FAQ

Hydrogen is believed to be one of the three elements produced in the Big Bang. Hydrogen can be found in stars which use it as fuel to produce energy and in "empty" spaces between stars. We owe most of our planet's energy to hydrogen, because the Sun's nuclear fusion process converts hydrogen into helium, releasing vast amounts of energy. Hydrogen is a chemical element which thus represents 75% of the mass of the Universe. It is also the lightest and simplest element, composed of a single proton and an electron, but it constitutes 2/3 of all the molecules on our planet.

On Earth, it usually does not exist by itself in nature and must be produced from compounds that contain it, for example from water (H2O). The only exception is a very small percentage that exists in Earth's atmosphere. This reduced percentage is due to its low density; Earth's gravity is unable to hold it, and it floats in space. The mass lost is around 95,000 tonnes of hydrogen per year.

About 10% of the weight of living organisms is made up of hydrogen - mainly water, protein and fat.

Hydrogen is a gas at room temperature, but turns to liquid at -252.8˚C, and from liquid to solid at -259.2˚C. It contains up to three times more energy per unit mass than diesel, and 2.5 times more than natural gas. Its combustion does not release CO2, SOx or fine particles - it only produces water.

But while the storage of natural gas is familiar to us through cylinders or the natural gas network, that of hydrogen is more complex: it is an extremely light gas that occupies a large volume at atmospheric pressure. It must therefore be stored at high pressure levels. The tanks on board ships store hydrogen at 350 bar, which is the current standard for buses, for example. Hydrogen-powered cars, like the Toyota Mirai, store their hydrogen at 700 bar.

In terms of "contained" energy: 1 kg of H2 = 11 Nm3 = 13.6L of liquid H2 = 23.3L of H2 at 700 bars and contains 33 kWh of energy produced by 52 kWh of electricity (in industrial practice, the yield is 63% by electrolysis before compression or liquefaction). One liter of liquid H2 weighs 73.5 g and contains 2.4 kWh so 4 liters of liquid H2 = 9.6 kWh. A liter of H2 at 700b weighs 43g and contains 1.4 kWh so 7 liters of H2 at 700b = 9.8 kWh. We deduce in terms of energy (approximately): 1 liter gasoline = 9 kWh = 3000L of H2 (at Patm) = 7L H2 / 700b = 4L of liquid H2 / -253 ° C.

Until now mainly used as a raw material for chemistry and petroleum refining, hydrogen is more and more identified as an energy vector of the future because of its storage capacities and the fact that its use does not emit any CO2. It is presented today as a possible substitute for hydrocarbons, and an effective means of facilitating the integration of renewable energies. While more than 95% of the 75 million tonnes of hydrogen produced per year worldwide are derived from fossil fuels, new technologies for producing carbon-free hydrogen continue to mature. The production of hydrogen from biomass or by electrolysis is supported by the emergence of new demand for "green hydrogen".

In industrial applications, the use of carbon-free hydrogen is expected to occur in processes traditionally using fossil hydrogen, such as ammonia production and petroleum refining, but also in new processes as a substitute for other fossil materials. Projects to experiment with new ways of integrating carbon-free hydrogen or upgrading fatal hydrogen into production chains have multiplied in recent years, and the 2019 climate energy law sets a target of 20 to 40% of low-carbon and renewable hydrogen by 2030.

In transport, hydrogen vehicles represent a suitable alternative to meet the challenges of sustainable mobility. They only release water, have a range equivalent to a combustion vehicle and recharge quickly. In addition to the multiplication of the number of hydrogen car models, the year 2019 has been marked by the acceleration of the dynamics of the hydrogen railway with the multiplication of orders for the train developed by Alstom, and by the growing interest of local communities for the deployment of hydrogen bus lines.

As part of an increasingly renewable future electricity mix, the hydrogen energy vector makes it possible to compensate for the intermittence of renewable energies by storing, in gaseous form, the excess electricity produced during periods of high production and low consumption (Power to Gas). The energy storage made possible by hydrogen also makes it relevant to extend the perspectives of self-consumption to the scale of a house, a building or a village.

Currently, 95% of the hydrogen produced in France is of fossil origin, as is nearly 99% of that produced in the rest of the world. This hydrogen is most often obtained from the process of steam reforming methane, the main component of natural gas. Each kg of hydrogen produced this way emits 12 kg of CO2, and its cost price varies from 1 to 2.5 € per kg. Almost 45% of world production comes from this technique.

About 25% of hydrogen production comes from "co-production" of refined products from hydrocarbons, which is then called "fatal" hydrogen. Its production cost is variable since in this instance it is a "waste" from the production of other chemical elements, and therefore its carbon footprint is too.

