Wikipedia
Power-to-X (also P2X and P2Y) has two meanings. First, power-to-X refers to a number of electricity conversion, energy storage, and reconversion pathways that utilize surplus electric power, typically during periods where fluctuating renewable energy generation exceeds load. Second, power-to-X refers to conversion technologies that allow for the decoupling of power from the electricity sector for use in other sectors (such as transport or chemicals), possibly using power that has been provided by additional investments in generation. The term is widely used in Germany and may have originated there.
The X in the terminology can refer to one of the following: power-to- ammonia, power-to- chemicals, power-to- fuel, power-to-gas, power-to- heat, power-to-hydrogen, power-to- liquid, power-to-methane, power-to-mobility, and power-to-power.
Collectively power-to-X schemes which use surplus power fall under the heading of flexibility measures and are particularly useful in energy systems with high shares of renewable generation and/or with strong decarbonization targets. A large number of pathways and technologies are encompassed by the term. In 2016 the German government funded a €30million first-phase research project into power-to-X options.