Surplus renewable electricity helps create renewable natural gas and renewable hydrogen gas that can be stored for future use.
Renewable energy sources like photovoltaic solar and wind turbines have grown greatly in recent years, helping to reduce greenhouse gas emissions. So much renewable energy is now being generated in California that frequently more electricity is created during the day than can be used at the time.
Robust mid-day generation is countered by sharply increased demand in the early evening, as people return home from work and school and solar electricity production wanes. Finding a way to store the excess renewable energy produced during peak generation periods so it can be used in future peak demand periods is becoming a significant challenge.
An exciting prospect for meeting that challenge is power-to-gas (P2G) technology that uses surplus electricity to create renewable hydrogen or renewable natural gas (methane) that can then be stored in natural gas pipelines and used as needed.
How does it work?
Excess renewable electricity is used to convert water into renewable hydrogen by employing the process of electrolysis. Electrolysis splits water (H2O) into hydrogen gas (H2) and oxygen gas (O2) in a piece of equipment called an electrolyzer that contains an “anode” and a “cathode” separated by an electrolyte or membrane.
As electricity flows through the electrolyzer the water releases oxygen and hydrogen. The oxygen is usually released into the atmosphere but the hydrogen is captured and can be mixed with natural gas and stored in the pipeline system.
Renewable Natural Gas
Converting the renewable hydrogen into renewable natural gas (methane) adds an additional step after the electrolysis process called methanation. When methanation is accomplished using a biological process it is called biomethanation.
In biomethanation, the renewable hydrogen is combined with carbon dioxide (CO2) and fed into a bioreactor in which single-celled microorganisms ingest the hydrogen and carbon dioxide and expel methane (CH4) to produce renewable natural gas (RNG).
The resultant RNG can then be injected into the natural gas pipeline system and can be used in everything from home appliances to industrial processes, engines and power plants.
SoCalGas® P2G demonstration projects
While there are many power-to-gas demonstration projects in Europe, SoCalGas® is a leader in bringing the technology to the United States.
University of California at Irvine (UCI)
SoCalGas has teamed with the National Fuel Cell Research Center (NFCRC) at the University of California at Irvine (UCI) to launch the first U.S. P2G project. An electrolyzer powered by the on-campus solar electric system was installed at UCI that feeds its renewable hydrogen to the campus power plant.
A second project with UCI involved a simulation of the campus microgrid that showed the fraction of renewable power used by the microgrid could increase from 3.5 percent to 35 percent by using a P2G strategy.
Most recently SoCalGas and UCI announced plans to design an “Advanced Energy Community” in an underserved neighborhood in Huntington Beach. The community will be planned as a replicable model that optimizes a full spectrum of diverse energy options, including solar, wind, and renewable natural gas. It will also consider the capability of storing wind- and solar-generated energy with power-to-gas technology.
National Renewable Energy Laboratory (NREL)
SoCalGas has also partnered with the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) to install the nation’s first biomethanation reactor system located at their Energy Systems Integration Facility (ESIF) in Golden, Colorado.
This project aims to accelerate the commercialization of P2G by further studying the efficiency and performance of P2G as a renewable energy storage strategy.
The photo above shows the bioreactor being installed at NREL in the fall of 2017.
Clean Energy Future
As California increasingly moves to a renewable energy future SoCalGas will continue to be a national leader in the ongoing development of renewable power-to-gas technology as an effective way to convert excess renewable electricity to long-term storable renewable energy.