Salt Water Batteries and Solar Battery Storage

An Aquion S30 battery stack

(Image courtesy of Aquion Energy)

Salt water batteries? It sounds kind of crazy, doesn't it? But Aquion Energy, a US-based manufacturer, has created a special kind of battery technology that they call 'Aqueous Hybrid Ion (AHI™)'. 

They're inherently safe due to their chemistry, and they boast a 100% depth-of-discharge capability, with a life cycle of around 3,000 cycles.

This isn't as much as lithium-ion batteries can boast – around 5,000-6,000 cycles with an 80% depth-of-discharge – but the technology behind Aquion batteries gives them a number of advantages over their lithium-ion counterparts. 

For one, they're non-flammable and non-explosive, require no maintenance, and are built entirely from non-toxic materials. In fact, they are the only batteries in the world to achieve 'Cradle to Cradle'(tm) certification.

Aquion's S30 batteries are optimized for long-duration daily cycling, which means 4 to 20+ hour charge and discharge cycles, which is ideal for solar. They are abuse tolerant and do not degrade from partial state of charge cycling, which is typical of solar applications.

They can also have individual modules replaced/expanded without any detriment to the rest of the battery setup. It is much harder to scale lithium-ion battery banks compared to the Aquion banks.

The main drawbacks are the slightly lower life cycle compared to lithium-ion and a 5-year warranty (as opposed to Tesla's 10-year warranty for the Powerwall). They also have a low power output per stack – about 0.68kW of steady power – which means that you need to buy at least 5 stacks (0.68kW x 5 = 3.4 kW steady power) to get enough power output to power an average Aussie home.

Aquion batteries are also suitable for both hybrid and off-grid solar setups.

How much will an Aquion battery + solar setup cost?

The Aquion Aspen 48S, a 2.5 kWh battery stack, costs roughly $2,200. A 5kW solar system (the minimum size we recommend for a battery + solar setup) costs about $9,000.

So, 10kWh of Aquion storage (a good amount for the average Aussie home) with a 5kW solar system will set you back roughly $17,000. Note that you would probably want to add at least 15kWh worth of storage to be able to get enough power out of the system for your home (as mentioned above).

Combining that price with its modular scaleability, the Aquion battery represents a cost-competitive battery storage option compared to lithium-ion. Although it is a new technology with the risks that entails.

Speaking of risks, As of March 8, 2017, Aquion has filed a voluntary petition under Chapter 11 of the United States Bankruptcy Code

UPDATE JULY 2017 : Aquion Energy is resuming operations.

As for availability, Aquion has established dealers and distributors in the Australian market.

(I'll be the first to admit that $15,000+ is a lot of money for the average Australian to find, even if they're extremely keen on adding battery storage to their solar PV system. My recommendation is for people to wait a year or two for battery prices to drop further before they consider adding them to their homes.)

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