Solar Prius

I thought the Solar Prius was that spot just below your ribs, where if you get hit it knocks the wind out of you. Evan can help with this.

Tom

 

LOve the innovation - hate the misinformation. There is NO freaking way he's getting six miles of electricity from that one flexible panel. Just can't happen. Not today. And not for less than a NASA budget (those guys get some pretty efficient panels!)

My back-of-napkin calc comes up with one mile of free energy per PERFECT day. And there aren't all that many perfect days in a year.

Yeah, I'm a solar and EV advocate. And I love to see this happening. I just don't like the fibs.

 

Hi All,

I will trust Darelldd, that there just is not enough sun to do what is claimed. The claimed improvement in fuel economy could be due to just having the larger battery pack. Which enables better hybrid operation. That is, recovering more downhill energy, quicker accell-longer cruise, more juice for the longer traffic jams (allows one to stay in electric, until higher speeds are permitted), etc.

 

I recall reading about this a while back. The company that does the Solar Prius mod is Solar Electric Vehicles of Westlake Village, CA. They have a white paper on their website that details the system.
http://www.solarelectricalvehicles.com/articles/prius-white-paper.shtml

The source of the 6-mile claim is right in the abstract:

The photovoltaic module is rated at 215 watts at AM 1.5. The module is connected to a DC-DC converter and peak power tracker. The output of the converter is directly connected to the primary motive NiMh battery.

The daily power production available for charging the Prius primary motive battery is estimated to be between 850 and 1,300 watt-hours. The car uses 150-175 watt-hours per mile. Thus, the expected range per day that the PV Prius would have on solar power alone would be between 5 and 8 miles. Based upon a nominal daily trip length of 28 miles the gasoline consumption of the PV Prius would be reduced by 17% to 29%.

Check out the white paper, and have at it.

 

Steve Lapp has also built a solar Prius:

http://www.treehugger.com/files/2005/08/solar-powered_t.php

He has about 270 W of more efficient panels and reckons on a 10% improvement in economy.

Peter Perkins also has a cool solar van, that he built for next to nothing and gets a fair proportion of its range from solar:

http://www.solarvan.co.uk

I think if the company in the link above does get 215 W from their panels, then they should be able to capture about 600 Wh per day (if parked outside in California), which is enough for 3 miles EV range.

My own view (and I should point out that many people have disagreed with me on this one here and on other forums quite vehemently in the past!) is that a car could easily be built in the future with 5 m2 of flexible panels (extending covers over all surfaces when parked) and 1 kW peak, giving maybe 3 kWh per day or 15 miles range.

 

You have to remember though, they never said they'd get 6 miles from one panel. They said with the additional battery packs, and the solar panels if they lived 6 miles from work they "theoretically" wouldn't need to ever fill up. So I'm guessing when the battery packs are completely full that's the range, maybe plus a little bit because the panels are doing some work.

But yeah, I doubt he could fill up those batteries with a 1 square meter (guestimate) panel, that'd be what, 150watts at the most?

 

If you read the white paper (see my post #5 previously in this thread) it sounds like they do indeed claim 6 miles ("5 to 8" is what they actually said) on the Prius roof panel alone. Later in the white paper they talk about an expanded system connected to residential solar panels.

In the white paper they say 215W for the panel.

Check it out.

 

Hmm, it says 215W rated, problem is they will NEVER get that rating. First there's the latitude shift the panel would need to be to ideally be facing the sun, not even at "high noon" will the sun-panel be in optimum alignment. Not to mention the front of the car has a slight slope and the back of the car is sloped in the opposite direction so if the car is going into/away from the sun part of the panel is going to be at an extreme angle to the sun resulting in a lower voltage across the bank of cells that's sloped away. I hope those cells are wired different than the "flatter" ones because if you have different voltages being supplied by different areas you're going to reduce the efficiency of the whole solar array.

Don't get me wrong, I love solar power, hell that was what I worked on in graduate school, but those claims smell more like snake oil to me. The paper seems to be based upon theoretical data as well and not real world testing.

Although I'm not trashing the idea completely, I'd just like to see some watt meter hooked up to the thing and record various power production values throughout the day.

 

Agreed. That seems to be the general concensus here regarding the Solar Prius. - Great idea. We love it. - But don't give us bogus numbers.

So here's another idea - the "Exercise Prius". - Install 2 sets of exercise bike pedal cranks for passengers in the rear seats and have them earn their ride with pedal power. - Should be able to get 200W that way, and it doesn't need to be sunny. I want to see somebody do that.

 

Hmm. They say 150 W-hr/mile? Can anybody confirm that the PRius can do anything near that at any speed above a crawl? I can't imagine that it is possible. Certainly not freeway speeds. I mean, that's about the theoretical best that we can do with an optomized EV drivetrain - which the Prius most certainly is not!

They seem to be assuming that the sun is always shining, that the panel is always tilted toward the sun, and that there are minimal losses in the system. White papers are great. What we need is some quantifiable, defendable numbers.

 

Maybe they are just going to have solar actuators on it Darell. They can double as windbrakes too. lol

 

watts/mile

Actually that is reasonable for speeds under 40 mph. 250 watts/mile is reasonable up to 55 mph. Keep in mind the Prius is the most aerodynamic mass-produced car today. I'm looking at http://privatenrg.com/, scroll down a couple screens worth and there's a table. Details on the tests for how they developed that table is described above. This page has been around a couple years. Graphic design is not their strong suit, but EE is.

So if you keep it under 40 mph, you're in a sunny area near the equator (or parked sideways on just the right incline), and your solar panels don't get too hot (most lose efficiency when hot), then you might really get numbers like they say.

 

AC-Propulsion's T-zero could manage 6 miles per kWh (170 Wh per mile) on gentle driving cycles.

For a Prius to manage 5 miles per kWh (200 Wh per mile) at 60 mph, it would need to be able to keep that speed using 12 kW, or 16 hp. Easy.

In the future when electric vehicles (or PHEVs) are more commonplace, manufacturers will realise that in order to have the best competitive advantage by providing the best EV-range per dollar, it is a lot cheaper to reduce the amount of energy used per mile than to put in a bigger battery. Reducing weight, improving aerodynamics etc will really matter then, because although higher fuel economy doesn't bring in the punters right now, longer range per charge really will.

 

True enough Clett, unfortunately the "I want to drive a toaster shaped car that can haul my life around on any moment's notice" mentality has to change.

 

As well as the idea that the only way to protect myself from a crash with a big vehicle is to have an equally big or even bigger vehicle. I remember a quote from a lady driving a big SUV (hummer?) who said "I like the idea that whatever I bump into, I win".

 

Solar Prius flaked

they were supposed to be at the ecofest this weekend in Van nuys, but they flaked, I got all dressed up for nothing.

 

Something very much like that already exists. It's called the bicycle. It even comes in two-seat and three-seat versions. And for extremists, I've seen pictures of a four-seater. Everyone gets to pedal. It's a LOT cheaper than a Prius, though it has less cargo capacity. And it's not real good on slippery roads or in inclement weather.