Still trying to understand how this is working. I'm imagining a transfer switch on the grid side, either the power goes to your house or to the batteries or is off. When your solar is charging can the grid still be connected to the battery?
-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
Plan: Off grid solar with a Model S battery pack at the heart
- Thread starter wk057
- Start date
-
- Tags
- Energy Environment Policy
Still trying to understand how this is working. I'm imagining a transfer switch on the grid side, either the power goes to your house or to the batteries or is off. When your solar is charging can the grid still be connected to the battery?
oneday said:
I've read the most of the manual for the Outback Radian. It's a remarkable piece of equipment for less than $5,000. There are actually two AC inputs. One is grid interactive and the other is basically a programmable battery charger. The Grid Interactive AC connection allows you to automatically sell power back into the grid based on several parameters. The most obvious use would be to let your solar charge the batteries and then, once full, sell the surplus into the grid, roughly maintaining the battery level. With Lead Acid batteries, you would hold the "Float Voltage" on the battery pack. The other AC input is referred to as a generator input, but it's really a programmable battery charger and can be connected to any AC source. Generators are generally quite noisy (electrically and sonically) and by having this input go straight into the battery and the inverters supplying power to the the load, you effectively clean up the power so that computers and other sensitive equipment (like a Tesla vehicle) can reliably use the generator power. Of course, if you're actually using a fossil powered generator some may think you're "doing it wrong". IMHO, if there's no grid power for two weeks during a winter storm, you do what you have to do.
Anyway, to answer your questions - "whole house UPS mode" can be configured in different ways. One way would be to set the Radian to maintain a nominally full battery at all times unless the grid power is lost. This is a traditional uninterruptible mode that cycles the batteries very little. You could also program the Radian through the communication interface to take advantage of time of use electric rates and not draw anything from the grid during peak hours and charge at off-peak hours. This would obviously cycle the batteries a lot more.
My understanding is that the solar goes straight to the batteries through the charge controllers and is not controlled by the Radian inverter at all. If you have solar, then you probably don't want to use the grid (or a fossil generator) to charge the battery unless and until the battery reaches some pre-defined low state of charge. This is all programmable, so I don't think this requires any external hardware like a transfer switch to accomplish.
Adrian
Title(D)
Interesting tidbit regarding fossil powered generators. Formula E uses a Glycerine-powered generator to charge the cars batteries: I Drank The Fuel That Powers Formula E
So, been busy with stuff unrelated to this project. 
Anyway, getting good data on how viable my setup would be without any changes to loads.
Since I have six panels setup for testing, I can multiply their output by 17 to get a low estimate of what my full setup would have produced. Using that data and my load data I calculated out that near sunset on the 12th the battery bank would be pretty much full.
Continuing on, the 13th, 14th, 15th, and today (16th) have been completely crappy weather days. Yesterday was the worst yet, with peak power output of only about 7.5% of rated. When I say it like that it sounds bad, but when I consider that this day was full of pretty heavy thunderstorms... it's not too bad.
Anyway, using this data and no changes to any loads or habits, since sunset on the 12th I would still be running right now. Without any changes to habits I estimate I would run out of battery power sometime this evening, though... and need a boost from the grid.
However, all is not lost. Part of the load in this time period was 67kWh worth of Model S charging between my two Model S. A side project is some HPWC hacking that will adjust charging based on solar input and stationary bank charge level. In this scenario I likely would not have charged either Model S yet, and both would be somewhere around or above 50% SoC still. Charging would wait until either I override because I need the charge or until the stationary battery bank was sufficiently recharged (75-80% maybe). This way the cars will just get topped off on the next sunny day. On an average spring day it looks like the battery bank could be recharged from dead to full by around noon... then excess power still goes to loads, which would be perfect for Model S charging. Could charge any time at a minor efficiency loss due to needing to store the power first, but charging from solar->inverters is a hair more efficient than solar->batteries->inverters, so that will be preferred.
Overall, I'm pretty stoked about getting this whole thing up and running.
Model S charging is the largest load on my system, with both HPWCs running being 40kW draw. In full sun that'd still leave ~5kW for other loads or stationary bank charging. So, some smart handling of that load will go a long way I think.
Anyway, getting good data on how viable my setup would be without any changes to loads.
Since I have six panels setup for testing, I can multiply their output by 17 to get a low estimate of what my full setup would have produced. Using that data and my load data I calculated out that near sunset on the 12th the battery bank would be pretty much full.
Continuing on, the 13th, 14th, 15th, and today (16th) have been completely crappy weather days. Yesterday was the worst yet, with peak power output of only about 7.5% of rated. When I say it like that it sounds bad, but when I consider that this day was full of pretty heavy thunderstorms... it's not too bad.
Anyway, using this data and no changes to any loads or habits, since sunset on the 12th I would still be running right now. Without any changes to habits I estimate I would run out of battery power sometime this evening, though... and need a boost from the grid.
However, all is not lost. Part of the load in this time period was 67kWh worth of Model S charging between my two Model S. A side project is some HPWC hacking that will adjust charging based on solar input and stationary bank charge level. In this scenario I likely would not have charged either Model S yet, and both would be somewhere around or above 50% SoC still. Charging would wait until either I override because I need the charge or until the stationary battery bank was sufficiently recharged (75-80% maybe). This way the cars will just get topped off on the next sunny day. On an average spring day it looks like the battery bank could be recharged from dead to full by around noon... then excess power still goes to loads, which would be perfect for Model S charging. Could charge any time at a minor efficiency loss due to needing to store the power first, but charging from solar->inverters is a hair more efficient than solar->batteries->inverters, so that will be preferred.
