Renewables like wind and solar have the potential to replace fossil fuels, drastically cutting down our carbon emissions. This requires deploying energy storage systems on a global scale to balance renewables’ intermittent power generation.
Most of this storage capacity today comes from pumped hydro and different battery technologies, which work great, but they have a problem. We can’t build hydropower projects anywhere we want, and most chemical batteries like lithium-ion, require scarce metals like nickel and cobalt, eventually leading to production bottlenecks and increased costs. But what if those same carbon emissions we’re trying to avoid actually hold the keys to a better way to store energy? I’m Ricky and this is Two Bit da Vinci. Join me as we dive into the CO2 battery.
Around the world, nations are phasing out coal power plants, in favor of solar and wind, to reduce CO2 emissions and because it’s cheaper. But there is a catch, wind, and solar isn’t constant, so you need energy storage as well.
And while carbon dioxide has been vilified for decades, what if it’s actually not the villain in this story, but the hero with properties that make it good for storing energy? Well, well, well. How the turntables (michael scott reference)… Yes a carbon dioxide battery, I’m Ricky and this is Two Bit da Vinci.
Carbon dioxide, or CO2, is frequently considered the main culprit behind global warming despite not being a particularly strong greenhouse gas. Yet we need greenhouse gases in our atmosphere because they help keep the Earth’s surface warmer than the freezing emptiness of the surrounding space.
The problem is the scale at which we’re pumping CO2 into the atmosphere by burning vast amounts of fossil fuels, which is upsetting the delicate balance between too hot and too cold.
This was the main driving force behind the research and development of clean and carbon-free renewable energy sources like wind and solar. However, the fact that these technologies are becoming more cost-effective than fossil fuels is what’s really driving most of the demand.
This is similar to how sleek design, performance, and low costs, and not the fight against climate change, is what makes Tesla’s and other new EVs so desirable.
But, as I mentioned at the start of this video, those technologies have a major hurdle to overcome—intermittency. They’re not always able to produce power when the grid demands it.
The key to overcoming this problem is energy storage. We simply produce all the renewable energy we can whenever we can and store any surplus production for when solar or wind power isn’t enough to meet the demand.
[Ad Break]
It’s thanks to energy storage coupled with renewables that you can enjoy a stable and reliable electricity supply at a lower cost than a traditional fossil-fuel-powered utility grid.
But, many of the current energy storage technologies are either too expensive, require massive amounts of space, or require energy-intensive mining of rare materials like nickel and cobalt which are in limited supply.
So, what we need most right now is a cost-effective, long-lasting energy storage solution we can build easily and quickly anywhere in the world, and that is made out of abundant, cheap, and easy-to-produce materials already in large supply.
Is that really too much to ask for?
Well, according to an Italian startup called Energy Dome, it’s not!
Their solution?
Build the world’s first CO2 battery!
Energy Dome made headlines earlier this year with their breakthrough CO2 Battery. Now, I know what you’re probably thinking:
“If I had a dime for every startup that claimed their breakthrough tech would change the game for this or that, only to watch a YouTube video two years later explaining why it didn’t…”
But Energy Dome is different. In less than three years, the Milan-based startup founded by Claudio Spadacini in 2019 has already built an operating commercial pilot-scale prototype in Sardinia, Italy. Now, it has secured funds to build a full-sized, utility-scale version for the European utility A2A. LINK
That was amazingly fast, and it’s a testament to how effective their technology is.
But how does the CO2 battery work?
In essence, the CO2 battery works very similarly to Liquid Air Energy Storage, only it uses carbon dioxide instead of air.
When charging, the system takes carbon dioxide gas from a huge bladder-like atmospheric gasholder or dome, and uses electricity to compress, condense and store the resulting liquid Carbon Dioxide in steel vessels at ambient temperature and pressures of around 60 to 70 bar [source].
When discharging, the liquid CO2 is evaporated, and the gas powers a turbine generating electricity. The turbine’s exhaust refills the dome with gaseous CO2 at ambient temperature and pressure, returning the battery to its initial state. LINK LINK LINK.
