Electrochemical Conversion of CO2 to Fuels for Power to Gas Energy Storage

Concern surrounding the increasing level of greenhouse gases in the atmosphere, such as carbon dioxide, is intensifying global interest in discovering sustainable methods for the utilization of fossil fuels and the products of their combustion. Moreover, the need for grid-scale energy storage to manage renewable energy intermittency and over-generation is evident in the US as well as abroad. How this Problem or Situation is Addressed – A Power-to-Gas system converts electricity generated during periods of high output and low demand, such as strong wind during off-peak hours, by splitting water into hydrogen and oxygen through electrolysis. The hydrogen is stored for future use as fuel, while the oxygen may be sold for industrial use or released into the atmosphere. One of the three potential uses for the stored hydrogen is combining the hydrogen (H2) with carbon dioxide (CO2) to create synthetic methane (CH4), which could be used as a replacement for natural gas. Sustainable Innovations is developing an electrochemical system, the CO2RENEW™, that directly generates chemicals and fuels such as methane from water or another hydrogen source, and CO2. Commercial Applications and Other Benefits – Power-to-gas is a solution to problems that arise when an increasing share of power is generated from sources that have a highly variable output. The California Independent System Operator (CAISO) forecasts such challenges for the California grid. The now famous “Duck Curve” could lead to annual surplus renewable energy of up to 12,000 GWh (nearly 10% of renewable production) under a 50% renewables scenario (California has a target of 33% renewables by 2020). This curve reflects the reduced load in the middle part of the day created by increasing amounts of self-generated solar energy, and the need for rapid ramping of replacement resources in the afternoon/evening, which will add cost and pose technical challenges for both the electric and natural gas grids. Solar and wind accounted for nearly 5% of U.S. net electricity generation in 2014, and they are forecast to account for a greater share of the emerging generation portfolio. The natural gas system in the US has well developed storage capability with over 300,000 miles of transmission pipelines and 3.9 Bcf of underground storage capacity at 400 sites. Key Words – Power-to-Gas, CO2 reduction, CO2 to usable products, energy storage, grid stabilization, CO2 to fuels