El hydrogen engine remains one of the bets for the future of the automotive industry. Its operation gives it a series of advantages that allow you to stay afloat despite your drawbacks. For this reason, brands such as Toyota, BMW, Mazda, Hyundai and Ford have made big investments in this technology.
In this article, we will take a look at how does a hydrogen engine work, what type there are and what are their main pros and cons. In this way, it can be understood why several companies continue to work on it, despite the expansion of the battery electric vehicles.
There are two types of engines that use hydrogen, combustion engines and fuel cell conversion engines. Let's see how they work and what advantages and disadvantages each one has.
Internal combustion hydrogen engine
these engines they use hydrogen like gasoline. That is, they burn it in combustion chambers to generate explosions (kinetic energy and heat). For this reason, a conventional gasoline engine can be adapted to burn hydrogen in the same way that they are adapted for the GLP o NCG.
How does the hydrogen combustion engine work?
The operation of this engine is very similar to that of a gasoline engine. The hydrogen is used as fuel and oxygen as oxidant. The chemical reaction is initiated by the spark, which can be produced by a plugs.
Hydrogen does not have any carbon atoms, so the reaction is union of two hydrogen molecules with one oxygen molecule, to release energy and water. Expressed in a chemical equation: 2H2 + O2 → 2H2O.
El result of its chemical reaction is simply steam. However, hydrogen combustion engines may produce some emissions derived from its operation. For example, small amounts of NOx, by the air and the heat of the combustion chambers, emissions produced by burn some oil that cross the piston rings.
As el hydrogen it is a gas, is stored in a tank at 700 bar pressure. Which is between 350 and 280 times more than the usual pressures in car tires (between 2 and 2,5 bars). Although there have also been cars that stored hydrogen in a liquid state at a very low temperature, as you will see below.
Hydrogen combustion engines offer some interesting and advantages over conventional combustion engines. For example, theoretically they could work with a very lean mixture (Lambda close to 2). That is, they could use little fuel to take advantage of all the air that enters and become very efficient.
Examples of hydrogen combustion engine
The bmw 750hl they are a good example of a hydrogen engine, which came to light in the year 2000. Although it was actually the BMW gasoline engine, adapted to burn hydrogen as well.
However, it had several drawbacks: the first, that it stored the liquid hydrogen. Which required a very expensive warehouse made of materials from the aerospace industry to keep it at temperatures below -250ºC. Something that could only be achieved for 12 or 14 days, a period in which the hydrogen gradually evaporated and was safely released into the atmosphere. The second drawback is that, by using hydrogen, lost much of its power and efficiency. The rear BMW Hydrogen 7 2005, it already partially solved these problems and took the hydrogen to 700 bar of pressure, without the need to keep it at a low temperature.
Another good example is the Aquarius hydrogen engine. A fossil fuel engine developed by an Israeli company, which was adapted to use hydrogen. The first functional version was presented in 2014 and later a modified and improved version arrived. According to its developers, it can work without lubricating oil and has a gas exchange system to reduce NOx emissions.
In addition, this hydrogen combustion engine is very light and has very few parts, so its production would be cheap. It could work as a range extender for electric cars or as a generator of electricity for the electricity grid.
fuel cell hydrogen engine
His full name is fuel cell conversion hydrogen engine. Despite the word "fuel", they do not burn hydrogen. They use it to produce electricity through a process that is reverse of electrolysis. That is why they carry a battery, where the chemical reaction takes place.
Operation of a hydrogen fuel cell engine
As in the hydrogen combustion engine, the hydrogen is stored in a tank at a pressure of 700 bars. Only instead of supplying it to an engine, it reaches the fuel cell with one anode and one cathode (like a battery).
Once in it, hydrogen (H2) passes through a membrane, which breaks it down into two hydrogen ions and two free electrons. Expressed as a chemical equation: H2 → 2H+ and 2e-. This happens because said membrane is electrically insulated and allows 2H+ to pass through, but does not allow electrons to pass through.
These electrons pass from the anode to the cathode. from the battery by an external circuit, thus generating the current electrical. The resulting hydrogen ions bond with oxygen from the air to form water. Expressed as a chemical formula: H2 + 1/2 O2 → H2O
For this reason, the fuel cell hydrogen engine yes it is zero emissions, as there is no production of NOx or gases resulting from burning oil, as is the case with combustion.
