During the winter, saving money on your heating bill is just a dumpster dive away. Daniel Strohl took 50 aluminum cans he had sitting around, drilled a few strategically placed holes to allow air to flow, painted them black, then sealed the whole thing up in a Plexiglas, 2 x 4-foot enclosure to create a solar heat pump. Since we all know black metal absorbs heat faster than an Emo kid on a sunny day, this do-it-yourself device ends up generating enough heat to increase the temperature anywhere from 10 to 15 degrees (Fahrenheit, most likely). Slap a wind-turbine fan on the heat exhaust and you have yourself a cheap space heater for your garage, camper or tent. Take that, electric company!
Yeah, I know, this doesn't do any of us living in the Northern Hemisphere any good right now, but you may need a little time to drink those 50 cans or soda. If soda isn't your thing, head down to the local college campus and get 500 empty "beverage" containers in just one weekend. That many cans would be enough to build a heat pump to warm a good-size room.