Solar Panels

material_claw · 07-05-2006, 12:10 AM

Hello all. My name is Nick, I am a long time reader and a fist time poster.

I noticed a lot of discussion about using a plug in modification, and a debate on weather or not it would be cost effective. However I was surprised to find very little about a solar alterative. I believe a few discreet solar panels might go a long way in mpg.

Wal-mart sells a solar panel strip that can be placed on a dashboard and is plugged in to the cigarette lighter. It is supposed to help keep a conventional car battery charged up a bit so supposedly you don’t have to worry about draining the battery if you leave you light on and such. There’s also a larger version that is advertised to be able to jump a car in 5-10 minutes. I was wondering if anyone else has noticed these products and wanted to know your opinion on using either to aid in the regeneration of the prius’s battery while in motion, or at a stand.

I will get more details about each on my next trip to Wal-mart.

tripp · 07-05-2006, 12:26 AM

I think the consensus is that these panels would not increase the MPG much at all. You really need a fair amount of juice (ie a pretty big solar array) to be effective. The 20W and 30 W panels just don't cut it. They will do a nice job of doing what you describe, however. Think about it this way. It takes about 200Wh to move a Prius a mile. Most places in the US get at least 5 hours of quality sunlight/day. So you'd need at least 40 W and 5 hours of sunlight to go one mile. From this you can see that you'd need a lot of solar capacity to augment the system in any meaningful way.

darelldd · 07-05-2006, 12:28 AM

Hi Nick -

Let me start by saying that my main car - a battery electric vehicle - is fueled from electrons made via solar panels (lots of detail on my EV pages linked in my sig). With that out of the way... let me tell you that it will take quite a bit of surface area and expense to significantly increase the range of the Prius. If all horizontal surfaces were covered with PV, you'd gain maybe three free miles on a perfect day. There aren't very many perfect solar days though - and once you park or drive in the shade, all bets are off. You'll also need a DC-DC converter somewhere to increase the voltage of the PV panels up to something that can charge the HV battery.

And this points out that you're looking at 12V panels. Those will ONLY help keep the AUX battery topped up. The Aux battery provides no traction power. Keeping it charged externally WILL draw less power from the traction battery to keep the Aux charged - but honestly - it won't be enough to notice any real difference. A few feet of range, maybe?

I don't want to be a downer on PV power (which is why I started this post the way I did). I'm a firm believer in driving on sunshine (we drive about 12,000 miles/year on sunshine!). But PV panels really belong on the roof or your home where they will always be in the best position to catch the sun.

Tripp beat me to it while I wasted time on my long post!

<div class='quotetop'>QUOTE(tripp @ Jul 4 2006, 09:26 PM) [snapback]281251[/snapback]</div>

Quote:

So you'd need at least 40 W and 5 hours of sunlight to go one mile. From this you can see that you'd need a lot of solar capacity to augment the system in any meaningful way.
[/b]

This is a best-case scenario, of course - and ignores the conversion losses which at this level are significant.

tripp · 07-05-2006, 12:28 AM

Ha ha. Beat you to it, darell. :P :P

material_claw · 07-05-2006, 12:38 AM

[quote]

Thank you for the qiuick and thorough response. What you both said made alot of sence.
I cant afford my prius just yet but when i do i want to get every little bit of effecency i can squeeze out of it. But ill pass probally pass on the wal-mart solar panels.

c4 · 07-05-2006, 01:20 PM

Not to mention that the Wal-mart and other low-cost solar panels are of the amorphous type which have better infrared response (so they make better use of that part of the spectrum), but lower overall conversion efficiency than the older crystalline silcon panels. Because of this, the amorphous type panels need to be much bigger for the same rating..

I'd love to hear Darell's opinion on this, but contrary to all those solar magazine articles expounding on the virtues of the amorphous solar panel and how, because of their comparatively low initial cost, they pay for themselves after only a year, I, on the other hand think that the amorphous type represent a big hole that you stuff your money into and never see it again.. Part of the reason is the surface area thing- you can cover your roof with cheap amorphous panels but get less than half the output that you'd get if you put up crystalline panels. Long term degradation of the panels is another issue- most amorphous type panels *lose* up to 60% of their capacity in the first year (ie, if you have a 300W panel, after one year, they're only putting out 200W at best), vs crystalline types which *retain* up to 90% of their output capacity after 10 years.. So, yes, amorphous panels may be so cheap that they pay for themselves after a year, but after that, you get steadily declining output, vs the crystalline type, which cost 2-3x up front, but have higher output and maintain that output for a lot longer..

