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

[ElektroPionir]

Wow... just wow... The dedication, planning, execution. Fantastic!

Also wondering about that electricity consumption, do you have any plans how to reduce consumption? Some additional insulation? LED Lights?
My family of four, in 2700 sq ft home, spends about 300kwh/month (electricity only partially used for heating, about 30%)

 

[wk057]

Wow... just wow... The dedication, planning, execution. Fantastic!

Also wondering about that electricity consumption, do you have any plans how to reduce consumption? Some additional insulation? LED Lights?
My family of four, in 2700 sq ft home, spends about 300kwh/month (electricity only partially used for heating, about 30%)

300 kWh/mo for four people in 2700 sq ft? Sounds kind of impossible! lol. That's ~10 kWh/day, or an average load of around 400W. You can barely run a few lights and a laptop with that, let alone HVAC for a 2700 sq ft house... Sure you don't mean 3000 kWh?

I think the big saver will be replacing the electric AUX heat setup with propane or solar heating. The AUX heat is the killer in the winter. If it weren't for electric heating I'd have been under 100kWh/day easily.

 

[Adrian]

Lovely updates! Been gone for a few days, cool to see some pictures again! , my memory is short however - do you have any news or pictures on the solarside?

 

[ElektroPionir]

300 kWh/mo for four people in 2700 sq ft? Sounds kind of impossible! lol. That's ~10 kWh/day, or an average load of around 400W. You can barely run a few lights and a laptop with that, let alone HVAC for a 2700 sq ft house... Sure you don't mean 3000 kWh?

I think the big saver will be replacing the electric AUX heat setup with propane or solar heating. The AUX heat is the killer in the winter. If it weren't for electric heating I'd have been under 100kWh/day easily.

No, didn't mean 3000kWh. In coldest winter months we spend about 400kWh/month, 330 in average, did the math in the meantime.
Also no need for typical us-style HVAC, our home is well insulated and there is no need for AC, even in the hottest summer months, (on our way to a so called passive home), and only reason for higher kWh/month will be swapping our diesel citroen for a model 3.
That is really the reason I'm asking, because, sure, one part of idea of having an autonomous electric system is the amount of storage, but for that storage to last, you need to be thrifty. I guess that is more european way of thinking.

That said, with your system at full capacity we would last for about 2-3 weeks that is just amazing

Really a pleasure to see someone so organised and dedicated to creating a great off grid solar system. Bravo!

 

[Robert.Boston]

FWIW, here's some facts about residential power use from the EIA. Of course, this statistic blends all residential accounts, which includes small apartments as well as large houses.

How much electricity does an American home use?

In 2013, the average annual electricity consumption for a U.S. residential utility customer was 10,908 kilowatthours (kWh), an average of 909 kWh per month. Louisiana had the highest annual consumption at 15,270 kWh, and Hawaii had the lowest at 6,176 kWh.

 

[FlasherZ]

FWIW, here's some facts about residential power use from the EIA. Of course, this statistic blends all residential accounts, which includes small apartments as well as large houses.

As another data point, here in the central US, the average customer of our rural electric co-op on rate 1 (includes homes and farms) is ~1,200 kWh/month, or 14,400 kWh/year. Very few apartments, if any, in that mix.

 

[MrPinrel]

some very efficient homes out there. I just looked it up and for our 6000 sq ft home in Kansas with 5 people, a Tesla, electric AC and gas heat, the average monthly use in 2014 was 1843kwh. Average bill was $225.

I would welcome opinions as to whether I am completely out of the efficiency ballpark and need to look at making the house more efficient. I am not looking to be the most efficient guy out there but don't want to be throwing money out the window either.

 

[FlasherZ]

some very efficient homes out there. I just looked it up and for our 6000 sq ft home in Kansas with 5 people, a Tesla, electric AC and gas heat, the average monthly use in 2014 was 1843kwh. Average bill was $225.

I would welcome opinions as to whether I am completely out of the efficiency ballpark and need to look at making the house more efficient. I am not looking to be the most efficient guy out there but don't want to be throwing money out the window either.

My 4,500 sq ft home uses an average of about 4000 kWh per month without solar PV offset and with propane heat, all new windows, and full LED lighting. Now, I'm a bit different because I run a lot of A/C and cooling units (small fruit orchard) along with a constant rack of IT gear, so you're definitely in a good range there compared to me.

