diy solar

diy solar

should i consider pointing my panels a bit east and a bit west?

A

ahreno

New Member
Joined
Apr 17, 2024
Messages
36
Location
redwood valley
i'm about to draw out my system plans for permitting and had someone suggest facing one row east and one row west which threw me for a slight loop. I do like the idea of having more actual solar power later in the day. not sure about due east and west. maybe 15-20° off south? any thoughts?

My system:

26 408 watt panels with up to 142w bifacial gang
2 tesla powerwalls (one Powerwall 2, one powerwall +)
most likely 2 Growatt 7.6kW Grid-Tie inverters (not purchased yet)

Ground mount, 2 runs of 13 panels. shouldn't be any shading, pretty good view from East all the way to west

I'm in Norcal, PGE and will be on NEM3.0 which pretty much sucks from what i understand.

I dont know if it matters, but i think i was able to figure out my average hourly usage over the last 5 months (before that i was growing weed so the numbers are not relevant to use)

|0:00|1.43 kWh|
--:|--:|
|1:00|1.17 kWh|
|2:00|1.21 kWh|
|3:00|1.14 kWh|
|4:00|1.23 kWh|
|5:00|1.22 kWh|
|6:00|1.45 kWh|
|7:00|1.25 kWh|
|8:00|1.86 kWh|
|9:00|1.67 kWh|
|10:00|1.68 kWh|
|11:00|1.57 kWh|
|12:00|1.89 kWh|
|13:00|1.55 kWh|
|14:00|1.73 kWh|
|15:00|1.20 kWh|
|16:00|1.78 kWh|
|17:00|1.86 kWh|
|18:00|1.85 kWh|
|19:00|1.66 kWh|
|20:00|1.75 kWh|
|21:00|1.42 kWh|
|22:00|1.50 kWh|
|23:00|1.00 kWh|
 
ahreno said:
i'm about to draw out my system plans for permitting and had someone suggest facing one row east and one row west which threw me for a slight loop. I do like the idea of having more actual solar power later in the day. not sure about due east and west. maybe 15-20° off south? any thoughts?
Click to expand...
East/west is relatively common here in Australia, as are various other combinations... (NE/NW, N and W, N/E/W are all found...)
In fact where I used to live, we had an east/west split gridtie- and a neighbour had an identical system but all facing north... (installed by the same company two days later no less, even the same crew...)
So we could easily compare the two...
In practice- you get basically the exact same daily total kWh generated- it has a lower 'peak'' but the extended generating times basically make it equal...
(We were over 100w from the 6kw array with only half the sun showing- his didn't start until an hour or two later... and same in the afternoon, ours finished far later...)
One thing that is good if you get lots of clouds- the east/west split loses total generating power (kWh per day made)- BUT- less than the all north facing array did, ours was usually 3-5kwh a day more than his with 100% overcast and showers all day...
1714630050664.png
That's the east facing PV array on the left, with the thermal HWS panel on the north roof, and the west facing out of sight on the far side, and an overhead shot from Google maps...
My current 'temporary' array at the shed that runs the caravan and the shed is similar- half facing north, and half facing west to get the afternoon sun... by the time the north facers are starting to drop, the west is just kicking into high gear and continue to produce until sunset...
1714630283554.png
The north facers are set for my latitude, but the west facing at 45 degrees...
(the final house array will be 6kw north, 6kw east, and 6kw west)

One big advantage is that you get a good charge into the battery bank right up until sunset, where the north facing bank has dropped waaay down in output by then (meaning if you have a heavy load on, you are already biting into your battery storage well before sunset- rather than taking advantage of those extra hours of sunlight...)
 
I have a traditional ground mount array at the standard (your latitude) inclination, and then two more arrays on a roof that’s mostly east/west facing, And I have to say, I was surprised how little difference it makes.

Since all the power companies are trying to get away from net metering, and (IMHO) time of use (or smart grid) is going to be the only way to integrate with the power company in the future, you should point them wherever it makes sense in your particular property, and add batteries to decouple your time of use from your time of generation.
 
  • Like
Reactions: Bop
wpns said:
I have a traditional ground mount array at the standard (your latitude) inclination, and then two more arrays on a roof that’s mostly east/west facing, And I have to say, I was surprised how little difference it makes.

