"Hydrogen is awesome and the fuel of the future!"
That was Roar Nicolaisen's, our resident Energy Storage Expert, answer when asked, how he views hydrogen and its future within our response to electrification and implementation of energy storage.
This particular statement will provide the foundation for this blog where we uncover the technology and reveals to you what uses it has in energy storage.
So far, we can imagine a future where electric vehicles will do the bulk of short trip transportation. Look out of the window, and you will already see that e-bikes, e-scooters, and e-cars are on the roads. But for vehicles that are operating on longer distances, such as trucks, the range and recharging time is an issue. If we look at the long-route shipping and aviation, the energy density of batteries becomes too low. The battery required for a trans-Atlantic flight becomes too large and heavy to fit on the airplane, and thereby fuel is a better option.
Enter Hydrogen! Hydrogen is the fuel that possesses the highest energy density of all alternate fuels, containing about three times the energy per kg compared to diesel. The drawback with hydrogen, however, is that each kg takes up a large volume or is required to be put under high pressure, for the volume of the gas to come down to a manageable size. A solution to the volume problem could be to combine the hydrogen with carbon or nitrogen atoms, and thereby produce fuels such as methanol or ammonia.
Okay, so we will still be needing fuels of some types in the future, but hydrogen could be the main component.
Is that the only benefit of hydrogen?
To achieve a sustainable society, we need to transition our electricity production from “on-demand” fossil fuel combustion to “intermittent” renewable energy sources like Solar cells (PV) and Wind turbines.
To simplify, let's imagine that 100% of all electricity consumed in Denmark had to come from either PV or wind turbines. In order to produce the least amount of electricity for consumption, we would need to have so many wind turbines to satisfy the societal demand for a single evening. But, if later that night, the wind speed was to pick up, then the same many wind turbines would produce a large excess of energy. Now what should we do? just turn some of the windmills off? A better way would be to try and store some of the excess energy and then release it later when our wind turbines are “underproducing” compared to the societal demand for electricity.
"But what can we do to store all that excess energy?" you might ask.
Well, we could try lithium-ion batteries, after all, they have gotten cheaper lately. If we were to store wind energy in a Lithium-ion battery we would (only) get about 26 full charge/discharge cycles in a year, as the weather patterns make it so that wind generally blows more one week (26 times charging) and a little the next week (26 times of discharging). Now, let’s primarily use Lithium-ion for short-distance vehicles, and to store PV energy. In combination with PV, Lithium-ion will get ~200 full charge-discharge cycles a year as there are about 200 days a year with good PV conditions at danish latitudes, much better use of the batteries.
And so, we arrive at hydrogen production.
For hydrogen production, the most expensive part is the electrolyser that converts electricity to hydrogen. Storing the hydrogen after it has been produced, is the cheap part. For example, let's say that we have a week with high wind speeds, then our wind turbines produce lots of electricity, in excess of the societal demand. For the entire week, we turn our electrolysers on and convert electric energy to chemical energy in the form of hydrogen.
Hydrogen thus is a potential solution to two problems. What do we do with excess electricity produced by wind turbines? How do we limit emissions from hard to electrify transport like long-distance shipping and aviation?
Did you find this interesting? Then consider reading our contribution to the technical catalog: https://ens.dk/sites/ens.dk/files/Analyser/technology_data_for_renewable_fuels.pdf#page=94