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RegGuheert
Posts: 5421
Joined: Mon Mar 19, 2012 4:12 am
Delivery Date: 16 Mar 2012
Leaf Number: 5926
Location: Northern VA

Re: Tesla Powerwall

Sun Nov 13, 2016 4:15 pm

arnis wrote:The worst thing to run on Powerwall is heating system.
+1
arnis wrote:OK maybe heat pump, but it is very rare in US I believe.
Not rare in the US, but certainly rare in MN. But even a heat pump uses a LOT of electricity. The big issue with the heat pump that we have here in VA is that we often do not need heat when the sun is out, only when it is dark.
Zythryn wrote:Well, my heating system is a geothermal pump ;)
It is quite efficient, we have been designing this with efficiency in mind, both for its own sake and for backup power purposes.
That can be workable, but it still uses a massive amount of electricity. The smallest ones still consume over 5 kW but since you live in MN, it is likely higher. On cold days, you probably need to run that load about 24 hours per day.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

Zythryn
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Joined: Fri Jun 04, 2010 4:49 am

Re: Tesla Powerwall

Sun Nov 13, 2016 5:35 pm

RegGuheert wrote:
arnis wrote:The worst thing to run on Powerwall is heating system.
+1
arnis wrote:OK maybe heat pump, but it is very rare in US I believe.
Not rare in the US, but certainly rare in MN. But even a heat pump uses a LOT of electricity. The big issue with the heat pump that we have here in VA is that we often do not need heat when the sun is out, only when it is dark.
Zythryn wrote:Well, my heating system is a geothermal pump ;)
It is quite efficient, we have been designing this with efficiency in mind, both for its own sake and for backup power purposes.
That can be workable, but it still uses a massive amount of electricity. The smallest ones still consume over 5 kW but since you live in MN, it is likely higher. On cold days, you probably need to run that load about 24 hours per day.


I'll let you know after we get into the colder season. 8-)
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Current owner of Model S
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BrockWI
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Leaf Number: 423875
Location: Green Bay, WI.
Contact: Website

Re: Tesla Powerwall

Sun Nov 13, 2016 5:45 pm

Geothermal heat pumps are not uncommon up here. We have a 4 ton heat pump with a 6 ton horizontal field which they over-sized becasue they thought we might need a 6 ton, which we don't. If our current heat pump ever goes out, I am getting a variable unit (or at least 2 stage), I would love to be able to use the 3kw of solar we have to run it, we can now, but running it pulls 4.5 kw and our inverter (XW6048) can only start it if nothing else is on, but most of the time we are grid tied so the grid picks up the starting surge. We do have natural gas as backup instead of resistance heat, and I watch the cost of natural gas vs off peak electricity taking in to account the COP (varies depending on field temp) and run which ever is less expensive, which right now is natural gas, but had primarily been geothermal in the past.

So for us when the power is out we use the natural gas instead of geothermal.

Back on topic, I like the compact size of the Powerwall 2 and the simplicity of it compared to our system. However I can power our house from, solar PV, the grid, one of two backup gensets, an idling vehicle or the Leaf :)
3 kw solar pv - XW6048 - 8 L16's
4 ton GSHP
2003 VW TDI 170k miles - 52 mpg lifetime
evse level 2 - Clipper Creek HSC-40
2013 S model with QC package Mar of 2013

arnis
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Re: Tesla Powerwall

Mon Nov 14, 2016 4:01 am

Geothermal stuff is awesome. BUT. What the heck.
Expensive machine is on/off type ?? :o :(

Whenever possible I would recommend inverter type heat pumps.
Like Nissan Leaf has - infinitely variable speed 100W to at least 2250W
(anybody knows the AC compressor electric motor power Leaf has?)


4.5kW input power makes at least 12kW of heat. Holy cow.
This pump should be off most of the time for average house :|
I live in a small-medium sized house (100m2), and at -15*C it needs 4kW of heat.
My inverter type split air-air heat pump can produce 3.5kW of heat with
1kW of electricity. And can handle the whole house down to -5*C.
Let's talk about insulation :lol: (nooot, way to awesome topic)


Inverter type heat pumps will level out once temperature has been reached.
For example 1500W of constant draw at xx outside temperature (and no hot water
used). It is possible to stop drawing power during peak electricity prices but that
needs large enough water buffer to keep house warm during that period.

This constantly slowly running compressor should last at least two decades
due to almost no cold starts. Also more efficient compared to on/off.

Interesting. Is Powerwall capable running in parallel with small gas generator.
Short range EVs <30kWh -- Medium range: 30-60kWh -- Long range: >60kWh
Charging: Trickle <3kW -- Normal 3-22kW -- Fast 50-100kW -- Supercharging >100kW

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RegGuheert
Posts: 5421
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Location: Northern VA

Re: Tesla Powerwall

Mon Nov 14, 2016 4:58 am

BrockWI wrote:However I can power our house from, solar PV, the grid, one of two backup gensets, an idling vehicle or the Leaf :)
To me, this is the key thing to have in place. I have a similar array of options for our home:

Heat:
- Air-source heat pump: Strictly grid-tied. I do not even have this set up to run from the generator.
- Wood pellet stove: We used to heat the entire house for the winter with this unit, but the price of pellets has doubled and we now have net-metered photovoltaic electricity that cover our heat pump's consumption. The fans and auger only consume about 120W of electricity when operating.

