[ZephyrP]

I calculated a similar maximum horsepower to your own estimation (6.1 hp) when I used the average direct solar radiation (164 W m^2 @ 27 m^2 surface). This rose to 41 hp when using values for "a typical cloudless day at solar zenith" (1120 W m^2) [1]. The wattage will square when doubling each side, so if you were to double each length of the surface, you'd be up to 151 extremely hypothetical hp - just like the Honda Insight!

Back on planet earth, the most common solar panels have efficiencies between 15-20% [2]. Direct radiation is diminished by the cosine of the angle of solar tilt. It takes another ~2 hp to overcome drag at just 30mph [3]. Who knows how much this setup would weigh. You'd have to be Speed Racer's long-lost brother in Arizona to win a mid-summer dead-heat race at noon with a go-cart.

[1] https://www.newport.com/t/introduction-to-solar-radiation

[2] https://css.umich.edu/factsheets/photovoltaic-energy-factshe...

[3] https://web.archive.org/web/20190616063447/http://phors.loco...