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Comment by nudded | Hacker News Reader

I think I miss something in your numbers. They say 83 Wh/km. which means that they expect to get 996Wh in an hour. How did you reach 5.59KW?

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At 12km/h it requires 5.59KW of sun energy to fall on the car (in total, not per sq meter as in original comment).

Actual figure given on website is 5m2 of panels on car. Assume 1Kw per m2 of sun power (near equator, no cloud, midday) @ 22% conversion efficiency gives 1.1kw electrical output from panels.

So one needs 5.59KW sun power input for 1.1kw output.

i am analyzing charging rates. they cite charge rate in km/h for an outlet providing 1.3KW and they cite a charge rate for solar, from which we can work out the power they expect to get from solar

I see, but that does not answer my question though. How is my math wrong? the expected range from solar in 1 hour equates to 996 Wh. You suggest they need 5.6kW of solar to achieve this?

you are forgetting that solar cells are not 100% efficient, and charging is not either. so you MUST use charge rates cites, not consumption rates

No, you must not. The energy required for the car to drive 12kms is 996 Wh. let's round to 1kWh.

Solar is DC. for instance Tesla powerwall is 97% efficiency for DC/DC conversion for charging its battery. So you need basically 1kW of solar to produce the needed energy to drive 12km (per hour). I think you are off by at least a factor of 3.

edit: at 20% solar efficiency that would require 5m^2.

so then your claim is they lose 66% on rectification of AC when they charge from a wall? :)

No, my claim is that their solar claim is not ridiculous ;)

Also, if I do the math on their AC charging. 35km/h gained --> 2905Wh energy. Standard 230AC, 16 amps is 3680W. So I guess the number there is also correct? Take about 85% efficiency, then you have 3000Wh in one hour from 230V AC

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