Beer was reportedly invented sometime around 5,000 B.C. So it's shocking to think that refrigeration wasn't invented until the 19th Century. Because that means that the majority of man drank warm beer for nearly 7,000 years. Which is kind of gross.
Nowadays we can all enjoy a cold beer whenever we want, and your correspondent might even be enjoying one right now, depending on whether or not your correspondent's bosses are reading this. But we rely on electricity and refrigeration to keep our brews frosty. Four fellows in Denmark, however, have figured out how to keep beer cold, outside, without using any power.