“Musk delved deeply into how solar cells work and the various compounds that can make them more efficient. He concluded the paper with a drawing of the “power station of the future.” It depicted a pair of giant solar arrays in space – each four kilometers in width – sending their juice down to Earth via microwave beams to a receiving antenna with a seven-kilometer diameter. Musk received a 98 on what his professor deemed a “very interesting and well written paper.”