A third method uses coal, burnt at very high temperature (1200 to 1500 ° C) to separate the hydrogen - which should be called dihydrogen H2 - from CO2, in the form of gas. This production, about 30% of the total, makes it possible to obtain hydrogen whose cost price per kg varies between 1.5€ and 3€ per kg, but releases 19 kg of CO2 per kg of hydrogen.

These are industrial models that make "gray" hydrogen. "Green" hydrogen, which only contributes less than 1% of world production (around 5% in France), comes from the use of low-carbon or renewable energies (solar, wind, etc.). The electrolysis of water, which allows a zero carbon footprint, represented only 0.1% of global hydrogen production in 2019, due to a relatively prohibitive cost compared to other production methods, one kg of hydrogen costing between 3€ and 12€ for its production alone (excluding the cost of transport, distribution, etc.).

To allow the large-scale deployment of "green hydrogen", electrolysis from a renewable energy source is one of the future undertakings , and it is clearly one of the strategies traced through the 2020 recovery plan, to make France and Europe champions of "green" hydrogen production.

Electrolysis breaks down water molecules (H2O) into gaseous hydrogen (H2) and oxygen (O2) using an electric current. Specifically, water is injected at the positive electrode (anode) where it is first broken down into oxygen, H + ions and electrons. The H + ions then migrate to the negative electrode (cathode) where they recombine with electrons to form hydrogen. The membrane is used to let protons migrate while blocking electrons to circulate them to the anode.

Industrial electrolysis uses 1L of water and 5kWh of electricity to produce a "Normo cubic meter" (Nm3) of H2, or 1000 liters of H2 in the form of gas at 0°C, at atmospheric pressure.

1 Nm3 = 0.08988kg H2

The energy consumption of an electrolyser strongly depends on the scope considered (stack, system, etc.) as well as on the power of the installation. At low power, the average efficiency of an electrolyser is lower than at a larger scale. PEM (Proton Exchange Membrane) electrolysis currently achieves slightly lower performance than alkaline electrolysis but has more room for improvement. For an average system, a value of 56kWhe / kg H2 can therefore be used.

As hydrogen is a very low density gas, its energy density per volume is also very low (3 kWh / m3). To reduce this large, bulky volume containing little energy, the hydrogen produced, if it is not intended for consumption on site (export, mobile use), is compressed to a pressure higher than when released from the electrolyser, which is typically 30 bars. While compression to 200 bars for transport is the current norm, the transition to 500 bars which is underway increases the weight of hydrogen transported per trip, volume being the limiting factor.

"Gray" hydrogen comes from the use of fossil fuels, and therefore emits CO2 during its production. It turns "blue" when this emitted CO2 is captured to be recycled and used in other applications or simply stored. "Green" hydrogen is produced from renewable energies, so it is carbon neutral. Finally, "yellow" hydrogen is produced using nuclear electricity, which, while it is carbon neutral, is not green as a renewable energy source.

The question may sound absurd, but it is not. If we consider the total annual production, whose figures vary between 75 and over 100 million tonnes depending on the source (in particular because part of the production is annexed to other chemical activities via "fatal" hydrogen), and considering a minimum of 10kg of CO2 emitted per kg of hydrogen produced, we obtain a total of over 1 billion tonnes of CO2 emitted during the production of "gray" hydrogen. This figure represents around 2/3 of CO2 emissions from maritime transport, or 2% of the world total, which is far from negligible. This is why it is essential to turn to the production of green hydrogen, and in the first place to decarbonize heavy industries and mobility.

According to the IMO (International Maritime Organization), the maritime sector accounts for 1.475 million tonnes of CO2 annually - which corresponds to around 3% of global emissions.

A fuel cell is a device that converts chemical energy (energy stored in molecular bonds) into electrical energy. A PEM (Proton Exchange Membrane) cell uses hydrogen gas (H2) and oxygen gas (O2) as fuel. The products of the reaction in the cell are water, electricity and heat. As O2 is readily available in the atmosphere, all you need is to feed the fuel cell with hydrogen which can come from an electrolysis process.

A fuel cell works by passing hydrogen through the anode and oxygen through the cathode. At the anodic site, the hydrogen molecules are split into electrons and protons. Protons pass through the electrolyte membrane, while electrons are grouped together through a circuit, generating electric current and excess heat. At the cathode, protons, electrons and oxygen combine to produce water molecules.

Fuel cells are modular. This means that the individual cells are linked together to form larger stacks, and in turn these stacks can be combined into larger systems. Fuel cell systems vary widely in size and power, from portable systems for recharging the battery of smartphones, to combustion engine replacements for electric vehicles, to large-scale multi-megawatt installations providing electricity directly to the distribution network.

While there are several fuel cell technologies, the most common for mobility is the one called PEM (Proton Exchange Membrane) technology, thanks to its maturity and great compactness.

