Comment by rootusrootus

5 years ago

Here's a recent analysis: https://teslatap.com/articles/solar-vehicle-roof-analysis/

To me it looks like it will never be a meaningful solution, due simply to physics.

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rootusrootus

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Retric  5 years ago

That has several really bad assumptions by assuming all solar roofs need to fit on an existing Tesla‘a roof.

> The usable clear area of a Model S glass roof is 42” x 45”

A Model S is actually 195.9” by 77.3 (ex. mirrors). Assuming a reasonable shaped solar car using 75% of that surface is covered in panels that’s 12x the area. But you also gain from panels covering the sides of the vehicle.

Further “Because the vehicle roof is flat, it collects less light than if it was positioned at the optimum angle to the sun.“ as I said your not limited by the roof. “Lastly, we lose at least 10% more due to the safety glass,” we don’t need glass and that’s already part of panel efficiency numbers. “and the inverter/charging is only 81% efficient.” Solar panels and batteries are both DC so you don’t need an inverter, the charge discharge efficiency of lithium ion can be over 90%.

San Francisco 5.34kWh/m * .3 efficiency * 7.33 square meters = 11.7kW/day /.3kW per mile = 35 to 39.14 miles in San Francisco depending on how much your charging the battery with plenty of areas getting more sunlight. Using the highest efficiency panels currently produced that goes up significantly, but cheap 30% efficient panels seems like a more reasonable mid term prediction.

PS: Example of a flexible 1m panel zero glass required at under 300$/m: https://www.amazon.com/dp/B082FCZ4MD/ref=emc_b_5_t?th=1

  • SAI_Peregrinus  5 years ago

    > Solar panels and batteries are both DC so you don’t need an inverter, the charge discharge efficiency of lithium ion can be over 90%.

    You'll still need a DC-DC converter, which is just an inverter with a rectification step. The 81% number is low, but there is a loss here.