Electric

# Fuel Cell Cost and Reliability

May 7, 2012, 6:23 pm
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Fuel cells today require some very expensive components. [1] In particular, the electrode/catalyst and polymer electrolyte membrane are literally worth their weight in gold.

A catalyst is a substance that promotes a chemical reaction without itself being consumed. As such, it must remain chemically inert under the conditions necessary for the reaction. Nearly all electrode/catalysts for hydrogen fuel cells contain platinum, a chemically inert metal that costs over $35 per gram, substantially more than the price of gold. At present, a typical fuel cell vehicle (100 kilowatt = 134 horsepower) contains over$70,000 of platinum. [2] Much of the current research on fuel cells focuses on minimizing the platinum needed for efficient catalysis. For example, one approach uses nanotechnology to produce tiny particles of platinum alloy with higher reactivity. These developments may someday bring platinum costs for a vehicle to below $5000. Then again, large-scale deployment of hydrogen fuel cell vehicles would increase the demand for platinum and thereby increase its price on world markets. Polymer electrolyte membranes in hydrogen fuel cells are usually constructed from a special type of Teflon called Nafion that is selectively permeable to positive electrical charges. This material is expensive, adding roughly$1000 to the cost of a vehicle. It also breaks down at temperatures above 80°C. Other materials, such as porous polyethylene film and aromatic polysulfone copolymers, may lower membrane costs to somewhere around \$10 and can operate at higher temperatures. [3] Higher temperatures allow for more efficient use of platinum in the electrodes. [4]

Vehicles must function dependably despite being subjected to constant vibration, rapid temperature changes ranging from cold starts to high running temperatures, frequent bombardment with dirt and water, and occasional neglect or incompetence. Hydrogen fuel cell vehicles may not be ready for such abuse. Their membranes must be thin to attain sufficient permeability to gases, but this increases their fragility. Their catalysts must have a high surface area to attain sufficient reactivity, but this makes them vulnerable to contamination by dirt or poisoning by carbon monoxide. The water and temperature management of hydrogen fuel cells is complex. The principal reaction in a cell generates not only electric current, but also water and heat. If a fuel cell floods with water, hydrogen will not reach the catalyst, and the reaction will stop. If a fuel cell has too little water or the water freezes or boils, the membrane will suffer damage and lose permeability, and the fuel cell will overheat. To sustain operation, a fuel cell must be maintained under environmental conditions that are just right.

[1] International Energy Agency (2005) Prospects for Hydrogen and Fuel Cells, Organization for Economic Cooperation and Development, Paris, http://www.iea.org/textbase/nppdf/free/2005/hydrogen2005.pdf.

[2] ERDC/CERL Fuel Cell Team (2007) Fuel Cell Information Guide. U.S. Department of Defense, http://dodfuelcell.cecer.army.mil/proton.html, accessed Aug. 8, 2007.

[3] Chalk, S. G. and J. E. Miller (2006) Key challenges and recent progress in batteries, fuel cells, and hydrogen storage for clean energy systems. Journal of Power Sources 159:73-80.

[4] International Energy Agency (2005) Prospects for Hydrogen and Fuel Cells, Organization for Economic Cooperation and Development, Paris, http://www.iea.org/textbase/nppdf/free/2005/hydrogen2005.pdf.

This is an excerpt from the book Global Climate Change: Convergence of Disciplines by Dr. Arnold J. Bloom and taken from UCVerse of the University of California.

©2010 Sinauer Associates and UC Regents

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