Help with small / Emergency system

[jb1331]

Hi,

I am piecing together a small "emergency" backup system, and intend on doing so with minimal expense. Today, I picked up 6 Used REC260PE Z-LINK 260 watt panels for $400 for ~ 1,500 watts of input. I bought used also because I live in Texas, and we are very prone to large hail storms which results in getting a new roof every 8-10 years paid for by insurance, so there is a strong chance I will be replacing panels as needed before 10 years . Yes, I do plan on racking these on the rear roof of my house facing South. All of the panels I purchased test good, and are in great cosmetic condition, and these used panels are making the rounds on the web having favorable reviews and produce on average 98% of their original rated power.. All came from a large Military installation and about 5 years old.

SPECIFICATIONS:
REC PEAK ENERGY Z-LINK SERIES
REC260PE Z-LINK
PEAK POWER: 260 W
RATED VOLTAGE: 30.7 V
RATED CURRENT: 8.50 A
OPEN CIRCUIT VOLATGE: 37.8 V
SHORT CIRCUIT CURRENT: 9.01 A
MAX SYSTEM VOLTAGE 600 V
MAX SERIES FISE 15 A
FIRE RATING: CLASS C
TYPE: POLYCRYSTALLINE SILLICON

DIMENSIONS: 65.55" X 39.02" X 1.5"
WEIGHT: 40 LBS

For inverter, MPT, and charge controller, LifePo4 .. I am simply thinking about picking up an EcoFlow Delta Pro (as an all in one), that I can keep inside in a climate controlled environment when not in use, and roll it out when needed. https://us.ecoflow.com/products/delta-pro-portable-power-station

EcoFlow Delta Pro Solar charge specifications:

Solar Charging Input​

1600W Max, 11-150V, 15A DC

Given the panels I purchased, and attempting to maximize Solar charge, what panel arrangement should I consider? No need for inverters as charge input is DC... Just need a little help with my math to stay under charge spec

2 in series x2 then parallel the 2 groups? 36v X 2 = ~ 72 volts, 1040 watts max, but what about amps?

3 in series would be safe... but kinda underpowered..


Thinking about other options too (not all in one).. I do not care for trying to sell power back (non grid tie), I just want power available at all times with battery (could go with something like an EG4 unit or 2), but those would end up in my garage which can get to be 100 degrees in the summer.

Any suggestions are appreciated..

Thanks!

 

[gnoeld]

Parallel and series combined makes sense unless you are going to have partial shade on any of the panels.
In a series any shade on any part of the panel reduces the power in all the panels. In a parallel set up the shade only impacts the panel it is on.
You probably already knew that.
In a series the amps stay the same but the voltage goes up
In Parallel the amps go up but the voltage stays the same.
How many amps from each panel 8?
Do you need max voltage or max amps? I am assuming that 10 and 20 amps would be perfect for charging.
Just my opinion but am interested in other thoughts

 

[jb1331]

No shade, full sun..

EcoFlow Delta Pro solar charging: 1600W Max, 11-150V, 15A DC

Each panel (max): 37.5 volts, 260 watts, 8.5 amps

so theoretically:

2 in series (max) = 75v, 520 watts, 8.5 amps

2 sets in series (parallel set of 2 / 4 panels --max): 150v, 1040 watts, 17 amps.... Volts: at the limit, Amps: over the limit.. 1,040 watts

3 in series (max) = 112v, 780 watts, 8.5 amps

4 in series (max) = 150v, 1040 watts, 8.5 amps (Volts are at the limit of the EcoFlow Delta Pro)... not sure how forgiving it is at limit.

6 in series (max) = 225v, 1,540 watts, 8.5 amps).. definitely over the capability of the EcoFlow Delta Pro


Really would like to be able to utilize all 6 panels (1,540 watts), so maybe I should consider alternatives...

 

[Wet1]

No shade, full sun..

EcoFlow Delta Pro solar charging: 1600W Max, 11-150V, 15A DC

Each panel (max): 37.5 volts, 260 watts, 8.5 amps

so theoretically:

2 in series (max) = 75v, 520 watts, 8.5 amps

2 sets in series (parallel set of 2 / 4 panels --max): 150v, 1040 watts, 17 amps.... Volts: at the limit, Amps: over the limit.. 1,040 watts

3 in series (max) = 112v, 780 watts, 8.5 amps

4 in series (max) = 150v, 1040 watts, 8.5 amps (Volts are at the limit of the EcoFlow Delta Pro)... not sure how forgiving it is at limit.

6 in series (max) = 225v, 1,540 watts, 8.5 amps).. definitely over the capability of the EcoFlow Delta Pro


Really would like to be able to utilize all 6 panels (1,540 watts), so maybe I should consider alternatives...

