That's an interesting question and Nelson Kruschandl is just the man to give you the answer. According to Speedace, he's a designer of solar cars and has endowed his knowledgeable verbiage with photographs and diagrams of his designs that will keep you enthralled for the entire length of the document.
The solar car is an electric vehicle that gets its energy from the sun's rays from photovoltaic cells (cells that generate voltage when exposed to light or any other electromagnetic radiation). A battery is used as a load leveling apparatus. Unlike other battery-powered cars, the solar car retrieves its potential from a "clean and renewable source of energy". Fuel cells (generate electricity by converting the chemical energy of a fuel and oxidant to electric energy) can substitute for or enhance batteries. Some things a solar car absolutely must have: efficient photovoltaic cells, an aerodynamic form, light and efficient batteries, a high performance motor, adequate controls, and weight of about 250-300kg. This endeavor might be considered more than a hobby and quite an accomplishment! Sunshine, so divine!
Nelson provides the necessary weight, power, cargo capacity, and step-by-step blueprints to get you started on your homemade Solar Buggy. By the way, he gives an estimated total cost of $10,000. Pittance!