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Wednesday, October 2, 2019

A new Battery technology

What would you say to a battery for static use that could be completely charged and discharged with no degradation of it's capacity over time.  A battery that today will hold ten kWh and in one year it will still have the same capacity. A battery that has no self discharge and so if you charge it up and come back in a year it will still have the same charge. Better still, a battery that uses very common cheap materials in it's chemistry so should be pretty cost-effective as production increases. And none of it's materials (like Cobalt) are produced in countries that use child labor.

This is the hype around a new battery chemistry and they are already in production.

Now just a disclaimer here.  I am basing this article on the literature around this battery and have no experience myself in owning such a battery.  In fact, they are in the stage of ramping up production and I haven't been able to find what they cost at present or what they project the price will be in the future.

This is a flow battery meaning that a fluid is pumped through the battery that does 'the  necessary'.  It is a plating battery that plates Zinc onto 'shelves' of plastic (dosed with carbon, I believe, for conductivity) during the charging phase.  The Zinc is stripped from the plates back into solution during discharge.  The other ion is Bromine so this is a Zinc bromide battery.

It has been developed in Australia and production at present is quite small, measured in hundreds per week  but, clearly, if it's promise is fulfilled, production is bound to climb as revenue flows in from initial sales.

The cycle efficiency of this battery is said to be 75-80%.  If you put in a kWh you will get an effective 0.75kWh back out.  

A disadvantage (minor) is that the plates must be stripped every three days to stop the build up of spicules of Zinc that would damage adjacent plates. In other words it must be totally discharged.  Apparently this is automated so it happens without your intervention.  I'm not sure what happens to the electricity which will be produced during a full discharge cycle but I can imagine it will be fed into the grid with the amount you earn from this being determined by the policy of your power company.

If you have more than one of these 10kWh batteries, power resulting from the stripping cycle could be fed into the other half of your batteries.  While operating,,,, one battery (or bunch of batteries) would be in use (discharging) while the other half would be charging.

Incidentally, some recent information on the mega Lithium ion battery provided to Australia by Tesla has shown some interesting results.  This battery holds 100mWh of power and cost $66m.  It's first anniversary will be in November and based on the present rate of return, it will have returned $20m by that time.  A 30% pa rate of return.  Wow!!!  It is installed in a large wind farm so presumably the earnings are due to not having to waste wind-generated power when the grid is producing all it needs.  The power is then sent to the grid when the demand and hence the price is high.

They could also be earning by buying power to charge the battery when power from the grid is in excess and hence cheap, and selling it back when there is a demand.

Another interesting wrinkle is that the response time of the battery is so fast, unlike other sources of electricity, that the quality of the power is increased.  In other words the voltage and frequency are stabilized, unlike when other generation sources  with slower response times are cut in and out of the grid.

Presumable this quality improvement would be the same with any battery system including the ZnBr battery.

Of course, Li ion batteries degrade over time and this is partially compensated for by battery management systems that don't ever charge up the battery to it's full capacity or discharge it to zero.  This slows but does not stop the decrease in it's capacity over time.

This points up the great advantage of the ZnBr technology over the Li technology.  The cost over time is bound to be less, and even more so when the price of the Zn battery per kWh becomes less than the cost of the Li battery as it is bound to do because of it's less expensive materials.  Note that this technology is only for static applications.  The Li ion battery is still king for mobile applications.

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