When I taught energy efficient food preservation methods for many years at the Midwest Renewable Energy Fair I used to bring this method up first and foremost, telling folks that most of them probably already owned a food dryer without even knowing it. My more advanced method ;>) has the car parked with the largest window facing south, usually front but sometimes back window, rolling windows down about 1", and covering foods with a dark colored cotton cloth to keep UV light off foods to preserve color and vitamins. The windows should be closed at night if stuff isn't dry enough after the first day. I had a couple of neighbors who used this method almost exclusively. One had an old 1970's clunker with lots of space and really big windows and he even dried blanched sweet corn on cookie sheets. Another used to work at Seed Savers in Decorah, Iowa and she "rescued" produce after harvesting seeds, especially sweet peppers, and had her car parked at work and would tend to stuff on lunch break.