Tesla PowerWall

2

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  • westbranchwestbranch Solar Expert Posts: 4,827 ✭✭✭✭
    thanks for sharing your thoughts.8) Thst makes a lot of sense, now if it can just be clarified /verified by tesla....
     
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  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    The tesla batteries will require proprietary tesla mppt controllers, and possibly an inverter/ voltage down convert controller for higher voltage. More than likely you would get the Tesla inverter that comes onboard the tesla model cars,w hich would require anti islanding feature, which the TESLA car does not have at the moment, for the tesla AC brushless motor.

    Its just reselling the same badged equipment for home use, which requires additional UL/ETL listings.

    Do you all believe Tesla would allow the end user to just get away purchasing their batteries??? A 10kWh battery with inverter, and their proprietary mppt copntroller will probably end up costing some where near $1.80 to $2.00 a watt (that's roughly $18,000 to $20,000 for 10kWh, 5 hour total run time?), no thank you. Lead acid batteries and chinese mppt's with 48V set ups are still less expensive.

    Elon Musk is trying to sell these units small as if on grid users need this. They are actually working in conjunction with solar city to sell less PV array and more batteries, quite honestly, its going to be a huge expensive failure unless the batteries come with on board mppt that works with the lithium BMS, and the voltage is reduced to 48V.

    True ROI is building agrid tied solar PV system for on grid use to 110%. Its an accelerated ROI, does not require a battery system that through out the entire life span of the solar system will be used less than 2% of the entire life of the grid tied solar system.

    Even for off grid do the math, its ridiculously expensive, just like a Tesla.

    Worthless investment, worthless pitch by Elon Musk.
  • Sun-Wind-KeeperSun-Wind-Keeper Registered Users Posts: 11
    I wonder if the rating is at the 6 hr./rate or 20 hr./rate? If it's 6 hr. I'm not so interested.

    Also, hanging on the side of a brick building in the summer is sure to add loads of heat to the cells...and the mysterious liquid cooling system
    I saw the YouTube....Musk said it even comes with a DC to DC converter?...I wonder if that was a mistake?
    Caveat Emptor!
  • BB.BB. Super Moderators Posts: 26,768 admin
    If they have their own solar charge controller--It is most likely a MPPT (maximum power point tracking) type of charge controller--Which is (usually) a DC to DC converter based device.

    For Lithium (and NiMHD) type chemistries--They have much lower internal resistance and higher surge current capabilities than Flooded Cell lead acid batteries (Peukert factor) Their C20 and C6 ratings are probably very similar (very small difference between the two Amp*Hour ratings).

    https://en.wikipedia.org/wiki/Peukert%27s_law

    From NAWS' Battery FAQ:

    http://www.solar-electric.com/deep-cycle-battery-faq.html
    Some Peukert Exponent values (not complete, just for info). We don't have a lot of data. Trojan T-105 = 1.25; Optima 750S = 1.109; US Battery 2200 = 1.20.

    For LiFePO4 batteries, the Peukert factors seems to be in the 1.05 range (1.00 is a "perfect" battery--No internal resistance or changes in capacity for different discharge rates).

    But remember, still need to store kWatt*Hours in the battery bank. And a bank large enough to store 2+ days of energy, usually has more than enough surge capacity for starting a Well Pump and such.

    For Lead Acid batteries, we typically use a ~90% to 50% state of charge range (~40-50% of capacity for daily cycling). For LiFePO4, it seems that you can use 80% to 20% state of charge for cycling capacity (60% of battery capacity for long life). The one caveat being that with Lead Acid, you still have 50% to 20% or another 30% points of discharge range for emergency/extraordinary situations... For LiFePO4 batteries, going below 20% SOC is not recommended.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Sun-Wind-KeeperSun-Wind-Keeper Registered Users Posts: 11
    Converters on the input and output would be pretty cool...on the output 24-48 VDC would allow most common inverters to stay on the wall.
    Let the high 380 VDC voltage inverters be an option too, and the world will be a better place!
  • DarrylDarryl Registered Users Posts: 9
    I understand Pika energy of Maine is making an inverter charger, 7.5 kW that will work with the Tesla powerwall
  • Sun-Wind-KeeperSun-Wind-Keeper Registered Users Posts: 11
    Yes with "islanding" capabilities. Good move for PIKA! Possibly a new thread on 380 VDC inverters is next?
  • jaggedbenjaggedben Solar Expert Posts: 228 ✭✭
    It's interesting that they announced that Solaredge is a partner, and also that Musk mentioned in his presentation that that the pack has a DC-to-DC converter. It's also interesting that the lower end of the voltage range coincides with Solaredge nominal voltage for 204V systems (though a bit odd that it doesn't go low enough for 3-phase).