One of the major advantages of a fuel cell is to be able to use the energy contained in hydrogen, produced from renewable energies such as solar, and thus to compensate for their intermittence, all this without emission of CO2 or fine particles, with an efficiency of over 42%. This means that out of 100 kW of solar energy, 42 kW of hydrogen can be stored. Without photovoltaic cells, which generates the energy needed to produce hydrogen, this solar energy is simply wasted!

A fuel cell is almost completely recyclable, the only rare metal is platinum (less and less used), 100% recyclable and recycled.

A fuel cell is made of metal, graphite, electrodes, and its process is effectively chemical. The REXH2® system designed by EODev is based on Toyota fuel cell technology. The Toyota fuel cell system has already proven its benefits for many years in the Mirai, but more recently also in other applications such as buses and trucks. Its use for maritime transport is once again one more step towards the development of the hydrogen society.

It is pure, totally demineralized, water. It is possible to drink some, but not too much, because it is not recommended. Not that it is not drinkable, but because it does not contain minerals useful for the proper functioning of the body.

The principle of a Stirling engine is based on the combustion of a fuel which can be hydrogen. But even the combustion of hydrogen will release NOx into the atmosphere. In addition, the efficiency of such combustion is about 30%. The electrochemical reaction in the fuel cell will generate electricity, heat only water. Thus, we consider that it is better to use a fuel cell than to burn hydrogen, alone or in combination with other fuels. For us, this solution, sometimes considered as a temporary palliative before the advent of hydrogen, is not satisfactory: rather than working on temporary solutions that are half valid, or half polluting (depending on whether we see the glass half empty or half full) we have chosen to develop 100% clean solutions. Even if they are less practical and economical in the short term, they aim for total decarbonization, because there can be no half measures in the decarbonization objectives for industry and mobility.

If we can store renewable energies instead of wasting them as we do today, they can have a key role in the energy transition for mobility, especially at sea. Mix renewable energy sources and a production line of on-board hydrogen, to guarantee total autonomy over long distances and without any emission of pollutants or noise, is certainly the solution for the future. The industrialization of these energy models is now supported by massive public investments in green hydrogen, particularly in France and the rest of Europe. Technology is evolving rapidly, technical feasibility is no longer really an obstacle, even if the constraints of storing hydrogen under pressure, and the volume occupied, remain complex. We can only hope that these developments can quickly establish themselves in maritime mobility.

It is true that the batteries are heavy and expensive. We are working hard to come up with solutions based on the use of hydrogen with a better weight / energy / cost ratio than batteries. Over time, hydrogen solutions will become more affordable and we believe that hydrogen will be widely used in marine applications in the future, whether in combination with batteries in the form of hybridization, or on its own. To better understand how fuel cells and batteries work together, read our article "Electro-hydrogen hybridization: how does it work?"

While batteries provide immediate short-term energy, hydrogen acts as a long-term range extender. The example of the Energy Observer vessel illustrates the huge advantage of hydrogen compared to batteries in real life. While the battery park weighs 1400kg for 112 kWh, the hydrogen storage and the fuel cell weigh a total of 1700kg for 1000 kWh. Comparing energy per kilogram, 1kWh therefore weighs 12.5kg when stored in batteries, and only 1.7kg when stored as hydrogen. In other words, this means that for equal weight, hydrogen storage contains 7.35 times more energy than battery storage, which is a considerable asset for mobility, whether maritime, land, or even air. For more details, see also the application example developed on board the Hynova 40, and the article on fuel cell - battery hybridization to be found HERE.

The example of the Energy Observer vessel is a good illustration of the intelligence of the system developed by our engineers. To put it simply, the boat has three main operating modes:

In normal navigation, solar or wind electricity directly powers the propulsion.

The batteries take over in the event of a momentary drop in production, for example in cloudy weather.

In the event of a long interruption, at night for example, the fuel cell takes over and acts as a range extender by converting the hydrogen reserves into electricity.

Conversely, strategies are also programmed to recharge batteries and hydrogen stocks at the right times, before these reserves run out. When the battery charge level drops below 30%, most of the electricity production is dedicated to recharging them. When the battery level is over 90% or the boat is stationary, the energy is used to produce hydrogen. Pilots can also automatically vary engine rpm (and therefore boat speed) to keep the battery charge level stable.

All of these decisions can now be managed in almost 100% real time by the system, although crew can take control of the decisions at any time. Thanks to the creation of dedicated software made up of 21 grafcets, connected to 200 alarms, 12 analog actuators and 13 digital actuators, 1,050 pieces of data are sent back via the internal digital network in real time. This data, in addition to ensuring navigation comfort for the crew, also constitutes a basis for developing routing software integrating renewable energies. Of course, this data can also be retrieved remotely to organize predictive maintenance of the entire system.

