El Solid hydrogen has gone from being almost science fiction to become one of the hottest fields in the energy transition. From startups born in university classrooms to research teams that have been grappling with the same problem for decades, they all share the same goal: to find a safe, cheap, and efficient way to store the renewable energy we currently waste.
That challenge has a lot to do with something we are already experiencing: There are more and more renewable energy sources, but their production is irregular.When the sun shines or the wind blows, we generate more electricity than we can consume at that moment, and if there isn't a smart way to store it, much of it is lost or "given away" to the grid at ridiculously low prices. This is where technologies like metal hydrides, magnesium discs, solid hydrogen cylinders, and others come into play. new nanomaterials that absorb gases as if they were a sponge.
Why energy storage is the big bottleneck
Many countries, such as Spain already suffers from energy tensions and inequalities because of this situation. There are areas where the renewable potential is enormousHowever, the grid and storage systems are not prepared to handle such a large surplus. This has led to conflicts between regions and serious doubts about how to integrate more and more renewable energy without overwhelming the system.
Today, several strategies are used to try to save that surplus: big stationary batteriesPumping water to reservoirs (to then use it for turbines), domestic batteries in self-consumption installations… But all have clear limitations: high cost, dependence on critical raw materials, need for specific locations or difficulties in scaling up to a national level.
That's why many experts agree that Storage is the missing piece. For renewables to be truly independent, without relying so heavily on combined cycle or nuclear power plants, a flexible, secure, and widespread way to store electricity is essential. It's unlikely these technologies will completely dominate the energy market.
Hydrogen as an energy carrier: what it offers compared to other solutions
In that context, hydrogen stands out as one of the most promising energy vectorsIt is the most abundant chemical element in the universe and is part of molecules as common as water and hydrocarbons. When used in fuel cells, it combines with oxygen from the air to generate electricity, heat, and water as the only direct byproduct, with no CO2 emissions during the conversion.
The green hydrogen, produced from renewables through electrolysisThis perfectly aligns with the need to utilize surplus electricity. Instead of wasting excess electricity, it is used to split water into hydrogen and oxygen. This hydrogen is then stored and reused later to produce electricity, power vehicles, or provide heat.
Another key advantage is its high energy density per unit massHydrogen contains approximately three times more energy than gasoline, making it a very attractive fuel for heavy transport, industry, or applications where weight is critical.
However, hydrogen presents a major challenge: how to store and transport it in a practical and safe wayTraditionally, two methods have been used: in the form of compressed gas at high pressure or in liquid form at cryogenic temperatures. Both methods require a lot of energy, involve complex infrastructure, and, in some cases, the use of potentially hazardous substances.
Does solid hydrogen really exist?
On a purely physical level, the Solid hydrogen as a pure element has been known since 1899Researcher James Dewar was the first to produce it by cooling it to extremely low temperatures, below about -259,14 °C, close to absolute zero. Under these extreme conditions, hydrogen solidifies.
Studying this material is not easy at all: The samples are minuscule and hydrogen interacts very little with X-raysThis greatly complicates the characterization of its internal structures. Even so, science has identified several solid phases of hydrogen, which depend on temperature and, above all, on the applied pressure.
In the call Phase IAt low pressures and temperatures, H2 molecules can still move freely. Increasing the pressure at low temperatures leads to... Phase IIup to about 110 GPa, where that movement is restricted. If the pressure is increased further to approximately 160 GPa, the following occurs: Phase IIIAnd by raising the temperature to a few hundred kelvin, at pressures above 220 GPa, one gains access to a Stage IV with even more complex properties.
In any case, under normal Earth surface conditions We cannot find solid hydrogen naturallyWhat is being developed for energy use is not so much that ultra-cold “pure” solid, but technologies that trap hydrogen within solid materials or compounds that behave, in practice, as a solid, safe and manageable storage.
ATOM H2: Metal hydrides for storing renewable surpluses
One of the most striking examples comes from a group of Spanish engineers who created the ATOM H2 projectWinner of the 2024 James Dyson Award and also recognized in entrepreneurship initiatives such as EmprendeXXI in Catalonia. This startup was literally born in the classroom: its founders, recent graduates in Industrial Design Engineering and Chemical Engineering, were determined that their academic work wouldn't just gather dust in a drawer.
The idea behind ATOM H2 is relatively simple to explain, although technologically complex: Use surplus renewable energy to produce hydrogen and store it in solid form using metal hydrides. Instead of using high-pressure gas storage tanks or cryogenic tanks, they use a special material that “absorbs” hydrogen and stores it in a compact and safe manner.
