You need pop or beer cans (aluminum) for the can solar heater, not food stuff cansWhy is that? Sure aluminum Is a great conductor but food cans made of steel conduct pretty well. I can get paid for aluminum but steel cans can be hard to get rid of because of a the inside coatings that aare used to make them safe for food use. ~gd
You can use some of your cans as filler in large planters. I saw some pics a long time ago where someone made 'rocks' using cans wrapped in a couple layers of chicken wire, then coated a few times w/ lightweight concrete. On the same note, you could use them as filler for a concrete edging around your drive or flower bed, too.