 

[Robert.Boston]

some very efficient homes out there. I just looked it up and for our 6000 sq ft home in Kansas with 5 people, a Tesla, electric AC and gas heat, the average monthly use in 2014 was 1843kwh. Average bill was $225.

I would welcome opinions as to whether I am completely out of the efficiency ballpark and need to look at making the house more efficient. I am not looking to be the most efficient guy out there but don't want to be throwing money out the window either.

I think you're doing pretty well, considering the loads you have. The average American home is much smaller than 6000 sq ft. Nonetheless, the payback on energy efficiency investments is generally good, so I'd recommend you at ways of reducing your usage, e.g.

• Replace all lights with LEDs
• Replace appliances (esp. refrigerators and freezers) that are more than 12 (or so) years old
• Install an attic fan to lower temps there during the summer
• Improve insulation, esp. around windows and doors

I know that power is cheap in Kansas, but by the same token, the sunshine is pretty good. Solar could have a good payback. And then @wk057 will come out and install some batteries....

 

[electrodacus]

I see some large amount of electricity used. If most of that is used inside the house than all of that will convert to heat and then AC will be needed to extract that heat. (But maybe most of that energy is already because of the AC).
I men tined before that my house is extremely small 65sqm (700sqft) it is also quite cold here in SK Canada and 1000kWh in the coldest month is what I need for heating (Is an extremely well insulated house) but still think about the fact that I need just a 1000kWh /month to maintain about 40C delta between inside and outside. Average temp here in January is about -17C with many days in the -30C and -40C
I want to install a 9kW PV array so that heating is electric directly with no battery with just PV and simple resetive heating embedded in the concrete floor. The concrete floor will act as a thermal battery.
So maybe if cooling is the most part of the electricity used that can be done directly without the use of battery. Normally you need AC mostly during the sunny days.
Anyway looking forward to your installation.

 

[jvonbokel]

191 kWh; 2,016 lbs of batteries; ~20 cubic feet.

I calculate 15,984 individual cells. Any way you slice it, that's some impressive energy density.

Curious... did you always intend to go beyond the first 85kWh? If not, what were the factors in your decision to add more storage? Based on expected need, good deal on more modules?

 

[wk057]

I run two PC near constantly, both pretty decent setups. I have a small rack of network/server equipment that runs constantly (~500W). A pool pump that runs quite a bit (~20kWh/day in summer). Two Model S (should come out to ~20-ish kWh/day average over the year, but don't have long term data yet). Almost all LED lighting. Some 12V landscape lighting (that currently use an AC->DC converter for power, but I'll probably replace this with a DC->DC... or LED that can accept 48V if I get time). Two electric hot water heaters. Three heat pumps/AC units. Electric aux heat for the winter (~25kW total!). Electric range/oven. Electric clothes dryer. Plus everything else you would find in a house (TVs, video games, cable boxes, phone chargers, etc etc etc.)

 

[electrodacus]

I run two PC near constantly, both pretty decent setups. I have a small rack of network/server equipment that runs constantly (~500W). A pool pump that runs quite a bit (~20kWh/day in summer). Two Model S (should come out to ~20-ish kWh/day average over the year, but don't have long term data yet). Almost all LED lighting. Some 12V landscape lighting (that currently use an AC->DC converter for power, but I'll probably replace this with a DC->DC... or LED that can accept 48V if I get time). Two electric hot water heaters. Three heat pumps/AC units. Electric aux heat for the winter (~25kW total!). Electric range/oven. Electric clothes dryer. Plus everything else you would find in a house (TVs, video games, cable boxes, phone chargers, etc etc etc.)

I'm sure your power consumption is well above an average house in US. This is less important since you can use as much as you want and you just need to pay for that.
I do not understand why will you want to go offgrid ? What is the benefit ? It's probably much more expensive than grid power at your location not including your work just the equipment.
It look like you are having fun with this installation so that may be a plus you do not need to include the work in the cost amortization.

 

[wk057]

I chose an off-grid setup because I think the existing concepts for grid-tied solar are flawed. Net metering in particular is not going to last. Eventually utilities are going to need to get income from people who are essentially using them as a free infinite battery, and I think that day will be sooner rather than later. When you can no longer use the grid as a battery for free your ROI time will be infinitely longer on a grid tie setup.