At its core, storing energy is about fighting the natural equilibrium of nature. Push electricity into a chemical battery, and a chemical reaction occurs that builds up chemical potential energy that can be released at a later time.
With air, picture a balloon. As you fill it up the pressure inside the balloon is much higher than in the room, and if you let it go, the balloon will try to reach equilibrium releasing that energy, and go flying across the room.
But, what makes this battery different, and, most importantly, why should you care?
There are several key advantages to the CO2 battery. The first is the working fluid itself, CO2. Contrary to air, carbon dioxide is one of the few gases we can compress into a liquid at ambient temperature. This eliminates the need for cryogenic storage that requires temperatures below –238 °F (–150 °C). LINK
The second advantage is that the system incorporates a Thermal Energy Storage system to capture the heat released when carbon dioxide condenses, and uses that same energy to evaporate the liquid carbon dioxide when the battery is discharging. This makes the battery more efficient than a liquid compressed air battery, which requires external heating to boil the liquified air.
Furthermore, and perhaps most importantly, the basic components of the CO2 battery are steel, carbon dioxide, and water, plus standard off-the-shelf equipment like pumps, compressors and generator turbines.
Since we can find steel, water and CO2 anywhere in the world, and equipment can also be shipped almost anywhere, there’s no place where we couldn’t, in principle, deploy a CO2 battery. Additionally, these resources are in large supply on the Earth’s surface. This means that this technology avoids the supply chain hurdles that Li-ion batteries and other technologies will almost certainly face in the future.
So, now we know HOW the system stores energy. But, HOW MUCH energy can it store and how does it compare to other technologies in terms of performance?
Well, the pilot plant has a capacity of 4MWh and is rated for a power of 2.5MW [source]. This is enough to power close to 4,400 average Italian homes for a little over an hour and a half [source]. Not much, but remember, this is a pilot plant.
Their larger utility-scale facility, which is expected to go online by the end of 2023, is a 200MWh battery that can deliver up to 20MW. That will be enough to power 35,000 average Italian homes for 10 hours straight, or 350,000 homes for about an hour.
The good news is that, if we need more powe or storage, these systems are relatively easy to scale by simply adding more liquid CO2 storage vessels, more generator turbines, and making the dome bigger.
According to Energy Dome, the system can store between 6 and 11 times more energy than any other compressed air storage device currently available, LINK and with a dramatically higher round trip efficiency of between 75 and 80% LINK, dwarfing compressed air’s 45 to 70% efficiency. LINK
These efficiency ratings compare pretty closely to Pumper Hydro storage systems, which can achieve about 80% efficiency. Pumped hydro currently makes up about the same percentage of Italy’s grid as wind, solar, and other renewables combined. LINK
But where the CO2 battery truly shines is in cost.
Since this battery uses no special equipment and no exotic materials like lithium or cobalt, the cost can be brought far below the competition, including Lithium Ion Batteries.
According to Energy Dome CEO, Claudio Spadacini, the Levelized Cost of Storage or LCOS for a full-scale, 25 MW/200 MWh plant will be in the range of $50 to $60 per MWh of stored energy. For comparison, the LCOS of a 4-hour 100 MW/400 MWh Lithium-Ion system is between $131 and $232/MWh, while CAES systems can cost a whopping $300/MWh or more! LINK LINK LINK LINK
Even pumped hydro systems, which can last up to 150 years, have LCOS around $186/ MWh — nearly 4 times the cost of the CO2 battery.
You could think that this doesn’t have anything to do with you, but remember, renewable energy needs energy storage, so the cost of that storage is unavoidably tied to the levelized cost of energy, which ultimately determines how much you end up paying for electricity.
Reducing the cost of storage by a factor of 2 or 3 could have a significant impact, making solar and wind even cheaper than they are now, helping phase out fossil fuels even faster.
But, of course, as everything in engineering, there’s a tradeoff.
