Tesla Power Wall / solar power

[Joan-eh?]

Hi!

Anyone using Tesla Power Wall?
Anyone know about using it in the Canadian / SW Ontario context?

Oh how I would love that it works for us.

I have been searching to see if anyone is discussing the Tesla Power Wall, but I keep getting this message "Please try again. If you come back to this error screen, report the error to an administrator"  I'm not sure how to report it. Or maybe Tesla is a banned word?? :-)  feel free to redirect me, if the search is just not working!

[Syonyk]

Re Power Wall:

You can't actually get one, you can't get one without writing a very large check to an installer, it only works with one quite expensive inverter, and there are very few cases where it makes any sense, other than to say you have a PowerWall in your garage.

It's rare to see any calculations indicate that it makes any sense at all, given that you can gain most of the benefits by time shifting your load ("run the dishwasher later").  If it's vitally important to run your dishwasher, dryer, heat pump, and charge your car at peak rates, the capacity will be drained in very short order, so you'll need to buy several.

That said, it's really a very good value for social signaling, since you can be "on the list" without having to actually spend money.  If you care about that sort of social signaling.

=========

Solar?  Go for it.  Do as much of it yourself as your local permitting climate will allow.

[BudgetSlasher]

Thanks for the insight.

I'm looking for a solution for the power outages we are getting frequently in the county. Everyone has generators. Most have diesel. A friend just got a natural gas generator. A propane generator has be recommended for my situation. I was hoping for something more "environmentally friendly".

Then I was thinking maybe just try to get basics on solar all the time. We already do geothermal exchange - heating and cooling -

Best resources to read about this solar?

I've been doing a fair bit of solar research slowly over the last year or so (for a project that is still 2-3 years away)

First, the Tesla Power Wall is a fancy package (probably with some high tech batteries) that is in a nice small wall mounted package. But, it is nothing new a charger controller and some basic batteries will do the same task and likely for less money.

Second, unless you are off grid you cannot "get basic solar on all the time" modern systems without batteries shut down when they detect the grid is down to prevent back-feeding into downed wires. Depending on the cause and time of the power failure solar might not be working that well either. At night you will have zero power and during a overcast period (say a rain storm) you will have greatly diminished output.

Third, generally you size a solar system based on the annual consumption and use batteries or the grid (net metering) to even things out when you have a high demand period. Remember the system is generating power when the sun is out (and you are at work or running errands or otherwise not using the power) and not making power when you are at home after dark cooking dinner (watching TV or working in the workshop). So, even if you were ok with power only during daylight hours you would have to size the system for the maximum load (without the grid or batteries) which will be even more expensive.

I wish I could give a definitive resource, but I have picked up a little here and a little there over the past 18 months or so.

For us having a solar system installed that would cover ~80% of our annual demand would be 2-3 times the price of installing a whole house generator with automatic transfer case and a smaller portable propane generator with connection port on the house with a manual transfer case and can only operate a few critical circuits would be a small fraction the cost of a solar array.

[Syonyk]

I'm looking for a solution for the power outages we are getting frequently in the county. Everyone has generators. Most have diesel. A friend just got a natural gas generator. A propane generator has be recommended for my situation. I was hoping for something more "environmentally friendly".

The right solution for power outages, even moderately frequent power outages, is a generator.  Running dozens of hours a year on a generator will be radically cheaper than solar as backup.  Put your computers on a UPS to handle the cutover time, get a generator with auto start, a transfer switch, and be done with it.

Now: If you want to go solar because you want to go solar, and are willing to pay the costs for it (which are substantial), awesome.  However, if you want solar plus off grid backup, your cost go up even more, because batteries aren't cheap, and homes use a lot of power.

Then I was thinking maybe just try to get basics on solar all the time. We already do geothermal exchange - heating and cooling -

Ground source heat pump, a thermally coupled house, or something else?

The problem is that "the basics" tend to be very power heavy.  Heat pumps are pulling, depending on the house, 5-6kW while running.  Ovens and stoves, also, pull insane amounts of power.  Lighting is pretty easy, though, but if you have power outages, you're better off just installing a battery backup for your lighting circuits, or using a generator.

Best resources to read about this solar?

The internet is a good start.

===================

Now, to play with some numbers:

A "house size" diesel generator (5-7kW, putting out two phases of 120, for your 240v needs) with auto start, would be in the range of $5k.  You can get them for less if you're willing to start them yourself, or just run a single phase of 120v.  Installed, you're well under $10k - and a lot less if you're willing to use less power or have a lot of your loads on natural gas/propane.

They'll burn a gallon every few hours - so, figure, $1-$2/hr operating costs.  Less if you keep power consumption low - diesels are super-efficient at low loads.

I've been getting quotes for a house-size solar system, and for an 8kW system (I typically use 30-50kWh/day), I'm looking at around $35k installed - for a grid tie system that won't get me power if the grid is down.

Even if I do all the work myself, I'm looking at $15k or so, plus having to get an electrician to do the final signoff.  If I want to add off-grid backup, I'm looking at another few grand, at least, in batteries, plus an inverter that can deal with them.  I'll probably go this route because I want it for other reasons, but it's not the cheapest way to get power outage standby power.

[Syonyk]

First, the Tesla Power Wall is a fancy package (probably with some high tech batteries) that is in a nice small wall mounted package. But, it is nothing new a charger controller and some basic batteries will do the same task and likely for less money.

It certainly has fancy batteries.  It's using more or less the same lithium ion batteries Tesla is using in their cars, just short-stroked for longevity (they last longer if you use the middle 80% or so of the capacity).