4s @ 150V is right at max, but once adjusted for temp you're likely over max V... which could likely smoke that expensive Delta Pro.

 

[MisterSandals]

Really would like to be able to utilize all 6 panels (1,540 watts), so maybe I should consider alternatives...

3S2P is the clear winner.

 

[jb1331]

I am starting to think bigger (and doing the math).. if I was doing whole house with these panels, I use about 12-13kWh a year. Even though we are currently paying only .11 a kW for pole power about $1,600 a year (for now, expected to rise in the coming years).... intermingle some DIY with a professional installer...

per: https://unboundsolar.com/blog/how-many-solar-panels-do-i-need

Daily Usage (kWh) ÷ Sun-Hours ÷ 0.9 inefficiency factor = Minimum Solar Array Output

Daily usage: 13,000 / 365 = 35.6 kWh a day.

Sun Hours per day in my area: 5.4 (per https://www.turbinegenerator.org/solar/texas/)

35.6 / 5.4 = 6.59 / .9 = 7.328 (minimum solar array output) = 7,328 Watt capacity system

7328 / 260W = 28 panels.

28 * $65 = $1,820 + .0825 tax = $1970.15 (in panels)

Let's say, I opt out on string inverters (for now... cost / benefit).. This is my first attempt at simple design / doing the math, so if I am wrong, feel free to correct me.


28 panel system:

2 sets of 7 (in series) parallel /14 panels on each phase): 530vDC, 3600 watts 17 amps (per phase) 7S2P per phase

Or

24 panel system:

2 sets of 6 (in series) parallel /12 panels on each phase): 450vDC, 3080 watts 17 amps (per phase) or 6S2P per phase


Then of course, I would need 2 inverters (one for each phase) to handle the load, and of course I would want all in one if available (MPPT, Charge Controller, etc).. I can add in battery later. Anyone have recommendations?

Theoretically, if I could pull this off (part DIY with installer) turn key for say ~ $10-12k (without battery for now) and the tax incentive, the payoff in 6 years at current electric rates is starting to look appealing.. The door to door guys are trying to sell $30k installs lol. Thoughts?

 

[Bluedog225]

Grid tied with no battery is one way to go. Little or no use during emergency.

Grid tied with battery backup and off grid with battery and you have something for emergency use.

Grid tied has pros and cons. Selling back to the grid over 20 years can add up and changes the equation substantially. But more involved.

 

[Wet1]

I am starting to think bigger (and doing the math).. if I was doing whole house with these panels, I use about 12-13kWh a year. Even though we are currently paying only .11 a kW for pole power about $1,600 a year (for now, expected to rise in the coming years).... intermingle some DIY with a professional installer...

per: https://unboundsolar.com/blog/how-many-solar-panels-do-i-need

Daily Usage (kWh) ÷ Sun-Hours ÷ 0.9 inefficiency factor = Minimum Solar Array Output

Daily usage: 13,000 / 365 = 35.6 kWh a day.

Sun Hours per day in my area: 5.4 (per https://www.turbinegenerator.org/solar/texas/)

35.6 / 5.4 = 6.59 / .9 = 7.328 (minimum solar array output) = 7,328 Watt capacity system

7328 / 260W = 28 panels.

28 * $65 = $1,820 + .0825 tax = $1970.15 (in panels)

Let's say, I opt out on string inverters (for now... cost / benefit).. This is my first attempt at simple design / doing the math, so if I am wrong, feel free to correct me.


28 panel system:

2 sets of 7 (in series) parallel /14 panels on each phase): 530vDC, 3600 watts 17 amps (per phase) 7S2P per phase

Or

24 panel system:

2 sets of 6 (in series) parallel /12 panels on each phase): 450vDC, 3080 watts 17 amps (per phase) or 6S2P per phase


Then of course, I would need 2 inverters (one for each phase) to handle the load, and of course I would want all in one if available (MPPT, Charge Controller, etc).. I can add in battery later. Anyone have recommendations?

Theoretically, if I could pull this off (part DIY with installer) turn key for say ~ $10-12k (without battery for now) and the tax incentive, the payoff in 6 years at current electric rates is starting to look appealing.. The door to door guys are trying to sell $30k installs lol. Thoughts?

Without batteries you'll only be able to use that solar power for "x" hours per day. So if you're sizing for your total yearly use, you'll have a ton of excess power during those "x" hours and no way to store that energy and still be relying on grid for the (majority of the) remainder of the day/night... That is, unless you have a favorable local net metering program available to you to "bank' the power. Most NM programs now only pay you a small fraction for your power compared to what you pay them for their power at the pole.

Also, you might have a hard time finding AIO systems that will handle 530V DC input, and don't forget to adjust that number for min temp (it will be higher). Even that 450V proposed system when adjusted for min temp might really limit you inverter choices.