    What I'm getting at is that if the battery is hooked up in parallel to the solar panels and inverter, and if all three components communicate on the DC line (as Solaredge already does), then the electrical hook-up is a piece of cake and the rest is just software.
    This would not provide any off-grid backup capabilities though. Of course that's an expensive proposition in most grid-powered homes purely because of the electrical work involved.
  • DanKegelDanKegel Registered Users Posts: 15 ✭✭
    Interesting tidbit:

    http://ecomento.com/2015/05/14/elon-musk-stop-pitching-battery-ideas/ mentions
    "While Tesla cars use a chemistry called nickel-cobalt aluminum (NCA), Musk said its Powerwall home batteries will use nickel-manganese cobalt (NMC) – a chemistry he’s reportedly derided in the past.
    Tesla even hired Jeff Dahn, a leading battery researcher at Dalhousie University and one of the two main inventors of NMC. Dan’s previous patents are owned by 3M, but he’ll presumably start producing new material for Tesla when his deal with the company takes effect next year."
  • JoshKJoshK Solar Expert Posts: 232 ✭✭
    From wikipedia:

    The PowerWall has two different models using 2 different generic cell chemistries.[2] Tesla uses proprietary technology for packaging and cooling the cells in packs with liquid coolant.[2] Although Musk has given away the patents for Powerwalls like he did with Tesla cars.[3]

    The daily cycle 7 kWh battery uses nickel-manganese-cobalt chemistry[4] and can be cycled 5000 times.[4][5] The other is a 10 kWh battery, using a nickel-cobalt-aluminum cathode[4] like the Tesla Model S,[5] and is for weekly or emergency use and has higher energy density but a lesser cycle life of 1000-1500 cycles.[6][7][8][9]
  • DanKegelDanKegel Registered Users Posts: 15 ✭✭
    Thanks for posting that!
  • MarkCMarkC Solar Expert Posts: 150 ✭✭✭

    An interesting article in Lithium based batteries:
    http://batteryuniversity.com/learn/article/types_of_lithium_ion

    Learn new stuff every day
    3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    So I am trying to understand the math here from a cost of power per kWh perspective.

    To me it seems mentioning the battery in kWh, makes it more deceptive as a marketing scheme than calling out in kVa, Ah, or discharge rate. The marketing behind the TESLA battery is deceptive when you compare to the rate of discharge in (1) hour elapsed time frame for true kWh. A true cost of power measured in kWh is how much discharge can the battery deliver in 1 hour of true time, not always what it can store. So TESLA takes a dangerous battery and limits its discharge rate so it doesn't achieve thermal runaway

    One battery is a 7kWh battery so that is essentially 380V X 19Ah=.7220watts ($.41), rate of discharge 2kWh continuous $.41 X 3.5= ($1.45 per discharged watt) 5000 cycles or so TESLA boasts.
    Other battery is a 10KWh Battery 380V X 26.5Ah= 10070watts ($.34 watt), rate of discharge @ 2kWh $.34 X 5 = ($1.74 per discharged watt) 1000cycles, non daily use...LOL

    Now lets take a STARK industrys (2) 125Ah, 12.8v (compatible with standard solar charge controllers) LiFePO4 $1189.00per battery $2378 for 2 batteries 3000 life cycles.

    12.8V X 250Ah = 3200watts (OR as TESLA Markets 3.2kWh "LOL"), ($.74 per watt), 2560watts can be discharged from the LiPO4 stark industries $.74X1.25= ($.92 per discharged watt)

    OR pay on AVG . $.46 per discharged watt using lead acid.

    Still don't understand where the power wall makes any sense on any level, unless we lived in the era of the zombie apocalypse.
  • soylentgreensoylentgreen Solar Expert Posts: 104 ✭✭
    Think in terms of time-shifting:

    $3000 can shift 7kWH per day for 10 years (warranty period) at 92% efficiency.

    $3000/(7*365*10/0.92) = about $0.13 per kWH shifted.

    If your utility has a greater than $0.13 price delta between Peak and Off-peak, then one could use the Tesla Powerwall to arbitrage this difference.

    Where I live, one of the TOU rate deltas is $0.48 - $0.17 = $0.31/kWH, so in theory, I could install some Powerwalls, buy power at night and sell it back during the day and make money.