The cost is competitive with a standard lead acid off-grid system, with one minor gotcha: You still can't get one.  And you can't get one for off grid use.  So it may as well be a paper launch, for all the usefulness one gets out of it.  I'd love one - it would be absolutely perfect for my office (which is off grid/solar powered), but, hey, can't get one, it won't talk to a standard charge controller/inverter, and it requires a really high panel string voltage (400 Volts or so).

Second, unless you are off grid you cannot "get basic solar on all the time" modern systems without batteries shut down when they detect the grid is down to prevent back-feeding into downed wires. Depending on the cause and time of the power failure solar might not be working that well either. At night you will have zero power and during a overcast period (say a rain storm) you will have greatly diminished output.

There are ways around that - you can run the panels and batteries into a critical loads subpanel with a transfer switch, so you put your lighting/fridge/freezer/etc on that subpanel and let the rest of the stuff go dark when the grid is disconnected.  It's a bit more complex, though.

Apparently line workers really don't worry that much about back feeding downed systems - any inverter trying to feed the neighborhood will overcurrent shut down long before it energizes much of anything.  It's only really an issue if your house feeder is the problem.

[BudgetSlasher]

First, the Tesla Power Wall is a fancy package (probably with some high tech batteries) that is in a nice small wall mounted package. But, it is nothing new a charger controller and some basic batteries will do the same task and likely for less money.

It certainly has fancy batteries.  It's using more or less the same lithium ion batteries Tesla is using in their cars, just short-stroked for longevity (they last longer if you use the middle 80% or so of the capacity).

The cost is competitive with a standard lead acid off-grid system, with one minor gotcha: You still can't get one.  And you can't get one for off grid use.  So it may as well be a paper launch, for all the usefulness one gets out of it.  I'd love one - it would be absolutely perfect for my office (which is off grid/solar powered), but, hey, can't get one, it won't talk to a standard charge controller/inverter, and it requires a really high panel string voltage (400 Volts or so).

Interesting, when I did my research most of the non-yayteslaisgreat fluff pieces read as this is nothing new besides a pretty package and you can do better yourself for less. I will admit, I have very little battery research, as the added cost is not worth it in my situation (about 2 miles from the step down and on a major road). But I do know that a 10.32kwh (close the to tesla 10kwh powerwall which was said to be 3.5k before it was killed) is 1,340 (http://www.wholesalesolar.com/1898710/crown/battery-banks/crown-430-ah-24vdc-10-320-wh-4-battery-bank) which leave over 2 grand to deal charging and transfer.

Second, unless you are off grid you cannot "get basic solar on all the time" modern systems without batteries shut down when they detect the grid is down to prevent back-feeding into downed wires. Depending on the cause and time of the power failure solar might not be working that well either. At night you will have zero power and during a overcast period (say a rain storm) you will have greatly diminished output.

There are ways around that - you can run the panels and batteries into a critical loads subpanel with a transfer switch, so you put your lighting/fridge/freezer/etc on that subpanel and let the rest of the stuff go dark when the grid is disconnected.  It's a bit more complex, though.

Apparently line workers really don't worry that much about back feeding downed systems - any inverter trying to feed the neighborhood will overcurrent shut down long before it energizes much of anything.  It's only really an issue if your house feeder is the problem.

So . . . I think we are in agreement on this point? As I prefaced my statement a "basic solar" system (which I interpret and stated) to mean without batteries will not function when the grid is down. Of course if you design a system with batteries it can run when the grid is down.

Further, you and I seem to be in agreement that a "basic solar" (without battieries) will go down with the grid; the difference appears to be "will detect and shutdown" which prevents back feeding vs "line workers don't worry" because "over current shutdown". Either way the end result is no power for the homeowner from their solar with a "basic solar" system.

[Syonyk]

But I do know that a 10.32kwh (close the to tesla 10kwh powerwall which was said to be 3.5k before it was killed) is 1,340 (http://www.wholesalesolar.com/1898710/crown/battery-banks/crown-430-ah-24vdc-10-320-wh-4-battery-bank) which leave over 2 grand to deal charging and transfer.

I agree that you haven't done much battery research.

You cannot cycle a lead acid bank to full capacity and expect it to last beyond a few hundred cycles.  The PowerWall is a 7kWh system that's rated for daily cycling with a 10 year warranty - so it's likely good for 4000+ cycles.  You can do that easily enough with a short stroked, thermally managed lithium pack.  That's exactly what they have.

Here's a chart from Trojan on their RE series batteries.  Using it because this is what I have in my office.



If I want 4000 cycles out of my pack, I can't drain it beyond 20%.  So, I need a 35kWh nameplate capacity pack to offer me 4000 cycles at 7kWh.

The cost of the pack for what it offers really is quite good.  You just can't get one, and you can't interface with more than about one inverter on the market, which isn't suited for off grid use.

The total system cost is around a wash for lead vs PowerWall right now, except you can get lead acid, and if you need more power, you can get it - you can run a deep cycle system down to 30% if you need to, and that's one advantage of a larger lead acid pack.  Power if you really need it.

So . . . I think we are in agreement on this point? As I prefaced my statement a "basic solar" system (which I interpret and stated) to mean without batteries will not function when the grid is down. Of course if you design a system with batteries it can run when the grid is down.

Further, you and I seem to be in agreement that a "basic solar" (without battieries) will go down with the grid; the difference appears to be "will detect and shutdown" which prevents back feeding vs "line workers don't worry" because "over current shutdown". Either way the end result is no power for the homeowner from their solar with a "basic solar" system.

Correct.  Unless you do something "weird," a grid tied solar system is useless without the power grid.