The ‘Battery’ That Absorbs CO₂ As It Charges
Source: Medium, Will Lockett
Photo: danilo.alvesd on Unsplash
Carbon dioxide absorbing supercapacitors could be the future of carbon capture
In 2021, the IPCC (The Intergovernmental Panel on Climate Change) released its sixth report with a damning indictment. If we want to avoid a climate catastrophe, we need to do far more than just reduce our emissions. We need to actively remove carbon from the atmosphere and work to undo decades of environmental damage. However, the panel also highlighted that our current carbon capture technology is lagging far behind where it needs to be. With any luck, a team from Cambridge University may be able to solve this problem, using their incredible carbon-absorbing supercapacitor. So how does it work? And can it save the planet?
First of all, we need to understand what supercapacitors are. Functionally, they are very similar to batteries, in that they store electrical energy. But unlike batteries, which store their energy in chemical form, supercapacitors store their energy in electrical potential form. They do this by using two metal plates (electrodes) separated by a thin electrical insulator (separator). When voltage is applied between the two plates, a positive charge will build in one and a negative in the other. Once this voltage is removed, these charges will take a long time to dissipate. So if you then connect a circuit to the two plates, the charge difference will begin pushing the electrons around, just like a battery.
Supercapacitors tend to be smaller and less energy-dense than batteries, and they can’t hold a charge for anywhere near as long as a battery. So they tend not to be used as the sole method of powering devices. But they are capable of charging and discharging far more quickly than any battery, making them perfect for applications that need to charge incredibly fast or dump a tonne of power.
So, how can a supercapacitor absorb carbon dioxide if it is just two metal plates and an insulator?
Well, it’s all very complex chemistry, which I’m not going to pretend to understand. What I can tell you is that this carbon absorbing device is an electrolytic supercapacitor. This design of supercapacitor swaps out one of the electrodes for an electrolytic liquid and, rather than using a separator, utilises the oxidation of the solid electrode. This allows for a greater surface area between the cathode and anode, which increases the supercapacitor’s energy capacity. But, when the Cambridge team’s supercapacitor charges, bicarbonate leaches out of the solid electrode and into the electrolyte. Carbon dioxide in the surrounding air is then absorbed into the electrode to “take the bicarbonate‘s place.” Then when the supercapacitor discharges, the reverse happens, and the carbon dioxide is released.
So, basically, it’s chemistry wizardry. Going forward, we only need to know that this supercapacitor absorbs carbon dioxide when charging and releases it when discharging.
The Cambridge team also studied how to make this process more efficient and how to make these incredible devices from more sustainable materials. They found that repeated short-burst charging, followed by a period of discharging, increased the machine’s efficiency at absorbing carbon dioxide. They also found that the supercapacitors could be constructed using sustainable materials, such as coconut husks. This means that their amazing supercapacitor is both affordable, remarkably eco-friendly (especially when compared to batteries), and can be used as an effective way to store carbon.
This is all very well and good, but can this technology save the world?
Well, this device is far cheaper than most carbon capture technologies while potentially being just as efficient, so it could help us scale up carbon capture to planet-saving levels without costing enough to bankrupt a large country. What’s more, its eco-friendly construction will mean that the environmental impact of this expansion will be minimised too, preventing further environmental harm, as is a common problem in most current carbon capture technologies.
So we could just use these supercapacitors as straight-up carbon capture devices by hooking them up to a power source and a carbon storage system. But we could be far more ingenious with this technology. For example, we could integrate it into our current solar tech by using it to build hybrid solar batteries. Let me explain.
Solar power isn’t consistent. Thanks to our ever-changing weather, solar farms can churn out gigawatts of power one minute and barely any the next. This is why we use giant batteries to store energy during plentiful periods, in hopes of sustaining solar energy during times where the sun is unusable. But there is a problem. In order to capture enough power during peak times and meet load demands, we need batteries that can charge up quickly and discharge quickly. These types of batteries don’t last long and will need to be replaced in about a decade. What’s more, these batteries tend to be more environmentally damaging to produce than slower-charging longlife batteries. This makes solar power less eco-friendly than it could be.
But by combining supercapacitors with longlife eco-friendly batteries (such as sodium batteries), we can solve this problem. The supercapacitors can charge up quickly and then slowly charge up the battery. This setup is known as a hybrid battery, and it allows us to get the best of both worlds: the fast charging of supercapacitors, and the high capacity long-term storage of batteries. This also enables us to use longer-lasting, slower-charging, and more environmentally friendly batteries without jeopardising solar storage. This, in turn, can reduce solar’s already low carbon footprint quite dramatically.
But, what if we used this carbon-absorbing supercapacitor in a hybrid battery system for a solar farm? To complete the package, we would also need to include a way of storing the captured carbon dioxide long-term. But more on that later.
This setup would allow our already existing renewable energy infrastructure to power carbon capture without drastically reducing its output. This would be a game-changer, making carbon capture far cheaper, less energy-intensive, and way more scalable, which is precisely what is required to meet the IPCC’s carbon capture demands.
Let’s quickly recap: this device is cheap, built from sustainable materials, captures carbon efficiently, can be integrated into our already existing renewable infrastructure, and can make solar energy more eco-friendly. So what‘s the catch?
Well, it has only just been developed. So more tests need to be done before it can be rolled out for widespread use. There could be reliability issues, required improvements in efficiency, or even unseen drawbacks. Moreover, carbon storage technology needs to be adapted to work productively with this supercapacitor if it is going to be of any use. This is actually a significant engineering challenge because we can’t just store carbon dioxide as a gas. We need to expend more energy and turn it into solid form. But overall, we have a variety of solutions that could work here. It just needs time, money, and development to figure it out.
So can this supercapacitor save the world by advancing carbon capture technology enough to meet the IPCC’s predictions? Not in its current state. But this is the start of a promising technology that could enable us to scale up carbon capture quickly, cheaply, and without further damage to the environment. Only time will tell if this technology can be developed and used quickly enough to stop our self-made apocalypse. Here’s hoping those brilliant minds at Cambridge can figure it out.