Tech Insights

Fuel-Cell-Inspired DAC System Captures More CO2 With Less Energy

March 27, 2024 by Shannon Cuthrell

Using 70% less energy, no heat, and no water, a fuel-cell-inspired direct air capture system from RepAir overcomes the common technical challenges in conventional air capture techniques. 

Israeli startup RepAir is developing a carbon removal system to address technical gaps in direct air capture (DAC) technologies. While conventional methods require copious energy to extract carbon dioxide (CO2) from the atmosphere, RepAir’s electrochemical system consumes 70% less energy than competing liquid sorbent DAC techniques. 


RepAir’s DAC field prototype.

RepAir’s DAC field prototype. Image used courtesy of RepAir


RepAir’s DAC system consumes under 600 kWh per ton of CO2 removed, including regeneration. Its carbon footprint is minimal, with less than 50 kg of CO2 emitted for every ton extracted. 

RepAir CEO Amir Shiner, who co-founded the startup in 2020, told EEPower the low energy consumption enables the system to be net-negative, even when connected to the power grid. 

“RepAir's exceptionally low energy requirements are a game-changer, enabling us to rapidly accelerate and even connect to the grid,” Shiner said. “[This] frees us from dependence on the scaling up of renewables, particularly amid uncertainty regarding sufficient renewable energy allocation for applications like DAC.” 


Direct Air Capture Advantages and Limitations

DAC is a relatively nascent field of carbon mitigation, targeting the gigaton levels of CO2 spewed into the atmosphere annually. Researchers estimate last year’s CO2 emissions surpassed 40 billion tons globally, including nearly 37 billion tons from fossil fuels. 

DAC technology borrows the concept of the original DAC application: planting trees. According to the European Environment Agency, one tree can absorb about 22 kg of CO2 annually, releasing oxygen in exchange. This is arguably the cheapest way to perform DAC, but it’s difficult to scale due to land constraints and the long maturation wait time. 

The climate industry is gaining interest in carbon-negative technologies for offsetting emissions with carbon storage and credits. Still, current DAC tech relies on expensive material inputs and fails to address limitations like site flexibility, maintenance requirements, and continuous function. 

Another common critique of DAC technologies is their high energy intensity. The benefits of CO2 removal are null if this energy comes from the power grid, which is fossil fuel-heavy in many countries—including the U.S., where coal and natural gas account for 60% of utility-scale electricity generation. However, some DAC systems are addressing this concern with renewable power sources


Video used courtesy of RepAir


RepAir boasts its DAC system’s only energy requirement is a renewable power source. Since it works at ambient temperatures, no external heating is needed. Shiner noted that while it still uses the grid, its small energy requirements offset the extra footprint. 

“Today we can rely on connecting to the grid due to our very low energy consumption, and despite the additional carbon intensity, deliver net negative removals thanks to our extremely low energy needs,” he said. “This will also allow for faster deployment.”


RepAir’s electrochemical approach compared to conventional DAC methods

RepAir’s electrochemical approach compared to conventional DAC methods. Image used courtesy of RepAir


Shiner added that renewable power supply will ultimately be secured directly from power suppliers (through power purchase agreements) or indirectly from low-carbon hubs or storage operators. The company is currently working with a carbon storage provider. 

It is also negotiating agreements with other underground storage partners in the European Union, Africa, and the U.S., intending to sign agreements later this year. 


How RepAir’s DAC System Works 

RepAir’s DAC system works similarly to a battery or fuel cell, using two electrodes divided by a separator. The dual-cell system doesn’t require water. Instead, it relies on humidity in the air. The process spans four steps. 

  • Step 1. Air is drawn into the cathode, where a current generates hydroxide ions. The CO2 molecules bind to create carbonate and bicarbonate ions. 
  • Step 2. Ions are transported through the membrane into the anode, and the binding process is undone. Hydroxides are consumed, and pure CO2 gas is extracted.


Steps 1 and 2.

Steps 1 and 2. Image used courtesy of RepAir


  • Step 3. The system runs continuously by switching cell polarity and inlet air flow every few hours. 
  • Step 4. Cells can be stacked to maximize CO2 removal capacity. Shiner says the cells are encased in recycled polymer hardware, with 200 to 300 cells in a stack. 


Steps 3 and 4.

Steps 3 and 4. Image used courtesy of RepAir


Unlike competing technologies constructed with rare metals, RepAir uses readily available materials like steel, cement, and plastic. Shiner said these materials have a carbon footprint below 5%. 


Launch of an Outdoor Field Prototype

RepAir took its technology out of the lab last year and demonstrated its technical performance in a rooftop field environment. The company achieved a technology readiness level (TRL) of 6, a significant milestone towards commercial viability and enabling carbon capture below $100 per ton. According to the International Energy Agency, TRL 6 involves testing a full prototype in preparation for deployment. Subsequent stages require real-world demonstrations before commercial operation. 

“The launch of the outdoor field prototype was a major achievement,” Shiner said. “[It] serves as an excellent tool for R&D to continuously assess results and implement necessary changes [to drive] the development of an optimal product.” 


Inside the container of RepAir’s field DAC prototype.

Inside the container of RepAir’s field DAC prototype. Image used courtesy of RepAir 


The company declined to disclose the prototype’s annual removal capacity, but it reports progress as the R&D team monitors its performance and makes adjustments as needed. 

“We are focused on elevating the performance of crucial technological metrics, including enhancing the lifespan of our core technological elements,” Shiner said. “We aim to refine our system design and optimize process control for increased efficiency and scaling up our core technology for commercial scale.” 

RepAir plans to scale up the technology with a commercial demonstration by 2025, targeting 200 to 1,000 tons of CO2 removal annually. It will begin operating a pilot manufacturing line for electrodes later this year. 


Engineers monitored the technical performance of the outdoor demonstrator with this user interface.

Engineers monitored the technical performance of the outdoor demonstrator with this user interface. Image used courtesy of RepAir 


Shiner added, “From there, our scaling strategy is to multiply the capacity of our plant by 10 every two to three years, reaching tens of kilotons per year in 2026, hundreds of kilotons per year in 2028, and the megaton level by 2030.” 


RepAir DAC’s Future Plans

Shiner said RepAir is in discussions with several potential partners and customers. 

The company’s strategic investors include oil and gas giants like Repsol, Shell, and Equinor, which are scaling large projects and have been evaluating RepAir as the leading candidate for their solutions. Shiner said RepAir’s DAC system will not be used in enhanced oil recovery (EOR) processes, unlike other membrane-based technologies configured to use captured CO2 to increase oil extraction from depleted wells. 

RepAir’s primary revenue stream will be sales of CO2 removal credits from offtake agreements. It has already secured credit pre-purchase agreements with payment services firm Stripe and its climate-focused fund, Frontier, which purchased 199 tons in 2022.