With my setup, electricity could go up to $100/kWh and... well, I wouldn't care (exaggerated, bu electricity isn't going to get cheaper). Net metering could switch to a different setup where sold capacity is paid at 30% of retail instead of 100% like it is now..... and I won't be affected (utilities aren't stupid). When the grid goes down.... I won't be affected. In a zombie apocalypse I'll still have power (until the zombies muck up my panels...).

 

[electrodacus]

I chose an off-grid setup because I think the existing concepts for grid-tied solar are flawed. Net metering in particular is not going to last. Eventually utilities are going to need to get income from people who are essentially using them as a free infinite battery, and I think that day will be sooner rather than later. When you can no longer use the grid as a battery for free your ROI time will be infinitely longer on a grid tie setup.
With my setup, electricity could go up to $100/kWh and... well, I wouldn't care (exaggerated, bu electricity isn't going to get cheaper). Net metering could switch to a different setup where sold capacity is paid at 30% of retail instead of 100% like it is now..... and I won't be affected (utilities aren't stupid). When the grid goes down.... I won't be affected. In a zombie apocalypse I'll still have power (until the zombies muck up my panels...).

I possible that utilities will not always pay the same for what you sell but even at 30% is good and you will still recover the investment. The PV panels last easy 25 years and if you use that as amortization period the cost will be 3 cent/kWh considering you paid 1$/Wh for them.
But most of what they produce will be used directly by the house and just a small portion you will sell at say 30% so ROI time will be quite good.
Electricity is usually quite inexpensive across North America but I do not expect to get more expensive in the future. Solar will probably drop even more the price of electricity. And energy storage will also improve quite a bit in the near future.
Of course your cost will not be $100/kWh but will probably be about 2x to 3x more expensive than your grid energy maybe around 25 to 40cent/kWh depending on how much you spend on the rest of the equipment.
In any case is a way better option than Lead Acid batteries by far. I was just saying that LiFePO4 are better (more cost effective) for this sort of application and much safer in case something goes wrong with the BMS.

 

[oneday]

What is your charge rate from the grid, basically from say 20% how long will it take for you to get all your modules back to 80%?

Do you have time of day rates from your utility? It seems like you could probably get considerable savings just using the batteries during peak and charge during off peak. this would, however, be a manual procces?

 

[wk057]

What is your charge rate from the grid, basically from say 20% how long will it take for you to get all your modules back to 80%?

Do you have time of day rates from your utility? It seems like you could probably get considerable savings just using the batteries during peak and charge during off peak. this would, however, be a manual procces?

No ToU rates here, unfortunately. Could easily automate that process though if I did have ToU.

For grid charging, I can charge at up to 64kW with my inverters. So, 20 to 80% would take less than 2 hours.

 

[ItsNotAboutTheMoney]

Actually, it's position was determined by that door.

The door is still able to open about 100 degrees.

I was thinking more about smacking it with stuff you bring through the door. But, duh, hinges. :redface:

 

[oneday]

Too bad this isn't in Ca, with ToU here the savings is an aggregate of .02 - .19 per kWh. Assuming an average of .05 per kWh and a 36mw annual use that's $1800 per year. I would think ToU plans would be good for everybody, I would have thought all utilities would offer this.

What's your max and/or your expected charge rate once your solar system is fully operational.

And once your solar is fully operational I am so envious of the days when you'll be able to use your creativity to deal with "excess" electricity, muah!

 

[wk057]

Too bad this isn't in Ca, with ToU here the savings is an aggregate of .02 - .19 per kWh. Assuming an average of .05 per kWh and a 36mw annual use that's $1800 per year. I would think ToU plans would be good for everybody, I would have thought all utilities would offer this.

What's your max and/or your expected charge rate once your solar system is fully operational.

And once your solar is fully operational I am so envious of the days when you'll be able to use your creativity to deal with "excess" electricity, muah!

Max solar charge rate will be ~45kW (under 1/4C), or about 1,100 amps DC at low states of charge. In the spring, summer, and fall I expect to have an energy surplus of up to a bit over double my expected usage... so definitely going to need to get creative.