Tesla is working with their customers to help put the infrastructure together in order to power the Tesla Semi. Solar power is said to be the main component of these stations and has guaranteed a 7 cent per kW cost to charge the trucks.
https://www.topspeed.com/cars/car-news/tesla-working-with-semi-customers-to-refine-mega-charger-plans-ar179669.html
https://www.topspeed.com/cars/car-news/tesla-working-with-semi-customers-to-refine-mega-charger-plans-ar179669.html