An energy vector, or energy carrier, is a substance or a method to transport energy from one place to another and to stock it. Thus, an energy vector contains energy that can be later converted to other forms such as mechanical work and heat, or to operate chemical or physical processes, to generate electricity for example. It is important to understand that an energy vector does not produce energy; it simply contains energy imbued by another system.
Primary energy forms, meaning the energy forms naturally available in the environment before any transformation, such as fossil fuels are energy sources. In comparison, electricity is an energy vector widely used by industrialized countries to efficiently deliver energy in an easily usable form.
The main energy vectors used today are heat, electricity, compressed air, mineral oil, and of course hydrogen.
Hydrogen offers a huge potential as an energy vector. Indeed, hydrogen would be a “bridge” between primary energy sources and end usages. This hydrogen energy vector process works in 4 steps.
First, energy must be created, as hydrogen remains an energy vector, and only carries energy produced by another system. In order to achieve a green hydrogen circuit, the energy must be decarbonized, thus created from renewable energies or nuclear energy.
The second step is the transformation of electricity into hydrogen, through water electrolysis for a green circuit. Here, the combination of electricity and water will create a decarbonized hydrogen (on a gaseous form).
The third step is the storage or transportation of hydrogen. The produced hydrogen is conditioned in a tank with different technologies depending on the applications. To be more easily stored, hydrogen can be compressed to occupy less space. In compressed form, hydrogen can be transported by truck or pipeline. Hydrogen can also be transported in liquid form. When cooled to an extremely low temperature, hydrogen is transformed into a liquid form enabling more convenient transportation by boat or truck. Finally, hydrogen can also be stored in solid form. For example, McPhy Energy, a French company, has developed a hydrogen storage solution using metal hydrides, which are chemical compounds of hydrogen with metal.
Hydrogen, and therefore the energy contained in it, can thus be stored without any particular time limit.
The final step is the conversion of hydrogen into electricity, when needed. This is achieved using a fuel cell, which is the reverse process of electrolysis. Indeed, here, from hydrogen and oxygen, electricity will be generated during the process.
Hydrogen energy is therefore presented as one of the best options for green energy storage. Furthermore, hydrogen releases four times more energy than coal and three times more energy than oil.
Energy storage, additional electricity injection in the grid, extended autonomy for vehicles, manufacture of methane… Hydrogen is a multipurpose gas that makes it a very efficient energy vector!
The rapid exhaustion of fossil fuel reserves and the adverse effects of climate change have attracted global attention and pose serious threats to mankind. Hydrogen is considered to be the solution as the future vector of clean and renewable energy.
Nowadays, most of the produced hydrogen is not green at all, as 96% comes from hydrocarbon-based production processes. Furthermore, most of the hydrogen is used in industrial processes. Thus, two main categories of use must be identified: hydrogen energy (hydrogen as an energy vector) and hydrogen for industry. Although current research focuses primarily on the first use, with the aim of obtaining a new energy vector for electricity storage, power-to-gas or mobility, practical applications in industry remain the majority. In these applications, hydrogen is mainly used as a raw material. The green hydrogen as energy vector sector must still develop considerably and seems to have considerable development opportunities ahead of it.
In fact, 3 major challenges have been identified for the hydrogen vector for the coming years. Firstly, within the framework of a future electricity mix strongly associating renewable sources, hydrogen brings flexibility and optimization solutions to energy networks. Power-to-gas, or the injection of hydrogen and synthetic methane, is a key way to connect electricity and gas networks. Secondly, the development of hydrogen electric vehicles adds diversity to the electric-mobility offer, addressing the sustainable mobility needs of today’s society. Finally, hydrogen provides new opportunities for the self-consumption of local energy at the scale of a building, an island or a village, especially for areas not connected to the conventional electricity grid.
Hydrogen represents a major opportunity for remote and isolated places without any connection to the conventional power grid.
Indeed, it allows the storage of energy surplus and the redistribution in the local micro-grid on demand. In the case of energy creation from renewable sources, the hydrogen solution provides a continuous supply of electricity. Hydrogen represents thus new opportunities for self-consumption of local energy at the scale of a building, a village, or even an island, especially for areas not interconnected to the power grid.
As a concrete example, the small villages of Mafate on Reunion Island, a French island in the Indian Ocean, near Madagascar, are few complete remote villages in the mountains that do not have any access to the conventional water and energy grid. In fact, there is not even a road that leads to this place. The only way to get there is either by foot or by helicopter. Thus, 20 years ago, many solar panels were installed in the villages to provide the 310 families, approximately 700 inhabitants, with electricity. However, during the last years, more and more tourists came to this place, and the energy needs of the villages has significantly increased. Power generators have been installed, but they are polluting, noisy and require a helicopter fuel supply. Thus, a long-terms viable solution had to be found.
First of all, aging individual solar panels were replaced by a collective photovoltaic equipment. This energy, renewable but variable, would be stored for one or two days by lithium-ion batteries. However, for unlimited time storage, this energy would be transformed into hydrogen through electrolysis and stored on site.
Thus, in case of consumption peaks or absence of sunshine, hydrogen can be transformed on demand into electricity via a fuel cell and the electricity would be immediately injected into the micro-grid of the villages. This creates a totally independent and stable renewable energy micro-grid.
This solution has been developed by the French company PowiDian and supported by EDF. In 2017, an investment plan of €15 million was intended for the realization of this project.
This project proves the hydrogen’s potential to ensure the complete energy autonomy of isolated micro-grids every day of the year without greenhouse gas emissions. Also, it proves the feasibility of this solution and its reliability. Finally, we can see through this project that this solution is reproducible to any remote region in the world. Thus, similar projects are currently under consideration in French Guiana.
In general, it seems that hydrogen micro-grids are also more economic than diesel. Thus, key players of the energy market are investigating local micro-grids as a way to recuperate from the financial crisis by securing the economy and maintaining resilience for energy systems. Indeed, the emergence of cheap renewables energies optimizes the generation’s cost in a microgrid and eliminates the reliance on fossil fuels. The benefits of a micro-grid, such as renewable hydrogen micro-grid, therefore extend beyond energy independence and zero carbon emissions; they are also economic!
In this regard, the International Energy Agency has projected that 30% of future electrification efforts will be supplied by micro-grids. This includes existing diesel micro-grids that could be integrated with renewables as well as future built micro-grids that will likely skip fossil fuels altogether and rely only on green energies.
Micro-grids are electric power grids that can function independently, with off-grid versions adopted in remote areas. The infrastructure generally consists of an energy generation, storage and energy load management which makes them such a reliable and efficient power supply. Micro-grids are usually implemented due to the remoteness of locations, lack of access to the national grid and economic reasons. In the last decade, renewable energy sources have been transforming the micro-grid landscape, consequently reducing or even eliminating the need for costly fossil fuels. This has been made possible through the use of hydrogen.
Introducing hydrogen to micro-grids solves the problem of seasonal or long-term storage that batteries cannot provide. This is the crucial part of the puzzle for all the green micro-grids. In fact, a typical micro-grid is often oversized with an average of 30% excess solar energy being lost as it cannot be stored for a time when needed. Hydrogen storage is therefore an essential part of an intelligent electrical system, stabilizing the micro-grid and ensuring total energy independence regarding renewable energies. It completely replaces the need for a diesel generator!
Although the progress of electrification around the world has been spectacular, more than one billion people on Earth still do not have access to electricity, mainly in South Asia and Sub-Saharan Africa. The reason, of course, is the poverty of these regions, but also the isolated situation of these territories.
Thus, this hydrogen solution could enable the creation of local independent energy grids in these regions and address environmental issues at the same time!
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