Safety PEMFC

Dehydration of the exhaust gases is also of crucial importance not only from technical economics considerations (H20 recycling) but also for operational reasons since the gas mass flow meters do not stand any humidity. For the moment the management of the produced H2 is still under debate either burnt or recycled in a PEMFC coupled to the electrical grid or used for qualifying another process or stored. In a pragmatic manner, the short term objective of H2 production by 2013 requires to conduct the safety studies on the simpler option that will be available at that time. 

Perrette, L., Chelhaoui, S., Corgier, D. (2003). Safety evaluation of a PEMFC bus. In "Hydrogen Power - Theoretical and Engineering Solutions, Proc. Hypothesis V, Porto Conte 2003" (Marini, M., Spazzafumo, G., eds.), pp. 599-610. Servizi Gra-fici Editoriali, Padova. 

The purpose of this project is to design, develop, and demonstrate solid state electrochemical sensors for the various controls and monitoring on PEMFC vehicles. During this first phase of the project, we focus on the development of a hydrogen safety sensor. 

The practical advantage of this compound is its safety when stored or delivered as a powder or liquid. The quality of water is not a serious issue and any water, such as rain, underground, river, waste, or seawater, is suitable when it is used to make liquid solutions for supplying hydrogen to actuate proton exchange membrane fuel cells (PEMFCs) in emergency and portable uses. 

So as it can not be considered to provide a fuel cell functioning at higher temperatures than 80 or even 100°C for the user s safety, the choice in the type of fuel cell to use in portable devices is limited to low temperature fuel cells such as PEMFC (for Proton Exchange Membrane Fuel Cell or sometimes Polymer Electrolyte Membrane Fuel Cell) and DMFC (for Direct Methanol Fuel Cell). 

In PAFCs the protic electrol3d e phosphoric acid is impregnated in a porous separator, e.g. silicon carbide. Thus, considerable amounts of free (highly concentrated) phosphoric acid are present in the cell, which can be a safety issue for certain applications. In case of HT-PEMFCs the protic electrolyte phosphoric acid is adsorbed in a temperature-resistant polybenzimidazole-t) e (PBI) polymer membrane. 

In view of rapid progress in fuel cell work and in response to the many inquiries received from industry, the International Electrotechnical Commission (lEC) in 1996 created Technical Committee 105 (Fuel Cell Technologies). In August 2004, the first International Standard on fuel cells, lEC 62282-2 Fuel Cell Technologies, was published. It covers the minimum safety requirements for modules (not systems) that manufacturers should comply with when producing fuel cells (AFCs, PEMFCs, MCFCs, and SOFCs) destined for use by customers. 

Because of the higher energy density and better safety of liquid fuels compared with gaseous hydrogen, the types of fuel cell under active development usually includes direct methanol fuel cells (DMFCs) [4], direct formic acid fuel cells (DFAFCs) [5], proton exchange fuel cells (PEMFCs) run by hydrogen generated from metal hydride [6], and membraneless microfluidic fuel cells [7]. 

The performance of DHFC was far superior with an AEM than with a CEM. Daihatsu Motor continued this research in cooperation with AIST and developed a DHFC with a cell performance comparable with that of pure hydrogen PEMFC without the use of precious metals, as shown in Fig. 6.8 [8]. The toxicity of hydrazine is one problem with a DHFC. Hydrazine may have mutagenic effects. To improve the safety of DHFC system, Daihatsu Motor developed a hydrazine-fixing material based on the reaction of hydrazine with carbonyl or amide groups in a polymer. Hydrazine is adsorbed in the polymer as a harmless hydrazone and released as hydrazine as required. 

---