The process begins with electrolysis of waterWhen there is surplus electricity from solar panels or other renewable sources, it is used to split water molecules (H2O) into oxygen and hydrogen. This hydrogen, instead of being compressed or liquefied, is placed in a tank where it reacts with a metallic material to form hydrides. This allows for the storage of much larger quantities of hydrogen in less space and at much lower pressures.
When energy is needed, the system releases hydrogen from those hydrides and sends it to a fuel cellThere, the gas reacts with oxygen in the air, generating electricity, heat, and water as a byproduct. The company does not specify in its public materials whether the water is recycled back into the system, but it does emphasize that the process does not generate polluting waste.
According to their theoretical estimates, this technology of Solid hydrogen could supply tens of millions of homes per yearHowever, they acknowledge that this figure is calculated on a large scale and that there is still a long way to go to reach that actual level of deployment. An interesting point is that the system is designed in a modular way: more storage units can be added as needed, which is key to adapting to different installation sizes.
From classrooms to telecommunications towers: real-world application of ATOM H2
In their early stages, the founders of ATOM H2 thought about apply their technology directly in homesallowing individuals to store their own renewable energy in the form of solid hydrogen. However, after speaking with many companies and analyzing different niches, they realized that the residential market wasn't the most immediate fit.
The real turning point came when they encountered the sector of the telecommunications towersThese critical infrastructures typically have backup diesel generators that start up in case of power outages or emergencies. These systems are reliable, but highly polluting and have increasing costs associated with fossil fuels.
The team saw a huge opportunity there: replace those diesel generators with a hybrid system based on solar power, batteries and solid hydrogenWhen the tower doesn't need all the energy it generates, the surplus is used to produce hydrogen, which is stored in its "solid tanks." When there's a grid failure or backup power is needed, the hydrogen is converted back into electricity using fuel cells.
This approach offers several advantages: on the one hand, It drastically reduces emissions associated with energy backup. In telecommunications, it offers advantages; on the other hand, it improves autonomy and reliability by eliminating dependence on diesel fuel. Furthermore, the high storage density of metal hydrides allows for compact and manageable solutions.
ATOM H2 is already in the phase of industrialization, raising a multi-million euro investment round, working on its first commercial implementation with a major operator like Cellnex and participating in international programs such as NATO's Defence Innovation Accelerator Atlantic (DIANA). Its short-term goal is to deploy its first commercial units and validate the model in the field.
Solid hydrogen disks: the French approach with magnesium and graphite
In parallel to the Spanish initiative, a A team of French researchers has developed a solid hydrogen storage system in the form of discs reminiscent of old 33 rpm vinyl records. This work, which has earned them a place as finalists in the Research category of the 2023 European Inventor Award, is the result of more than two decades of study combining physics, engineering and industry.
The project started in the Néel Institute of Grenoblewhere the team led by Daniel Fruchart spent a decade researching ways to store hydrogen in a solid state. Subsequently, Patricia de Rango's group took over, focusing their efforts on the design of efficient and reversible tanks.
The key technological factor was the use of magnesium hydride (MgH2) combined with expanded graphiteMagnesium is one of the most effective materials for absorbing hydrogen, but the release process is accompanied by a release of heat that must be carefully managed. Expanded graphite acts as a "thermal manager," helping to dissipate this heat and better control the reactions.
This reversible approach was promoted when Fruchart and the industrialist Michel Jehan founded the company McPhy in 2008Jehan contributed his expertise in manufacturing magnesium granules and microscopic powders, as well as large-scale machinery, which made it possible to translate laboratory results into solutions closer to the market, despite the typical difficulties of a startup.
The result is a disk system that It can be stored stably and consumes less energy than compression or liquefaction.It does not react spontaneously with air and maintains its capacity over time. These discs can be placed on a surface without risk of combustion, which facilitates their handling and transport.
International marketing and potential uses of solid disk drives
Far from being just a laboratory experiment, the Solid hydrogen disk storage has already been commercialized in countries such as Italy and Japan. Furthermore, the team is in advanced talks in Norway to adapt this technology for ferries, maritime transport, and large chemical industries.
The potential of this system lies in the fact that It offers high storage density in a compact and modular format.By being able to handle the discs almost as if they were "solid fuel", their integration into environments where high-pressure gas tanks are complicated or unsafe is facilitated.
From road and maritime transport to distributed electricity generation or industrial applications, there is a wide range of sectors that can benefit from stable and reversible solid hydrogenThe ability to adapt the system to different scales — from small modules to large tanks — opens the door to highly flexible energy architectures.