 

[jb1331]

Without batteries you'll only be able to use that solar power for "x" hours per day. So if you're sizing for your total yearly use, you'll have a ton of excess power during those "x" hours and no way to store that energy and still be relying on grid for the (majority of the) remainder of the day/night... That is, unless you have a favorable local net metering program available to you to "bank' the power. Most NM programs now only pay you a small fraction for your power compared to what you pay them for their power at the pole.

Also, you might have a hard time finding AIO systems that will handle 530V DC input, and don't forget to adjust that number for min temp (it will be higher). Even that 450V proposed system when adjusted for min temp might really limit you inverter choices.

Great points.. this really takes me back to my original thoughts of "some solar" with battery.. let me think through some more configurations .. I do want to keep the DC volts lower, not bother with micro inverters, or net metering... Thanks!

 

[Wet1]

Great points.. this really takes me back to my original thoughts of "some solar" with battery.. let me think through some more configurations .. I do want to keep the DC volts lower, not bother with micro inverters, or net metering... Thanks!

If you're willing to DIY, you might want to consider something like the panels you proposed, the Megarevo 8k inverter (handles up to 500V DC &12A MPPT x4, plus has CT's to limit GT exporting), and build your own battery. You can build a ~14kWh battery for under $2500, with the inverter, you're looking at around $5k. Add whatever you want for panels, racking, wiring, breakers, etc and you'd have a nice system for under $10k that would cover most of your current daily usage. Just a thought.

 

[gnoeld]

Here is a general question,
What is better for a solar battery system off the grid
A) 600 watts with 8 amps (2) 300 watt panels in series
B) 300 watts and 16 amps (2) 300 watt panels in parallel

 

[Wet1]

Here is a general question,
What is better for a solar battery system off the grid
A) 600 watts with 8 amps (2) 300 watt panels in series
B) 300 watts and 16 amps (2) 300 watt panels in parallel

Two of the same 300W panels connected either way is going to give you 600W regardless. Which way they are connected is typically dictated by the specs on your supporting equipment and possibly your installation requirements, so there is no right answer.

 

[timselectric]

A) is more efficient, if your system supports the VOC in cold weather.
B) is also 600w, as stated by wet1.
Series, add up the voltage.
Parallel, add up the amperage.
Watts is Watts, either way.

 

[jb1331]

So as I have been kicking this around more, and after seeing Will's excellent video here:

..

I am planning on going this route, but could use some guidance / validation of my assumptions:

1.) 1 Growatt SPF 3000TL LVM-ES 3kW: https://watts247.com/product/spf-3000tl-lvm-es/ .. Can I tie this into my existing panel for additional input power to the inverter in addition to solar? (I will not output to my existing panel for grid tie, and will install a new panel with breakers to cover a couple of areas in my home that I will output from the Growatt). Not going to worry about dual phase as only my 5 ton AC uses it, and i have other options for emergency cooling for a room or two..

2.) Start with 1 EG-4 48v / 100 Ah (5kWh).. May add in 2nd parallel for 10kWh: https://signaturesolar.com/eg4-lifepower4-lithium-battery-48v-100ah/

3.) I currently have 6 260watt panels as noted for a total of 1,560 watts of solar input. Per this link: https://www.solarchargecontrollercalculator.com/ , going straight series with the panels will exceed the input voltage of the Growatt SPF 3000 (80A MPPT Charge Controller (up to 4.5kW of Solar ) at panel voltages between 120Vmp to 250V open circuit), so I will need to config another arrangement (working through the math, see below)..



4.) Per these calculations (https://altenergyoptions.com/how-many-solar-panels-does-it-take-to-charge-a-100ah-battery/) for battery charge rate, I am estimating ~ 4 hours to fully charge

6 x 260w panel = 1,248 watts effective charge rate accounting for conversion loss.

a single 48v 100Ah battery needs 4,800 watt hours to charge fully: 3.84 hours

If I want 10kWh of battery, it would take effectively 8 hours of optimal solar to charge with 6 panels, so I probably should consider adding in additional panels... a 12 panel config would probably exceed max amps of the Growatt SPF 3000TL LVM-ES 3kW (80 amps / 250v input), and 12 of these panels would be 81.2 max amps.. so in order to NOT overload input tolerances, I will limit the number of max panels with the Growatt to 10 panels to stay under max volts / amps..

with the 10 panel config below (2,600 watts input), TWO 48v 100Ah batteries in parallel will need 9,600 watt hours to charge fully: 4.61 hours (which ties closely to average sun hours in my area @ 4.5), and I will not exceed the input tolerances of the Growatt SPF 3000TL LVM-ES 3kW