RFX 4.55% 10.5¢ redflow limited

"For most domestic locations in Australia we expect that no...

  1. 335 Posts.
    "For most domestic locations in Australia we expect that no special actions will need to be taken with our battery in this regard. However some very cold areas, it might be necessary to place the battery indoors or in an otherwise warmer-than-ambient environment to avoid reaching the minimum operating temperature of the electrolyte."

    there will be extreme areas (such as the snowy mountains?) where the outside temperature is likely too low. The key point is though that it is suitable for 'most domestic locations in Australia'.

    The reason Redflow can't provide an exact temperature limit is because it will depend in large part on the use of the battery. If you cycle the battery fully every day, it will warm itself easily through very cold conditions. If there are days it is used significantly less, it will cool down.

    Some math:
    Cycling ZCell once a day generates about 7.2 MJ of heat, which heats both the electrolyte fluid and the cell stack.
    Let's find out how many degrees this heats the battery.
    For simplicity, lets assume the electrolyte fluid has the same thermal density as water (I don't know the thermal density).
    We start with 7.2 MJ of energy, divided by 100 kg (of water), giving us 72 J of heating per gram.
    We divide that by the conversion constant 4.2 to arrive at 17, which is the temperature increase in celsius.

    So there is a significant amount of internal heat that can be generated by the battery daily as part of its normal operation, up to 17 degrees Celsius if cycled once fully.

    It is my understanding that the enclosure was designed to satisfy the insulation needs of most of Australia and the internal heat generated by the battery would have been taken in to account.

    "you will need to build a specially built insulated and ventilated enclosure with a heater to ensure that the electrolyte stays at its optimum temperature"

    The coldest locations in Australia are mostly rural. There will typically be a shed or other enclosed area close to the residence that would not require you to build a specially insulated enclosure.

    "All this toxic gas stuff kind of detracts from the 'green' credentials of the Zcell"

    Let's look at the operational manual for the battery:
    "Gas Emissions
    No measurable gas is emitted during normal operation of (my emphasis)
    the ZBM2. However, there may be small amounts of potentially
    hazardous hydrogen and/or bromine gases emitted via the
    ZBM2’s pressure relief valve, as a result of an operational issue.
    This gas is automatically diverted to the ZBM2’s Catch Can,
    which traps gases before they reach areas external to the ZBM2,
    reducing the concentration of any emissions. "


    The point here is that I would rather have a battery that emits small amounts of gas in the event of an operational issue rather than having a lithium battery catch fire due to an issue.

    Redflow actually has a patent that allows the battery to operate without releasing gas:
    http://www.freepatentsonline.com/9099722.html
    Its a recombinator that catches released hydrogen and reinserts it into the electrolyte fluid, somehow.

    "How many environmentally conscious early adoptors are going to pay $19,500 for a product that is (1) more expensive than the competition by every measure, (2), probably wont work (or only work intermittently) during the Southern Australian winter, and (3) will occasionally release small quanties of toxic gas??"

    responding to your closing points above one by one:
    1) how is Redflow more expensive? I note you didn't reply to my question of where in the Powerwall warranty it states that 16025 kwh is warranted. The main lithium battery that can contend with Redflow on price is the LG Chem, which is a cent or so more expensive per warranted kWh over the life time of the battery.
    2) depends on use and insulating properties of the enclosure. your view that it 'probably' won't work is speculation and ignores Redflow's natural incentive to build an enclosure suitable for most of Australia.
    3) no gas should be released during normal operation.

    Of the two companies, it is Tesla that is vague, having recently stripped its warranty of guaranteed capacity levels over time. If you want a battery and work it hard without losing capacity over time, don't get a Powerwall (or any lithium battery).
    Last edited by NewEconomy: 04/08/16
 
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