Another strong point is the inherent security of solid-state storageBecause hydrogen is integrated into a material, the risk of catastrophic leaks or explosions is significantly reduced compared to compressed gas systems. This can facilitate its social and regulatory acceptance in sensitive environments.
If we add to all this the increasing pressure to reduce emissions in sectors such as shipping or heavy chemicals, it becomes clear why these types of technologies generate so much interest. It would allow processes to be decarbonized without giving up a versatile fuel. like hydrogen.
Photoncycle: solid hydrogen cylinders for homes and buildings
Another line of innovation comes from Northern Europe. The startup Photoncycle is developing a seasonal energy storage system based on a copper cylinder insulated with a thick layer of polystyrene foam containing a patented solution of hydrogen in solid form.
This prototype, currently installed in the basement of a science park in Oslo and roughly the size of a chair, aims to grow to reach a three cubic meters In its commercial version, it is buried a few meters from residential buildings. Its function is simple: to connect to nearby solar panels, absorb all the electricity that is not used in summer and release it as usable energy during the winter.
According to its founder, Only about 50% of solar energy is used which is produced in the summer in many northern countries. The rest ends up being wasted or sold to the grid at very low prices. If this surplus can be stored as solid hydrogen and used later, when demand and prices rise, it generates enormous added value for both users and the electrical system.
Photoncycle uses a high-temperature reversible fuel cellIt is capable of operating in both directions: producing hydrogen from electricity and, conversely, generating electricity—and heat—from that hydrogen. The key difference of their proposal is that the hydrogen is "enclosed" in a non-flammable solid, with an energy density higher than that of lithium batteries, and without the need for cryogenic cooling.
One of the challenges the company is addressing is the heat loss management during the conversion of hydrogen inside and outside the fuel cell. In fact, their goal is to harness that heat to cover some of the heating needs of homes, which is significant considering that approximately 70% of domestic energy consumption is used for heating.
Photoncycle's installation, target market, and strategy
The Photoncycle system is designed to install in a single dayThis includes the installation of solar panels and connection to the building's existing infrastructure. Once operational, it could completely replace natural gas in a combined heat and power (CHP) system, providing electricity and heating from stored renewable energy.
Another attractive point is that the owners could sell back to the grid the surplus they do not consumeimproving the profitability of their renewable energy investments. This type of solution is particularly well-suited to countries with very high energy prices, such as Denmark, which is the company's chosen test market.
From a security point of view, the fact that the Photoncycle solid hydrogen is not flammable under normal conditions And because they don't require extreme operating temperatures, they reduce many of the concerns associated with this gas. Their higher energy density compared to batteries also allows them to offer long-term autonomy without taking up as much space.
The company continues to work on optimizing efficiency, heat recovery, and reducing costs, but its approach illustrates this very well. how solid hydrogen can be integrated directly into buildingsnot only in large industrial facilities. If they manage to scale up the technology and make it cheaper, they could change the way solar energy storage is conceived in cold climates.
Australian ball milling method: gases trapped in nanopowders
A radically different approach to the problem of gas storage comes from Deakin University, in AustraliaA team of researchers has developed a process called "ball milling" that allows large quantities of gas—including hydrogen—to be separated, stored, and transported in solid form, drastically reducing energy costs and generating no waste.
Essentially, the method consists of introducing a boron nitride powder inside a chamber that also contains small stainless steel balls and the gas or gas mixture to be processed. The chamber rotates at increasing speeds, causing the balls to collide with the powder and the walls, triggering a physical reaction that traps the gas within the solid nanomaterial structure.
Depending on the gas, the absorption rate variesThis allows for selective separation of the gases when working with mixtures. Once trapped in the powder, these gases can be transported very easily and safely. When they need to be recovered, simply apply controlled heating to return them to their original gaseous state, while the powder also returns to its initial form, ready for reuse.
The researchers repeated this experiment dozens of times until they were convinced that the results were consistent. The process can be repeated. up to 50 cycles with the current formulationmaintaining a very high absorption capacity. Furthermore, by operating at room temperature, it does not require cryogenic systems or enormous energy consumption.
In terms of efficiency, the team calculates that this method It uses about 77 kilojoules per second to store and separate 1.000 liters of gases.This energy is comparable to that needed for an average electric vehicle to travel about 320 kilometers. Applied to hydrogen, they estimate that the energy required could be a third or even a quarter of that needed to compress the gas using traditional methods.
