Key Technology: Solid Absorbent Materials.

Hydrogen Power Plants: Given that cryogenic installations are not exactly lightweight, and also require a significant energy input, there is a very promising line of work in solid adsorbent materials as they offer the possibility of storing hydrogen efficiently in a more compact volume compared to high-pressure or liquid cryogenic storage methods. In principle, these materials are able to adsorb (retain) hydrogen molecules in their crystalline or porous structure through physical chemical bonds.

The energy density that solid adsorbent materials can achieve varies depending on the specific material and storage conditions. However, in theory, these materials could achieve energy densities comparable to, or higher than, those of high-pressure storage tanks, and in line with that of liquid fuels.

Examples of solid adsorbent materials include certain metals and alloys, organic compounds, and nano porous structures such as metal-organic frameworks (MOFs) and porous coordination polymers (PCPs).

It is important to emphasize that hydrogen storage technology using solid sorbent materials is still under development and faces technical and economic challenges. Researchers are working on optimizing these materials to improve their hydrogen absorption capacity, their absorption (and de-absorption) rate as well as their stability over time.

Hydrogen Power Plants: Addressing Cost Challenges in Solid Adsorbent Materials for Hydrogen Storage

The development and implementation of such materials in hydrogen Power Plants, face several challenges, and cost is one of the factors that can influence their commercial viability. Some of the cost-related factors include:

1. Advanced Materials: many of the solid adsorbent materials that show promising properties for hydrogen storage can be expensive to synthesize or manufacture due to the need for high purity materials and specialized manufacturing processes.
2. Research and Development: Research and development to optimize and design effective solid absorbent materials can require significant investments in terms of resources and time. R&D investment contributes to the upfront costs.
3. Production Volume: In the initial stage of the technology, production volume may be low, which can increase unit costs. As production increases and economies of scale are achieved, costs might decrease.
4. Performance Evaluation: The evaluation and especially the characterization of solid absorbent materials require specialized production equipment and techniques which affects costs.
5. Stability and Durability: Ensuring the long-term stability and durability of materials is essential for commercial viability. This may require a multitude of tests under all kinds of conditions over the time.

It is important to note that while costs can be a challenge in the early stages of development, innovation and technological progress can help address these concerns as the technology matures. As advances are made in materials synthesis, manufacturing processes, and understanding of performance requirements, it is more than possible that costs will come down as manufacturing volumes grow.

Continued research and collaboration between academia, industry and government institutions can be critical to overcoming cost challenges and moving solid sorbent materials technology towards more robust commercial viability.

Empowering Hydrogen Power Plants: Unveiling the Potential of Structural Batteries

Nevertheless, it is necessary to mention that hydrogen fuel cell propulsion will necessarily require a certain battery capacity; otherwise, power management would have to be exclusively through the fuel cell, and this would not be feasible in an air vehicle. We need to ensure the following aspects in order to ensure the viability of the system:

1. Instantaneous Power Management: Hydrogen fuel cells have a relatively slow response time to increase or decrease their energy output, as the chemical reactions in the cell require time to adjust. Batteries, on the other hand, can quickly provide the required power during acceleration or intense maneuvering.
2. Energy Regeneration: Batteries can recover energy during descent and deceleration, something that can be more difficult for hydrogen fuel cells. This regenerated energy can be stored in the batteries and used later for propulsion.
3. Improved Efficiency: By operating hydrogen fuel cells in more stable conditions and near their optimal efficiency point, and letting the batteries handle the instantaneous power demands, greater overall system efficiency can be achieved.
4. Reducing Battery Size: By combining hydrogen cells with batteries, it is possible to reduce the size of the hydrogen cell, as it does not need to handle peak power demands.

This combination of technologies, known as hydrogen cell and battery hybrid systems, has become more common in advanced mobility applications, including air and ground vehicles. Intelligent energy management between the hydrogen cell and batteries is essential to optimize performance and efficiency in these applications.

Carbon Fiber as Energy Storage: Challenges and Opportunities

The concept of storing electricity within the carbon fiber structure itself is an intriguing avenue of research, particularly relevant to hydrogen Power Plants. This innovative approach utilizes conductive composite materials integrated into the carbon fiber structure, enabling efficient storage and distribution of electricity. Referred to as ‘structural supercapacitors’ or ‘structural batteries,’ this technology holds significant promise for enhancing the energy efficiency and functionality of Hydrogen Power Plants.

The main idea is to harness the carbon fiber structure to act as an energy storage material while providing strength and structural rigidity. This could have advantages in terms of weight and space reduction compared to traditional energy storage systems that are separate components in a vehicle or structure.

Challenges and Opportunities in Carbon Fiber Energy Storage

It is important to note that this technology is still at an early stage of development and faces a number of technical and engineering challenges. Some of these challenges include:

1. Storage Capacity: Ensure that the energy storage capacity in the carbon fiber structure is sufficient to meet the needs of the application without compromising structural integrity.
2. Load Distribution: Ensure an even distribution of electrical load on the structure to avoid stress concentrations and minimize the risk of failure.
3. Charging and Discharging Cycles: Achieve adequate service life and good efficiency in terms of repeated charging and discharging cycles.
4. Component Integration: Design systems that allow proper integration of supercapacitors or batteries into the carbon fiber structure without adversely affecting structural characteristics and aerodynamics.
5. Safety and Regulation: Ensure that energy storage in the structure complies with relevant safety standards and regulations.

While the concept of storing electricity in the carbon fiber structure is exciting, its commercial viability and practical application in vehicles and aircraft is still under evaluation and development. It is an interesting area of research that could have a significant impact on the way future vehicles and advanced mobility systems are designed and built.

The State of the Art

An example of the application of the concepts outlined in this article is the recent demonstration flight of the HY4 prototype last September 2023.

H2Fly’s efforts to bring the technology to the air transport sector were impulse by the flight of the HY4 demonstrator aircraft at Maribor Airport in Slovenia.

The demonstration flight, which followed earlier test flights and ground tests, try to validate the concept that the use of cryogenic liquid hydrogen storage technology could be safely applied to aeronautical applications.

Hydrogen Aviation Milestone: HY4 Prototype Demonstration

The HY4 demonstrator aircraft (a retrofitted Pipistrel twin fuselage electric Taurus 4G model) has completed over 115 take-offs since 2016, of which five were LH2-powered flights. The three-hour flight around Maribor airport was executed successfully without any battery support during cruise flight. It used about 10 kilograms (22 pounds) of hydrogen.

Nevertheless, H2Fly is not the only actor of this film: Universal Hydrogen, for instance, has operated several flights tests this year of its 40-seater De Havilland Canada Dash 8-300 hydrogen-electric demonstrator, powered on one side by a megawatt-scale hydrogen fuel cell propulsion system. ZeroAvia in July completed the 10th flight of the Dornier 228 testbed aircraft, with one Honeywell TPE331 turboprop engine replaced by the prototype hydrogen-electric powertrain ZA600.

Although both previous platforms plan to use liquid hydrogen technology, so far, they have used gaseous storage to ease the development. H2Fly, is applying the same strategy, temporarily opting for the same solution.

As we have discussed previously in this article, the use of liquid h involves a somewhat more complex installation, although it can enable a much longer range. As an example, the HY4 demonstrator aircraft using gaseous hydrogen gets a range of 750 kilometers. With the liquid hydrogen tank, the range would grow up to 1,500 kilometers.

According to the experts, the market is out there waiting for the appropriate platforms. The necessary technology is already mapped out and the development is ongoing. It seems that it is only a question of time until this market reaches full expansion.