What do I have to expect if I choose a hydrogen-powered car?

hydrogen-car

Photo by Office of Naval Research

We have come to the end of my overview of alternative fuels, compared to the “classic” petrol and diesel, which we can currently find available in the lists of the main OEMs.

Today I would like to talk about hydrogen as fuel, which has only recently hit the headlines as the most ecological fuel ever!

You will find, at the end of this post, the links to the other posts concerning the other fuels already written about (LPG, CNG, Hybrid and Electric cars).

Hydrogen (H2), in contact with air, forms explosive mixtures even at low concentrations; it is enough a hydrogen gas leak in the atmosphere to trigger a violent explosion, or an invisible and dangerous flame that produces water.

The tragedy of the Hindenburg blimp is a famous example.

Hindenburg

Photo by San Diego Air & Space Museum Archives

The use of hydrogen as a possible source of energy for motor vehicles would have the advantage of using fossil fuels to directly obtain gas (methane, for example).

Used as fuel in the means of transport, reacting with Oxygen (O2), it would produce only water waste, eliminating the CO2 emissions (typical of thermal cars) and the related climatic-environmental problems linked with them.

Therefore, the hydrogen can actually be used for energy purposes, such as car fuel or in fuel cells, to obtain energy in the form of electricity.

The disadvantage is in the density of the generated energy, which is much lower than traditional fuels, and therefore it needs to be compressed to have proper autonomies; during storage we arrive up to 700 bar!

idrogeno

Photo by DoctorTac

The real problem is that atomic and molecular hydrogen is very uncommon in nature and is combined with other elements; in other words it is not a primary source of energy such as natural gas, oil and coal, and must be produced artificially by spending energy from primary energy sources.

That is to say that it can be used as an energetic vector, but the production cycle is inefficient from the thermodynamic point of view, since its production requires more energy than the one obtained through its ‘combustion’.

CAR APPLICATIONS

We will only deal with the applications done on the cars not dwelling on the heavy truck.

We have currently only two types of applications:

  1. Hydrogen as fuel in Otto cycle heat engines;
  2. Hydrogen as fuel for cell to produce electricity.

SOLUTION 1

Since the amount of energy generated in the combustion is less than about 1/3 compared to that of methane (and about half of the petrol), we need solutions that store more hydrogen.

To do this there are currently two different storage possibilities:

  • The use of liquid hydrogen at -253C°

This solution has been applied by BMW on the 7 series.

Liquid hydrogen advantage is the need of a tank of much lower capacity compared to the gaseous one, but there is the problem of keeping it at -253C°.

The very low number (*) of suppliers of liquid hydrogen is a big limit; there are only two in all Germany.
Furthermore, the tank must have very sophisticated thermostating and safety systems, that is to say a very high thermal insulation to prevent it from exploding.

In fact, when the liquid hydrogen passes into the gaseous state, it increases in volume and the pressure on the tanks, if manufactured with the technology similar to those of LPG, would not stand more than 60/70 bars.

hydrogen

Photo by Bob n Renee

(*) The low number of liquid hydrogen suppliers is due to a whole series of safety issues.

Indeed the vehicle to be recharged must be left in a specific area of the filling station, without anyone on board and, from the control room of the distributor, all the operation is done by a robotic systems; from opening to closing the cap.
All because even a small leak at -253C° would cause incalculable damages.
So opening a distributor like that involves an astronomical expense.

  • Use of gaseous hydrogen at room temperature

In 2000 a Tuscan company used Fiat Multipla Metano Monopower cars for this application.
The autonomy, from over 600km of methane, collapsed to less than 200km.

So to obtain a similar autonomy as for the methane, it would be necessary to use a volume of hydrogen three times higher than the methane and, not being able to install other tanks, you can only compress it more.

For this reason it have been developed cylinders for a working pressure of 700 bar but in many countries, including Italy, they are not currently allowed; currently there are no vehicles registered with this configuration.

