I think the box cooler is the best one. You can make it out of anything. Then put glass on top to trap the heat. Put the food inside and food will slowly cook. The box cooker can reach tempatures of at least 350°. It can also trap the most heat. if the the stays in then the food will faster. If the food can get cooked faster then, you can get it to people who need the food faster. This is why I think the box cooker is the best solar cooker.