The California Public Utilities Commission (CPUC) is seeking comment on a study about the feasibility and safety of injecting hydrogen into the natural gas system as a means of helping the state meet its decarbonization goals.
The CPUC commissioned the Hydrogen Blending Impacts Study in compliance with Senate Bill 1369 and as part of its ongoing Renewable Gas Rulemaking.
The Rulemaking examines expanding renewable hydrogen by establishing standards and interconnection protocols for injecting renewable hydrogen into natural gas pipelines.
The study was done by the University of California at Riverside.
The study found that hydrogen blends of up to 5 percent in the natural gas stream are generally safe but going beyond 5 percent results in a greater chance of pipeline leaks and the embrittlement of steel pipelines. In addition, hydrogen blended into the natural gas stream at levels above 5 percent could require modifications of appliances such as stoves and water heaters to avoid leaks and equipment malfunction.
Hydrogen blended at levels above 20 percent present a higher likelihood of permeating plastic pipes, which can increase the risk of gas ignition outside the pipeline. And because hydrogen has a lower energy content than natural gas, more hydrogen-blended gas would be needed to deliver the same amount of energy to users.
The researchers concluded that more study on the effects of blending hydrogen into the gas system is needed to ensure the safety of the practice. The researchers also said it is critical to conduct real world demonstrations of hydrogen blending under safe and controlled conditions to determine “the appropriate blend percentage suitable to mitigate operational risks such as ignition.”
In March 2020, the Northern California Power Agency said it was preparing to install equipment at a 304-megawatt (MW) power plant so it could burn hydrogen mixed with natural gas.
In December 2019, the Los Angeles Department of Water and Power said it planned to phase out the 1,800-MW, coal-fired Intermountain Power Project (IPP), which it participates in with electric power cooperatives and other public power utilities in California, Nevada and Utah, and replace it with natural gas-fueled generation that would eventually be fueled entirely by hydrogen.
“This Study provides additional insight into the possibilities and limits of California’s pipeline infrastructure as we explore options for supplying zero-carbon energy to hard to decarbonize applications,” Clifford Rechtschaffen, the CPUC commissioner assigned to the Renewable Gas Rulemaking, said in a statement. “I look forward to party comments on hydrogen-methane blending and its role in decarbonization strategies.”