The current electrical grid is largely fueled by natural gas and coal power plants. If we want our energy grid to be fully reliant on renewable sources, we have to solve the issue of intermittency. This refers to the problem that solar and wind power simply don’t work when the sun isn’t shining or the wind isn’t blowing. The clearest way forward is to use batteries to create a more stable flow of power to the grid. We simply need to charge the batteries when these intermittent power sources are active and discharge them when they are not to keep power flowing to the grid at all times. The fundamental issue is finding a battery that can supply power for long enough to fill the gaps when renewable energy sources are dormant and robust enough to deal with harsh environmental conditions. The battery should also have a low energy loss rate to minimize how much energy we lose in the storage process and a low degradation rate to avoid needing to replace these batteries often. Over the last two decades, there have been several different battery technologies that competed for dominance in this area, but none have been out rightly successful yet. I firmly believe that we are on the cusp of a major breakthrough in this area, and I think the following four battery technologies will form the basis of a game changing grid level battery industry.
Lithium Ion Batteries
Lithium Ion batteries are by far the most well known and commonly used battery on this list. Despite not being a long duration energy storage system, it’s a good place to start because these batteries are already being used in grid level projects around the world. Tesla’s megawall is the industry leader, setting the standard for long duration grid batteries to beat. Here’s a general overview of the battery’s properties to set a baseline of comparison for the rest of the article:
Lithium ion batteries have an energy efficiency of around 70 to 80%. The battery can be cycled 300 to 500 times before breaking down, with a cycle referring to a complete charge and discharge. It degrades at a rate of 0.025%-0.048% per cycle giving a lifetime of two to three years depending on how often the battery is cycled.
The main issues for lithium ion batteries come in their low discharge duration and their inability to withstand harsh conditions. Lithium ion batteries were created by Sony for handheld devices. They needed to be as efficient as possible in typical conditions, charging and discharging quickly. They didn’t need to be able to hold charge for long periods of time or be able to withstand extreme conditions. This tradeoff of efficiency for robustness and duration reveals itself in the battery’s relatively limited max operating conditions – 10 to 55 degrees Celsius. When the battery exceeds its maximum operating temperature, it has a potential to begin venting, which may cause it to combust. There is also the issue of physical degradation, with the form of the battery actually expanding over charge cycles and metallic dendrite microstructures forming on the negative electrode. These conditions make lithium ion batteries practically unusable and even dangerous once they begin to exceed their max operating conditions or reach their lifespan. The battery can also only output power for four hours, which is alright for a laptop or phone, but not for an electrical grid. This limitation requires the grid to cycle the battery more often than expected for the typical use case of a lithium ion battery. With a 300-500 cycle limit, this low duration leads to a relatively short lifespan.
For grid level batteries, this is a huge problem. We need batteries that will withstand environmental conditions, discharge for long periods of time, and not need to be replaced often. If a heat wave causes an entire field of lithium batteries to exceed their maximum temperatures, it could cause a massive chemical fire and potentially blackout the electric grid in the process. We need a better solution. Luckily, there are more robust, longer duration batteries that are being built with grid level energy storage in mind.
Ambri – Liquid Metal Batteries
For over a decade, Daniel Sadoway has been developing a fundamentally new type of battery that is more robust than anything else we’ll see on this list – liquid metal batteries. The battery contains a layer of liquid magnesium above a layer of antimony, separated by molten salt. These liquids stay separate, like oil and vinegar. As the battery discharges, the magnesium forms an alloy with the antimony, releasing two electrons per reaction in the process. When the battery charges, this alloy is separated back into pure magnesium and antimony, recovering their distinct layers. This article is meant to just give a brief overview of each of these batteries, but I’d like to go more in depth into the mechanics of Ambri’s battery in future articles. The beauty of the liquid metal battery is just how much abuse it can withstand while remaining fully operational. The battery can be cycled tens of thousands of times with virtually no degradation between cycles, It has operating conditions above 600 degrees Celsius, and, unlike lithium ion batteries, the consequences of dipping below this standard are negligible. The liquid metal will simply cool down and will need to be heated back up by running current through it before being functional again. The battery heats itself through the energy released in the chemical discharge reaction, maintaining its operational temperature. Thus, this new battery flips the dangerous lithium ion battery heating problem on its head, now facing a much more manageable and safer cooling problem. The battery only has a duration of 5 hours of discharge, but given its incredible ability to cycle without degrading, it can be charged and discharged rapidly without needing to be replaced for decades. Beyond its ability to withstand harsh conditions, liquid metal batteries are also remarkably cheap. Donald Soddway is popularly quoted for remarking that “if you want to make something as cheap as dirt, make it out of dirt.” This was a comment on how magnesium, one of the two metals used in the battery, is a primary component in dirt. This allows these batteries to be about ⅓ to ½ the cost of common lithium batteries, even despite the drastic price drops in lithium batteries over the last twenty years.
