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Old 06-05-2010, 08:31 AM
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Default solar car

Hello, all. I am new here. Since October of 2009, I have had an interest in solar cars, the ones that are built for the solar races that take place. If anyone has been on solarpowerforum.net, I have a thread there, too, but I haven't been able to reach that website for months. I am planning on constructing one myself, since my eZip bicycle (which is a great bike) won't quite make the trip back and forth to school. Even if the bike could make it, I still wouldn't like leaving a $500 bike sitting outside where I can't keep an eye on it. Since I'm trying to phase fossil fuels out of my life, I don't want to drive a gas powered car and release more CO2. I want to stop riding the bus to save some diesel since less weight = less fuel required = less emissions.

The solar car will be powered solely by the 1000 watts of monocrystalline solar panels on the car, and will charge the on-board 200 Ah, 36 volt Thundersky LiFePO4 batteries at any time when the panels are producing more power than what the car is consuming. The car will automatically use any available power from the panels first, then will make up the difference with the batteries. There is also the capability of the car to transfer power from itself to an external load (i.e. power tools, lights, etc.). It will have a 13 HP sepex DC motor linked to a NuVinci CVP to maintain optimum motor speed to reduce overall power consumption and to provide maximum hill climbing power. Any tips or pointers?
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  #2  
Old 06-06-2010, 01:15 AM
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Default Re: solar car

Hi Tim

The first thing you need to do is to make yourself a basic spreadsheet

You need
Distance,
Watt hours / mile/Km
angle of your panels
time in sun
Power in from panels

Some of these numbers will be engineering estimates (wild assed guesses)

Put them on the forum and people will help you to be reasonable

This will tell you how practicable your plan is

I suspect it will tell you that the best way is to use stationary solar cells on your car port
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Old 06-06-2010, 07:39 AM
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Default Re: solar car

The motor pulls 300 amps at full acceleration, but I suspect it would only use about 25 amps for normal cruising through town (35 mph, fairly level). The car weighs about 850 lbs., a round trip to school and back is 15 miles. If my application gets through at where I plan to work, a round trip is 25 miles, both school and work have high speeds (~50 mph), a fair amount of turns, and two big hills (nice opportunity for regen on the trip in the morning).

The panels on the car sit completely flat, providing over 1,000 watts in full sun. At school, the car would sit in the sun for approximately 7 hours before I drive it again, which will also sit in the sun until it sets at my house. I would prefer having the solar on the car in case that if something in the car would run the batteries near LVC, I could fix the problem and let the car sit for a little bit to gather some sun, then drive home extremely efficiently, where as if the panels are on my house, the car would be stranded as the school has no exterior outlets. This is the primary reason for not converting my brother's old Honda Civic. I made my own design which should be attached. Even though it says "not to scale, everything is except for the body's thickness, which would appear to be ~18", but it's actually going to be 26" from belly pan to solar array. Overall height is 59".

Nice guess on my name, my forum name is Tm (no 'i') PV1, which the name I have given to the car. I'm still trying to work out what the t and m should stand for.
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File Type: jpg Final drawing with dimensions.jpg (60.1 KB, 59 views)
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Vehicles:
1. Mitsubishi i-MiEV in the Garage- Purchased February 21.
2. Currie eZip hybrid electric bicycle - solar powered
3. PV1 solar car --- on hold

Last edited by Tm PV1; 06-06-2010 at 07:49 AM.
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Old 06-06-2010, 07:43 AM
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Default Re: solar car

Quote:
Originally Posted by Tm PV1 View Post
Hello, all. I am new here. Since October of 2009, I have had an interest in solar cars, the ones that are built for the solar races that take place. If anyone has been on solarpowerforum.net, I have a thread there, too, but I haven't been able to reach that website for months.
I am a Moderator on that forum. How can I help you? The site is up and working.
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Old 06-06-2010, 08:02 AM
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Default Re: solar car

It might be my internet, I keep getting that the server could not be found. I had a friend try it on his iPad, said he was able to access no problem. The last time I was able to access was before the big snow that hit the eastern US. Are there any new posts on my thread on solarpowerforum since the last time I replied?
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2. Currie eZip hybrid electric bicycle - solar powered
3. PV1 solar car --- on hold
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  #6  
Old 06-06-2010, 10:08 AM
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Default Re: solar car

Quote:
Originally Posted by Tm PV1 View Post
Are there any new posts on my thread on solarpowerforum since the last time I replied?
Cannot find the post using a few search terms I tried. I remember a few post in the past. What is your user name over there?

Anyway you are not going to get a lot of help over there as most of the membership is just clueless homeowners looking to stick it to the man trying to build DIY panels only to find out they cannot be used in a grid-tied application or fail shortly after they make them trying to use on battery systems and find out out they have to pay 30 times more for electricity trying to make it themselves. I am one of the very few engineers on that forum. So you will get more useful info here as the membership does have quite a few engineers and technicians.

Now back to your project. I have not built an EV, so I want to make that clear. But I am an electrical engineer with 30 years or so of power generation, distribution, battery plants, and process control. I do however modify golf carts and learning the principles which is very similar to EV's.

One huge obstacle you will run into is just plain physics trying to power an EV by solar alone. In the golf cart world you can buy a roof with a 200 watt solar panel. 200 watts is about all you can get dues to th ephysical area limitations of the cart. Here is the point, the panel can only extend the range of just a few miles at best. It is incapable of fully powering the golf cart.