Impact on oil refining, green hydrogen, and transport
One of the most striking findings pointed out by the researchers is that current processes of Cryogenic distillation for refining oil consumes about 15% of the world's energyTheir new method could reduce that cost by up to 90%, which would be a revolution not only for the hydrocarbon sector, but for any industry that needs to separate and handle large volumes of gas.
In the case of hydrogen, ball milling opens the door to to store enormous quantities of green hydrogen in a solid, safe and reusable waywith very low energy consumption compared to compression or liquefaction. The nanomaterial generates no waste and the gas is only released when heated to a few hundred degrees, guaranteeing remarkable stability under normal conditions.
This approach can be crucial to facilitating the long-distance hydrogen transportThis allows it to be transported as a solid powder and released at its destination. The researchers do not rule out applications in transportation (cars, trucks), although they acknowledge that further work is needed on specific tank designs, controlled release mechanisms, and adapted refueling procedures.
Beyond hydrogen, the same technique could be applied to gases such as ammonia or other gaseous fuelsThis greatly expands the range of potential uses. Currently, it is a relatively early stage of research, but it has enormous potential to transform both the energy and chemical sectors.
Taken together, these types of innovations show that The idea of “solid hydrogen” is not limited to a single technological pathIt could be a metal hydride, a magnesium disc, a cylinder buried next to a building, or a gas-charged boron nitride nanopowder; all aim to make hydrogen a practical and competitive vector against fossil alternatives.
The role of fuel cells in this new ecosystem
All this deployment of storage technologies would make little sense without a device capable of convert hydrogen back into electricity cleanly and efficientlyThat's where fuel cells come in, whose history dates back to 1839, when William Grove developed the first hydrogen and oxygen cell.
For much of the 20th century, progress was slow, but from the 1960s onwards fuel cells became a essential component of NASA's space missionsproviding electricity and drinking water to astronauts. Since then, they have evolved into much more varied terrestrial applications.
The basic operation is relatively simple to understand: Hydrogen enters through the anode and oxygen through the cathodeAt the anode, hydrogen is split into protons and electrons. The electrons travel through an external circuit, generating a useful electrical current, while the protons pass through the electrolyte. At the cathode, they combine with oxygen and the returning electrons, forming water and releasing heat.
There are several types of fuel cells, differentiated by the materials and operating temperature. alkaline and deca-acid batteries polymer membrane (PEM) They operate at low temperatures and are ideal for mobile and portable applications, with PEM batteries being the most widely used in current hydrogen vehicles. piles of molten carbonates and solid oxide They operate at higher temperatures, suitable for large-scale stationary generation and cogeneration, and can operate with fuels other than hydrogen, such as natural gas.
These technologies are already being used in a wide variety of contexts: portable generators, stationary systems for homes and businesses, light and heavy vehicles, trains, ships and even submarinesTheir main advantage is that they allow electricity to be produced very efficiently and without local CO2 emissions if the input hydrogen is renewable.
Outstanding challenges and prospects for fuel cells and solid hydrogen
Despite all these advances, both fuel cells and the various forms of Solid hydrogen still faces several challengesOn the one hand, it is necessary to continue improving the durability of the systems, especially in mobile applications and in intensive charge and discharge cycles.
On the other hand, the Costs remain a major obstacleThere are expensive components (such as certain catalysts) and manufacturing processes that have not yet fully benefited from economies of scale. The hydrogen distribution and supply infrastructure also needs to be expanded for these solutions to be deployed on a large scale.
However, the direction seems clear: there is increasing investment in R&D, strong regulatory pressure to reduce emissions, and a ecosystem of startups, universities and industry very active. The stories of projects like ATOM H2, Photoncycle, the French magnesium disk team, or the Australian researchers at Deakin demonstrate that many paths are being explored in parallel.
Everything points to hydrogen—in its various storage forms, including solid state in advanced materials—being a key piece of the energy puzzle Along with other technologies such as batteries, hydroelectric storage, and smart grids, these solutions are likely to mature and become more affordable, eventually moving from laboratories and pilot projects to becoming a normal part of the energy landscape for cities, industries, and homes.
Looking at this whole picture, a future emerges in which Renewable energy is not wasted when the sun shines too brightly or the wind blows too strongly.but can be trapped in seemingly harmless solids—discs, cylinders, powders, hydride tanks—and put into play just when needed, powering fuel cells that transform that hydrogen into electricity and heat without smoke or noise, thus closing an energy circle that is much cleaner and more flexible than the one we have known until now.