Since all the power companies are trying to get away from net metering, and (IMHO) time of use (or smart grid) is going to be the only way to integrate with the power company in the future, you should point them wherever it makes sense in your particular property, and add batteries to decouple your time of use from your time of generation.
Click to expand...
That's become the norm for new installations here in Australia- and many owners of older systems are adding battery storage as well (usually BYD or Panasonic- the Tesla offerings are far more expensive per kWh, and have a shorter service life, making them less attractive economically)

Effectively becoming a 'semi-offgrid' system, using solar and battery power mainly, with the grid supply as your 'emergency generator', with any excess over what is needed to recharge the battery bank sold as per a normal gridtie after the battery bank has been recharged...
 
Bop said:
That's become the norm for new installations here in Australia- and many owners of older systems are adding battery storage as well (usually BYD or Panasonic- the Tesla offerings are far more expensive per kWh, and have a shorter service life, making them less attractive economically)

Effectively becoming a 'semi-offgrid' system, using solar and battery power mainly, with the grid supply as your 'emergency generator', with any excess over what is needed to recharge the battery bank sold as per a normal gridtie after the battery bank has been recharged...
Click to expand...
Exactly, there are even new Smart Grid standards being developed so the power company can request settings changes either directly or through integrators, so they can do large scale load shedding or request grid support, though those open up a whole other can of worms.
 
The only advantage I see is starting the solar production earlier, and ending it later.
The total daily amount of PV produced will not change either way.
There is no gain, it always averages out.
 
I have done something similar.
Inclination matching latitude.
3 strings pointed 155⁰ and
3 strings pointed 205⁰.
I sacrifice absolute peak power at 12: 20 p.m. ( my solar noon) for a wider production curve.
The array wakes up earlier and lasts longer in the afternoon.
All 6 strings to a 6 to 1 combiner box.
 

Attachments

  • 17146556775986674261483332097982.jpg
    17146556775986674261483332097982.jpg
    300.1 KB · Views: 3
ahreno said:
i'm about to draw out my system plans for permitting and had someone suggest facing one row east and one row west which threw me for a slight loop. I do like the idea of having more actual solar power later in the day. not sure about due east and west. maybe 15-20° off south? any thoughts?

My system:

26 408 watt panels with up to 142w bifacial gang
2 tesla powerwalls (one Powerwall 2, one powerwall +)
most likely 2 Growatt 7.6kW Grid-Tie inverters (not purchased yet)

Ground mount, 2 runs of 13 panels. shouldn't be any shading, pretty good view from East all the way to west

I'm in Norcal, PGE and will be on NEM3.0 which pretty much sucks from what i understand.

I dont know if it matters, but i think i was able to figure out my average hourly usage over the last 5 months
Click to expand...


To maximize savings under NEM3.0 (small credit for backfeed except during a couple hours, maybe 6:00 to 8:00 PM),

Aim all panels due South.
Use Insolation calculator to find tilt that maximized annual production.
Store all PV production in batteries during non-peak rates. and draw from grid to supply house.
Discharge batteries during peak rate times to supply house and export all stored power to grid.
(If export credits vary during those couple of peak hours, export as much as possible during highest rate times.)

If inverter can't dump 100% of stored power during that couple of hours, get a bigger inverter. Or at least use that power to avoid drawing from grid some of the non-peak times.



To maximize utility of system when grid is down, above recommendation with all panels aimed South if fine if battery can store entire day's production. If not, some East and West oriented strings will spread production over the day when you also consume, reduce depth of battery cycling at night (might get by with smaller battery.)

5 months data isn't enough, need to know summer vs. winter consumption.
Use insolation calculator to select tilt for production which best matches summer and winter production.

10.608kW (STC) of panels (neglecting bifacial), might make 75% to 85% under typical conditions, 8kW to 9kW peak.
15.2kW of inverters, able to process all.
If half of panels were oriented SE and half SW, a single 7.6kW inverter would generally process all without clipping. Even facing due South, array size is a good fit single inverter, not much clipping most of the year.

About 6 hours effective sun in the summer, 54kWh.