The biggest challenge Ambri is facing right now seems to be related to economies of scale. Although Ambri’s batteries are cheaper than most competitors, large batteries are still expensive to produce. Ambri needs sufficient business to be able to create enough batteries to prove their ability to meet expectations on a grid scale. Ambri just received such an opportunity early this year from TerraScale for their new, fully sustainable Energos data center in Reno, Nevada. If this contract goes well, I will not be surprised if Ambri becomes a direct competitor with Tesla’s megapack lithium battery.
Form Energy – Iron Air Batteries
Form’s iron-air battery looks more traditional than the liquid metal battery we saw earlier. It has two major defining features that strictly set it apart though – cost and discharge duration. Form’s battery is able to discharge for a remarkable duration of 100 hours, putting it in a category of its own when it comes to long duration energy storage systems. A battery like this introduces the potential for multi-day energy output from batteries. On top of this, iron air batteries are even cheaper than liquid metal batteries at just $20/kWh. Mark Jacobson at Stanford’s Energy/Environment program stated that such low costs and high durations for a battery would be a “sustainable breakthrough” and could potentially accelerate our adoption to renewable energy. Form is currently in its Series D, having already raised a $76 million Series C round. The verdict is still out on whether Form will be able to deliver a battery that can meet all of the properties it’s stated in a grid scale project, but we’ll get our first look in 2023, when the Minnesota cooperative Great River Energy is set to test the efficacy of Form’s iron air batteries on its systems. I’m extremely excited about what this battery holds for the future of our electric grid. I genuinely feel that it will play a defining role in our adoption of renewable energy over the coming decades given that its significantly cheaper and has a longer duration than any battery we’ve seen so far.
Highview Energy – Liquid Air Batteries
This is the closest long duration battery on this list to being in full grid-scale use. It has been in construction at the Trafford Energy Park since mid-2020 and is set to begin storing energy and powering their grid by 2022. Liquid air batteries function by condensing air, pumping this largely liquid nitrogen into storage tanks, and then bringing it back to its gaseous state at room temperature to spin a generator. Highview Power, the creators of this battery, released an informative animation about their system that I recommend watching at the link below.
The defining property of these liquid air batteries are their high degree of modularity. As the animation shows well, the system is broken up into three parts – an industrial liquifier, high pressure storage tanks, and a generator. This means that if a system needs to store more energy, rather than needing to buy entirely new batteries, a system operator just needs to add more liquid air storage tanks. This allows the system to have impressive duration times between four hours to four weeks depending on the number of storage tanks used. That said, this system is significantly less efficient than the batteries discussed previously, with an energy efficiency of only about 65 to 70%. They are also the same cost as lithium ion batteries at $100/kWh. I believe that liquid air batteries will play a role in the transition to renewable energy on the grid, given that they’re closer than most other long duration energy storage systems to being fully implemented at scale. Eventually, I think they will be phased out by more efficient, cheaper batteries like the liquid metal and iron-air batteries once they prove their reliability at scale.
Overall, the field of long duration batteries is an exciting one, full of rapid innovation and change. Lithium ion batteries are currently the only grid-scale battery to have fully proven their abilities in practice so far. No long duration battery has yet reached this standard. I expect that the field of long duration batteries will explode into a billion dollar industry within the next ten years. The fundamental challenge right now is for technologies like liquid metal and iron air batteries to prove themselves in grid-level projects, verifying that they can out compete lithium ion batteries. Once this occurs, they will likely be quickly and widely adopted. This will finally allow intermittent renewable energy resources to become a promising substitution for coal and natural gas power plants, which currently dominate energy production on electric grids.
Sources:
https://www.osti.gov/servlets/purl/1409737#:~:text=Conversion%20road%2Dtrip%20 efficiency%20is,and%20the%20photovoltaic%2Dbattery%20application
https://www.mpoweruk.com/liquid_batteries.htm
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