La membrane used in these engines it's expensive because it's made of platinum. However, there are works to solve this high cost. For example, at the Technical University of Berlin they have developed an iron alloy that could lower costs a lot, if it could be put into production.
Examples of fuel cell hydrogen powered cars
This type of engine has been chosen by many car brands. For example, Honda with its Clarity Fuel Cell, or Toyota with the Mirai and other heavy transport work such as hydrogen powered truck.
To these must be added the Hyundai Nexo, Hopium Machine, the Land Rover defend hydrogen, BMW i Hydrogen NEXT, Mercedes GLC F-CELL and the truck of the same brand GenH2.
Disadvantages of the hydrogen engine
- The catalysts used in the chemical reaction of a fuel cell hydrogen engine are of expensive materialslike platinum. At least until it is replaced by a cheaper one, like the one mentioned before from the Technical University of Berlin.
- To obtain Hydrogen, it must be carried out with thermochemical processes for fossil fuels or electrolysis of water, which requires an energy expenditure. Main criticism of hydrogen engines, since the electricity could be stored directly in the battery of an electric car for use.
- Once the hydrogen is obtained, it must be introduced under pressure into the cells or tanks. A process that also requires extra energy expenditure.
- The hydrogen cells are expensive to produce, they need to be very resistant to withstand the high pressures at which hydrogen must be stored.
Advantages of the Hydrogen Engine
- El weight of hydrogen cells is less than that of electric vehicle batteries. That is why its use in heavy transport is being studied as an alternative to battery electric trucks. To be able to cover long distances, the weight of these is very great.
- Recharging hydrogen is faster than charging the battery of an electric car today.
- Unlike a battery electric vehicle, a fuel cell hydrogen-powered vehicle does not need a large battery. That's why requires less lithium or other materials that may be in short supply. A hydrogen combustion engine does not directly require a lithium battery or other similar ones.
- Fuel cells last the life of the car. Unlike electric batteries, which due to their size and capacity are very expensive to replace. The battery associated with a hydrogen engine is smaller and therefore cheaper to replace.
- Compared to a fossil fuel engine, fuel cell hydrogen engines use an electric motor, so they are extremely quiet.
How hydrogen is refueled
Hydrogen engines have the drawback that their tank or fuel cell must contain hydrogen at very high pressure. Therefore, the supply points must also comply with 700 bar pressure they carry.
Esto requires the creation of an infrastructure of supply to be able to refuel this type of vehicle. That is, the same problem that battery electric vehicles have. Nevertheless, the refueling operation is much faster than that of these, because it is the same as that of LPG or GLC vehicles.
autonomy of a hydrogen car
Current cars with a hydrogen fuel cell engine have autonomy similar to those of gasoline. For example, the Toyota Mirai announces 650 km with the cell full, the Hyundai Nexo 756 km and BMW iX5 Hydrogen 700km.
others like the Hopium Machina announce a range of 1.000 km, although it is a figure that for now has to be confirmed when it occurs. In any case, autonomy is not as important as in an electric battery since refueling is much faster. What you do have to take into account is the number of refueling points.
Is a hydrogen car safe?
Brands have been working for years on this type of engine to improve efficiency, lower costs and, of course, get them to be tan payments such as fossil fuels.
In addition, safety standards required in Europe, USA and Japan, are a guarantee that hydrogen-powered cars are safe. Without going any further, Toyota boasts that the tank of the Mirai is so resistant that it is bulletproof.
Will we see the day come when all cars are powered by hydrogen? Time will tell. What is clear is that the brands continue to invest and that it has some advantages that keep it as a plausible alternative in zero-emission transport.
How can I make a flow chart of the hydrogen engine's operating processes?
interesting page
I've been visualizing hydrogen engines for days, why that change? if we have fossil combustion engines. (gasoline), does it not work with hydrogen? The whole problem is the deposit, if it were like the gas cylinders (interchangeable) we would not have, in my opinion, any difficulty.
On the other hand, the storage batteries when their useful life ends, where they are recycled, when now it is a simple shoe box and the plug-in hybrids are basically the entire vehicle. Thank you