Plan: Off grid solar with a Model S battery pack at the heart

[frisco]

hopefully it's not overpriced or a lease model like solarcity.

A local college here in SW Florida recently installed a large solar setup using a 200kwh battery provided by Tesla. I asked how much they paid for the battery, and the response was "Hundreds of thousands of dollars." So I seriously doubt Tesla will be providing them at a reasonable cost (at least compared to the cost of salvage modules). I inquired with the stationary battery division of Tesla to see if I could buy a 100kwh stationary battery for a project I am working on, but they said they aren't available, so the college must have just been a test case.

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• Battery capacity
  • 36 modules from 2.25x Tesla 85kWh packs
  • 191.25 kWh (DC side)
  • ~4,200 Ah
  • 43.2V nominal @ 3.6V per cell
  • 15,984 cells (!)
• Inverter capacity (8x Outback Radian GS8048A)
  • 240VAC @ 60Hz w/neutral
  • 64kW continuous AC output
  • 30 minute surge: 72kW
  • 5 second surge: 96kW
  • 100ms surge: 135.76kW
  • Grid->Battery Charging Capacity: 57kW
  • Expected AC output from pack after safe SoC window and efficiency considerations: ~160 kWh usable AC
• PV Capacity (In Progress)
  • 102 Panels @ 435W (20% efficiency)
  • 44,370 Watts DC
  • Split into 17 sets of 6 panels (3 parallel of 2 in series)
  • 17 individual MPPT charge controllers (Midnite Solar Classic 200)

As for cost, I'm going to actually keep that total to myself for the moment. It, admittedly, has gotten a bit out of hand, but it has been too awesome of a project not to see through to the end... budget be damned.

WK- To get a battery charging capacity of 57kw from the grid I'm assuming you're figuring you'll be charging at 50v x 115.5a x 8 inverters = 57kw?

 

[nwdiver]

My prediction is 2 modules (~10kWh) packaged with a ~4kW grid-tie inverter with at least a 120v outlet available for grid outages similar to the Secure Power Source SMA has started to include with some of their inverters. Cost: ~$5k

The tricky part is that there is a VERY limited market for storage. There is currently absolutely no economic benefit to storage for most people with a residential rate structure.

 

[Robert.Boston]

A local college here in SW Florida recently installed a large solar setup using a 200kwh battery provided by Tesla. I asked how much they paid for the battery, and the response was "Hundreds of thousands of dollars." So I seriously doubt Tesla will be providing them at a reasonable cost (at least compared to the cost of salvage modules). I inquired with the stationary battery division of Tesla to see if I could buy a 100kwh stationary battery for a project I am working on, but they said they aren't available, so the college must have just been a test case.

Something sounds off with that account. The step-up from 60 kWh to 85 kWh is $8000 (net of Supercharger access), or $312.50/kWh. At the price, 200 kWh would cost $62,500.

 

[brianman]

Something sounds off with that account. The step-up from 60 kWh to 85 kWh is $8000 (net of Supercharger access), or $312.50/kWh. At the price, 200 kWh would cost $62,500.

Perhaps the cost of the pack(aging) has an influence here. Also for stationary storage officially delivered by Tesla has some additional requirements vs. "bare" car packs.

 

[bluenation]

hopefully it's not overpriced or a lease model like solarcity.

thats what i dont get.

why dont they sell this thru solarcity? are they llooking to sell directly from tesla to end users?

dont they want to do some cool cross branding? and clean up the shaky customer satisfaction with Kimbal's company?

 

[wk057]

A local college here in SW Florida recently installed a large solar setup using a 200kwh battery provided by Tesla. I asked how much they paid for the battery, and the response was "Hundreds of thousands of dollars." So I seriously doubt Tesla will be providing them at a reasonable cost (at least compared to the cost of salvage modules). I inquired with the stationary battery division of Tesla to see if I could buy a 100kwh stationary battery for a project I am working on, but they said they aren't available, so the college must have just been a test case.

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WK- To get a battery charging capacity of 57kw from the grid I'm assuming you're figuring you'll be charging at 50v x 115.5a x 8 inverters = 57kw?

Each inverter can pull 30A from the grid at 240V for charging. So that's 240A (120A from each of my 200A grid panels), or 7.2kW per inverter. Comes to 57.6 kW total. The spec says 115ADC per inverter, which would be about 40kW at 43.2VDC... but when I did a full test it didn't seem to enforce this limit and I was getting near max of 57kW. I'll probably limit it to 45kW anyway, to match my array.

 

[TheTalkingMule]

The tricky part is that there is a VERY limited market for storage. There is currently absolutely no economic benefit to storage for most people with a residential rate structure.

Huge market for storage in Germany and Tesla already has their sales network established in Europe.

 

[nwdiver]

Huge market for storage in Germany and Tesla already has their sales network established in Europe.

True.... hadn't thought about Europe....

I wonder if people in areas where the utilities are blocking new solar interconnects like Hawaii would be able to do what wk057 is doing...

