries and a nice glass of brandy (sorry, we added that last bit for our own edification). The 2001 Prius's hybrid-drive system underwent extensive re-engineering under Lapp s guidance, and the finished product resulted in a 10% fuel efficiency improvement initially, from 52 mpg to 59 mpg.
The solar subsystem, which outputs 300 VDC (volts, direct current), is attached to the switched side of the original Prius battery, so the system can only recharge the Prius's NiMH battery while the ignition is on — meaning the solar panels are not an alternative to a "plug-in" system. Still, we're all for as many Prius hacks as guys like Lapp are willing to attempt, and he says this is a rough prototype to explore what's possible.
Solar-Powered Toyota Prius Project [Treehugger]
Hot Rod Hybrids? [internal]