Solar Power with Grid Backup
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Hedges
I See Electromagnetic Fields!
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What Snoobler posted above.
No, actually this (and a couple more arrays like the one on the left.)
Hedges
I See Electromagnetic Fields!
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Yes, about 2x the PV that would be needed if gas heat used.
Also 2x the Sunny Island battery inverter needed. They only have 56A relay for pass-through from grid, and because I got them cheap enough I doubled up for 112A at 120/240V
If you got two Sunny Island (about $4000 for a pair on eBay) and a Sunny Boy (about $1700 for current model) that should power your house.
Because I replaced existing GT inverters I used older models (on the Sunny Island compatibility list at the time.) For a new permitted installation, you may be required to have "Rule 21" or other features of the new model. The latest Sunny Boy has since been added to compatibility list.
An alternative to two 6kW Sunny Island (or one with a 120/240V transformer) is 6 kW Sunny Boy Storage ($2500). It requires an (expensive) 400V battery, maybe DIY with compatible BMS is an option but haven't heard of someone doing that. For backup, requires "Automatic Backup Unit" which is 200A transfer switch and transformer that SMA offers. Looks like that is $2700
SMA 200A Automatic Backup Unit w/ Energy Meter (SKU Part Number SBS-ABU-200-US-10)
SMA 200A Automatic Backup Unit w/ Energy Meter (SKU Part Number SBS-ABU-200-US-10)
Sunny Boy Storage is designed to shift peaks, consumption/production around in time. It is anemic in surge capability.
Sunny Island is not designed for peak shifting. It has strong surge to start motors.
GXMnow
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My system is a little toy compared to that. Just 16 x 300 watt panels with Enphase iQ7 inverters, AC coupled on the output side of a Schneider XW-Pro inverter, with a 17 KWH bank of Chevy Bolt LG Li NMC cells making 360 amp hours at 48 volts nominal. Currently, I only have four 20 amp circuits on the backup panel that feed a few things when the grid is down. Grid failures here have been very rare. My circuits feed the gas furnace, refrigerator, gas stove igniter, microwave, 2 PC's and the networking gear, a TV and Dish Network system, and lights in the bathrooms, hallways and some living space. While on grid, the XW-Pro allows the Enphase to back feed through to feed power to the main panel and if it still makes more than that needs, export to grid. And the XW-Pro can also back feed from battery to the main panel and export to grid. Here is my arrays from a drone. Yeah, I could fit more panels, but this maxes out my 100 amp panel feed in. Flat garage roof may be getting DC panels to charge the battery bank.
Thought I had pics of the XW install, but they are not coming up. But it's not much to see compared to Hedges. Just the single XW, with the gateway next to it, a breaker panel under it, and my single cabinet of battery.
Thought I had pics of the XW install, but they are not coming up. But it's not much to see compared to Hedges. Just the single XW, with the gateway next to it, a breaker panel under it, and my single cabinet of battery.
Hedges
I See Electromagnetic Fields!
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Here's my idea for tilted pairs of panels.
The pairs should be spaced apart enough that they don't shade each other until angle of sun is at least 45 degrees past orthogonal to panel.
If pair has 90 degree angle to each other (45 degrees to roof) that distance would be infinity so a compromise.
90 degree angle gives peak power 0.7x what both flat would be. More flat would be closer to 1.0x
60 degree angle would have peak 0.5x or same as a single panel (I'm considering that for truck roof rack, single tilted pair rather than multiple which would shade each other)
In my area, panels under 18" high (and under 40# per mounting point) don't require structural permit.
That is enough height to allow a decent tilt. One low-profile rail and one high-profile could hold a column of panels on roof.
It won't give you more watts at any hour of the day than overpaneling with a completely covered roof. With panels sufficient to cover 50% of the roof, it might give a broad, lower peak that fits feed-in or battery charging limits. Also recharges battery sooner, keeps it full later.
The pairs should be spaced apart enough that they don't shade each other until angle of sun is at least 45 degrees past orthogonal to panel.
If pair has 90 degree angle to each other (45 degrees to roof) that distance would be infinity so a compromise.
90 degree angle gives peak power 0.7x what both flat would be. More flat would be closer to 1.0x
60 degree angle would have peak 0.5x or same as a single panel (I'm considering that for truck roof rack, single tilted pair rather than multiple which would shade each other)
In my area, panels under 18" high (and under 40# per mounting point) don't require structural permit.
That is enough height to allow a decent tilt. One low-profile rail and one high-profile could hold a column of panels on roof.
It won't give you more watts at any hour of the day than overpaneling with a completely covered roof. With panels sufficient to cover 50% of the roof, it might give a broad, lower peak that fits feed-in or battery charging limits. Also recharges battery sooner, keeps it full later.
GXMnow
Solar Wizard
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Looking at my roof, I could add another 4 panels to the lower roof array. In the space between the existing array and the upper level wall. If I lifted the right edge about 1 meter, at 2 meters of width, That would angle the 4 new panels about 30 degrees. This would not impact morning shading of the existing array at all. It would still be lower than the second story which casts a shadow there until 10 AM. Having panels flat on the roof there would not get much production until 10 am, due to that shadow on the second floor. But having them tilted up like that would greatly increase evening production. I could probably parallel those 4 new panels with the bottom row of the existing panels as they get late day shadows from my 2 remaining palm trees anyways. This could give a decent increase in late day production. But having them climb up to over 3 feet off the roof may draw attention.
pollenface
Solar Addict
I have grid backup using a 5amp 36v power supply connected to an epever pwm charger and triggered by the LVD/LVR parameters of one of my mppts using 2x relays set to power on @ 25.2v and power off at 27v. I put the relays on the mains-side of the power supply because I didn't want it sitting idle burning up juice.
My batteries are usually hovering around 25.4v before the sun comes up but for the odd occasion that I use a bit of extra power through the night it covers me.
My batteries are usually hovering around 25.4v before the sun comes up but for the odd occasion that I use a bit of extra power through the night it covers me.
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