For maintaining the 12V aux battery in my Prius, I started out with an amorphous 5W panel which gave a true output of max 2-3W (usually much less, but that makes 5W about the smallest size panel you can consider for 12V maintenance) when under the windshield glass, but I swapped it recently for a 15W crystalline panel. The crystalline panel was 2x the cost of the amorphous, but is actually about 1" shorter in one dimension, and generates a real output of about 6W under glass.. In other words, I paid 2x for a panel that generates up to 3x the power using roughly the same surface area, and is expected to last years longer to boot..

240sxer · 07-05-2006, 04:12 PM

<div class='quotetop'>QUOTE(c4 @ Jul 5 2006, 10:20 AM) [snapback]281506[/snapback]</div>

Quote:

Not to mention that the Wal-mart and other low-cost solar panels are of the amorphous type which have better infrared response (so they make better use of that part of the spectrum), but lower overall conversion efficiency than the older crystalline silcon panels. Because of this, the amorphous type panels need to be much bigger for the same rating..

I'd love to hear Darell's opinion on this, but contrary to all those solar magazine articles expounding on the virtues of the amorphous solar panel and how, because of their comparatively low initial cost, they pay for themselves after only a year, I, on the other hand think that the amorphous type represent a big hole that you stuff your money into and never see it again.. Part of the reason is the surface area thing- you can cover your roof with cheap amorphous panels but get less than half the output that you'd get if you put up crystalline panels. Long term degradation of the panels is another issue- most amorphous type panels *lose* up to 60% of their capacity in the first year (ie, if you have a 300W panel, after one year, they're only putting out 200W at best), vs crystalline types which *retain* up to 90% of their output capacity after 10 years.. So, yes, amorphous panels may be so cheap that they pay for themselves after a year, but after that, you get steadily declining output, vs the crystalline type, which cost 2-3x up front, but have higher output and maintain that output for a lot longer..

For maintaining the 12V aux battery in my Prius, I started out with an amorphous 5W panel which gave a true output of max 2-3W (usually much less, but that makes 5W about the smallest size panel you can consider for 12V maintenance) when under the windshield glass, but I swapped it recently for a 15W crystalline panel. The crystalline panel was 2x the cost of the amorphous, but is actually about 1" shorter in one dimension, and generates a real output of about 6W under glass.. In other words, I paid 2x for a panel that generates up to 3x the power using roughly the same surface area, and is expected to last years longer to boot..
[/b]

Have you noticed any difference in MPG with the pannel? I'd assume it would probably be so little that it could not be accuratly measured. However I'd still like some on my prius because anything that will help i'll do. I recently went to sythetic and 44/47psi in my stock tires. If I get a .5mpg increase i'll be happy. That's probably unlikely. Anyway, can you post some links to the pannels you have and exactly how you have them wired. Pix would be nice.

Cheap! · 07-05-2006, 05:19 PM

<div class='quotetop'>QUOTE(240sxer @ Jul 5 2006, 03:12 PM) [snapback]281597[/snapback]</div>

Quote:

Have you noticed any difference in MPG with the pannel? I'd assume it would probably be so little that it could not be accuratly measured. However I'd still like some on my prius because anything that will help i'll do. I recently went to sythetic and 44/47psi in my stock tires. If I get a .5mpg increase i'll be happy. That's probably unlikely. Anyway, can you post some links to the pannels you have and exactly how you have them wired. Pix would be nice.
[/b]

Google "Steve Lapp solar prius"

240sxer · 07-06-2006, 11:10 AM

Ouch, I don't want anything that crazy. I just want a tiny little 10w or something like that mounted under the glass.

psibill · 07-06-2006, 12:57 PM

For solar conversions that DO yeild a fair amount of "free" electric miles, look at www.solarelectricvehicles.com. Their poly-crystalline cells cover the entire roof (and are curved to match!), and they add an aux battery for storing the solar power, which then feeds into the main battery when the car is on.

