Side batteries

For the clean car of tomorrow, we envisage the advent of a true "hydrogen economy" because this element, inexhaustible on a global scale, can become an energy vector as important as electricity.

Research on multiple fuel cell technologies is booming. This diversification paves the way for many non-polluting energy offerings, ranging from vehicles to power plants to portable applications.

The fuel cell (PaC) is a "very old innovation". Very simple, the basic principle of its operation was discovered and demonstrated, as early as 1839, by the English physicist William Grove (see diagram below).

For more than a century, however, the primacy of the development of thermal machines and electric batteries overshadowed this invention. This was no longer studied outside of certain laboratory developments, which remained unheard of.

Discovered as early as 1839, the fuel cell principle is extremely simple. Two electrodes connected externally by an electrical circuit and separated by an electrolyte are powered, in the presence of a catalyst, one by hydrogen - which acts as fuel - and the other by atmospheric oxygen.

The hydrogen atom at the anode splits into a positively charged proton or ion, and an electron. The ion migrates through the electrolyte to the cathode, where it combines with oxygen to form water (and heat release), while the electron travels through the electrical circuit giving rise to a current. However, its application varies greatly depending on the form of hydrogen brought to the anode (these may be chemical elements containing hydrogen) and the nature of the electrolytes.

Boost from Space

The first, space research will highlight the contemporary use of paCs. In the 1960s, NASA chose to turn to generators of this type to equip the Gemini and Apollo programs. The development of the very specific technologies of the PACs used in space has continued to progress and have been applied since then.

From the '70s and '80s, this space demonstration led, especially across the Atlantic and Japan, to a growing interest in this sector, especially in the automotive world and for various so-called 'stationary' applications. This research has opened up a great diversification of technological options. In addition to the conventional supply of the first batteries requiring pure hydrogen (obtained by electrolysis), PaCs operating with hydrogen produced by reforming hydrocarbons (petrol, natural gas, ethanol) have developed, but also methanol from biomass and carbon dioxide.

This widening of the fuel spectrum certainly reduces the "cleanliness" of the process, by reintroducing carbon emissions, but is not in common with the nuisances of internal combustion engines. On the other hand, reforming has significantly increased the interest of fuel cells by allowing widespread and industrially controlled hydrogen production processes.

A large family

In addition, diversification focuses on the types of electrolyte through which the H-or O- ions pass, depending on the type of PaC. There are batteries of alkaline potash (developed mainly in the space sector), phosphoric acid (the most "mature" technology at present, but limited in its applications), polymer membrane, molten carbonates, oxide Solid. Each category has specific properties in terms of fuel supply, operating temperatures and resulting applications.

The most promising progress - on which the European programmes have focused - concerns first the family of polymer membranes (so-called PEMFC). This type of PaC can be supplied with pure hydrogen or reformed, with operating temperatures ranging from 80 to 100 degrees Celsius. In particular, it equips the main automotive prototypes expected soon on the market as well as stationary applications of small power, especially in the residential sector.

A second category of polymer membrane batteries, fueled by methanol (DMFC), is of particular interest to low-power "portable" applications (mobile telephony, computing, etc.). Its development, however, currently faces a number of technological obstacles.

Operating at much higher temperatures (600 to 1,000 degrees Celsius), carbonate (MCFC) and solid oxide (SOFC) PACs compete for the development of high-power units for the cogeneration of electricity and heat, as well as for maritime applications. They have high yields and can be powered by a variety of fuels - methane, methanol, biogas, gas coal.
Fuel Cell (FC)

- AFC (Alkalin): Alkaline (especially in the space niche)
- PEMFC (Polymer Exchange Membran): proton exchange polymer membrane
- DMFC (Direct Methanol): direct methanol
- PAFC (Phosphoric Acid): phosphoric acid
- MCFC (Molten Carbonate): with molten carbonates
- SOFC (Solid Oxyd): solid oxide

European research in crescendo

Europe has become increasingly involved in the fuel cell issue over the past decade. At EU level, a large number of research and demonstration projects were devoted to them in the fourth framework programme (1994-1998), supported by financial aid of 54 million euros.

This impetus continued in the following programme (1998-2002), where some 150 million euros were provided in support of some 70 paC and hydrogen projects. Most PAC projects were specifically focused on polymer membrane electrolyte technology, currently the most promising in terms of market. The challenge is to develop membrane batteries (PEMFC and CFMD) operating at higher temperatures (80 to 180 degrees Celsius) than the PACs developed to date, which would improve performance while reducing the cost.

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