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." .....