@transparent Steady on @transparent !😉

Posted by: @agentgeorge

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Biggest advantage for the planet is sodium is available from sea water, lithium is mined and causes environmental issues

And arguably even more important, sodium will be hopefully processed in more than one country... diluting excessive concentration of power.

Posted by: @agentgeorge

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no one has explained where the extra electricity will be generated from in 2030 when we have 2 million cars, 4 million trucks, hundreds of HS2 power hungry trains and thousands of local busses to charge up

Right now, when the wind blows strongly enough, a lot more could be generated than can be consumed, at least around this part of the world. But good news on that front, with the building of new "energy superhighways" (love these new names for otherwise dull infra projects..)

Posted by: @agentgeorge

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final obstacle is the grid interconnection is not capable of adding the solar farms and wind farms currently built but not cant operate as the wait is 5-10 years for some areas to get hooked up

This "lack of processing capacity" to build new grid connections seems to have been cleared to a large extent... Surely the fossil lobby will still try to appeal the unclogging of the connection queue (with lots of dormant applications by dead companies being removed).

But coming back to topic, it would be great to have a simpler way to mix use of lithium and sodium batteries and allow them to be managed by a single inverter... I assume from a safety perspective it would not be possible (or advisable) to just extend the use of modbus protocol to control operation of a mixed bank of batteries?

Posted by: @transparent

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I too had spotted the Na-ion battery and matching inverters from Eleven in Cambridge.
it's good to see a British company designing something for the obvious gap in the market.

Note that their inverters can only be used with their own Na-ion battery.
It's not a generic approach. They need to be transferring data between their own BMS and the inverter across the CAN-bus to make the system work.

 

Just continuing from a different thread.  

Eleven (that seems to be getting some coverage in the diy solar forum) offers sodium battery based systems with a 10 year warranty and that splits the components (battery and inverter). But also noted that neither is meant to be used except with each other. 

Eleven are proposing a battery pack voltage range much broader but around the lithium voltage (so it must use more than 16 cells). This should remove the potential issue with having to use very thick cables between the inverter and the batteries. 

Also I did not find any proper diagram describing the connections to the sodium batteries (even if it can be worked out from some of the photos in their brochures). 

Victron seems to have been the inverter brand with a more research focused user community (but I do not see the manufacturer getting involved). They have been configuring to use with sodium batteries, starting with 12v, from as early as 2019. The obvious need to use more cells and also thicker cables is always highlighted. Some simple high level cost comparison via this link: https://community.victronenergy.com/t/natrium-sodium-batteries/46888/11  

Posted by: @jamespa

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Apart from relative immaturity and slightly larger per unit power stored, what are the issues which lead you to say this?

The three technical issues I'm considering are:

• BMS suitability, for either ELV or 'high voltage' (above 75v DC)
• inverter functionality
• cable connections for larger batteries

Batpred mentioned Victron as a BMS supplier.
There are actually a number of possible alternative generic BMS units which allow wide-range configuration of settings.
JiKong, JBD and Batrium products would be usable in a notional 22S battery (22 Na-ion cells in series).

However they'd be less capable at two key functions which users of LFP technology tend to look for

• cell balancing current/efficiency
• reporting the SoC (State of Charge)

SoC should be easier to detect with Na-ion technology, but the BMS units were designed with Lithium chemistries in mind.

If you look at the North Sea inverters from Eleven, you'll notice that they can't (yet) offer parallel operation, despite having a pair of RJ45 sockets labelled "Link".

Designing a system which can safely/evenly share the load across 2 or more inverters isn't easy,
and the Chinese manufacturers are at least 5 years ahead of Western manufacturers for load-sharing.

Even they can't yet handle the concept of a failure of one inverter in the set.
It usually requires manual intervention to restart the remaining inverter array.

For the same reason, Eleven currently only offer single-phase inverters.

The sheer bulk of an Na-ion cell is also significant.

We're used to see a typical 4.5kWh or 5kWh battery in a rack-mounted enclosure which can be assembled by a two person team.
That restricts the lifting weight to 25Kg each (H&S rules)

But the 4.5kWh Na battery from Eleven weighs a whopping 54.5Kg.
It's 555mm deep and 150mm high.

For comparison, a 5kWh LFP battery from Pylontech would fit in the same 19"-rack frame, but would be 450mm deep and weigh 40Kg.

Commercial BESS containers seem to be using the same sort of LFP rack-mounted  units as the domestic market.
Switching to Na-cells would necessitate a larger overall container which would be heavier to transport to site.

The odds are still in favour of LFP technology.