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Name: Jerry
Status: Other
Grade: Other
Location: NY
Country: United States
Date: November 2007

Can I make an ice cube with a bike? (guaranteed to be an original question!) We are a group of long distance sailors who sometimes find ourselves in remote parts of the world. It is nice to have a fridge on the boat on these trips, but boat fridges are take up valuable space, break a lot, and require you to run the engine every day just to keep them cold. I do without a fridge, but really miss having ice cubes in my drink at the end of a hard day's sailing. I joked to my friends that I should hook up my bike (on board the boat) to a condenser. I could then peddle to pressurize the Freon, which would be expanded around a container just big enough to freeze one ice cube. My idea was met with skepticism, since most believe you would have to bike a long time. So our question (finally) is: how long would a reasonably fit person have to bike to generate enough power to make an ice cube from room temperature water? I did some calculations and came up with one minute. But this just sounds wrong.

Hi Jerry,

Well, yes, that definitely was an original question! The answer is there is no problem in one person providing enough "power" to run the compressor. A normal refrigerator compressor only uses about 1/3 horsepower, and a reasonably fit human should have no problem generating that much power....

....for a short time! And therein lies the problem. It typically takes an hour or two for a normal refrigerator to freeze ice cubes. So the question is not whether you could supply enough power, but rather can you supply enough energy. That is, the product of power and time! My suspicion is that you are going to get very tired before the water freezes!


Bob Wilson.

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