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Green hydrogen could transform our energy system and solve many supply and emissions challenges. Whether this happens will depend on how economically it can be produced and how attractive it will be to consumers.
Among the promising technologies for powering a net-zero future, hydrogen is a bit of an outlier. While solar panels, wind turbines, and hydropower plants all harness energy provided by nature and transform it into electricity, hydrogen doesn't fit into that mold. Andreas Züttel, head of EPFL's Laboratory of Materials for Renewable Energy, explains why: "Hydrogen is not an energy source, it's an energy carrier."
Already today, hydrogen is at the core of our energy system. Packing more energy per unit mass than any other substance known to man, hydrogen serves as the primary energy carrier in our fossil fuels. Hydrogen's free combustion with oxygen has blasted rockets into space. And thanks to our ability to control its combustion in fuel cells, it now powers a steadily growing fleet of vehicles on our roads.
According to Züttel, the problem with the hydrogen used today is that most of it, some 95%, is dirty. Where we rely on it, as in hydrocracking in oil refineries, producing synthetic fertilizers, and in the chemical industry, we source it from fossil fuels—which means a hefty carbon footprint.
A challenging shift to green and clean
Surprisingly, this very same substance is being hailed as a vital contributor to a net-zero-emissions energy system. The Swiss Federal Office of Energy (SFOE) sees clean, green hydrogen playing an important role in Switzerland's clean energy mix by 2050, starting from close to zero today.
Achieving this will require a major hydrogen cleanup. To shift from dirty hydrogen to clean hydrogen will require addressing hydrogen's many inherent challenges. Chemically, its lack of a liquid phase at room temperature makes it difficult to store. It is notoriously explosive, making it delicate to handle. Moreover, its inability to be odorized complicates leak detection.
In terms of energy efficiency, hydrogen lags behind other energy sources, requiring vast amounts of energy—66 kilowatt hours per kilogram—to be produced. The same is true from an economic perspective, with the cost per kWh of energy carried by hydrogen around two to three times higher than the market price for electricity.
Given all these drawbacks, why is there so much hope for hydrogen? Because, under the right conditions, this renewable energy carrier's properties could address challenges that will arise as we move towards a cleaner and greener energy mix.
The Swiss Army Knife of energy carriers
Research into hydrogen as an energy carrier surged in the 1990s, says Züttel. "When I entered the field 32 years ago, we thought hydrogen would replace all fossil fuels. In those days, we weren't yet hoping to combat global warming, we were trying to address the fear that fossil fuels would soon run out." As new fossil fuel deposits were discovered and increased production drove down their cost, the hydrogen hype cooled down.
Provided by Ecole Polytechnique Federale de Lausanne
