Chemical and Electrochemical Energy
Chemical and electrochemical energy systems harness the energy stored in chemical bonds and the electron transfer processes of electrochemical reactions to store and convert electrical energy. These technologies form the foundation of modern energy storage, enabling everything from portable electronics to grid-scale installations. By reversibly converting electrical energy to chemical potential and back, electrochemical systems provide efficient, scalable solutions for the growing demands of renewable energy integration and electrification.
This category explores the diverse landscape of electrochemical energy technologies, from advanced battery chemistries that store energy within electrode materials to flow batteries that decouple power and energy through liquid electrolyte storage. Understanding the underlying electrochemistry, materials science, and system engineering of these technologies is essential for designing effective energy storage solutions across all scales of application.
Articles
Flow Battery Technologies
Store energy in liquid electrolytes pumped through electrochemical cell stacks. Coverage encompasses vanadium redox flow batteries, zinc-bromine flow batteries, iron-chromium systems, organic flow batteries, hybrid flow batteries, membrane technologies, electrolyte management, stack design optimization, flow field design, pump and control systems, grid-scale applications, microfluidic flow batteries, solar charging integration, flow battery monitoring, and redox-active materials.
Fuel Cell Systems
Convert chemical energy directly to electricity through electrochemical reactions. Topics include hydrogen fuel cells, proton exchange membrane cells, solid oxide fuel cells, direct methanol fuel cells, microbial fuel cells, enzymatic fuel cells, alkaline fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, reversible fuel cells, fuel cell stack design, balance of plant systems, hydrogen storage integration, reformer systems, and portable fuel cells.
Metal-Air Batteries
High energy density electrochemical cells using atmospheric oxygen as cathode, including zinc-air, lithium-air, aluminum-air, and emerging technologies. Topics include air electrode design, electrolyte systems, bifunctional catalysts for rechargeable systems, and applications ranging from hearing aids to electric vehicles.
Key Concepts
Electrochemical Fundamentals
Electrochemical energy systems operate through redox reactions that transfer electrons between species at electrode surfaces. Oxidation releases electrons at the anode while reduction consumes electrons at the cathode, with the spontaneous direction of these reactions determining whether a system produces or consumes electrical energy. Cell voltage depends on the difference in electrochemical potential between the electrode reactions, while current capacity depends on the amount of electroactive material available.
Energy and Power Relationships
Energy storage capacity measures the total electrical energy a system can store, typically expressed in watt-hours or kilowatt-hours. Power capability describes the rate at which energy can be delivered or absorbed, measured in watts or kilowatts. The relationship between energy and power varies significantly among electrochemical technologies, with some optimized for high energy density and others for high power density. Understanding these relationships enables selection of appropriate technologies for specific applications.
Efficiency and Losses
Round-trip efficiency measures the ratio of energy delivered during discharge to energy consumed during charging. Losses arise from various sources including ohmic resistance, charge transfer overpotentials, mass transport limitations, and parasitic reactions. System-level losses from power conversion and auxiliary loads reduce overall efficiency below the electrochemical cell efficiency. Optimizing efficiency involves balancing these various loss mechanisms against cost and performance requirements.
Applications
Chemical and electrochemical energy systems serve applications across all scales. Grid-scale installations support renewable energy integration, provide frequency regulation and spinning reserve, and defer transmission infrastructure investments. Commercial and industrial systems manage demand charges, provide backup power, and enable participation in electricity markets. Residential systems store solar energy for evening use and provide backup during outages. The unique characteristics of different electrochemical technologies enable optimization for specific application requirements.