Mr. Vale showed the class many different types of heat engines and the different types of functionalities that each one had. One of the heat engines used solar energy to keep itself powered. Mr. Vale said that this type of heat engine comes in many different forms. There was also a heat engine that used water to power itself. Lastly, Mr. Vale showed us an electric bug swatter that used an electric charge to kill bugs. If you placed anything against the netting, a spark would occur. All of these different heat engines were said to come in many different forms, but all were said to be fully functional.