Overall, I'm pretty stoked about getting this whole thing up and running.
Model S charging is the largest load on my system, with both HPWCs running being 40kW draw. In full sun that'd still leave ~5kW for other loads or stationary bank charging.
So, some smart handling of that load will go a long way I think.
TheTalkingMule
Distributed Energy Enthusiast
So with minimal conservation changes when the weather is extraordinarily uncooperative you're basically off grid 99% of the time. How do you think you'll fare in the dead of winter?
This is amazing. Imagine what a similar off the shelf system will look like in 10-15 years.
This is amazing. Imagine what a similar off the shelf system will look like in 10-15 years.
As things with my HVAC system stand... probably not well. I need to replace my electric resistive aux heat with something more efficient. My HVAC system needs an overhaul anyway (one of the zones is overworked and equipment undersized for the area).
Also, upgrading to a heat pump hot water heater. Might do geothermal heat pump for winter heating eventually too.
I think this coming winter I'll probably end up tapping the grid for heat a few times if I don't stay on track with efficiency updates. Other than that, I expect to have plenty of power overall in the winter as well.
I'm considering a propane backup generator also... something like 10kW maybe, just to recharge the battery bank in a grid outage and extended crappy weather situation. This is probably a couple of years away though.
Would you say you gain about 10% by charging cars straight from solar as opposed to going through stationary storage? If so, that's definitely double digit kWh saved per week, obviously dependent on a lot of factors, but still.
Have you thought about using all three phase pumps and compressors for heating cooling and pool pump?
Have you thought about using all three phase pumps and compressors for heating cooling and pool pump?
Actually, it's closer to 1-2% if my calculations are right. The batteries don't seem to lose hardly any input power.
Switching to three phase would be a huge task for minimal benefit I'd think. My compressors all appear to already be power factor corrected, so, little loss there.
mitch672
Active Member
not to mention that three phase power is generally considered a commercial service, and generally not availble to residential customers. even if the poles carrying all three phases pass by your home, it would be unheard of to get 3 phase power in a home (if your neighborhood has underground service, you'd need to install a pad mount transformer as well)
Depending on how cold it gets, system sizing and efficiency, often one can get away with disabling the aux-heat on many heat-pump setups which saves a ton of power.
Yeah, I tried that. Unfortunately this just made the heat pumps run continuously with little to no overall heat gain when the temps got into the 30sF or lower. I have Nest set to not use aux heat above 38F.
My HVAC system needs an overhaul, though. The previous owners finished the basement space. When that work was done they just cut new vents and a return into the existing duct work for the first floor system for the basement, basically doubling the square footage the first floor system has to handle. The first floor HVAC equipment wasn't upgraded to handle this added space.
So, I'll likely install another heat pump HVAC system (fourth!) for the basement and seal off the cut-ins they made from the first floor system. This way every floor has it's own heat pump/AC appropriately sized for the area. (Basement, first floor, second floor, loft/bonus room.)
I'm looking into some insulation upgrades, too, in hopes of holding some more heat in the winter.... but not so much as to make the AC work harder in the summer.
nwdiver
Well-Known Member
llavalle
Member
Fujitsu makes great unit too. I have a 15RLS2 Low temp at home.
Wall Mounted 9 - 15,000 BTU Hi SEER - Fujitsu Ductless Mini-Splits
During our last, very cold winter, It only stopped working 2 or 3 days. It's also very quiet (variable speed compressor).
+1
The manual on the Radian is a good read. While evaluating the configuration of what is now our system (which includes the Radian), I read that cover to cover. I didn't retain it all (and I'll be reading it again).
llavalle
Member
I have around 980 sq ft and the 15 000 btu was enough to heat it all at around 72F with an outside temp of around -15F.
But keep in mind that houses here are very well insulated - outside walls are made with 2x6 and all windows use thermal glass.
The only downside is that since I wanted my bedroom at around 70F, I had to set the heat to 76F so it was a bit hotter in my living room (split air is in living room and my bedroom is at the opposite side of my house) - my grilfriend seemed to enjoy that
Tedkidd
Member
Home performance is my profession. I routinely help people cut consumption 20-50%. Google my name.
Turning 900 square feet of unintentionally conditioned basement into conditioned basement isn't likely to impact load significantly. And usually equipment is grossly oversized (both to house, and ducts) because 1: It increases the HVAC guys profit, and 2: he views it as the path to overcoming enclosure deficiencies caused by crappy building practices, in which case MORE equipment is not the energy efficient answer.
First step to fixing comfort and energy problems is an audit including measuring leakage with a blower door, and duct blaster (particularly not you have ductwork "outdoors"). From there, good modeling will help prioritize opportunities and settle on work scope.
It would be fun to contribute/participate in this project. Feel free to connect. We can chat about this and maybe find someone qualified in your area to do this work.
Turning 900 square feet of unintentionally conditioned basement into conditioned basement isn't likely to impact load significantly. And usually equipment is grossly oversized (both to house, and ducts) because 1: It increases the HVAC guys profit, and 2: he views it as the path to overcoming enclosure deficiencies caused by crappy building practices, in which case MORE equipment is not the energy efficient answer.
First step to fixing comfort and energy problems is an audit including measuring leakage with a blower door, and duct blaster (particularly not you have ductwork "outdoors"). From there, good modeling will help prioritize opportunities and settle on work scope.
It would be fun to contribute/participate in this project. Feel free to connect. We can chat about this and maybe find someone qualified in your area to do this work.
