What is the easiest and cheapest way to use solar energy in a classroom?

Hi, I’m doing a school project. We are required to design a classroom which exists in a "storage" container, with the idea that this classroom could host 25 learners and be self-sufficient so that it would be able to be used in rural settlements.
What is the easiest and cheapest method of using solar energy? The energy would only need to be used in winter for lighting and maybe a heater/radiator of some sort.