Powerwall 2, 5kW, 13.5 kWh


Powerwall +, 7.6kW, 13.5 kWh


The two PowerWall are able to store peak output from your array, but only half the kWh.
They can export 12.6kW during peak hours, 25.2 kWh in the approximately 2 hours of peak credits.

You would double credits if you doubled storage capacity.
If you consume about 25kWh during the day for air conditioning, then you will avoid wasting power backfeeding off-peak for a paltry credit.

Instead of the two Growatt GT PV inverters, consider a batteries-optional hybrid. For instance, a SolArk. Without batteries, it will do the same as GT PV. With optional batteries, about 25kWh ~ 30kWh, it will store what PowerWall doesn't. It will also be able export most of that during peak hours.


PV panels are relatively cheap. Consider putting in more if that's what it takes to supply 100% or more of your needs most times of the year even with SE and SW orientation. While grid and NEM 3.0 are there, you can use it as seasonal storage and for times of little sun (I think NEM 3.0 does that.) Without grid you'll have power except for extended times of low production, need generator and reduced consumption.
 
greenfuturesd said:
The total DC power is only 10.6kw, then why do you need 2x Gorwatt 7.6kw? Just find ONE 10kw or 8kw inverter.
Click to expand...
its 10k with zero gain from bifacial.

i've been told the growatts work good with the powerwalls.

im open to suggestions on inverters. two growatts were suggested often, are more affordable than an eg4 18whatever. but i'm openfor more suggestions.
 
timselectric said:
I don't think that you are going to be happy with the ROI of solar.
Click to expand...

lol. i'm just doing it because i got free powerwall batteries. I'll have $3500 into panels and another $2k into inverters. few hundred in conduit. i've got most of the pipes for ground mount and a few hundred feeet of 4awg wire laying around. i just want to cut down my pge bill some. it's fucking ridiculous what they charge.
 
I've got about 1/4 of my panels facing north, on a fairly flat roof, because that is what works best for my setup. Go for it.
 
wpns said:
I have a traditional ground mount array at the standard (your latitude) inclination, and then two more arrays on a roof that’s mostly east/west facing, And I have to say, I was surprised how little difference it makes.

Since all the power companies are trying to get away from net metering, and (IMHO) time of use (or smart grid) is going to be the only way to integrate with the power company in the future, you should point them wherever it makes sense in your particular property, and add batteries to decouple your time of use from your time of generation.
Click to expand...
i'll have 10kWh of batteries and i have a good view of the whole sky. east through south through west is basically wide open
 
Hedges said:
To maximize savings under NEM3.0 (small credit for backfeed except during a couple hours, maybe 6:00 to 8:00 PM),

Aim all panels due South.
Use Insolation calculator to find tilt that maximized annual production.
Store all PV production in batteries during non-peak rates. and draw from grid to supply house.
Discharge batteries during peak rate times to supply house and export all stored power to grid.
(If export credits vary during those couple of peak hours, export as much as possible during highest rate times.)

If inverter can't dump 100% of stored power during that couple of hours, get a bigger inverter. Or at least use that power to avoid drawing from grid some of the non-peak times.



To maximize utility of system when grid is down, above recommendation with all panels aimed South if fine if battery can store entire day's production. If not, some East and West oriented strings will spread production over the day when you also consume, reduce depth of battery cycling at night (might get by with smaller battery.)

5 months data isn't enough, need to know summer vs. winter consumption.
Use insolation calculator to select tilt for production which best matches summer and winter production.

10.608kW (STC) of panels (neglecting bifacial), might make 75% to 85% under typical conditions, 8kW to 9kW peak.
15.2kW of inverters, able to process all.
If half of panels were oriented SE and half SW, a single 7.6kW inverter would generally process all without clipping. Even facing due South, array size is a good fit single inverter, not much clipping most of the year.

About 6 hours effective sun in the summer, 54kWh.

Powerwall 2, 5kW, 13.5 kWh


Powerwall +, 7.6kW, 13.5 kWh


The two PowerWall are able to store peak output from your array, but only half the kWh.
They can export 12.6kW during peak hours, 25.2 kWh in the approximately 2 hours of peak credits.

You would double credits if you doubled storage capacity.
If you consume about 25kWh during the day for air conditioning, then you will avoid wasting power backfeeding off-peak for a paltry credit.

