Solar’s role in popularizing green hydrogen
Photovoltaics, with its array of complementary technologies and applications, is expected to be an integral part of another process to decarbonize the electricity grid: creating a carbon-free fuel source.
Hydrogen cells are an energy source that, when consumed, releases no carbon, only heat and water vapor. They are commonly used in food and fertilizer production, metal treatment and petroleum refining, but hydrogen can be used as both a source of electricity and a fuel cell. The biggest concern with hydrogen fuel production is that most of it is made with fossil fuels, about 95% worldwide.
However, there are many ways to produce hydrogen fuel and each production source is color coded. The use of natural gas as an energy source is referred to as blue or gray hydrogen; the use of nuclear energy is called pink, purple or red hydrogen; black and brown hydrogen is produced from coal; and of course it uses carbon-free energy sources such as solar green hydrogen.
Hydrogen fuel cells are created by splitting water molecules (H2O) to form separate hydrogen and oxygen molecules. This process is called electrolysis and is carried out by an electrolysis. The material composition of electrolyzers varies, but the general idea is that a water molecule passes between an electrified cathode and anode, splits into the two elements and expels the positively charged hydrogen and oxygen molecules, producing energy.
With a greater deployment of hydrogen production activities alongside renewable energy projects, there is the potential to produce a carbon-free fuel source that has a number of applications beyond what PV solar can currently power.
Application of solar energy with green hydrogen
As the name suggests, the process of electrolysis requires a lot of electricity, so renewable energy sources such as solar energy are a possible source of production. One hurdle to widespread green hydrogen production is that electrolyzers (the systems that use electricity to make the H2O-molecules) are still quite expensive. Analysts expect the cost of an electrolyzer halved by 2040.
A recently published study of the Carnegie Institution for Science found that regions with high reductions in solar, wind, and hydro could instead use that excess energy to produce green hydrogen. A once “wasted” electricity bank could be diverted to help electrolyzers.
Like storage technologies combined with solar projects, hydrogen fuel can be used as a backup of energy. It can be stored as gas or liquid and used as needed for various applications such as grid backup and transportation. It is possible to couple solar energy with hydrogen electrolyzers and storage units to provide instant backup where that electrical load is needed.
A challenge to properly store backup hydrogen is that it requires large tanks if it is in gaseous form. In scenarios such as grid backup, where there is ample space to place or bury tanks, that is less of an issue than in transportation and even small-scale distributed generation applications.
But another appeal of hydrogen, especially in vehicles, is that it has three times the energy density of gasoline. Cars can go much further on a liter of hydrogen than on gas – and it’s cleaner. Electric vehicles are a solution to decarbonise transportation and are certainly leading that effort, but the technology exists to power hydrogen-powered vehicles. Where a vehicle owner can power their electric car directly with solar panels installed on their home, solar energy could indirectly power hydrogen-powered vehicles by producing the fuel itself.
Electric vehicle manufacturers are trying to crack the code of electrifying heavy transport vehicles, such as semi-trucks, ocean freighters and airplanes. However, hydrogen fuel cells are a more viable solution for zero-carbon vehicles on that scale, experts say, and this could hold true for industrial use as well. Like conventional EVs, hydrogen fuel cell vehicles also use an electric motor, but have a fuel tank for transporting hydrogen gas.
Significant infrastructure expansion is required before hydrogen-powered vehicles are as widely available as even electric cars. In mid-2020 there were only 43 public hydrogen fuel cell service stations in the United States.
Green hydrogen is still an emerging fuel source in the United States, but development is on the horizon. The Biden Administration recorded it as a solution to the greenhouse gas reduction targets, and solar energy will undoubtedly be part of its production.