A thermopile is a device that is used to measure temperature or to convert heat energy into electrical energy. However, there are a few other words that can be used as synonyms for thermopile. These include heat sensor, thermocouple, thermoelectric generator, and pyrometer. A heat sensor is a device that can detect changes in temperature. A thermocouple, like a thermopile, uses temperature differences to generate electricity. A thermoelectric generator is a device that can convert heat energy directly into electrical energy. Finally, a pyrometer is a type of thermometer that is used to measure high temperatures, such as those in furnaces or engines.