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savaszengin View Drop Down
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    Posted: 19 November 2016 at 10:16pm
Hello my frinds. Is there anyone here who worked on super-capacitors for solar cars? I would like to get some advice about super-cap.
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Richo View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richo Quote  Post ReplyReply Direct Link To This Post Posted: 21 November 2016 at 12:45pm
I don't see why there would be anyone who used super caps for solar cars.

Batteries are more than capable at delivering the power.
Batteries are cheaper.
Batteries leak less energy.
Batteries weight less per Wh.

As an example assume a solar car is using 2000W (2kW) for 30 minutes.
The energy used 1000Wh.

Now assume we used some 2.7V 650F caps at USD$31ea
These have an energy of 0.66Wh and weight 160g with max current of 54A continuous.
So to store 1000Wh we need 1515 super caps.
This would weight 242kg
It would cost USD$47,000.
Have a peak power of 220kW.

Now for simplicity sake we compare it with headway batteries.
Each cell is 3.2V 10Ah 32Wh 330g USD$21ea.
So to store 1000Wh we would need 32 batteries.
This would weigh 11kg.
It would cost USD$672.
Have a peak power of 9,600W (9.6kW).

So the batteries easily can produce the 2kW power and cost 100x less.

Given the idea of solar car is designed to be as efficient as possible I doubt they would need the instantaneous power the caps can provide.

Did you have a specific question as my answer is generic?
If the sun's not up turn your lights ON - duh! Help prevent road rage - get outta my way!!
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Richo View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richo Quote  Post ReplyReply Direct Link To This Post Posted: 22 November 2016 at 12:33pm
How about this example then?

A HYBRID petrol/electric where the electric is used to accelerate only.
So in this example 100kW would be the peak electric power.
And we will assume that it takes 10 seconds to accelerate.
Over the 10 seconds the AVERAGE power is 50kW.
So the energy used is 139Wh.

Using the caps from the previous example we would need 210 caps.
Cost would be USD$4410
But peak power would be limited to 30kW and weigh 34kg.
Cost is fair and weight is ok but the 30kW power limit is disappointing.


Although the discharge curve wouldn't suit when peak power is required.
To achieve 100kW we would need 686 caps.
That bumps the cost up to USD$14,406 weigh 110kg!
So for a realistic 100kW hybrid Super caps don't really make sense either.
Even if the cost came down or wasn't a consideration the weight is still unrealistic.

Anyone still pumped up about "super" caps
If the sun's not up turn your lights ON - duh! Help prevent road rage - get outta my way!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richo Quote  Post ReplyReply Direct Link To This Post Posted: 22 November 2016 at 12:45pm
Now lets move on to the leakage...

In the above examples the caps "leak" ~1mA.
It is a published spec - I haven't made it up.
Doesn't sound like much.
So when fully charged that's a leakage of 2.7mWh
Over a day that's 64.8mWh gone into the aether.
For 210 caps that's 13.6Wh.
Remember that the pack was 139Wh.
So charge the pack now and in 24 hours you have lost 10%.
So it's not like you could store the sun and use it over night and expect to use all that was captured.

So not really exciting for solar car use either.

If the sun's not up turn your lights ON - duh! Help prevent road rage - get outta my way!!
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