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How will the super-duper Tesla battery work? And more on the price of electricity

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Image: Thermo Fisher Scientific Inc.

I received an email the other day from the Australia Insitute. I don’t know how that happened, I’ve never heard of the organisation. Apparently it’s Australia’s most influential progressive think-tank (self-described) and apparently I subscribed to it recently while in a barely conscious state. All good.

Anyway the topic was timely: ‘Rising Energy Bills: Blame Gas’.

In a very recent post I quoted from a few apparently reliable sources on the reason for South Australia’s very high electricity prices. Unfortunately there wasn’t too much agreement among them, though at least none of them blamed renewable energy. But neither did any of them blame gas, though one did point a finger at wholesale pricing. The Australia Institute’s email put it thus:

Yesterday, we released the latest Electricity Update of the National Energy Emissions Audit for July 2017. The report revealed a stunning correlation between domestic electricity prices and gas prices — particularly in South Australia — despite gas making up only 10 percent of electricity generation.

So this is a subject I need to return to – in my next post. This post will focus on batteries and storage.

Neoen, a French renewable energy company, is building a 315MW, 99 turbine wind farm near Jamestown in South Australia. Connected to this project will be an array of Tesla’s lithium ion Powerpack batteries. According to this ABC News article:

The array will be capable of an output of 100 megawatts (MW) of power at a time and the huge battery will be able to store 129 megawatt hours (MWh) of energy so, if used at full capacity, it would be able to provide its maximum output for more than an hour.

It will be a modular network, with each Powerpack about the size of a large fridge at 2.1 metres tall, 1.3m long and 0.8m wide. They weigh in at 1,200 kilograms each.

It will have just slightly more storage than the next biggest lithium battery, built by AES this year in southern California.

But Tesla’s 100 MW output would be more than three times larger than the AES battery and five times larger than anything Tesla has built previously.

I’m no electrochemist, but a nice scrutiny of these sentences identifies a clear distinction between output and storage. And the output of this planned battery is the pioneering aspect.

So here’s a very basic summary of how a rechargeable lithium ion battery works. Each battery (and they vary hugely in size) is made up of a number of cells, each a battery in itself. On opposite sides of the cell are conductive surfaces, aka current collectors, one of aluminium and the other of copper. Inside and joined to these surfaces are electrodes, the positive cathode and the negative anode. The cathode is made from a lithium metal oxide such as lithium cobalt oxide or lithium iron phosphate, which needs to have the purest, most uniform composition for maximum performance and longevity. The negative anode is made from graphite, a layered form of carbon. The layered structure allows the lithium ions (Li+) created by the current to be easily stored at and removed from the carbon surface. Between these electrodes, filling the cell, is an electrolyte fluid through which lithium ions flow from one electrode to the other, which charges and discharges the cell. Again the purity of this fluid is a vital factor (research is being done to come up with a form of solid electrolyte). Between the two electrodes is an insulating plastic separator, essential to keep the electrodes separate and prevent short-circuiting. This plastic membrane allows the lithium ions to pass through it. The battery is charged when the lithium ions have passed through the separator and become attached to and stored in the layered graphite of the anode. The battery is discharged by reversing the flow.

Lithium ion batteries are found not only in Tesla Powerpacks but generally in electric car batteries and many other devices such as my own iPhone and iPad. They’re lighter and have much less energy density than lead-acid batteries. The technology of lithium ion batteries is described in a number of useful online videos, of which the most comprehensive, I think, is a webinar from the American Chemistry Society (ACS), essentially an interview with Dee Strand, a lithium ion battery specialist and expert. Her talk also provides interesting ideas on how these types of batteries can be improved.

So a fully-charged cell has stored energy, and a discharging cell is producing output. There are variations in lithium ion battery technology, for example variations in the electrode materials, the electrolyte composition and the like, so we don’t know precisely what Tesla will be using for the South Australian battery system, but we have a fair idea.

In any case, there seems no obvious reason why this proven technology can’t be scaled up to meet the sort of need that was identified after last September’s state blackout. Now we just have to wait and see whether Musk will lose his bet regarding completion time come December.

Refs and info

http://www.tai.org.au/

http://www.abc.net.au/news/2017-07-07/what-is-tesla-big-sa-battery-and-how-will-it-work/8688992

https://www.thermofisher.com/content/dam/tfs/ATG/CMD/cmd-documents/sci-res/pub/comm/env/AR-Lithium-Ion-Battery-Degradation-RandD-Mag-042214.pdf

http://www.abc.net.au/news/2017-07-07/sa-to-get-worlds-biggest-lithium-ion-battery/8687268

Just type in ‘lithium ion battery’ in youtube

 

 

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Written by stewart henderson

July 19, 2017 at 1:00 pm

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