Hydrogen: novel Green Chemistry for energy generation

Hydrogen Drone

Hydrogen on electric vehicles

Environmental stress to Earth has stimulated a quest for innovative energy systems. They must be able to lead to a significant reduction of greenhouse gas emissions on a global scale. To meet this challenge, Chemistry, as a standard way of energy generation, offers new revolutionary approaches. For instance, Hydrogen is an ideal energy carrier for the transport sector. Its gravimetric energy density is very high. Moreover, Hydrogen is abundant and its oxidation product (water) does not pollute.

However, there are still significant challenges towards its mass usage. Its production from renewable energy sources, development of infrastructures, difficult on-board handling and storage, or yield in energy conversion devices, among others, are still questions to be answered.

These limitations are particularly relevant in transportation, which is the leading cause of global warming. It represents 22% of energy-related greenhouse emissions worldwide and a quarter of Europe’s greenhouse gas emission [1]. In the last few decades, major efforts have been undertaken to introduce green hydrogen-based technologies in electric vehicles (EV) as they are the most feasible alternative to internal combustion engine vehicles.

Nevertheless, the wider adoption of EV based on hydrogen is far from being realised. Even through significant progress has been made in lithium batteries and hydrogen-based technologies, they have still undeniable drawbacks that call into question their potential to power the world’s needs for sustainable energy in the long run.

As these limitations restrain the deployment of a sustainable electrical mobility model based on green hydrogen, there is still a great demand for alternative disruptive technologies able to provide a safe and clean hydrogen production method that makes use of abundant, sustainable, and low-cost materials to expand hydrogen as a clean viable energy alternative.

The traditional chemical hydrogen production process from hydrocarbon catalytic reforming is environmentaly obsolete, so new green chemical processes are required.

Research effort in this field over the past decade have not yet paid off: Green Hydrogen chemical production methods using materials such as as NaBH4, LiH, MgH2 have been extensively investigated [2] as potential hydrogen storage materials for fuel cell applications. The problem is that they have usually failed [3] to control the reaction and the yield of the hydrogen generation. Sodium borohydride (NaBH4) has had its momentum due its higher stability. However, its handling and storage is difficult due to its high degree of chronic toxicity with critically harmful effects over the central nervous system [4].

Novel process for Hydrogen generation

A novel way of generating green hydrogen is by means of a reaction between an alkali metal, alkaline-earth metal, or an alloy of any of such metals and water. Particularly, the disruptive process refers to a controlled on demand in situ hydrogen generating system using a recyclable liquid or solid metal fuel.

This kind of green chemical process to generate energy are unique using a number of chemical reactions between metals and water (WSR: Water Splitting Reaction).They have been discarding during decades due to the difficulties to control the reaction rate and generate the hydrogen smoothly.

Especially preferred suitable metal reagents are sodium (Na), Magnesium (Mg) and Lithium (Li), and a particularly preferred metal reagent is Na due that has a relatively low melting point (97ºC) and it is abundant in nature.

The hydrogen generation process is based on the following chemical reaction:

X + n H2O -> X(OH)n + n/2 H2

Where X is a specific metal fuel mixture which depends on the application and its performances required. As a result of this chemical reaction, pure hydrogen with certain degree of hydration is obtained to feed a fuel cell system to produce electrical energy for example.

Almost all the reactions between alkali metals, alkali-earth metals, or the alloys between themselves are very fast. Depending on the metal physical state, form and size the reaction can be explosive due to the fast pressure build up. Nevertheless, a reaction delay time (initiation time) is always observed. The understanding of the events occurring during this reaction initiation time is critical to understand how reaction is carried out in reality. The control of this type of reactions is very dependent of the reaction interface geometry and dimension. Once the proper conditions are established the reactions are easily controlled and the hydrogen generation is carried out smoothly if oxygen is not present.

A feasible technology

Drage & Mate International (D&M), a Spanish technology-based SME specialised in chemical engineering, proposes disruptive technology with the potential to overcome current limitations in hydrogen production for EV. The Company has been developing since 2007 the so-called METALIQ technology which presents a unique selling proposition thanks to its remarkable features:

Based on a controlled metal-water reaction at stable thermal conditions (below 60ºC), that can be induced in seconds, producing applicable green hydrogen.
Attaining total gravimetric energy densities between 600 Wh/kg and 4.000 Wh/kg, thus multiplying by 2 or even by 7 (depending on the type of vehicle) the current range of EVs and the total weight of their payload.
On-demand and in-situ hydrogen generation in the vehicle. There is no need for hydrogen storage.
METALIQ reaction mainly based on water and sodium or magnesium, two of the most abundant components on Earth. This avoids the issues derived from the scarce materials used to manufacture lithium batteries.
Easiness of storage and distribution.
METALIQ reaction by-products Na(OH), sodium hydroxide, or Mg(OH)2 are easily recyclable using sustainable energy sources.  

In short, METALIQ is a state-of-the-art sustainable power solution based on a 100% carbon free for controlled on-demand in-situ hydrogen generation for vehicle propulsion. Its main competitive advantage is its higher gravimetric energy density over current technologies. This enables increased engine autonomy (operation time) and at a very competitive price. METALIQ technology is protected by two patents which have been granted in several countries PCT/ES2016/070377 and PCT/EP2011/057399.

The feasibility study of METALIQ was performed under the SME-Instrument Phase 1 project [4]. During the project execution, the potential of this technology and the multiple market applications suitable for its current state of development (TRL-7) were assessed.

METALIQ technology can be used for multiple types of electrical vehicle propulsion systems: Ground Vehicles (GV), Unmanned Aerial Vehicles (UAV), Unmanned Surface Vehicle (USV) and Unmanned Underwater Vehicle (UUV), among others. In particular, METALIQ has major potential to be used in ground electric vehicles in light of an increased need for low and zero-emission vehicles.

The system is composed by fixed components (refillable demineralized water tank) and fuel replaceable cartridges. The fuel cartridges can be replaced easily when they are exhausted by others full cartridge. Empty fuel cartridges can be refilled at very competitive cost. The storage, handling and transportation of such refillable cartridges is a very safe operation. Once a new fuel cartridge is installed and activated, the pressure and flow in hydrogen supply line to Fuel Cell is permanently maintained. This technology proposal is based on the direct energy to material conversion using high energy density compounds like alkaline, alkaline-earth and alloys between themselves. The complete energy-material-energy cycle shows a theoretical yield higher than 33%.

In the future new other WSR reactions can have interest from the industrial perspective but today this technology is just a reality. As Jules Verne [5] said: “Water will be the coal of the future”.


REFERENCES

[1] Lefevre, B & Enriques, A. (2014) Transpiration Sector reaction Key to Closing the World’s Emissions Gap, World Resources Institute. Link: https://www.wri.org/blog/2014/09/transport-sector-key-closing-world-s-emissions-gap

[2] Ley, M. B., Jepsen, L. H., Lee, Y. S., Cho, Y. W., Von Colbe, J. M. B., Dornheim, M., … & Jørgensen, J. E. (2014). Complex hydrides for hydrogen storage–new perspectives. Materials Today17(3), 122-128.

[3] Office of Energy Efficiency & Renewable Energy. Hydrogen Storage Challenges. Link: https://www.energy.gov/eere/fuelcells/hydrogen-storage-challenges

[4] European Comission. Green Ultra Light Weight Energy Storage System for Propulsion. Link: https://cordis.europa.eu/project/rcn/196652_en.html

[5] Jules V. (1874) The Mysterious Island. Pierre-Jules Hetzel Publisher; Paris, France.

* Foto de Tecnología creado por kjpargeter – www.freepik.es

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