DIY Solar Powered Window Air Conditioner: Part 6, Reengineering

Peltier modules are really neat. Put some electricity, one side gets hot and the other side gets cold. One little module can easily freeze over on one side, which being uncomfortably hot on the other. This leads makers to attempt to build all kinds of air conditioners, refrigerators, and other things from them. Most of these projects fail to live up to expectations, or are incredibly inefficient. Many Makers, faced with their first failed cooling device, assume that Peltiers just aren’t worth the effort and will never work. This is only partially true.

Cries of inefficiency have led to some Bloggers, Youtubers and Makers to say using these devices are impossible, or absolutely the worst possible way to cool something. They pull out a compressor system and talk about the Coefficient of Power (COP). The talk about how a Peltier can never be as efficient as a compressor, or never as efficient a heater as a resistive element. This is also only partially true, but not as true as you’d think.

I’ve learned a LOT about cooling with Peltiers, but it wasn’t until I tried heating something with them and dug into the science behind them that I learned how they really work, and how to get the most efficient transfer of heat from them. It’s like building a battery. Building a simple battery is easy, slap a potato and some dissimilar metals on the table and light an LED. Building a good battery that can charge a cell phone, or drive an eBike, requires the same fundamental concepts, but really…