    This is, I think, why folks think this is such a potentially disruptive technology.

    Lots of assumptions here, of course which could move the price up or down a bit, but I'm pretty sure this beats Lead acid by a wide margin.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Think in terms of time-shifting:

    $3000 can shift 7kWH per day for 10 years (warranty period) at 92% efficiency.

    $3000/(7*365*10/0.92) = about $0.13 per kWH shifted.

    If your utility has a greater than $0.13 price delta between Peak and Off-peak, then one could use the Tesla Powerwall to arbitrage this difference.

    Where I live, one of the TOU rate deltas is $0.48 - $0.17 = $0.31/kWH, so in theory, I could install some Powerwalls, buy power at night and sell it back during the day and make money.

    This is, I think, why folks think this is such a potentially disruptive technology.

    Lots of assumptions here, of course which could move the price up or down a bit, but I'm pretty sure this beats Lead acid by a wide margin.



    The only thing disruptive is the misinformed bandwagon of TESLA and Solar City shareholders, spewing sales gimicks and lies to consumer's for those in solar leases that do not under stand Net Energy Metering agreements and that out right owning solar, as a producer receiving your annualized overproduced equal value energy back in the form of credits.

    The POWER WALL is a SCAM for GRID TIED PERIOD.

    If you own solar, and you enter in to a NEM agreement, it is of equal, energy for energy daily annualized value. At the end of the year it is called energy over production true up CREDIT because winter insolation is so low in production that the utility provider has to credit the producer a kW value of $.0397kW, at the end of annualized credits.

    IF YOU INSTALL A POWER WALL AND YOU OWN SOLAR YOU WILL LOSE 8% OF YOUR ANNUALIZED TRUE UP CREDITS MINIMUM, AND LOSE MORE IN INITIAL BUILD COSTS, IF YOU BUILD TO 100% to 110% OF YOUR ANNUALIZED CONSUMPTION VALUE. THIS SLOWS DOWN THE RETURN ON INVESTMENT AND DOES NOT ACCELERATE INVESTMENT OF GRID TIED SOLAR IN ANYWAY.

    Those that are off grid could use a power wall, but then look at the kWh demand issues, standard LiFePO4 batteries do the job better in discharging and deliveing power closer to grid parity pricing than the TESLA power wall.
  • BB.BB. Super Moderators Posts: 26,768 admin
    In California, we have time of use net metering. I can receive almost $0.30 per kwh for noon to 6pm production summer weekdays. Off peak is around $0.10 per kwh.

    So peak shifting loads/production can make sense.

    Although, some utilities do not allow (or are trying to stop) battery based net metering to prevent people buying off peak power and selling during peak times. (Net metering is renewable energy program, not a power arbitrajing plan)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    BB. wrote: »
    In California, we have time of use net metering. I can receive almost $0.30 per kwh for noon to 6pm production summer weekdays. Off peak is around $0.10 per kwh.

    So peak shifting loads/production can make sense.

    Although, some utilities do not allow (or are trying to stop) battery based net metering to prevent people buying off peak power and selling during peak times. (Net metering is renewable energy program, not a power arbitrajing plan)

    -Bill



    Its credit for credit annualized, anything that is overproduction is .0397kw, in E1, I believe you are refering to the E2, E6 rates. or you are in a really old NEM agreement, things have changed since the CSI program ended. Either way all my clients are happy, I build to 110% and they have enough over production credit that PG&E deducts the natural gas bill which typically comes out to $0 to my clients before they receive their true up check.

    If the TESLA power wall is capable of islanding it is not allowed in Northern California. Its actually established in CPUC electric rule guidelines, and if it has the capability of anti islanding, this means it requires a transfer switch.

    In either case if the battery is incorporated into the grid tied system it must maintain an efficiency of 95.5% in both the charge and discharge which it does not. So sorry uninformed TESLA share holders no go for install in california, pull your stock while you can...LOL
  • BB.BB. Super Moderators Posts: 26,768 admin
    I am pg&e.... yes, you are correct, the plan was designed to net zero at the end of one year. They did not want people to install a 50 kWatt array in the back yard and make money selling power at retail.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • soylentgreensoylentgreen Solar Expert Posts: 104 ✭✭
    If you own solar, and you enter in to a NEM agreement, it is of equal, energy for energy daily annualized value..

    Not where I live - as mentioned above California has some TOU+Net Metering plans, where the calculation is done on a dollars rather than kWh basis.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭

    Not where I live - as mentioned above California has some TOU+Net Metering plans, where the calculation is done on a dollars rather than kWh basis.