A golf cart is weighs around 550 to 700 pounds depending on the make and model. Battery to wheel efficiency is around 175 wh/mile depending on terrain and driving habits. Top speed using a 4.8 Kw motor is about 25 to 27 mph on flat level hard surface like a paved road. With a panel mounted horizontally flat at 0% tilt in Tuscon AZ in summer can only generate with a 5.2 Sun Hour day 200 watts x 5.9 hours x 66% efficiency = about 800 watt-hours. So when you factor in the battery to wheel efficiency of 175 wh/mile we are talking about 800 wh / 175 wh /mile = 4.5 miles range extended per day.

So as stated in an earlier reply you need to sit down on work out the math to see what it will really take.
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Old 06-06-2010, 10:43 AM
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Default Re: solar car

Thanks for letting me know that I'm not missing much on solarpowerforum. I think my user name over there is T-solar, don't remember thread name. As for the car, i figured sticker rating of the array is 960 watts, plus the MPPT at 36 volts, so not much line loss. Even at reduced output of 700 watts, the math shows that I can charge the batteries in 11 hours, which is not a huge deal to me (battery bank size is 7,200 watts). At best, I figured a full charge in 7.5 hours, but I won't likely run the batteries to LVC every time I drive it. Since I use my own laptop for school, I will need to keep it charged up, so there is 200 Wh right there per school day, plus alarm system, EABS (lifts the solar array up with actuators for ingress/egress and maintenance), lights, ventilation, gauges, and radio. The only things that are constantly powered are the alarm, BMS, and the radio's clock. There is little phantom power in this. All the lights are LED's (depending on their brightness, I might substitute the LED headlights for halogens), and the radio I've found can be easily powered by a 12 volt, 15 watt amorphous solar panel during a rainstorm. My one friend is a big Apple computer fan, so I'm gonna see if he can make a custom alarm app for my iPod Touch, reason being is for the flexibility and the motion sensing. I have a parts list and description on my website at home.earthlink.net/~timster but they are a little out of date, so I'll hopefully update those soon. If my estimation of 25 amps cruising current is correct (which I hope it is), the solar array has the potential to completely power the motor (full output, of course). Sound realistic?
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1. Mitsubishi i-MiEV in the Garage- Purchased February 21.
2. Currie eZip hybrid electric bicycle - solar powered
3. PV1 solar car --- on hold
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  #8  
Old 06-06-2010, 03:44 PM
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Default Re: solar car

Quote:
Originally Posted by Sunking View Post
I am a Moderator on that forum. How can I help you? The site is up and working.
Well, I cant get in to www.solarpowerforum.net either ???

Roy
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  #9  
Old 06-06-2010, 05:17 PM
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Default Re: solar car

Quote:
Originally Posted by Tm PV1 View Post
Thanks for letting me know that I'm not missing much on solarpowerforum.
Your thread is still there. Last reply was from you on 2-21-2010

Quote:
Originally Posted by Tm PV1 View Post
I think my user name over there is T-solar, don't remember thread name. As for the car, i figured sticker rating of the array is 960 watts, plus the MPPT at 36 volts, so not much line loss. Even at reduced output of 700 watts, the math shows that I can charge the batteries in 11 hours,
Ok first I am not sure how you calculated the charge time, but a huge mistake people make is assuming the panel develops rated power when ever th esun is shinning on it. That is really far from reality. Second most common mistake is people think if the shines for 14 hours per day they get a full 14 hours of rated power. Again not reality.

For a vehicle you will will have to use a horizontal orientation with 0 Degree tilt angle. Next you have to determine your local area Solar Insolation data to see what kind of insolation you really have. Next is it varies by the season. For example let's say you live in Kansas City KS. Your December insolation is 1.9 hours and in July for a few brief days is 5.9 hours.

In December the most you could ever expect to generate with 70% efficiency is 960 watts x 1.9 hours x .7 = 1.8 Kwh, and in July 4 Kwh at the very best. If you could achieve say 400 wh/mile that is a range of 4.5 miles to 10 miles per day and only if the sun shines all day and all the power is strictly used for the motor.
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Old 06-06-2010, 06:14 PM
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Default Re: solar car

I calculated charge time by finding out how many watts the batteries will hold, which 36 volts * 200 Ah = 7,200 watts. If the solar would provide 960 watts for a full 7.5 hours (highly unlikely without a tracker), it comes out to 7.5 hours. My other charge time of 11 hours is more likely, but I only need enough charge to go 75 miles in a normal week. When I'm not driving it (on weekends is likely), I would probably leave the car sit in the sun, but be transferring power from the car to charge my solar battery at my house since the only solar panel on the house right now is a 15 watt amorphous that seems to work pretty well in any weather condition, but is still too small to keep the voltage up. If the monocrystalline panels don't perform as well in less than ideal conditions, I might make an amorphous solar array for those days or weeks where the weather isn't to sunny, since amorphous work much better in overcast (I've actually traced output on a full moon night ). Am I correct about this or have I been misinformed? Also, how much of an increase can I expect using an MPPT such as the Midnite Classic?
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2. Currie eZip hybrid electric bicycle - solar powered
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