07-05-2006, 12:26 AM	#2
tripp Which it's a 'ybrid, ain't it? Join Date: Oct 2005 Location: Denver, CO Posts: 3,773 My Car: 2005 Prius Package: #3 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 4	I think the consensus is that these panels would not increase the MPG much at all. You really need a fair amount of juice (ie a pretty big solar array) to be effective. The 20W and 30 W panels just don't cut it. They will do a nice job of doing what you describe, however. Think about it this way. It takes about 200Wh to move a Prius a mile. Most places in the US get at least 5 hours of quality sunlight/day. So you'd need at least 40 W and 5 hours of sunlight to go one mile. From this you can see that you'd need a lot of solar capacity to augment the system in any meaningful way. __________________ Cheers, Tripp 2005 Silver Pkg 3, OEM Block Heater, Coastal Tech EV mod, BT Tech Chassis Stiffener, hell damned infernal reverse beep disabled Boulder Real Estate Howay the Toon! "Sometimes when you aim for the stars, you hit the moon." -- Ian Holloway

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07-05-2006, 12:10 AM	#1
material_claw Join Date: Apr 2005 Location: New Port RIchey Posts: 2 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Hello all. My name is Nick, I am a long time reader and a fist time poster. I noticed a lot of discussion about using a plug in modification, and a debate on weather or not it would be cost effective. However I was surprised to find very little about a solar alterative. I believe a few discreet solar panels might go a long way in mpg. Wal-mart sells a solar panel strip that can be placed on a dashboard and is plugged in to the cigarette lighter. It is supposed to help keep a conventional car battery charged up a bit so supposedly you don’t have to worry about draining the battery if you leave you light on and such. There’s also a larger version that is advertised to be able to jump a car in 5-10 minutes. I was wondering if anyone else has noticed these products and wanted to know your opinion on using either to aid in the regeneration of the prius’s battery while in motion, or at a stand. I will get more details about each on my next trip to Wal-mart.

07-05-2006, 12:28 AM	#4
tripp Which it's a 'ybrid, ain't it? Join Date: Oct 2005 Location: Denver, CO Posts: 3,773 My Car: 2005 Prius Package: #3 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 4	Ha ha. Beat you to it, darell. :P :P

07-05-2006, 12:38 AM	#5
material_claw Join Date: Apr 2005 Location: New Port RIchey Posts: 2 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	[quote] Thank you for the qiuick and thorough response. What you both said made alot of sence. I cant afford my prius just yet but when i do i want to get every little bit of effecency i can squeeze out of it. But ill pass probally pass on the wal-mart solar panels.

07-05-2006, 01:20 PM	#6
c4 Join Date: Mar 2005 Posts: 523 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Not to mention that the Wal-mart and other low-cost solar panels are of the amorphous type which have better infrared response (so they make better use of that part of the spectrum), but lower overall conversion efficiency than the older crystalline silcon panels. Because of this, the amorphous type panels need to be much bigger for the same rating.. I'd love to hear Darell's opinion on this, but contrary to all those solar magazine articles expounding on the virtues of the amorphous solar panel and how, because of their comparatively low initial cost, they pay for themselves after only a year, I, on the other hand think that the amorphous type represent a big hole that you stuff your money into and never see it again.. Part of the reason is the surface area thing- you can cover your roof with cheap amorphous panels but get less than half the output that you'd get if you put up crystalline panels. Long term degradation of the panels is another issue- most amorphous type panels lose up to 60% of their capacity in the first year (ie, if you have a 300W panel, after one year, they're only putting out 200W at best), vs crystalline types which retain up to 90% of their output capacity after 10 years.. So, yes, amorphous panels may be so cheap that they pay for themselves after a year, but after that, you get steadily declining output, vs the crystalline type, which cost 2-3x up front, but have higher output and maintain that output for a lot longer.. For maintaining the 12V aux battery in my Prius, I started out with an amorphous 5W panel which gave a true output of max 2-3W (usually much less, but that makes 5W about the smallest size panel you can consider for 12V maintenance) when under the windshield glass, but I swapped it recently for a 15W crystalline panel. The crystalline panel was 2x the cost of the amorphous, but is actually about 1" shorter in one dimension, and generates a real output of about 6W under glass.. In other words, I paid 2x for a panel that generates up to 3x the power using roughly the same surface area, and is expected to last years longer to boot..

07-06-2006, 11:10 AM	#9
240sxer Senior Member Join Date: Jan 2006 Posts: 125 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Ouch, I don't want anything that crazy. I just want a tiny little 10w or something like that mounted under the glass.

07-06-2006, 12:57 PM	#10
psibill Member Join Date: Jun 2006 Posts: 55 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	For solar conversions that DO yeild a fair amount of "free" electric miles, look at www.solarelectricvehicles.com. Their poly-crystalline cells cover the entire roof (and are curved to match!), and they add an aux battery for storing the solar power, which then feeds into the main battery when the car is on.