Perpetual Energy Wasting Machine” is a rope and pulley mechanism, installed in the staircase of the WRO Art Center in Wroclaw, Poland. The mechanism connects the sliding doors of the elevator in one floor with the elevator call button on another floor. Operating in two directions on the first and on the second floor, the contraption automatically moves the elevator cabin in an infinite loop between those two levels.
How much energy does the setup waste?
The “Perpetual Energy Wasting Machine” moves the elevator in recurring cycles. In the first half cycle, the elevator is lifted up one floor, while the latter half cycle brings the elevator down to its original position again. As this is an hydraulic elevator, and as the cabin´s mass is not equalized by a counterweight, only the movement up consumes electricity. Estimating that the empty elevator cabin has a mass of 350 Kilograms, the wasted energy is about 11.8 Kilojoules per cycle (which equals to the metabolic energy of ca. 1/3 grams of fat, according to Wolfram Alpha ). A modified printing calculator inside the elevator cabin keeps track of the wasted energy, automatically adding up 5.9 Kilojoules for each half cycle. The results of this symbolic calculation – which does neither regard energy loss by friction, nor a heavier cabin due to possible passengers – go straight to a waste bin, located beneath the printing calculator.
But what about the law of conservation of energy?
As we’ve learned in school, and as most of the readers might still remember, energy cannot be wasted. It can only change its location within a system. So what happens to the energy in this elevator system? Where does it go? Well, firstly, electric energy is used to lift up the elevator cabin (via a pump, with a hydraulic cylinder). When the elevator has reached the second floor, this energy has transformed to potential energy of the elevator cabin in its high position. The potential energy is released when the elevator returns to the first floor. In theory, this obviously doesn’t require any electricity, as the cabin could be just dropped. However, this kind of rapid plunge would cause discomfort for possible passengers. Thus, having a controlled descent using the hydraulics might be a good idea: For example, the hydraulics oil could be released gradually from the cylinder through a valve. I don’t exactly know how this elevator type works in practice – but let’s assume that the opening of a valve is all what happens. Now, pushing the oil through the small hole of the valve heats up both, the valve and the oil, due to friction. So finally, when the elevator has returned to its original position, the electric energy used to lift the cabin has been turned into heat.
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