We don’t believe in the hydrogen economy, much hyped in the past, for the simple reason that hydrogen does not exist in nature and needs to be produced. That production invariably goes hand in hand with conversion losses. So why would you want to use electricity, generated by solar or wind, to produce hydrogen first, to power a tram with it next. It makes more sense to directly pump the electricity in the grid and use it to power the tram in the conventional way.
Hydrogen perhaps has its place as a means to store energy for selected niche applications in a renewable energy economy, but the best way to store energy is in batteries or pumped hydro storage in mountainous areas.
The hydrogen economy won’t fly as things stand now.
[alternative-energy-news] – Hydrogen-powered tram developed in China
[wikipedia.org] – Hydrogen economy
Efficiency electrolysis water:
Current best processes have an efficiency of 50% to 80%
So you already lost 20-50% in the conversion process electricity –> H2.
An Otto cycle internal-combustion engine running on hydrogen is said to have a maximum efficiency of about 38%, 8% higher than a gasoline internal-combustion engine.
Compare that to the efficiency of an electric motor:
BLDC motors are typically 85–90% efficient or more. Efficiency for a BLDC motor of up to 96.5% have been reported, whereas DC motors with brushgear are typically 75–80% efficient.
See? Hydrogen does not make sense at all in the case of trams.
[phys.org] – Why a hydrogen economy doesn’t make sense
In a recent study, fuel cell expert Ulf Bossel explains that a hydrogen economy is a wasteful economy. The large amount of energy required to isolate hydrogen from natural compounds (water, natural gas, biomass), package the light gas by compression or liquefaction, transfer the energy carrier to the user, plus the energy lost when it is converted to useful electricity with fuel cells, leaves around 25% for practical use — an unacceptable value to run an economy in a sustainable future. Only niche applications like submarines and spacecraft might use hydrogen.