Canadian Prius cuts fuel consumption by .5L/100km (52 to 59 MPG) with a solar panel array connected to a charger that tops off the traction battery while it's in use. This proves that it's practical, even using conventional PV cells to augment power to a hybrid with solar energy. Additional improvements could be made with the ability to charge the battery while the car is off.

http://www.greencarcongress.com/2005...oweraugme.html

2001 Prius Photos       2005 Prius Photos
'97 Prius Simulation Prius inner workings

Great catch Schwa, and thanks for directing us to Green Car Congress. Couldn't help noticing though, the mention of 2 amps. This *must* be at the 12 volt level. A very small complaint; the fuel economy increase seems impressive and we may see a few more of these.

DAS

That's what I was thinking too, but then that doesn't make sense either because he's got WAY more solar power than just 2 amps of 12vdc (~24w) plus he's got additional batteries. His solar panels should be able to deliver 20-25 amps of 12v.

So what I think it refers to is the peak capacity of the charger on the 300v side because he's added a few 12v sealed lead-acid cells so that the panels can charge them while the car is off, then once it's on (the HV relay enabled) it will pass the charge from the 12v battery to the HV battery at the stated 2 amps for a short time, then charge at whatever rate the PV cells generate power at.

2001 Prius Photos       2005 Prius Photos
'97 Prius Simulation Prius inner workings

I am wondering how much addition drag there is on the highway. We have a older Prius which our teens drive and usually averages around 57 mpg. I wouldn't mind getting an increase but wonder if the gains would be offset by the weight and drag. Have fun, Rick

I guess it depends if you do a lot of highway driving or not. If you are on the high speed driving path anyhow there's not much of a 'boost' that solar panels could give you because not much power comes from the battery when on the highway. I think this setup would be more suitable for people doing low-medium speed and stop & go type driving.

The real problem is cost. Solar panels are not affordable, especially when you want 200-300 watts worth. It's an interesting experiment but not really practical from a cost-saving point of view, yet.

2001 Prius Photos       2005 Prius Photos
'97 Prius Simulation Prius inner workings

Now better focussed on this, I'm guessing that the area (about 2 square meters) of solar panels would max about 360 watts, or 30 amps at 12 volts. Upconvert through a 110 vac inverter and get 320 watts. Step it up 3x voltage through a transformer and get 300 watts. After rectification, 290 watts, or just less than 1 amp to the HV battery under the noon sun, no clouds. Getting twice that would require the finest photovoltaic panels (as seen on the electric car racers), but nobody can afford those!

The weight issue is in the added 12 v lead batteries and (less so) the transformer and inverter. As a guess, at least 30 kg added.

Wind resistance is insidious at highway speeds, but could be minimized with flexible solar panels attached directly to the roof. Those are quite expensive.


Guess I won't be doing this anytime soon to my NHW11 Prius, because the added stuff will cut into (limited) trunk space, and I do put the Yakima rack (for bikes, etc.) on top sometimes. Cannot imagine getting it all done for less than $1000. Calculate your own payback times, but getting 13% higher mpg to post on greenhybrid: Priceless.


The Prius HV electrical system is very sensitive to small current leakage to ground, and I would be surprised if this inventor has not had to work around such problems already.


After all these negatives, I again applaud the work! So many have talked about adding PV to the Prius, and at last someone has done it, and reported better fuel efficiency improvements than we might have anticipated. Do the front hood next, do! Nobody puts bikes there.

DAS