Instead of the two Growatt GT PV inverters, consider a batteries-optional hybrid. For instance, a SolArk. Without batteries, it will do the same as GT PV. With optional batteries, about 25kWh ~ 30kWh, it will store what PowerWall doesn't. It will also be able export most of that during peak hours.


PV panels are relatively cheap. Consider putting in more if that's what it takes to supply 100% or more of your needs most times of the year even with SE and SW orientation. While grid and NEM 3.0 are there, you can use it as seasonal storage and for times of little sun (I think NEM 3.0 does that.) Without grid you'll have power except for extended times of low production, need generator and reduced consumption.
Click to expand...
lots to digest here and not sure my brain is capable. i dont want to get too complicated with all this stuff, i just want to get it done.

do you suggest half SE and half SW? are you talking pure SE and SW or some variation of directly SE and SW?

i wont run too much A/C. i have slab on grade floor and my house stays quite cool besides a couple weeks when it gets stupid hot. Couple the concrete slab with a whole house fan (my area drops to 55° almost every day when the sun goes down) that sucks in the cold outside air and kicks out the hot house & attic air... i barely have the need for A/C. i do have a mini split system i can use if needed. i figure i'll run it later in the afternoon if there's a lot of excess power.

unfortunately, 5 months of usage data is all i have. everything prior is dirty data as i ran dehumidifiers, air conditioners, fans, even some LED grow lights that wont be used again. my heat is wood, backed up with propane (infloor radiant heat provided by propane water heater) with a very seldom used mini split (i think i used it two times this year for 15 minutes just to take the chill off when sick). summer usage will increase a bit with a little A/c usage but shouldn't be a huge drastic ton (i wont be running my hot tub and instead a little A/C).

more batteries isn't in the budget right now, i'm only doing this because the batteries were free, the panels and inverter are less than $6k. small investment to try to combat PGE prices.

from what i have been told / researched etc... the power walls essentially make their own grid and i dont need a hybrid inverter, just a grid tie. not sure if it's because they are high voltage or just how they work.


i honestly dont even know if i even need an inverter since the powerwall + has an inverter. They just changed to the powerwall + on their plans yesterday.
 
millsan1 said:
I've got about 1/4 of my panels facing north, on a fairly flat roof, because that is what works best for my setup. Go for it.
Click to expand...
go for which? i'm doing ground mount and can face them anyway needed really. just trying to figure out if there's a best way... and it seems to be 50/50 argument of whats best.
 
The old powerwall was battery only. Do no models include PV MPPT?
I don't think so, and you need PV inverter if you have PV.
Powerwall by itself acts as UPS for house (maybe requires external transfer switch). But long power outage will drain it. It should AC couple to Growatt or other PV inverter, let you keep running indefinitely.
However, if loads exceed PV, it can't keep up. Will need to disconnect heavy loads. Battery can't charge without AC, and your loads could overload and shut off AC. (my system has a load-shed relay. And some loads direct on grid, not on battery.)


NEM 3.0 will force you on a different rate schedule, so have to consider the pricing.
DIY GT PV hardware will make power for about $0.025/kWh (amortized over 20 years), fast payback compared to $0.40 ~ $0.60/kWh utility rates.

Exact orientation and tilt could be optimized for different purposes, summer vs. winter best production, etc.
Partly a SWAG, partly preference for how yo want it to behave. Everything is a guess or predition.

To the first order, I assume the area presented to sun based on geometry determines production.
Due East and due West would give more flat production during summer, much less in winter.
I oriented 100% of my panels toward 2PM summer sun, for NEM 1.0. I've since added panels due East because peak times now later in the day. A bush now shades one array so I want to orient South East, more power than shaded and charge batteries earlier.

It is nice to have something that works well when grid is down.
 
ahreno said:
go for which? i'm doing ground mount and can face them anyway needed really. just trying to figure out if there's a best way... and it seems to be 50/50 argument of whats best.
Click to expand...
Go for the east west thing, if it fits you best. My north facing panels are useless 6 months out of hte year, but 6 months they give me tons of power, which is what I wanted.
 
You must log in or register to reply here.
Back
Top