How would you move the solar energy into the piles of dirt? You’d need something like an array of mirrors focusing the rays, which has definitely been done already but has drawbacks. Electricity can easily be moved to where it’s needed.

It's been done, but not without controversy. https://en.wikipedia.org/wiki/Ivanpah_Solar_Power_Facility

At home, it's suitable in warm climates but is more challenging in snowy / very cold regions. Generally speaking, converting to electricity then using an electric water heater is more efficient because there's much less insulating, heat loss, and piping that can leak and cause water damage.

If you look at "evacuated solar" panels this is as close as you could get, and they don't get anywhere near the temperature you need to generate consistent steam. Concentrated solar is closer, but cost impracticalities make it unattractive here as well.