Sterling engine and Climbing Stairs

Sterling Engine

The way a sterling engine works is a piston moved the air inside the cylinder from the hot side to the cold side.  The gas expands when it is on the hot side and pushes up the piston and it contracts and pulls the piston down when it is on the cold side.  We put a hot water reservoir on the bottom of the sterling engine and a cold reservoir on top by placing ice cubes on top of the engine. The bigger the temperature difference between the reservoirs, the quicker it will turn.  All sterling engines have low cycles per second which in turn makes them have low power, so they won’t do a good job running a car because the power to weight ratio is low.  These engines are also used for solar energy production.  A big plate painted black is outside of the ground so the sun shines on it to warm it up and other half is underground to stay cool.  Efficiency of these sterling engines are 1 – Th/Tc.  The average ground temp is approx. 10 degrees Celsius and the sky is about 40 degrees Celsius so the efficiency is 1- 270/300 which is .1 or 10% efficiency.  Efficiency improves with the bigger temp difference, but what this engine creates is creates mechanical work and so you have to put it through a generator to convert it to energy

Climbing Stairs

We were asked how many floors per minute you would have to climb to generate 760 Watts.  We determined that a floor is approximately 5 meters by sticking a meter stick through the roof until it hit the bottom of the floor above us.  Assuming we weighted 100 kg and that one floor was equal to 5 meters , we found that you would have to walk 9.30 floors per minute to generate 760 Watts.  Although I could probably run one or two sets of stairs in what seems like no time, I don’t believe that I would be able to keep that up for 9 floors and keep my time under a minute.