What are some ideas of a solar system project that does not cost much?

Solar energy is basically heat so why not heat a fluid and use it to run an electrical generator. Get a old large antenna dish and cover it with aluminized mylar. It can be constantly aimed at the sun for a small price in several ways. You can find one that tracked satellites and retrain it. At the focus a ball with the liquid flowing through it gets heated. Use it to run a steam engine or to heat the house. A half pipe approach doesn't require constant tracking. The medium flows through a pipe in a half round channel at its' focal point. As a community project for a school or community building the price could come way down. Window box heaters where you make a rectangular box with channels for heat flow. It is painted black taking air in from the room at the bottom and heated air coming out the top and into a window. Just putting a black plastic hose on your south facing roof will give you steaming hot water. Bread box heaters are very cheap. Just a black box with piping inside that heats water. Do it right and cheap you might develop a salable project. Even the "making of" book or video would be fun to make .