FAQs

Are “electrical storage in a liquid” and “flow batteries” referring to the same thing?

Yes we are referring to the same thing in our use of the term. The technical term “flow battery” denotes a battery with liquid flowing through it’s energy converter during the charging and discharging of the battery. But fundamentally, we are simply storing electrical energy in a liquid so we can use it later, on demand.

Why is a flow battery fundamentally better than lithium ion for stationary storage applications?

Lithium ion batteries were originally developed for portable power applications in laptop computers and smartphones. They were chosen for their ability to store lots of energy in a small, lightweight package. Recently, they have been adopted for use in transportation applications also because of their lightweight benefit. However, as we have all experienced, these batteries gradually lose their capacity over time as you charge and discharge them over many deep cycles. Stationary applications do not value lithium ion’s lightweight benefit; rather these applications require high durability, over 10,000 deep cycle lifetimes to be economically viable. Flow batteries have extreme durability, whereas lithium ion batteries can only last up to 2,000 full cycles at most and then need to be replaced.

How is liquid storage more durable than lithium ion?

The key to battery durability is based on the physical principles involved in storing the electrical energy. For lithium ion, use of the battery stresses the solid storage material in such a way that the material is microscopically damaged and therefore degrades every cycle. The process is cumulative until the battery reaches a point where it no longer has adequate storage capacity and needs to be replaced. We have all experienced this with our smartphone and laptop batteries. For flow batteries, the storage process happens in a liquid, and there is no physical damage or degradation of the storage medium, even under deep cycling conditions. We say in effect that the storage liquid is “immortal” and will continually charge and discharge with no degradation over the long term.

Why hasn’t liquid storage of electricity been commercialized earlier?

The basic principles of liquid storage have been known since the 1970s via work at NASA and even in some earlier scientific papers. Some of the first liquid storage systems built to attempt commercialization were in the 1990s. All of these early systems had multiple technical challenges that made the overall system not commercially viable. It turned out that much more learning and R&D were required to get the technology to the current state. The bulk of this continued effort has been funded by government and private entities over the last 30 year period. WattJoule now has exclusive access to some of the latest key developments and intellectual property for flow batteries, in addition to developing its own intellectual property.

What is the WattJoule “special sauce” that makes your offering highly competitive and economically viable?

Our “special sauce” has 4 key ingredients:

  1. Liquid electrolyte
  2. Energy conversion stack
  3. Core material set
  4. System software.

These core components are based on a unique WattJoule intellectual property portfolio consisting of patents issued, patents pending, exclusive licenses and trade secrets. And of course, no special sauce would be special without the chefs behind it!

How do you know your life cycle costs are better than lithium ion?

Life cycle cost is based on installed cost, battery lifetime and operating costs. It turns out that even though we have advantages in all three attributes, it is our superior durability that gives us the lowest life cycle cost. Keep in mind that you cannot refurbish a solid lithium ion battery — you must replace it. Our ElectriStor™ system can be completely refurbished for extended life operation. For example, you can easily replace pumps every 5 years as they wear out, and for a small fraction of the system cost.

Why is it that the longer the ElectriStor™ storage rating in hours, the lower the cost per unit of energy stored vs. lithium ion?

This is an advantage of ElectriStor™ liquid based batteries and flow batteries in general. For lithium ion you need to add more batteries if you want to store more energy. Since lithium ion batteries contain both the energy conversion and energy storage functions in the same package, you are paying for both functions. In contrast, our platform consists of two parts, the energy conversion hardware and the energy storage liquid. If you want to store more energy you simply increase the size of the tanks and add more liquid, BUT the energy conversion hardware stays the same. This means that as you build systems for longer duration and more hours of storage, WattJoule costs drop relative to lithium-ion and approach the cost of just our liquid electrolyte.

Does ElectriStor™ require industrial grade air conditioning equipment for cooling like large lithium ion for stationary applications?

No, WattJoule does not require this extra equipment. This lowers both our capital and operating expense, and it boosts our overall round-trip energy efficiency. Lithium ion batteries used for stationary applications, under continuous deep cycling, generate heat and this heat must be dissipated to prevent the batteries from getting too hot. Heat accelerates the degradation of these batteries over time so it must be reliably controlled or pre-mature failure will occur. ElectriStor™ also generates heat during its operation but it has a much larger temperature operating window, so we only require simple fan cooling. In fact, we have engineered our system so that heat makes the entire system run more efficiently. We love the heat!