Preservation is paramount to a year-round supply of food. There are many ways to preserve food, but the easiest methods for the self-producer are refrigeration, drying, and canning.
Food preservation is one of the most important stages of food production. Without efficient preservation, we would never be able to make it through the winter or the hungry gap of the early spring.
When something is in season, you have more than you can handle, and then there's nothing for the rest of the year. So the obvious solution is to preserve your food when you have it in abundance, and drying with the sun is one of the easiest, most energy efficient ways to do so.