Cooking:
- Everything is electric except we have a propane cooktop (and a propane oven which draws about 300W for its igniter).

Water:
- We have a well pumped by a 1/2 HP submersible. The pump is 240VAC, but I added an autotransformer after the pressure switch to allow it to be run from 120VAC if needed. It has a high starting surge, but only draws about 1000VA when operating.

Hot Water:
- We have a heat-pump water heater that only draws 600W when running. It is also 240VAC, but I do not have it set up to run from 120VAC through an autotransformer since we sometimes (but rarely) use the 4.5kW resistive heaters. I have a couple of autotransformers kicking around here, so I certainly could wire it for 120V if needed.

Dryer:
- We have BOTH a propane dryer AND an electric dryer. We used to use propane when the house was off-grid, but I switched it for an electric unit when we decided to move to a grid-tied arrangement. The propane unit could be switched in if needed for emergencies (or we could simply hang the clothes to dry).

Electricity:
- Our house is powered by grid electricity with just over 100% of our consumption offset by net-metered, grid-tied PV.
- We have a 6500VA Honda generator which is connected to run everything except our heat pump and our electric double oven. It can simultaneously run the wood pellet stove, the well pump, the water heater and charge the LEAF.
- We have 800Ah (nameplate) of 12V AGM batteries. I got them for free because they were badly sulfated down to only 200Ah of capacity. My little BatteryMinder 1500 is dutifully pounding away on them to try to recover their capacity. Last time I tested them, they were up to 300Ah! Since there's no hurry, I just let that thing continue to do its work of recovering capacity.
- To go with the 12V batteries, we have a 2000VA Outback inverter that puts out 120VAC. This should be able to run any of the loads which the generator is connected to, although I have not tested it with the surges of the well pump or water heater yet. The most important load for these batteries is the pellet stove, which it should be able to run for a day with the current capacity of the batteries or three days if they ever get fully desulfated.
- In a pinch, I could rewire one or more PV panels to charge the 12V batteries.
- Then there is the LEAF. I have a couple of 120VAC inverters which work with it. Since there is a fridge and deep freeze in the garage, those are its primary loads, but I have used it to run the pellet stove in the past, since it is easy to set up.

Overall, we are set up to provide the essentials and more in case of an emergency.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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keydiver
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Re: Tesla Powerwall

Mon Nov 14, 2016 9:10 pm

I just got an invitation to a "Tesla Social" down in Boca Raton on Sunday. I've never gone to one before, but this time: " This month we are giving you an inside look into our newly launched Powerwall 2, Tesla’s next generation home battery solution."

So, hopefully I will get more detailed info on what the Powerwall can and can't do, as so far there have been few, if any, details. I was planning on adding some solar to the guest house that I built here for my parents, and if the Powerwall 2 can do everything an SMA inverter can do, plus add battery backup, I'm going for it. :D
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RegGuheert
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Re: Tesla Powerwall

Tue Nov 15, 2016 4:48 am

keydiver wrote:So, hopefully I will get more detailed info on what the Powerwall can and can't do, as so far there have been few, if any, details.
Thanks! If any of the covers are off, could you please snap pictures of what is hidden behind them? TIA!
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

BrockWI
Posts: 510
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Location: Green Bay, WI.
Contact: Website

Re: Tesla Powerwall

Tue Nov 15, 2016 7:58 am

Correct me if I am wrong, but it sounds like the box is a grid tie inverter, downstream UPS with batteries and a solar charge controller with a solar input.

So grid in, solar in and backup / solar out. Can it back feed the grid or is it only downstream?
3 kw solar pv - XW6048 - 8 L16's
4 ton GSHP
2003 VW TDI 170k miles - 52 mpg lifetime
evse level 2 - Clipper Creek HSC-40
2013 S model with QC package Mar of 2013

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RegGuheert
Posts: 5421
Joined: Mon Mar 19, 2012 4:12 am
Delivery Date: 16 Mar 2012
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Location: Northern VA

Re: Tesla Powerwall

Tue Nov 15, 2016 11:02 am

BrockWI wrote:Correct me if I am wrong, but it sounds like the box is a grid tie inverter, downstream UPS with batteries and a solar charge controller with a solar input.

So grid in, solar in and backup / solar out. Can it back feed the grid or is it only downstream?
From Tesla's website:
Tesla wrote:Supported Applications
- Solar self-consumption
- Time of use load shifting
- Backup
- Off grid
Given this, the inverter should be both grid-tied AND autonomous. I seriously doubt that it would contain a solar charge controller and I doubt that it contains a transfer switch since that would seem to be a function which would not be required in every unit if they were paralleled.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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