Even though the system is about as efficient as pumped hydro, an efficiency of 75 to 80% implies that we lose about 20-25% we use to charge the battery. Compared to lithium Ion batteries, which boast some of the highest RTE ratings at around 90% — that means CO2 batteries waste over twice as much energy as their Lithium-Ion counterparts.
Another important performance metric is energy density, which measures the amount of charge per unit volume. This gives us an idea of how small we can make a battery. According to Energy Dome, liquid carbon dioxide at 70 bar has an energy density of 66.7 Wh/L.
But that’s just for the CO2. The real energy density for the entire sistem is much lower, because we have to factor in the volume of all the necessary hardware, the water tanks, the turbines and, let’s not forget, the huge dome that houses the CO2 gas when the battery is discharged, all of which drops the energy density down even further.
Let’s do a quick calculation. As I said a minute ago, the biggest commisioned storage plant is set to store 200 MW-h and the closed system is said to pack a couple of hundred metric tons of CO2, so let’s assume 200,000 kg. When the battery is discharged, all that CO2 is stored as a gas in the dome at ambient temperature and pressure.
With this information plus CO2’s molecular weight, which is 44, a pressure of 1 atmosphere and a temperature of 298K (which is pretty much standard ambient conditions), we can use the universal gas law to calculate the volume that that CO2 will occupy, and therefore the volume of the dome:
V=nRT/P =(m/MM)RT/P=(200,000,000/44)(0.08206)(298)/1=111,154,000 L
Compared to the dome, the size of the other parts of the system are negligible, so, we’ll use that volume to estimate the energy density of the system:
Energy Density=(200 MWh)/(111,154,000L)=1.8×10^-6MWh/L=1.8Wh/L
=1.8×10^-6MW
This is almost at the high end of pumpued hydro, which is one of the least energy-dense storage systems we know of. But if we compare it to a Li-ion cell, the CO2 battery has a density almost 200 times lower [source], so we won’t se Teslas driving around with a huge dome on the rooftop anytime soon (though that would be real steampunk meets cyberpunk, if you ask me).
Either way, while not an option for mobile applications, Energy Dome’s CO2 battery has other things going for it that make it an ideal candidate for stationary storage where size and weight matter less.
For example, CO2 batteries last at least twice as long Li-ion batteries, (around 30 years) without any degradation or loss in capacity. This is one of the factors that makes the cost to store energy this way so cheap, and it’s why I think we’ll see these massive white pockets of corbon dioxide lining many future solar and wind farms in places where hydro isn’t an option.
It’s no wonder that Energy Dome already struck a deal with Ørsted, the first energy company to transition to renewables from fossil fuels and the world leader in off-shore wind power, to build a series of 20MW/200MW-h storage facilities in some of their wind farms.
Again, remember that this is happening only 3 years after the company’s foundation!
In terms of safety and environmental impacts, there is very little risk of CO2 leaking to the atmosphere, since it’s in a closed system, similar to the freon gas in our car’s AC. But even if it did, the amount wouldn’t be that significant compared to the 6,000 million metric tons of CO2 already in the atmosphere or the amount coming from burning fossil fuels. LINK LINK
While the CO2 battery won’t take carbon dioxide directly from the atmosphere and store it, it will need to be charged at the beginning of its operation.
From an economics point of view, this could create market demand for industrial carbon dioxide, boosting the development and deployment of carbon capture devices like the ones I covered in a previous video (links in the description).
But what I find even more exciting is how simple this technology really is, and with big utilities the likes of Ørsted and A2A jumping onboard the CO2 battery bandwagon, I don’t think it’ll be long before other companies catch on and start developing newer and even better CO2 batteries to compete with Energy Dome?
In my opinion, the fact that this technology actually exists today in the real world and that it’s already set to hit commercial utility scale in only one year’s time, is what makes this the future for stationary energy storage, effectively turning carbon dioxide from foe to friend.
But I want to know what do you think? Is the cost, scalability, and ease of construction of a project like this worth it, even if it isn’t the most efficient technology? Is there something about the CO2 battery that I missed? Sound off in the comments below.
