Fuel cells

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Sustainability: clean energy research for long-term bond

Yves Martin, L'Argus de l'Automobile, 6.2.2003

What will succeed the petroleum in the heart of our cars? If multiple systems are in the running, nothing comes to win, so the challenge is difficult to meet.

The transport issue

Become an indispensable tool, transportation is hunted by his enemy No. 1, pollution. Indeed, the ever increasing production of carbon dioxide (C02), responsible for the greenhouse effect that causes global warming, has become a major environmental issue. This is why many industrialized countries - except the United States - signed, in 1997, the Kyoto agreement in which they commit to reduce their production C02.

After this agreement, the European authorities have introduced stringent emission standards for automobiles.

Toutefois, la limitation des émissions polluantes des voitures n’est pas une finalité en soi. En outre, comme le souligne Pierre Zerlauth, coordinateur technique lors du Challenge Michelin « les polluants locaux (NDLR : au niveau de la voiture elle-même) sont mieux maîtrisés ». La pollution engendrée par la chaîne de production — du stockage à la distribution de l’énergie utilisée dans la voiture — doit également être prise en compte. On parle alors de bilan énergétique global, c’est-à-dire de la pollution « du puits à la roue ».

« Du puits à la roue »

Studies have been conducted on different energy sources to determine the most advantageous in reducing emissions C02.

Among these, are the LPG (liquefied petroleum gas), CNG (natural gas for vehicles), electricity, hydrogen (either used as fuel or in fuel cells).

Cependant, comme le souligne Philippe Pinchon, directeur du centre de résultats moteurs-énergie de l’IFP (Institut français du pétrole) : « Lorsque l’on parle de bilan énergétique, il faut tenir compte de quatre facteurs : l’effet de serre, le rendement énergétique, le coût et la disponibilité de l’énergie. »

This is where it gets complicated! Take for example the electric motor: the most environmentally-friendly ever. According to the method adopted for the production of electricity, the ecological balance could be disastrous. For example, one produced in Germany, after thermal plants fueled by coal, a negative balance with a production of C02 460 grams per kilowatt hour, which is roughly the European average. In contrast, electricity from French nuclear power plants emit only 100 g / kWh. The most disastrous record is that of Greece, where electricity production generates about 900 g / kWh of C02.

Following this reasoning, we see that the use of a fuel cell is not as environmentally friendly as this.

Indeed, two methods exist for producing hydrogen, base fuel of a fuel cell: either the rise in the vehicle, via a reformer (unit that extracts hydrogen from hydrocarbons) or it comes from central and distributed as a conventional fuel (gaseous or liquid). If the first solution reduces the production of C02 it emits many other pollutants harmful to the environment because of the non complete mastery of reforming. This is why it is preferable to produce hydrogen in a central or process is better controlled, but in this case the problem (insolvent?) Of the distribution and storage of hydrogen arises.

Referring to Table emissions C02 below, we see that the use of liquid hydrogen offers no interest.

Indeed, the energy required to liquefy the gas is important and increases 50% Production CO2 of this sector. The advantage therefore for the use of compressed hydrogen. Again, depending on the country and the source of extraction, the results vary from one extreme to another. So,the best result is achieved when producing hydrogen from natural gas using electricity from French nuclear power stations c. However, this solution has the disadvantage of a price exorbitant amounts to EUR 24 29 to gigajoule (against 7 EUR / GJ for the production and distribution of premium unleaded 95 and 98 and 6 EUR / GJ for gas oil and 13 EUR / GJ for LPG).

The solution is to combine several solutions to get the maximum benefit from these courses.

Thus, the car that would offer the best balance between cost, pollution and efficiency should adopt a diesel hybrid engine and electric motor with a high-capacity battery (able to store a lot of energy) and with a battery fuel supplied to the compressed hydrogen. The unique hybrid car sold in France (note: still a very high price), the Toyota Prius is still very far from this refinement.

Comparative table of transport technologies (click to enlarge)

Diesel ; Diesel FT diesel Fischer-Tropsch (synthetic diesel); DME dimethyl ether (synthetic fuel); VOME methyl esters of vegetable oils: gasoline; ETBE ethyl tertiary butyl ether (derived from the fermentation of sugar beet or corn and oil); EtTOH ethanol; natural gas ; GPL; H2 fuel; H2 compressed; H2 liquid; MeOH methanol; gasoline

The alarming increase C02

For a century, the greenhouse effect tends to pack, causing a general rise in temperatures via increased carbon dioxide (C02) in the atmosphere. By itself, this gas is responsible for half of this.

C02 concentration is greater today quarter than it was in the last century. An unprecedented level of pollution in recent years 600 000.

This carbon dioxide comes mainly from use of fossil fuels (coal, oil, natural gas) in different sectors: industry, energy and transport. They represent more than a quarter of C02 emissions in industrialized countries, and this proportion is increasing. The many perspectives outlined by the International Energy Agency (IEA) forecast a significant increase in total emissions C02 in the next decade: between 31 42% and% ...

From Rio to Kyoto, a slow evolution

1992 in June in Rio de Janeiro, 178 50 countries and international companies committed to sustainable development and signed an agreement to stabilize concentrations of greenhouse gases from all generation sources (IPOA called Agenda 21). This framework agreement then recommended for developed countries to reduce their emission levels than 1990.

Three years later, in Berlin, the states have engaged in a new process leading to the reduction of emissions of C02. A protocol was adopted in December 1997 after the Kyoto conference. Only the United States have not signed.

The European Union, for its part, has committed to reduce its production of 8% CO2 by 2010. This decline will be distributed according to the statement emission levels in 1990 in the different member countries, their need for development and demographics. Thus, the goal is for Germany a decrease of 21%, that of Greece, limited to 25% increase, and that of France, equality.

The car park is about 12% of the total production CO2 manmade continent, and 2% globally. In 1995, a new European car emitted 165 g / km, against 191 g / km for a Japanese, and 260 g / km for an American.

In July 1998, the European Automobile Manufacturers Association (ACEA) has taken vis-à-vis commitment of the European Commission. This one includes a double objective. Initially, the Association is committed to producing cars for the European market whose emissions will not exceed CO2 120 g / km 2012 (an average consumer to the 4,9 100 km). She then committed to a middle tier for cars sold in 2008, with an average level of emissions of CO2 140 g / km, an average consumption of the 5.7 100 to km.

Learn more about fuel cells

- comparative article Sciences et Avenir
- CHP study with a fuel cell


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