by Eric Hill
Are you confused by the never-ending technology changes happening in energy storage for stationary reserve power applications? Well, you’re not alone. A lot has been happening over the last 20 years in this industry and it can be frankly overwhelming to keep up with all the modifications. From the enhancements in lead-acid to the advent of lithium-ion and other exotic storage technologies, one can find themselves just downright confused on which storage option makes sense for their application. Manufacturers are racing to release the next best thing to improve overall energy capacity, efficiency, power delivery, and improved sustainability. Below we will answer two key questions: “What’s out there today?” and “What’s coming tomorrow?”
What’s Out There Today?
- Lead Acid – Around for over 150 years, the lead-acid chemistry is the proven workhorse of reserve stationary power. Flooded Lead Acid (FLA) and Valve Regulated Lead Acid (VRLA) provide good energy density, temperature tolerance, great float service life for emergency backup, and has a well-established recycling process to provide closed-loop recovery of raw materials. New enhancements like high-temperature tolerance, carbon additives to negative active material, and pure-lead plates are prolonging service life in the most extreme conditions. Lead-acid also remains the most cost-competitive in terms of upfront asset cost.
- Lithium-Ion – With the increasing need for renewable energy and achieving better battery service life in cycling applications such as utility demand response, lithium-ion has become the next revolution for energy storage. Lighter weight, longer cycle life, and improved communications over older chemistries like lead-acid make lithium-ion a very attractive option. There are a few main chemistry options for lithium-ion batteries: Lithium cobalt oxide, lithium iron phosphate, lithium nickel manganese cobalt, lithium nickel cobalt aluminum, and lithium titanate. Improvements in upfront asset cost, battery management systems (BMS), cell construction, and safety standards are driving the lithium-ion technology further into adoption.
- Nickel – Around almost as long as lead-acid, nickel batteries are a great option for extreme environments where energy storage is a must for stationary electrification. They remain one of the most rugged and tolerant battery chemistries but require great maintenance to keep long life. Nickel batteries today do have the lowest cost per cycle compared to lithium-ion or lead-acid. Nickel batteries can be divided into 2 main technologies in stationary applications: Nickel Cadmium and Nickel Metal Hydride.
- Others – Alternatives to the main three mentioned above are also gaining traction like sodium sulfur, vanadium flow, hydrogen fuel cells, and aqueous hybrid ion, all have unique benefits in their respective chemistries for stationary power applications. Depending on the specifics, these chemistries can potentially show even longer service life and further advance energy storage use.
What’s Coming Tomorrow?
A lot actually, and frankly too much to mention here, but here are just a few of the chemistries at the top of the list.
- Bipolar Lead Acid – this is a revolutionary breakthrough for lead-acid chemistry not seen since the invention of the VRLA variation. Bipolar plates are stacked in a different configuration from traditional lead-acid, which eliminates the need for more plates and top-lead cell welding. This means higher cycle life and lighter weight. The chemistry is still mostly in trial phases, but most lead-acid manufacturers are working on a version of bipolar which could prove very promising to continue the product life cycle of lead-acid.
- Solid-State Li-Ion – turning liquid electrolyte, found today in most lithium-based batteries, into a solid electrolyte is being actively developed in lithium-ion laboratories. Solid state is being primarily developed for the electric vehicle market (EV) due to its increase safety and energy density. This promising advancement can also lead to more efficient, more energy-dense batteries for stationary reserve power.
- Lithium-Sulfur – using more abundant materials combined with the ability to provide even higher energy density makes lithium sulfur an interesting option to consider. Having very limited cycle life and lower than expected energy throughput efficiency makes this still a laboratory experiment for the most part.
- Lithium-Air – combining the concepts behind zinc-air and fuel cells, the lithium-air chemistry uses a catalyst for oxygen reduction and evolution combined with an electrolyte and lithium. The driver behind this chemistry is the potential of greater energy density but much lower cycle life. The chemistry is still under development in research laboratories.
- Sodium-Ion – taking a similar approach with lithium-sulfur by using abundant raw materials like sodium but also being able to discharge fully and potentially ship without hazardous restrictions makes this chemistry very appealing. This chemistry could prove to be a direct alternative to existing lithium-ion as we know it today. There are a few companies today working on cell development to improve cycle life.
Prepared for Today & Tomorrow
As you can see, there are many options available today and much more being developed for the future. Stationary energy storage across the board is mandatory to achieve our zero-carbon goals by modernization of the utility grid and develop a sustainable future for generations to come.