 

[mitch672]

actually there is a market, a "whole house UPS" for a reasonable price, for example, I can't install solar, or a generator (I live in a detached home that is part of a condo complex, the HOA's prohibit modifying/installing anything on the exterior), I can put whatever I want in the garage or basement though. Also, they could be doing this in partnership with utilities, and even have utility rebates, if you allow the utility to control the units charge/discharge rate/schedule.. with enough of these, they can avoid spinning up peaker generation, etc.

 

[brkaus]

actually there is a market, a "whole house UPS" for a reasonable price, for example, I can't install solar, or a generator (I live in a detached home that is part of a condo complex, the HOA's prohibit modifying/installing anything on the exterior), I can put whatever I want in the garage or basement though. Also, they could be doing this in partnership with utilities, and even have utility rebates, if you allow the utility to control the units charge/discharge rate/schedule.. with enough of these, they can avoid spinning up peaker generation, etc.

This is a good point. There are lots of areas that have generators to keep power on during storms. The community my relatives live in near the coast in Virginia was hit hard by a generator salesman.

I guess it would depend on size and what would be the minimal energy requirement. Definitely lower maintenance requirement and the utility rebate idea is good. But utility rules change slowly.

However, based on the average age of the people in their community I'm not sure some new fangled technology would sell.

 

[wk057]

Until my solar panels are installed my system is operating in whole house UPS mode. Works as expected. I cut off my main grid breakers and everything keeps ticking like nothing happened. I cut them back on and back to grid power with the inverters topping off the batteries. Pretty cool.

 

[TheTalkingMule]

True.... hadn't thought about Europe....

I wonder if people in areas where the utilities are blocking new solar interconnects like Hawaii would be able to do what wk057 is doing...

Absolutely. And anywhere in Europe where electricity is $.26 and they only pay you $.12 to dump to the grid at peak.

I'm in PA, so it's gonna be an awfully long time til this makes sense, but in the mean time Tesla can make a killing if the price is right.

 

[mwulff]

My prediction is 2 modules (~10kWh) packaged with a ~4kW grid-tie inverter with at least a 120v outlet available for grid outages similar to the Secure Power Source SMA has started to include with some of their inverters. Cost: ~$5k

The tricky part is that there is a VERY limited market for storage. There is currently absolutely no economic benefit to storage for most people with a residential rate structure.

Depends on where you live. In my country we pay about $0.15 in tax for every kWh we draw from the grid. The power we sell back to the grid does not refund this tax. So with a kWh price of $0.30 when purchased and a $0.15 price when sold it becomes interesting to store the energy.

We also tend to live in smaller homes and could conceivably go off-grid with 10-15 kWh of storage.

 

[wk057]

Figured I'd throw a couple more pics up real quick now that I've cleaned up my electrical room.

Everything hooked up except for solar panels. Just have to build the case around the battery rack and I'll be ready for inspection later in the week.

Running in UPS mode now. I have one inverter (Inverter D, 4th from right) that started acting crazy saying the battery voltage was 1.2V and AC input was 445VAC... called Outback support and after a little bit of diagnosing on the phone they're sending me a new control board for that inverter. Awesome support based at their HQ in Washington state. Can't ask for much more than that.

 

[bluenation]

.....damn, yo.

now im interested in what really goes on in your...labs

 

[jjkroll]

Very impressive setup. I installed a small off-grid cabin setup, for my father, 2 years ago. Only 2kW solar, 30kWh AGM and 4kW inverter. We have the classic 150 charge controller which has worked very well. It is amazing to me how easy and affordable this is now compared to a decade ago.

Have you considered a large buried thermal mass to store your excess energy? You could look into ground source heatpumps at the same time. My mother's house, in central PA, has had a ground source heatpump for 22 years that has been very reliable and efficient. We never even hooked up the electric backup heater. She has only replaced one circulating pump in 22 years.

 

[pgiralt]

My OCD doesn't like those two Red cables facing to the left! I'm guessing that's where the door knob hits or something?

 

[electrodacus]

I'm also quite curious to see what Tesla comes up with for home energy storage. I expect around 10 to 25kWh battery but I may be surprised.
Using that as a hole house UPS makes sense if you have often outages for convenience. But it will never be able to recover the investment in any country. Even the Sony or Bosch that have something similar for quite a few years and is based on the better LiFePO4 (better for stationary energy storage) will not be able to recover the investment based even on 20 cent /kWh delta between low and high rates.

wk,

It looks nicely organized but it seems like an off-grid distribution setup for a small village I will say that seems good for about 16 to 17 small off grid houses each with his own solar charge controller and a 4kW inverter.

 

[wk057]

My OCD doesn't like those two Red cables facing to the left! I'm guessing that's where the door knob hits or something?

They're actually where I have a different fuse setup that has a double fuse instead of one. Going to use those to snatch fused power for a couple of low power 48VDC things later.

 

[flankspeed8]

wk057: I think that I honestly say that this is the most fascinating thing that I have read about on these forums. Absolutely incredible. Well done and thanks for sharing!