Power-to-Gas (P2G) is an integrative technology that builds a physical bridge between the electricity, gas, and heat systems. It offers a number of unique properties not shared by other energy storage technologies:
- High-capacity/high-duration energy storage: P2G utilizes the existing natural gas pipelines and storage caverns which offer practically unlimited energy storage capacity. As a consequence, a power-to-gas facility is never “fully charged”, which enables the multi-day “charging” periods required in energy systems with high penetration of renewables.
- Geographic energy transmission capability: Once in the natural gas grid, the renewable gas can easily be transported over long distances to the final point of use. This feature is unique to P2G and is not shared by electron-storing facilities (pumped hydro, batteries, etc), for which the charging and discharging locations are the same. The ability to transmit energy geographically is desirable to alleviate electricity grid congestion and regional supply/demand imbalances and to defer capital investment in transmission grid expansion.
- Flexibility in energy use: The renewable energy storage as gas can be converted back to electricity, but power production is just one of the utilization pathways. The gas can also be used as a renewable fuel in transportation, for heat production in households and industry, or as a feedstock in chemical processes. As such, P2G promotes the convergence of energy systems.
- Provision of ancillary services: With response rates of less than 5 seconds and an ability for fast ramping and intermittent operation, P2G units are highly flexible and can provide frequency regulation and tertiary reserve energy to balance the power grid.
- Dissociation of charging/discharging, zero self-discharge, and seasonal storage: Energy stored as methane can be returned to the energy system within hours, days, weeks or months after grid injection at minimal loss or self-discharge. The long storage duration enables seasonal storage, a unique feature of P2G that is particularly useful for shifting wind and solar energy from energy-rich to energy-poor seasons.
- High scalability: The modular nature of P2G enables the distributed deployment of units in sizes optimal for the specific task at hand. P2G units can be deployed in sizes as small as 100 kW and as large as dozens of megawatts, allowing facilities to be sized optimally with regards to grid requirements and available resources.
- Low cost/long lifetime: P2G units can be deployed at low unit capital cost. The lifetime of the majority of system components reaches up to 30 years. While the electrolyzer’s cell stacks have to be replaced after 8-10 years, their lifetime is generally independent of cycling patterns.