In a not too distant past the “hydrogen economy” was thought to be the follow up of the fossil fuel economy. The idea was to use hydrogen as the central storage medium.
|Fuel||Energy density [kWh/kg]|
[wikipedia.org] – Hydrogen economy
Enthusiasm for that concept has come down considerably since, mostly because of fundamentally low conversion efficiency (50-80%) and storage problems. But that doesn’t mean that hydrogen couldn’t play a role in a renewable energy future. This IEA article makes the case that renewable hydrogen production for NH3 (Ammonia), to be used as fertilizer in agriculture, could become viable in the near future, circumventing at least the hydrogen storage problem (boiling point −252.879 °C (−423.182 °F, 20.271 K)), by converting it immediately into Ammonia (boiling point −33.34 °C (−28.01 °F; 239.81 K)).
Indeed, producing hydrogen via renewable energy is not a new idea. Until the 1960s, hydrogen from hydropower-based electrolysis in Norway was used to make ammonia – a key ingredient for agricultural fertilizers. But with increasingly lower renewable costs, renewables-based hydrogen production could once again be competitive with SMR (steam methane reforming)…
But under the right conditions, producing industrial hydrogen in this fashion could have massive consequences for the sustainability of one industry in particular – agriculture. About half of industrial hydrogen is used in ammonia production. Ammonia production alone is responsible for about 360 million tonnes of CO2 emissions each year, or about 1% of the world’s total emissions. By 2050, we expect that the consumption of ammonia will increase by around 60%.
The vision of cars driven by hydrogen has not materialized. Instead the battery and electricity seem to have won the competition. With airplanes it is different. Although electric planes could be reality in a decade or so, for longer distances this is not an option. Hydrogen could very well be.
The German Aerospace Centre DLR in Jülich has recently opened a research facility consisting of an artificial sun, with an intensity of 10,000 times the original. The idea is is to study how sun light can be used to generate “solar fuels”, like hydrogen.
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.
Solar panels are on the march worldwide. One of the disadvantages of solar power however is its intermittent character, making storage an essential ingredient of every solar based energy system. Researchers of the École Polytechnique Fédérale de Lausanne (epfl) have presented a new Perovskite solar cell able to split water and produce hydrogen at an acceptable efficiency of 12.3%. Hope exists that this efficiency could increase to 20% by applying semi-conductors. This could breathe new life into the moribund hydrogen economy. As things stand now large scale hydro storage is the most attractive proposition backing up a large scale renewable energy system.
[spiegel.de] – Billig-Zelle verwandelt Licht in Wasserstoff
[sciencemag.org] – Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth-abundant catalysts
[wikipedia] – Michael Grätzel
[cleantechnica.com] – Perovskite Solar Cells Beat New Records (In The Lab)
Note that Lausanne combined perovskite solar cells with electrochemistry.
Over the last five years, perovskites have been found to rival the efficiency and cost of silicon in converting sunlight to electricity.
Organisations from Scandinavia and Asian car manufacturers have signed a memorandum of understanding to set up an infrastructure based on hydrogen in combination with producing cars with a fuel cell by 2015. Car manufacturers: Toyota, Hyundai, Honda & Nissan. Hydrogen providers: HyOP AS and H2 Logic A/S. Mode of operation: fuel cell.