Increasing the share of RES in the energy mix of countries is one of the primary objectives of the energy transformation of national economies. However, their instability is an obstacle, which generates the necessity to look for tools for effective energy storage, also in a long-term perspective. This is where hydrogen as an energy store plays a significant role.
Decarbonization of individual sectors of the economy and increasing the share of renewable energy sources in the energy mix are becoming the most important points of climate strategies and roadmaps of most countries. However, even the most ambitious assumptions collide with the reality, which is the instability of RES. This, given the plans to abandon the use of conventional fuels in the coming years, carries the risk of destabilizing energy systems and interrupting energy supplies.
Without a doubt, RES is crucial to the transformation of the global energy system, which accounts for over 73% of total carbon emissions. However, to think about transformation while ensuring full energy security, tools are needed to reduce possible risks. Including hydrogen for long-term energy storage, which will be supported by low-carbon biomass and nuclear.
Hydrogen as energy storage
Thanks to its properties, hydrogen can be used as an energy carrier and energy storage for balancing national energy systems. Among other things, hydrogen is highly efficient because it has the highest heat transfer coefficient of all gases. Its combustion also produces on average three times more energy than other fuels – gasoline, propane, or methane. However, it has so far played a minor role in Europe’s electricity sector. In 2019, it accounted for less than 2% of total energy production. It was mainly used in refineries, petrochemical plants, and metallurgy. However, as the European Union’s ambitious plans show in 2050, it may already account for more than 25%.
As the demand for renewable energy grows rapidly, so does the need for storage, and thus the importance of hydrogen itself. This, for a long time, has been considered one of the most promising substances for the storage of chemical energy, which can be converted back into heat and electrical energy. And not only for large-scale industrial or energy installations but also for the end-user.
The more we talk about hydrogen, the more we see its advantages over other alternatives. We cannot fail to mention that at present there is a whole range of energy storage technologies that differ mainly in capacity parameters, energy storage time, charging and discharging time and, of course, installation prices. Battery systems dominate among them. Apart from them, kinetic (flywheel storage) and thermal energy, compressed air, and pumped-storage power plants are also used. However, the average storage time remains relatively short. In the case of batteries, energy is stored on average from a few minutes to a few days and mostly in the range of 10 MW. Kinetic energy provides average storage of up to 100 MW in a few minutes to several days. Thermal energy provides average storage of more than 100 MW in a few to several days. Pumped storage plants, on the other hand, store more than 1000 MW for up to several days. Hydrogen and hydrogen fuels, such as ammonia, clearly stand out from these. They allow average energy storage of up to 1000 MW for several weeks to several months. Some studies have shown that with low losses, they can store energy for up to a full year. This becomes one of the most important advantages of hydrogen concerning ensuring energy security.
Especially that the market dominated by battery systems may eventually run out of lithium for the production of batteries in such technologies as LFP (Lithium-iron-phosphate), NMC (Lithium-nickel-manganese-cobalt-oxygen), LCO (Lithium-cobalt-oxygen) or LMO (Lithium-manganese-oxygen). The demand for this raw material is constantly increasing, among others due to the development of electromobility. As experts emphasize, with the growing production of batteries resulting from the current demand (96 million vehicles in 2018), the resources of raw material estimated at 40 million tons may be exhausted in the next 300 years. And this is an optimistic scenario. With estimated resources of 11 million tons, the time of depletion of deposits is the perspective of the next 100 years.
How to store hydrogen?
The production of hydrogen from RES uses electrolysis. It splits water under the influence of electricity into hydrogen and oxygen. In this way, we obtain zero-emission green hydrogen, which can be used directly, stored for later use, or converted back into electricity.
Several hydrogen storage technologies are currently available and are continuously being improved to ensure the highest possible hydrogen storage efficiency with specific physicochemical properties and thus the safety of use. Hydrogen can be stored, among others, in specially adapted pressure vessels (compressed and liquefied), post-mining salt caverns (compressed and stored on an industrial scale), hydrogen-rich chemical compounds in the form of metal hydrides, and porous substances.
Re-converting hydrogen into energy is possible with fuel cells. This is a more efficient method of converting hydrogen than, for example, burning it directly. Its efficiency is currently around 60%.
Hydrogen storage – hydrogen hub
Hydrogen as energy storage is not a song of the future, but an increasingly close reality. And although this technology is not yet widely popularized, it will soon constitute the basis for the energy transition. This is because it makes it possible to increase the use of RES, to which all countries have access while maintaining the security of supply.
Hydrogen hubs, a decentralized concept that combines all elements of the hydrogen supply chain with a local reference, will play a huge role in the emerging hydrogen economy. A hydrogen hub encompasses the production, storage, and distribution of hydrogen and renewable energy for cities, local businesses, utilities, and manufacturing while reducing the need for hydrogen supply from centralized generation units.
Therefore, our hydrogen hub concept involves both hydrogen production using a proprietary electrolyzer from large-scale RES installations, its distribution, and storage, and includes the use of fuel cells to convert the hydrogen back into energy, meeting the needs of cities, businesses, and end-users.
