The best (but probably also most complex = expensive) hardware would be to make this pack act as grid energy storage and stabilization, though that would not be ideal with this pack - EVs are much better at the high power levels required for stabilization (though I do not see anything preventing the solution, other than that the spec is for a low power from the battery, I mean 8 Amps at around 400V is not an EV power level, it is actually rather underwhelming - I wonder why Tesla with a profile of high-power application is releasing such a low power spec.
What I think though is that it will be promoted especially as a backup solution for "when the grid goes down" and by recharging it only from your solar, you will always have power even if the grid goes out for longer periods. Of course you can also charge it from the grid (at night, when power cost may be down to ~6 cents per kWh) to replace some of the power that you consume at the highest tariff, but this will be questionable if this has a good business case. However, sometimes it is more about the feeling than the pocket book, so that may also be why they are making such a big deal out of a smallish pack of batteries not too different from what you can buy online everywhere. Indeed it looks like it is optimized for direct DC input from a solar array at a typical string voltage under 600V, probably the built-in DC/DC converter can take this, do MPPT (although the PowerWall specs are short on details) for charging from the sun in an optimal way - you'd only need to connect the inverter to get your humongous UPS system, which is something that I did to my EV: add a 3kW inverter and if the grid goes down, I have power for a while... Cor van de Water Chief Scientist Proxim Wireless office +1 408 383 7626 Skype: cor_van_de_water XoIP +31 87 784 1130 private: cvandewater.info www.proxim.com This email message (including any attachments) contains confidential and proprietary information of Proxim Wireless Corporation. If you received this message in error, please delete it and notify the sender. Any unauthorized use, disclosure, distribution, or copying of any part of this message is prohibited. -----Original Message----- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Mark Abramowitz via EV Sent: Monday, May 04, 2015 10:34 AM To: Electric Vehicle Discussion List Subject: Re: [EVDL] virtual power plant Not very efficient at that scale, I'm told. At you move to larger scale and longer periods of storage, other solutions surpass batteries. Sent from my iPhone > On May 4, 2015, at 10:20 AM, robert winfield via EV <ev@lists.evdl.org> wrote: > > > dont forget aggregating, say, 1,000 of these 10kW Powerwalls into a 10 > megawatt virtual power plant VPP, (or any multiplier) for microgrids > of distributated generation > -------------------------------------------- > On Fri, 5/1/15, Robert Bruninga via EV <ev@lists.evdl.org> wrote: > > Subject: Re: [EVDL] Tesla plugs into new market with home battery > system (backup foolishness) > To: "Electric Vehicle Discussion List" <ev@lists.evdl.org> > Date: Friday, May 1, 2015, 9:39 PM > > Huh? Plenty wrong with > your assumptions. > >> $6k > of golf cart batteries is about 60 of them; that's around 80 KWH of > storage! Who on earth needs that much for a home. > > My > solar panels produce typically 60 to 70 kWH every sunny day. If I do > not use every bit of it every day, then I am wasting my solar > investment right? Hence, I sell it to the grid every day and buy it > back when I need it at no net cost.. > > If I had to store it > in batteries (at your proposed 10% daily depth of > discharge) then I would need 600 kWh of batteries or $60K investment > (and replace it every 10 years). Again, batteries MAKE NO ECONOMICAL > SENSE WHATSOEVER compared to grid-tie. > BUT... > > BUT, if utilities > began paying the homeowner the same TEN-TIMES PEAK rates they have to > pay for power during summer peaks, then of course, batteries coiuld > make some economical sense. They don't have to handle the full > working load of my solar array, but only enough to meet those > instantaneoud peak value periods... > > Bob > > > > -----Original Message----- > From: EV [mailto:ev-boun...@lists.evdl.org] > On Behalf Of Lee Hart via EV > Sent: Friday, > May 01, 2015 7:02 PM > To: Electric Vehicle > Discussion List > Subject: Re: [EVDL] Tesla > plugs into new market with home battery system > (backup foolishness) > > Robert Bruninga via EV wrote: >>> A quality GC2 golf cart battery > (Trojan, US Battery, etc.) is 220-240 >>> amphours at the 20-hour rate, and > costs $75-$150. They are good for > 5-10 years, and 600-1200 discharges to 50% or so state of > charge. >> >> No, not > BOTH. One or the other. 5-10 years just sitting there > doing >> nothing but waiting for the grid > to go out (4 hours a year around > here)... > > Correct. They are "used > up" once they have accumulated 600-1200 cycles, > *or* are 5-10 years old. > >> OR they barely will last 2 years in daily > solar-off-grid use (and >> note, you are > only getting 50% of their capacity just to last that > long)... > > That > would be the case if you discharge them 50% or so every day. > But 50% > is an excessively deep discharge if > you're going to use them every day. > > For daily use, you would limit your depth of > discharge to just 10% or so. > Then they would > still last for their calendary life; 5-10 years. > > Note that life is a function > of depth of discharge for *all* types of > batteries. If you expect them to last, the > shallower the discharge, the > better. > You'd also murder a lithium pack in a few years, if you > deeply > discharged it every day. > > If you really have a situation > that requires daily deep discharges, you > probably have to use the old Edison nickel-iron > cells. Aside from quality > or abuse, they are > the only type with an indefinite cycle life. > (There are 100-year-old Edison cells still in > use). > >> Yes, may as well > just throw $6k in the trash every few years since you >> never use them. The cost of the > electricity for the 4 hours average > outage per year is only about 80 cents. (1 kW for 4 > hours). Amazing >> how many people will > spend $6k for that 80 cent problem. > > I see a pretty heavy thumb on the scale here, > Bob. :-) $6k of golf cart > batteries is about > 60 of them; that's around 80 KWH of storage! Who on > earth needs that much for a home. > > You have to select the size > and type of battery according to the > application. Some will be best served with > lead-acid, some nickel-iron, > others lithium > etc. Some applications aren't appropriate for batteries > of > any type. > > If all you have to cover is 4 hours of outage > per year, then dumb old > lead-acids are going > to be the cheapest by far. Like I said, they will die > of old age before you wear them out. > > -- > Don't > worry about people stealing your ideas. If your ideas are > any good, > you'll have to ram them down > people's throats. -- Howard Aiken > -- > Lee Hart, 814 8th Ave N, Sartell MN 56377, > www.sunrise-ev.com > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use > NEDRA > (http://groups.yahoo.com/group/NEDRA) > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA > (http://groups.yahoo.com/group/NEDRA) > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA > (http://groups.yahoo.com/group/NEDRA) > > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
