Although I was sick and didn’t have the chance to go to class and listen to Tom Vales presentation about the various engines and machines, but one of my friend is still nice enough to explain to me what has happened in that class. The first thing he showed us was the stirling engine. The engine was invented by Robert Stirling back in 1816, making the engine has about 200 years of history. As he describes, the engine we use is still the same today, however, the engine is still 80% effective, and it runs at the bottom of the machine by heat. This engine is still used nowadays, such as in submarines, to keep it quiet and power the generator. Tom later on placed the engine on top of the warm cup of water, so that the heat the warm water releases will be absorbed by the engine, and therefore, making the machine work. 
The next thing he showed use was the Peltier Junction. The Peltier Function has uses the copper and metal to generate a electric current. In the experiment, he used two coffee cups, one containing hot water, and the other cup containing cold water. Tom then puts one junction in the hot water and while the other one in the cold. The function will then generate a type of energy, and the energy could be used to run the motor. However, as he describes, the function is inefficient.
The third thing that he showed us was the Mendocino Motor. Saying its a motor, this motor doesn’t create any energy, but it is sure a good teaching tool. The rotor on the machine is floating on a magnetic fields, and when the light shines on the rotor, the rotor will then eventually spins. Therefore, the sun could be a source replacing the light to making to rotor to move.
Due to fever, I didn’t go to class and can’t see the presentation with my own eyes, however, when my friend describe it to me, it still fascinates me! It was amazing how even using hot water and cold water can also generate energy.