    Older CSI programs had TOU coupled with NET metering as an incentive.

    CSI since January of last year phased out, so any one entering into NEM now is in a standard NEM which is just total annualized production at true up.

    Before CSI closed the pay out was $.09 kWh coupled with the NEM which has always been .0397kWh.

    TOU technically doesn't exist for new agreements. Reason being the true up credit is always applied.

    I researched this with 3 clients in NEM of this year.

    One client we signed NEM in E2.
    Another Client signed NEM in E1.
    The third client signed NEM in E6 electric car.

    What we found in the difference between all 3 agreements was absolutley nothing in the rates either being E1 or E2 and above TOU rates if all the systems are built for NET 0 at 110%.

    It wouldn't matter if we charged cars at peak hours or off hours that charged a .09kWh rate between 10pm and 2am.

    In simplicity any new agreements are just true up with the $.0397 KW rate.

    If every one invested into a solar system and built to 110%, VS installing a system at 90% and installing a power wall. The system built at 110% will accelerate the return on investment by 30%, VS a system built at 90% with power wall no matter how you slice the investment/initial build costs.
  • SonlightSonlight Registered Users Posts: 4
    westbranch wrote: »

    How many PV companies are still around, that were top of the pile 10 years ago?? Does the name Evergreen ring a bell? What is the likelihood of this warranty being any good? Just saying...

    I think Tesla has proven itself. Elon Musk has had his ups and downs but when NASA grants him over a Billion dollars for his SpaceX company I believe we can trust this one. The price is right and seems worth it to me but I am a newbee just learning although I am almost finished with, "Elon Musk: Tesla, SpaceX, and the Quest for a Fantastic Future" a 13 1/2 hour book. The book is quite interesting and gives you quite an inside view of Elon Musk, not really accomplished from a non-biased position before author Ashlee France took it on!
  • bmetbmet Solar Expert Posts: 630 ✭✭
    JoshK wrote: »
    Briux, It has solar-input, not sure on output. It would work with any brand solar panel as I understand.

    very dirty math, trying to spec what it would take to charge 10KWh, especially since Mr. Musk does not mention capacity(AmpHours). He only mentions what the PowerWall can supply in one cycle. Bill, let me apologize in advance for my misunderstanding….
    You all know this one.
    Watts x Direct Sun Hours/perday divided by 2
    Assume that you are using a 300W solar panel.
    4 = amount of average direct-sun hours per day.
    300W x 4Hrs / 2 = 600 Watts 1 panel would supply to a battery bank in the 4 hours the sun is tracking directly over your panel.
    A 10KWh battery bank would need to be charged in the 4 hours of direct sunlight hitting the panels.
    10KWh / 4 hours = 2500Watts per Hour. Because we lose half of our electricity in infrastructure, we would need to have twice as many panels to sustain 2500 W an hour. Let's get 5000W of panels:
    5,000 W / 300W = 16.6 solar panels to give enough Wattage to the system to charge Mr. Musk's battery in 4 hours of direct sunlight.
    Bill, I apologize that I am mixing KiloWatt Hours(USEAGE), but this is the figure that Mr. Muck gave. He never once mentions Amp Hours(STORAGE).
    I understand that these are different quantities, but it's as close as I can get using his term that his product cycle is 10KWhs. Capacity is never mentioned.
    Could Sixteen 300W solar panels recharge his PowerWall in one sunny day?
  • BB.BB. Super Moderators Posts: 26,768 admin
    Not a problem, the only math fixes I would do:
    bmet wrote: »
    300W x 4Hrs / 2 = 600 Watts
    • Would be 600 Watt*Hours
    Also, for Watt*Hours to the battery bank, 50% is a bit severe... I would use 0.77 as a conservative derating for panel+charge controller:

    5,000 Watt array * 0.77 Derating * 5 hours per day (nominal sunny weather--hey this is marking 101) = 19.250 Watt*Hours = 19 kWH of available power for storage

    Since a good Lithium chemistry is very efficient--There should be very low losses for direct storage of energy (95% to 99%???). However, there may be power losses for the Battery Management System, possible coolant circulation, networking for remote monitoring, and of course the 85-95% efficient AC Inverter losses.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    BB. wrote: »


    Since a good Lithium chemistry is very efficient--There should be very low losses for direct storage of energy (95% to 99%???). However, there may be power losses for the Battery Management System, possible coolant circulation, networking for remote monitoring, and of course the 85-95% efficient AC Inverter losses.

