By Geoff Milburn

it was the summer of 2005, during my third year of civil engineering at the University of Waterloo (that's in Canada), and I was miserable.

I lived on the first floor of an old house in the middle of what can only be described as a student ghetto. Rows of old houses surrounded the university, long ago surrendered by suburbia to college students. Nobody could afford an air conditioner, and fans just moved the stifling air around. Sometimes I took a shower at 4 a.m. just to feel the cold water on my skin.

One day, my girlfriend, Emily, and I decided to seek air-conditioned sanctuary at the movies with a few of her friends. Unfortunately, they wanted to see The Sisterhood ofthe Traveling Pants. As we approached the ticket counter, it dawned on me that I would never get the next ninety minutes of my life back. I needed a good excuse—and fast. Earlier in the week, I'd begun pondering a way to build a homemade A/C. I figured now was as good a time as any to give it a shot. I turned to Emily and mumbled something about solving all our problems. She looked mildly annoyed, but not enough to make a scene. "I'll be at the Home Depot," I said, realizing as I said it that the store would also be gloriously air-conditioned. "Enjoy the movie. I'll pick you guys up in an hour and a half." And then I fled.

I was armed with a student's budget and a half-formed concept involving cold water, coiled tubing, and a window fan. If this worked—if I figured out how to keep us cool tonight— Emily would forgive me for running out on the movie. If not, the temperature in the apartment we shared would be the least of my problems.

Twenty-four dollars and an hour and a half later, I picked up the girls and we headed home. I assembled my materials: an old garbage can, vinyl tubing, copper tubing, my roommate's floor fan, and a large package of zip ties—those small, flexible, plastic fasteners used to secure almost anything that needs securing. I began by coiling the copper tubing in a spiral along the front of the fan, securing it with zip ties as I went. I used an X-Acto knife to slice the vinyl tubing into two pieces, which were then attached to the ends of the copper tubing on the fan. One end went to the bottom of the garbage can filled with ice water that sat on my apartment floor; the other hung out my first-floor window.

I went outside and started to suck as hard as I could on the end of the vinyl tubing. My theory was that the elevation difference between the water in the garbage can and the end of the tubing would be enough to sustain a siphon effect. (A siphon allows fluid to drain from one container to another, using only the difference in elevation between the two containers to power the flow. Probably the most common—and illegal—application is using a garden hose to siphon gasoline from the tank of someone else's car. In my case, I was just trying to siphon some ice water through a contraption that hopefully wouldn't flood my room.)

I had been sucking on what felt like a glue milkshake for a minute or two when a trickle, then a spurt, and finally, to my elation, a smooth stream of water started flowing from the end of the tubing. The siphon had managed to pull water up from the garbage can, through the copper tubing surrounding the fan, and then out my window.

My hope was that the flow of cold water would chill the copper tubing. The fan would then blow the hot, stagnant air in my room across the tubing, cooling the air. And the damn thing actually worked! While it didn't reach the goose-bump level of the movie theater or Home Depot, it knocked ten degrees off the temperature in the room and removed a bit of humidity as water condensed on the copper coils.

I replaced the garbage pail with a water supply fed by a garden hose patched in through the window. The hose could supply much more water than a single garbage can, allowing the system to run longer. But most importantly, as soon as Emily

walked into the cooled bedroom, she forgave me for skipping out on the chick flick. Chalk one up for science.

Geoff Milburn wore makeup for the first time in his life when his "Homebrew A/C" attracted the attention of local media, and led to a TV interview about it. For more on his invention, go to wwweng.uwaterloo.ca/—gmilburn/ac/.

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