SOLUTION 2

Even if we used hydrogen as fuel for batteries to produce electricity there could be two different technical variants:

  • Hydrogen that powers a fuel cell

Today several car manufacturers include in their catalog cars with this type of power: Honda FCX, Toyota Mirai, Hyundai ix35 Fuel Cell and others.

Fuel cells generate energy in the form of electricity from hydrogen oxidation, without switching from combustion, and power the electric drive train of the vehicle.
The hydrogen is stored in cylinders currently at maximum pressures of 220bar.

  • Hydrogen produced in the car through a process of “a methanol” powering the fuel cell

The methanol reformer is a device used in fuel cell (or battery) technology to produce pure hydrogen from a mixture of methanol and water (in the form of steam) by the releasing of carbon dioxide.

Reforming

Photo by alyssalaurel

Its use avoids storing hydrogen in pressurized gas tanks. The problems related to the dangerousness of the same could thus be overcome.
The advantage of methanol in this context is that it is available in liquid form.

However, methanol, like petrol, is toxic and highly flammable.
Furthermore, the methanol reforming process generates as a by-product carbon dioxide as well; which, as well known, is one of the main greenhouse gases considered responsible for the global warming.

HOW A HYDROGEN CAR WORKS

The hydrogen cars, in which the hydrogen is used as fuel in the Otto Cycle heat engines (Solution 1), work like simple bifuel, such as CNG/LPG engines.
So much so that they use similar cylinders, if not the same, except for the steel that must have components, which do not react with hydrogen.

Hydrogen cars, which are used as fuel for batteries to produce electricity (Solution 2), are simple electric cars but the energy is generated from the fuel cell.

CONCLUSIONS

Even for the hydrogen the same applies for the electric cars.

If we consider a car with this fuel, its use is with zero emissions, but as usual we must take into account its production, which depending on the source, has an influence on the production of pollutants, about 97% of the hydrogen is currently obtained from fossil fuels.

In the case of the fuel cell, hydrogen must have a purity (absence of other materials or gases) of more than 99% to avoid its own damage and this increases their cost even more.
In 2000 I did a study hypothesizing the production of a car of the B segment, with a volume of about 500 cars / day, the final cost of the cars was higher than 100,000€ because of the cost of the fuel cell in platinum and ruthenium of around 80,000€.

Today the few cars on the market have costs of 70,000€; I think, however, that they are political and not real prices.

Another aspect must also be considered; the hydrogen cars, in generating energy produce water as “waste”.

h20

Photo by donnierayjones

This means, however, that hydrogen (H) combines with oxygen (O), generating H2O molecules. The use of the oxygen, considering that there are currently more than 1.2 billion vehicles (data Navigant, 2015) in circulation could lead to an impoverishment of the oxygen absolutely not negligible.

ADVANTAGES

  • I don’t see it right now.

DISADVANTAGES

  • An excessive cost of the vehicle
  • Near-zero refuelling points
  • Its extreme dangerousness in case of tank leaks due to its flammability

*****

My personal opinion about hydrogen-powered cars is that the hydrogen cars of the Solution 2 will be interesting only as an fame car because of the high cost.

While for the Solution 1, despite being the cost comparable to a bifuel, we still have a hydrogen autonomy too low depending on the traditional tank that, for safety reasons, cannot exceed 220 bar.

*****

  1. What do I have to expect if I choose a CNG car?
  2. What do I have to expect if I choose a LPG car?
  3. What do I have to expect if I choose a hybrid car? (Parallel hybrid)
  4. What do I have to expect if I choose a hybrid car? (Hybrid series)
  5. What do I have to expect if I choose a hybrid car? (Parallel/series)
  6. What do I have to expect if I choose an electric car?
  7. What do I have to expect if I choose a hydrogen-powered car?

Translated by Federica Izzo

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What do I have to expect if I choose an electric car?

The sixth post of this my examination about the motorisation proposed by the OEMs; the Electric car.

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