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Aluminum Electrolytic Cell with Heat Recovery

ARPA-E Award: 
Pittsburgh, PA
Project Term: 
03/31/2014 to 07/20/2018
Project Status: 
Technical Categories: 
Critical Need: 

Primary production of lightweight metals such as aluminum is an energy-intensive and expensive process that results in significant carbon dioxide (CO2) and other emissions. Lowering the energy consumption, cost, and emissions associated with processing aluminum would make it competitive with incumbent structural metals such as steel. Enabling its widespread use in vehicles in particular--without compromising performance or safety--would substantially reduce fuel consumption and CO2 emissions from transportation.

Project Innovation + Advantages: 

Alcoa is designing a new, electrolytic cell that could significantly improve the efficiency and price point of aluminum production. Conventional cells reject a great deal of waste heat, have difficulty adjusting to electricity price changes, and emit significant levels of CO2. Alcoa is addressing these problems by improving electrode design and integrating a heat exchanger into the wall of the cell. Typically, the positive and negative electrodes--or anode and cathode, respectively--within a smelting cell are horizontal. Alcoa will angle their cathode, increasing the surface area of the cell and shortening the distance between anode and cathode. Further, the cathode will be protected by ceramic plates, which are highly conductive and durable. Together, these changes will increase the output from a particular cell and enable reduced energy usage. Alcoa's design also integrates a molten glass (or salt) heat exchanger to capture and reuse waste heat within the cell walls when needed and reduce global peak energy demand. Alcoa's new cell design could consume less energy, significantly reducing the CO2 emissions and costs associated with current primary aluminum production.

Potential Impact: 

If successful, Alcoa's redesigned cell could offer significant improvements over current cells while consuming less energy, thus producing more cost-effective aluminum.


Light-weighting vehicles to improve fuel efficiency could reduce U.S. dependence on foreign fossil fuel resources used in the transportation industry.


Adopting a new cell design could lead to an energy reduction of 0.1 quad/year across the entire U.S. aluminum industry, resulting in a substantial reduction in CO2 emissions.


Reducing aluminum production costs increases the appeal of light weighting vehicles due to the cost savings from improved fuel efficiency.

Innovation Update: 
(As of March 2017) 
In early 2018, Alcoa plans to scale its self-heated pilot cell to demonstrate the technology. Given a successful demonstration, Alcoa will scale for either internal deployment or licensing. There are two potential paths to market—greenfield and retrofit applications. Based on Alcoa’s economic models, using the sloped cathode design in a greenfield facility could enable 5% savings per ton of aluminum produced. By retrofitting the technology into their existing smelters, Alcoa primary aluminum production could increase to about 645k metric tons per year from about 360k metric tons per year with reduced energy and cost. 
Alcoa developed an unconventional cathode design for an electrolytic cell to improve the current aluminum production process and reduce energy consumption. Alcoa redesigned the electrolytic process by placing the cathode on an angle and protecting the cathode surface with titanium-based ceramic plates. This construction material assures greater aluminum wetting than today’s cells and enables a significantly reduced anode-cathode distance. Alcoa’s models show that these changes would reduce energy consumption by more than 20% for a greenfield design using the optimum side angle. 
For a detailed assessment of the Alcoa project and impact, please click here.

ARPA-E Program Director: 
Dr. Scott Litzelman
Project Contact: 
Mr. Mark Ripepi
Halotechnics, Inc.
University of California, Berkeley
Release Date: