Deuterium-tritium fusion produces neutrons, which can be used to turn lithium into tritium. So in some sense, the required fuels are deuterium and lithium, both

Deuterium-tritium fusion produces neutrons, which can be used to turn lithium into tritium. So in some sense, the required fuels are deuterium and lithium, both of which are abundant enough to be used for fusion. The sun is a great fusion reactor, but it is also kind of far away. By the time its energy gets to Earth, it's spread out to about 1.4 kW/m^2. The actual power produced per m^2 of solar panels is about 20 times smaller, since the Earth's surface area is 4 times its cross-section, and solar panels are around 20% efficient. The United States consumes about 3,911,000,000,000 kW h / yr for an average power consumption of 446 GW. By my calculations, an area of 6.37 billion square meters would be required to supply this through solar power. According to Wolfram Alpha, this is about twice the area of Rhode Island. As well as taking up a large amount of land, that is going to require an enormously large amount of materials to make those solar panels, including some with polluting production processes. This is without worrying about storage, or any other details like that. I like solar power, and I think it certainly has its place, but I hope you see why people also want to make artificial fusion work.