Highschool Solar Car

System

Hi, I'm a member of a solar car team from Kingston, Ontario. We've just built an all aluminum solar car... and we're looking for solar cells that we can put on our car. We want individual solar cells that are pretty efficient (15%+) and preferably, we would like each of them to be 150mm x 150mm (5.9 in x 5.9 in). But it can be smaller than that too... Does anyone know any place to get solar cells that fit our requirements... price should not be an issue, the school covers for us. Thanks.

BB.

Re: Highschool Solar Car

Here is a list of Solar Panel / cell manufacturers in Ontario/Canada... Might give a few of them a call.

Good Luck!
-Bill

System2

Re: Highschool Solar Car

Thanks a lot, I will take a look. Also we don't mind buying from the US now since the dollars have evened out. As long as the company can ship cells to Canada, it should be fine.

BB.

Re: Highschool Solar Car

Since you are a school project--I would suggest that local collaboration, engineering and/or sponsorship would be very helpful as they would have interest in supporting your community (plus, you don't have to pay international taxes/shipping--Canada/US tariffs are not insignificant--check before you buy US--it is expensive to go cross boarder, unless it is smuggled in).

I don't have ties with any solar manufacturer... Sorry.

-Bill

System2

Re: Highschool Solar Car

Ok thanks for the help, I'll see what i can find. There is a university in Kingston that also has a solar car team... The only difference is their budget is 150K larger than ours... I guess highschools don't get the same attention lol. They might be able to help us with ideas and what cells to get and where. For now I'll see what I can find in Ontario. Thanks again.

Roderick

Re: Highschool Solar Car

I see SunPower cells a lot in solar competitions.

It may be worth contacting SunPower directly, to see if they might give you a deal in exchange for advertising / publicity.

In interest, what is your budget, and how many watts of cells did you have in mind?

System2

Re: Highschool Solar Car

We're prepared to spend up to $2000 on solar cells, that's about a fifth of our total budget. What we're trying to do is put as much watts as we can on an 8ft x 4ft surface. So getting the most efficient cells (even if they cost a lot) is more important than getting "Ok" cells at a good deal... but if we can get efficient cells at a good deal... that would be nice too lol.

BB.

Re: Highschool Solar Car

Retail for a finished panel is around $5/watt retail. That would give you about 400 watts--or two 200 watt panels (plus or minus).

If you can use finished panels, you might get a good set that can be sold later (or used in another project, or somebody's solar cabin) so that they are not "wasted" after the project is completed.

If you are using bare cells, it might be much more difficult to use them else where (plus you will need to solder/bus them all together).

-Bill

James

Re: Highschool Solar Car

You might try BP SOLAR (British Petroleum)
From my observation, they seem to have a hugh marketing budget.
A corporate sponsorship may be possible. Thier website does show a grant program for schools and education use. They do mention in thier information and application pages that they contribute refurbished panels. Perhapes they will have indivdual cells available for such uses as yours.

(I have no afilliation to BP, I just remember them from an education project I tried to set up for a local school)

SolarJohn

Re: Highschool Solar Car

You'll find what you need here:

http://www.fieldlines.com/story/2005/1/5/51211/79555

http://pyronet.50megs.com/RePower/Homemade%20Solar%20Panels.htm

http://www.goldmine-elec-products.com/prodinfo.asp?number=G4497

http://www.canrom.com/index.htm

http://www.gatewayelex.com/

http://www.allelectronics.com/

http://www.siliconsolar.com/index.php

http://solarjohn.blogspot.com

John

niel

Re: Highschool Solar Car

If all else fails you can try this one that is not far from me.
http://www.solarpowerindustries.com/index.htm

System2

Re: Highschool Solar Car

Good luck with your car, some thoughts from a solar car guy. Making solar panels is very time consuming, and it is hard to out preform manufactured ones. Things to consider
1) weight -choose light panels.
2) durability- panels and connections will vibrate
3) endorce corporate sponsors and experts.
4) finish early, and practice as much as you can. races/events are won on reliability and teamwork, more than high tech. Drivers make a big difference
5) Regen, regen, and more regen all about managing energy!

Build a good team have fun

Bill

System2

Re: Highschool Solar Car

Thanks for all the help everyone, this has been very usefull. I've talked to the team and we will contact the companies mentioned here and hopefully within a month our car will actually be solar. Feel free to post anything else that you think will improve our car. Here's a bit of information on the electrical components of the car:

- 24 Volt (2 12 volt 45AH batteries in series)
- 1/2 hp Leason DC electric motor (draws 10 amps when going max speed)
- Solar controller (Shows the solar amps and prevents batteries from discharging through the solar panels)
- Motor controller (Sets the max/min amps and acceleration of the motor, also allows us to plug in a potentiometer for throttle controll)

Those are the major parts, we also have a small 20mhz microproccesor that restricts the steering wheel according to speed and turning radius (so we don't flip over or skid).

So that pretty much covers up the electrical components of the car, if anyone has a suggestion on how we can improve feel free to write it down here. Thanks again for all the help so far.

SolarJohn

Re: Highschool Solar Car

Ark,

If you're going to put a microprocessor in it, couldn't you also incorporate an efficiency meter? I'm thinking that you might compare motor amps to speed, and maybe use a bar graph to give a visual indication of efficiency. The driver could then adjust his driving style in order to achieve greater efficiency, and therefore greater distance.

I agree with a previous comment regarding buying solar panels rather than building them. Not only will this probably cut down on weight, you can use the time you'll save for other tasks.

