Alkaline fuel cells (AFCs) are an electrochemical conversion device that combines hydrogen fuel with oxygen from the air to produce electricity, water, and heat. Like other fuel cells, AFCs operate continuously as long as fuel and oxygen are supplied but do not require recharging like batteries. They were one of the earliest fuel cell technologies developed in the 1960s for the U.S. Space Program.
Key Components and Operation
An Alkaline Fuel Cells contains three main components: an anode, a cathode, and an alkaline electrolyte between them. Hydrogen gas is supplied to the anode where a catalyst separates it into protons and electrons. The protons pass through the electrolyte while the electrons are routed through an external circuit, generating an electric current. Oxygen gas or ambient air is supplied to the cathode. The electrons returning from the external circuit via the circuit react with the oxygen and protons to form water. The electrolyte plays a critical role by conducting hydrogen ions from the anode to the cathode while keeping the gases separate. AFCs typically use a concentrated solution of potassium hydroxide (KOH) as the electrolyte, which provides high ionic conductivity.
Advantages of Alkaline Fuel Cells
Low-Temperature Operation - AFCs can operate at temperatures lower than other fuel cells, around 60-250°C. This allows them to start quickly and provides advantages for system design and control.
High Efficiency - AFC efficiencies generally range from 50-70%, which is on par with other fuel cell technologies. Efficiencies exceeding 80% can be achieved in large stationary installations.
Long Durability - When properly maintained, individual AFC cells and stacks have demonstrated lifetimes exceeding 40,000 hours of continuous operation.
Non-Precious Metal Catalysts - AFCs use non-precious metal catalysts like nickel rather than expensive platinum, lowering material costs.
Applications of Alkaline Fuel Cells
Spacecraft - One of the first applications of AFCs was to power NASA spacecraft in the 1960s, including the Apollo command module. Even today, AFCs provide reliable onboard electricity and water generation.
Military - AFCs found early use powering military portable generators and batteries to provide reliable off-grid power. Their silent operation made them well-suited for stealth applications.
Commercial Transportation - Alkaline technology has powered passenger buses, light rail vehicles, delivery trucks and cargo carriers. Trials demonstrate they can serve as drop-in replacements for diesel gensets.
Distributed Power Generation - Stationary AFC systems have been used for utilities, telecom towers, rural electrification, and microgrids. Their modular nature suits distributed applications.
Back-up and Prime Power - As a reliable distributed source of backup or primary power, AFCs deliver continuous electricity during emergencies or for off-grid locations.
Limitations and Challenges
Limited Lifetime of Electrolyte - The concentrated KOH electrolyte can gradually degrade over long-term operation, limiting lifetime to a few years unless replaced.
Carbon Dioxide Sensitivity - Exposure to CO2 can cause the electrolyte to form carbonates which eventually clog the membrane, requiring a pure hydrogen stream.
Bulk and Cost - The large tanks needed to store compressed hydrogen gas increase overall system bulk, while use of expensive catalysts and membranes impacts costs.
Durability for Vehicle Use - While used in transport trials, more testing is still needed to prove AFC durability over standard vehicle operating lifetimes and duty cycles.
Overcoming Challenges through Research
Considerable research continues focused on addressing remaining AFC challenges to expand commercial applications:
- Non-corroding electrolyte formulations and gasket technologies aim to eliminate electrolyte replacement needs.
- Bipolar plate and gas diffusion layer developments target reduced costs and improved water and thermal management.
- Membrane electrode assembly improvements target increased power densities, current densities and efficiency.
- New catalyst formulations incorporating non-precious metals pursue lower costs with maintained activities.
- Hydrogen storage innovations explore onboard gas vs liquid options and integration with fuel cell stacks.
With ongoing development, AFCs show promise as a reliable clean technology for both portable and stationary power generation where the benefits of their inherent characteristics can be leveraged. Their availability helped enable historic space missions and today continued innovation brings the prospect of more widespread commercial and industrial use.
Get this Report in Japanese Language:
Get this Report in Korean Language:
About Author:
Money Singh is a seasoned content writer with over four years of experience in the market research sector. Her expertise spans various industries, including food and beverages, biotechnology, chemical and materials, defense and aerospace, consumer goods, etc. (https://www.linkedin.com/in/money-singh-590844163)