It is the energetic brain of the system. Aggregating multiple sources of intermittent renewables and storage is one thing. But using them wisely to propel a ship and keep the crew comfortable is another. This challenge requires the intervention of an essential central body: the Energy Management System (SME or EMS). It is a set of automatons controlling and coordinating the different systems, accessible to human pilots via the on-board computer.

In a very synthetic way, we can consider the following solutions, with their drawbacks.

• Batteries: Ships require a large reserve of energy, resulting in a battery size which, with current technology, is too large, too heavy, and too expensive. In addition, there is no real way to recharge large battery packs during a port call, due to limited charging infrastructure and excessively long charging times;
• Photovoltaic panels: the usable surfaces on most ships are generally not large enough to provide 10% of the power required; it can therefore only be a complement;
• Wind energy: sailboat technologies are evolving, with (among others) new rigid wings whose efficiency is remarkable. But these solutions are not sufficient to ensure propulsion at high speed; they can act as a complement to other solutions to save the energy used, or also produce energy that can be used directly;
• Nuclear power: it is too expensive, currently impossible to provide, and requires too many trained personnel to be profitable on a commercial vessel. And there remains the issue of radioactive waste management, which has not been resolved;
• Biofuels: there is not enough biomass available and, unless all processing plants use zero CO2 energy, it does not reduce net CO2 emissions enough to meet the 50% emission reduction target;
• Green ammonia: as a fuel, it is toxic, and produces more NOx during combustion;
• Green methanol: as a fuel it is interesting but has drawbacks - it is toxic and emits CO2 during combustion. The only option, difficult to prove, is that the original CO2 used for its production has already been captured in the air; thus it would be a question of recycling the existing CO2 so as not to increase the mass of GHG emissions.

Overall, the use of hydrogen is safer than that of conventional liquid fuels such as diesel or gasoline in our cars, or even natural gas. This in no way implies that hydrogen is not dangerous - there are many situations in which hydrogen, like any other fuel or energy storage device, can cause an accident.

However, its very low level of flammability and its low energy density mean that the heat given off during a hydrogen fire is low, and that the damage caused by a "hydrogen" flame is less than the damage created by the flame of other gases. It is thus no more or less dangerous than a cylinder of Butane used to light a gas barbecue!

If not confined, it disperses easily in the atmosphere. And if it is confined, you just have to make sure that it can be easily dispersed, like any flammable gas. Ventilation is therefore the main safety measure to prevent build-up to a flammable level.

There are standards used around the world for hydrogen. For the automotive sector, the EC79 / 2009 standard governs the application of hydrogen as a fuel to road vehicles. ADR regulations cover the transport of dangerous goods, including compressed and flammable gases such as hydrogen. The IGF code covers all areas that require special attention for the use of gas or low flash point liquids as fuel.

Type 4 tanks used by EODev undergo extensive testing (corrosion testing, mortar testing, perforating bullet testing, drop testing ...) to ensure that they are as safe as possible to comply with EC79 / 2009. They have also been tested to withstand a pressure of 1,800 bars. They are equipped with thermal decompression devices (TPRD) which relieve tank pressure in the safety vent lines in the event of a leak or fire, to prevent the risk of tank rupture. The valves also include decompression devices to evacuate hydrogen in the event of overfilling, and excess flow devices.

EODev solutions are equipped with hydrogen detectors, which are ATEX classified fast response sensors, as well as certified marine heat detectors and infrared flame sensors. On ships, sensors are used in fuel cell compartments and storage areas to detect the smallest leaks and shut down the system before levels reach the flammable limit. If flames are detected, the system is automatically stopped, the distribution valves closed, so that the gas is cut off at the source without operator intervention.

On our solutions there are two types of leak detection systems, which we will call static and dynamic. Failure of the static leak detection (verified at each engine power cycle) will cause the tanks to close, disabling the hydrogen cycle until the leak check is passed on the next power cycle. This ensures that small leaks cannot turn into large leaks, the tanks are sealed and the only hydrogen that can escape is the small amount left in short high pressure lines and longer low pressure lines. During normal operation, our dynamic leak detection system constantly compares the measured gas consumption with the use of the storage cylinders. A difference between these two measurements results in the declaration of a leak and the shutdown of the system. Of course a manual shutdown is also always possible.

Independent experts validate the safe operation of our systems, in particular when they are on board ships such as the REXH2, as well as refueling procedures. Certification is a three to six month process and a mix of internal and external experts identify potential hazards and threats affecting people, equipment and the environment. It is only after agreeing on all aspects of the operation of the hydrogen system, and identifying and assessing any issues that may pose risks to personnel or equipment, that they agree on the measures to ensure that the system can be operated safely, including an analysis of the risks of failure.