Modified Train Cars Use Energy From Braking to Clean Air of CO2, Help Fight Climate Change

Utilising the energy generated when a train brakes, US-based CO2Rail has worked with researchers from The University of Sheffield to develop Direct Air Capture (DAC) equipment that can help tackle climate change and clean the air around a rail car. The device's design would allow it to be installed in special rail cars in currently running trains. It would capture and utilise vast amounts of sustainable energy generated when a train decelerates or when brakes are applied. The energy can be used to separate carbon dioxide (CO2) from the air, which in turn returns clean air into the atmosphere.  

When brakes are engaged in a train, a massive amount of energy is produced. To give an estimate, during every braking manoeuvre, the energy generated is enough to power 20 homes for an entire day. If one could capture the energy produced during every such stopping or deceleration then it would be 105 times more than the energy generated by the Hoover Dam in the US in the same time period.

However, due to lack of any such device that can harness it, the energy is wasted. Now, researchers are gearing up to fill this void and utilise the large amounts of energy produced during the braking process. The DAC technology in the rail cars works by using the large intakes of air that extend up into the slipstream of the moving train. It guides the air into large cylindrical CO2 collection chambers and obviates the need to use fan systems that require large energy and are necessary with stationary DAC operations.

Following this, the air undergoes a chemical process where CO2 is separated from air and the clean air is released out of the back or from under the train. This helps in returning clean air to the atmosphere.

Once enough CO2 is captured, the chamber is closed and carbon dioxide is collected, concentrated, and stored in liquid reservoir. It can later be dumped into CO2 rail tank cars during a crew change or fuelling stop. The harvested CO2 can be utilised in the carbon economy as a value-added feedstock or in geological landfill sites, according to the researchers.

“The technology will harvest meaningful quantities of CO2 at far lower costs and has the potential to reach annual productivity of 0.45 gigatons (Gt) by 2030, 2.9 Gt by 2050, and 7.8 Gt by 2075 with each car having an annual capacity of 3,000 tonnes of CO2 in the near term,” said Peter Styring, Director of the UK Centre for Carbon Dioxide Utilization at the University of Sheffield.  Styring is also the co-author of the research published in Joule.

The team of researchers is also working on a technology that is based on the similar system and helps remove CO2 emissions from diesel-powered locomotives.