Physics help: create a car that harnesses wind energy to propel forward.?

For my physics cl I need to create a car that will harness the wind energy produced by a 20 in box fan. We are thinking that you would need to use some sort of windmill to harness the energy. The car has to use the wind from the fan and somehow move towards the fan. The only materials we can use is coat hangers, staples, glue, tape, index cards, file folders, tin or aluminum cans, rubber bands, string, thread spools, pins, paper clips, and a maximum of one BIC pen. The wheels can be created out of anything circular other than an actual wheel. The fan will be about 1 meter away from the car and the car must travel a minimum of half a meter. Any type of help would be greatly appreciated. Thanks!