    -Bill

    There is a trade off.
    Tesla claims efficiency is 92%, this is only on the basis of it's charge rate.
    Discharge efficiency rate from BMS is only 38% efficient based on a kWh discharge rate. Maximum 3.3kWh, 2kWh continuos.

    AGM efficiency is roughly 87%.
    Discharge efficiency rate is 87%.

    A battery is only as efficient as it's charge and discharge capabilities.

    What we will not have an understanding of with the TESLA Power Wall is rate of leakage. There is obviously leakage in order to maintain the BMS.
  • bmetbmet Solar Expert Posts: 630 ✭✭
    BB. wrote: »
    Not a problem, the only math fixes I would do:
    • Would be 600 Watt*Hours
    Also, for Watt*Hours to the battery bank, 50% is a bit severe..

    I used 50% following your math of known variables from end-to-end, panel to battery. I recall you came up with a 0.52 figure which I rounded off.
  • BB.BB. Super Moderators Posts: 26,768 admin
    The 50% number is based on "end to end" efficiency (solar panels to charge controller to battery bank to AC inverter to load).

    I thought you were trying to figure out Tesla's Battery WH or AH capacity--So, I "dumped" the battery+AC inverter losses and just focused on charging losses. I may have miss understood your intent.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • soylentgreensoylentgreen Solar Expert Posts: 104 ✭✭

    Older CSI programs had TOU coupled with NET metering as an incentive.
    ...

    SolarPowered - you are talking about PGE - please understand that PGE, while large, is not the only electric company in California. And though it pains us both to admit it, there are 49 other states in the USA.

    In fact, I believe there may even be other Countries on this planet!

    Saying "The POWER WALL is a SCAM for GRID TIED PERIOD" because it doesn't pencil out in PGE is silly.
    I will trust your experience on PGE but you may want to consider limiting your claims to PGE.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭

    SolarPowered - you are talking about PGE - please understand that PGE, while large, is not the only electric company in California. And though it pains us both to admit it, there are 49 other states in the USA.

    In fact, I believe there may even be other Countries on this planet!

    Saying "The POWER WALL is a SCAM for GRID TIED PERIOD" because it doesn't pencil out in PGE is silly.
    I will trust your experience on PGE but you may want to consider limiting your claims to PGE.


    This isn't a PGE thing.
    These are guidelines set by both the FPUC and the CPUC.

    By 2017 all jurisdictions with the acceptions of Hawaii and Alaska. Are to follow the electric rules.

    California just happens to be on the leading edge of establishing the electric rules, and the fed uses California as a template if the economics work.

    Now power walls in 3rd world countries....
    Great idea, if the 3rd world can afford a power wall at it's price tag.

    As far as a 3.3kWh discharge for $3500. I would rather stick to 12volt batteries for $1200.
  • sub3marathonmansub3marathonman Solar Expert Posts: 300 ✭✭✭


    This isn't a PGE thing.
    These are guidelines set by both the FPUC and the CPUC.

    By 2017 all jurisdictions with the acceptions of Hawaii and Alaska. Are to follow the electric rules.

    California just happens to be on the leading edge of establishing the electric rules, and the fed uses California as a template if the economics work.

    OK, I'm from one of those other states, so where can I find the guidelines set by both the FPUC and the CPUC? Is there any documentation for this 2017 deadline?

  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭

    OK, I'm from one of those other states, so where can I find the guidelines set by both the FPUC and the CPUC? Is there any documentation for this 2017 deadline?



    Take back my comment on Hawaii entering into NEM, they are not excluded.

    Most of the information you will want you can get from seia.org. It keeps consumers and solar producers current on both federal and state legislations.

    Right now 43 of 50 states have entered into NEM. I believe Alaska (some not all of Alaska) has contingencies because some of the power is imported out of state for regulatory issue.

    seia.org, will explain all you need to know about NEM, and FIT. It isn't a deadline, Its a mandate with exceptions which means its not enforceable. The problem is utility companies in most states are still fighting not to pay FIT in some jurisdictions of some states. FIT when coupled with NEM has to go through each independent state legislation to determine the cost of FIT.

    Most of what you need to know will be detailed in AB's (State Assembly Bills).
    Utility companies have to prove a burden of loss to the local state assembly in order not to pay an FIT to the solar producer.

    www.seia.org

    www.dsireusa.org

    Also I miss defined FPUC its actually FERC
    http://www.ferc.gov/CalendarFiles/20...on,%20CPUC.pdf
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