A power generation system comprising: a heat source adapted to have a temperature being increased or decreased over time; a flow passage through which a heat medium heated by the heat source passes; a power generation device including a power generation element and a first electrode, so adapted that when a temperature of the power generation element is increased or decreased over time depending on temperature change of the heat medium, the power generation element is electrically polarized by the temperature increase or decrease thereof, the power generation element including a dielectric with a Curie point, the first electrode extracting electric power from the power generation element; a temperature detection unit that is disposed on an upstream side relative to the power generation device in the flow passage and detects a temperature of the heat medium passing through the flow passage; a voltage application unit that applies voltage to the power generation device; and a control unit that activates the voltage application unit when the temperature detection unit has detected a temperature increase of the heat medium and deactivates the voltage application unit when the temperature detection unit has detected a temperature decrease of the heat medium, the temperature detection unit including: a temperature detection element, a temperature of the temperature detection element being increased or decreased over time depending on the temperature change of the heat medium, characterised in that the temperature detection element is adapted to be electrically polarized by the temperature increase or decrease thereof, the temperature detection element including a dielectric with a Curie point that is more than or equal to a temperature 50°C lower than the Curie point of the power generation element; and a second electrode that is adapted to detect electric polarization of the temperature detection element by detecting an electromotive force from the temperature detection element. a heat source adapted to have a temperature being increased or decreased over time; a flow passage through which a heat medium heated by the heat source passes; a power generation device including a power generation element and a first electrode, so adapted that when a temperature of the power generation element is increased or decreased over time depending on temperature change of the heat medium, the power generation element is electrically polarized by the temperature increase or decrease thereof, the power generation element including a dielectric with a Curie point, the first electrode extracting electric power from the power generation element; a temperature detection unit that is disposed on an upstream side relative to the power generation device in the flow passage and detects a temperature of the heat medium passing through the flow passage; a voltage application unit that applies voltage to the power generation device; and a control unit that activates the voltage application unit when the temperature detection unit has detected a temperature increase of the heat medium and deactivates the voltage application unit when the temperature detection unit has detected a temperature decrease of the heat medium, the temperature detection unit including: a temperature detection element, a temperature of the temperature detection element being increased or decreased over time depending on the temperature change of the heat medium, characterised in that the temperature detection element is adapted to be electrically polarized by the temperature increase or decrease thereof, the temperature detection element including a dielectric with a Curie point that is more than or equal to a temperature 50°C lower than the Curie point of the power generation element; and a second electrode that is adapted to detect electric polarization of the temperature detection element by detecting an electromotive force from the temperature detection element. a temperature detection element, a temperature of the temperature detection element being increased or decreased over time depending on the temperature change of the heat medium, characterised in that the temperature detection element is adapted to be electrically polarized by the temperature increase or decrease thereof, the temperature detection element including a dielectric with a Curie point that is more than or equal to a temperature 50°C lower than the Curie point of the power generation element; and a second electrode that is adapted to detect electric polarization of the temperature detection element by detecting an electromotive force from the temperature detection element.