John

System2

Re: Highschool Solar Car

SolarJohn wrote: »

If you're going to put a microprocessor in it, couldn't you also incorporate an efficiency meter? I'm thinking that you might compare motor amps to speed, and maybe use a bar graph to give a visual indication of efficiency. The driver could then adjust his driving style in order to achieve greater efficiency, and therefore greater distance.
John

We might be able to do that, but the microproccessor is very limited... I believe you can only write about 400 lines of code on it. I'm not the computer guy in the team so i don't know if that's enough or not. But I'll tell our computer guy and see if he can do it.

Also I had a question about charging our batteries. What voltage should the solar panels be charging the batteries. The batteries are 2 12 volt batteries in series.

BB.

Re: Highschool Solar Car

You need to identify the type/brand/model of your batteries... Are they lead acid (and there are different types of L-A batteries), or NiCAd, etc...

Once you have identified the type of battery, then you will need to match a charge controller with the batteries and the solar panels. The charge controller needs to be able to manage the voltage/current of the panels, and match the charging characteristics of the batteries. And here there are two basic types of charge controllers--one that simply connects the panels to the batteries when they need charging and disconnects when full (PWM is a variant of this time) to those that have MPPT (Maximum Power Point Tracking). The first type need to match the panel voltage to the battery bank for best efficiency. The MPPT type uses a DC to DC converter that can transform high voltage/low current into low (battery) voltage/higher current--and is more efficient overall.

But the MPPT type are usually larger, heavier, and need a minimum amount of solar panel power (~200-500 watt minimum) to make up for the "extra power" loss running a DC to DC switcher power supply.

Lastly, just an FYI... Most battery chemistries are severely damaged by over discharging (some below a certain voltage, most when the cell voltage is reversed), and some batteries by under charging. Some batteries should be stored charged, others 1/2 charged... Accurately monitoring the battery voltage helps, but using a battery monitor that meters the total charge (current*time) in/out of the batteries is usually more accurate.

To be honest, there are a whole bunch of variables here... And a lot of them involve money, weight, size, time and availability of components for your needs...

We here have discussed another school electric car project before and you will have to make your own trade-off decisions... My suggestion would be to create a few different excel spread sheet models (create parts lists for Lead Acid / NiCAD / NiMH / Lithium batteries, "24vdc panels + pwm controller" vs "xx VDC high voltage panels + MPPT charge controller", etc.--and make sure all of the components play together well, estimate power generation, weight, and range for each of the solutions) and see which works best for you.

-Bill

GreenerPower

Re: Highschool Solar Car

Ark wrote:

...What we're trying to do is put as much watts as we can on an 8ft x 4ft surface. So getting the most efficient cells (even if they cost a lot) is more important than getting "Ok" cells at a good deal... but if we can get efficient cells at a good deal... that would be nice too lol.

Here is "efficient cells at a good deal", put 8ftx4ft worth of fresnel lenses, you can have 4 suns (or more) on 1/4 of cells (and can use cheaper, less efficient cells) and still have the same wattage (or more). For us, this might void guarantee on the PVs but for your project, should it be OK ?

GP

niel

Re: Highschool Solar Car

i don't think the use of fresnel lenses would be a good idea. it would not only burn up the cells faster, but lead into other complications such as the mounting of the lens and the now necessary tracking of the sun. it adds too much complexity for a small extra return, not to mention more weight.

GreenerPower

Re: Highschool Solar Car

niel wrote: »

i don't think the use of fresnel lenses would be a good idea. it would not only burn up the cells faster

I meant "slightly" focus the sun light to get 3 - 4 times the insolation (something like 1/2 or 2/3 way up from the tip of the focus cone), not at the optimum focus point where it would be 100s of times to get burned.

...but lead into other complications such as the mounting of the lens and the now necessary tracking of the sun.

with properly selected focal length fresnels, you can fix mount it something like 1-foot or less above the PV to get 3X, 4X insolation and don't really need tracking (if it's only for 1 or 2 hrs around noon for a solar race car project, not a normal household installation)

... it adds too much complexity for a small extra return, not to mention more weight.

4 times insolation = 400% in PV power, not a small return, and those plastic fresnels are very light, easily mounted with wire frames (also considering 1/4 the weight of the panels you would need).

Well, I meant to leave these details for the kids to figure out and they'll learn more ... PV energy vs. insolation, fresnel optics ...

GP

niel

Re: Highschool Solar Car

"Well, I meant to leave these details for the kids to figure out and they'll learn more"

like what, how to spend a bunch more money only to learn new swear words?

System2

Re: Highschool Solar Car

ok, on the battery charging issue... I pulled one of the batteries out of the car today and wrote down all the information I could find on it. Here are the stuff I found:

Enerwatt batteries

- Sealed Rechargable Valve Regulated Lead Acid Battery
- 12V 45AH
- Constant Voltage charge
- Cycle Use: 14.10 - 14.40
- Standby Use: 13.50 - 13.80
- Initial Current: Less than 18A
- 14.07 kg

Model #: WP45-12

So according to this information, can someone tell me what would be the needed voltage to charge these batteries. Don't forget we're trying to charge 2 of these batteries (in series) at the same time with our solar panels.

BB.

Re: Highschool Solar Car

Here is a pretty good PDF document of the properties of this battery...

And another PDF data sheet with other information...

Both of these should answer most of your questions and help you predict performance.

-Bill

PS: I should probably add that this is not the same manufacturer--but I believe that these batteries share similar requirements and performance values (close enough for government work).