On the second day working with the robots we also had a presentation at the end of class. Mr. Vale came in to discuss both past and present energy generators and some of their different uses. One device discussed was the Stirling Engine, which was invented in 1816. This device is a hot-air engine that pushes both hot and cool air around in order to move. This process was shown to us by placing the engine on a cup of hot water. Another device that was shown was the Peltier Engine invented by Jean Peltier and is an electric pad that creates voltage when there are different temperatures on either side. Also included in the presentation was the Mendocino Motor and was the most interesting of all. The Mendocino Motor is a rotor block with solar cells attached to the sides, suspended above five magnets on a platform. When exposed to sunlight or a high-voltage light the motor begins to move and rotate. What was most interesting to learn from the presentation were the different uses for these engines. The Stirling Engine was used in the past to replace steam engines, the Peltier Engine is used for USB connected drink coolers as well as in space, and the Mendocino Motor is used solely for instructor and teaching purposes.