Funny story about the east-west panel spread-out idea

[HarryN]

I have used small systems like this to power my off grid shop for several years.

The reason that I can get away with it is that I have some panels on the racks that allow pointing them at the sun early in the morning and late in the afternoon. When I had the minivan, I had 300 watts on top of it, now I just have 150 watts on the explorer.

In the photo it is just capturing the late afternoon sun.

The ability to capture the sunlight all day long is critical to how it all works with so little battery storage.

It has battery SOC monitoring but I just glance at it - don't capture it for trending.

Very roughly what I see is that if I were using a fixed configuration based on how this setup works, I would face:
~ 25% toward the early morning sun
~ 25% facing roughly up
~ 50% facing the very late in the day sun

Yes I know it is very simplistic but it works.

 

[Warpspeed]

The ability to capture the sunlight all day long is critical to how it all works with so little battery storage.

Bingo !
I think this cuts right to the point.
Not everyone has this undersized battery problem, but for a small system, its something well worth experimenting with.

 

[HarryN]

Bingo !
I think this cuts right to the point.
Not everyone has this undersized battery problem, but for a small system, its something well worth experimenting with.

Yes - it is only 2 kW-hrs (nameplate ) of storage so I can run it for a while after the sun goes down but obviously there are limitations.

 

[SilverbackMP]

Bingo !
I think this cuts right to the point.
Not everyone has this undersized battery problem, but for a small system, its something well worth experimenting with.

Might even be worth experimenting with if you have a bigger system with AC coupling like SMA if you are trying to make sure you have possible amps available as much as possible (goes back to the post I started a couple of days ago referencing the ability of Sunny Islands and max amp capacity).

I may break down a put a a string on my shop’s east roof and a couple of strings on the west roof though I was trying to avoid roof mounts for a plethora of reasons.* But I do have a spare Sunny Boy 7.7 that could be put to use. At the very least, I’d boost available energy for battery storage in the winter.

*servicing a pain the a$$
*cleaning a pain in the a$$
*tempermental rapid shutdown if you want to comply with current NEC (I don’t have to, but still)
*metal roof, lots of wildlife, and high voltage DC = high voltage welder if things go wrong
*how long are sealants going to last? Turning a 50-100 year roof into a 20 year roof is not a good idea. Especially when there is spray foam involved.

 

[wattmatters]

how long are sealants going to last?

There are metal roof mounts which do not require penetration. Depends on the type of roof.

 

[SilverbackMP]

There are metal roof mounts which do not require penetration. Depends on the type of roof.

Mine is ag. I’d been another year building the shop if I tried finding a standing seam guy in these crazy a$$ed times.

Closest I can come are the ones that screw to the side of the ribs rather than the valleys and that has its own concerns (not tied into the purlins).

I have house wrap between the foam and the metal which has pluses and minuses. The minus in this case is that the roof structure is not glued together as well as could be (the plus is that repairs and alterations are a hell of a lot easier).

I probably also overthink things.

 

[cods4]

Here's some real data from my system:
I have only had it since early October last year, so hasn't had a full year cycle yet. But I still have some reasonable data.

I have tried to capture data from some perfect blue bird days throughout the last 8 months. This wasn't easy over the summer as I have an export limit of 5kW, so the other 10kW that are being generated during the middle of the day have to be used, and only a small amount could go into my battery.

Location: About 37.7 degrees South in New Zealand
Roof pitch: 15degrees
Arrays: 6 in total, all equal size 2460W, 2 facing ENE, 2 facing WSW, and 2 facing NNE
Total production of ENE Arrays: 4251kWh
Total production of NNE Arrays: 4365kWh
Total production of WSW Arrays: 3825kWh

Edit: Ignore the cables lying on the roof etc, this photo was taken during installation.


Mid-spring. You can see that one of the East facing strings gets going a bit earlier (the other one was shaded). But in the evening the North and west facing arrays are pretty much the same.


Mid-summer: This one had some cloud unfortunately, but there was very little difference between the arrays in the morning and evening. The North facing array just has a bit more total production.


Early Autumn - Like in spring, the east facing arrays definitely get going quite a bit earlier in the morning. The slightly south facing 'West' arrays have noticeably lower production in the middle of the day.



Same as above.

Late Autumn: still very similar, I don't have a good explanation for the strange kink in the late afternoon.

 

[robby]

It's not instead of south facing.
It's in addition to south facing.
Panels are the cheapest part of solar.

Yep!
The best Plan in my mind for people who already have their inverters at or near capacity with South facing panels is to just add a separate low cost SCC with two MPPT inputs and load each MPPT with East and then West panels. Your batteries are getting charged earlier in the morning plus that precious evening charge.

 

[HarryN]

Might even be worth experimenting with if you have a bigger system with AC coupling like SMA if you are trying to make sure you have possible amps available as much as possible (goes back to the post I started a couple of days ago referencing the ability of Sunny Islands and max amp capacity).

I may break down a put a a string on my shop’s east roof and a couple of strings on the west roof though I was trying to avoid roof mounts for a plethora of reasons.* But I do have a spare Sunny Boy 7.7 that could be put to use. At the very least, I’d boost available energy for battery storage in the winter.

*servicing a pain the a$$
*cleaning a pain in the a$$
*tempermental rapid shutdown if you want to comply with current NEC (I don’t have to, but still)
*metal roof, lots of wildlife, and high voltage DC = high voltage welder if things go wrong
*how long are sealants going to last? Turning a 50-100 year roof into a 20 year roof is not a good idea. Especially when there is spray foam involved.

It isn't the roof that you should be focusing on. Mount them on the west facing vertical wall so they are getting sunshine from 16:00 - to - as late as possible.

 

[SilverbackMP]

It isn't the roof that you should be focusing on. Mount them on the west facing vertical wall so they are getting sunshine from 16:00 - to - as late as possible.

Can’t. Mature trees would cast shade there in the mornings and evenings. I’m not taking out the trees (already took out a bunch). The top two thirds of the roof remains unshaded though.

 

[SeaGal]

Can’t. Mature trees would cast shade there in the mornings and evenings. I’m not taking out the trees (already took out a bunch). The top two thirds of the roof remains unshaded though.

Mount them on the trees then...

Interesting tree mount for morning light

Hi all. tall tree to the east of home blocks light until about 10 AM, this is our booster idea that followed some property maintainance. Surplus everything except the pvc box. The buried wire is #2 (in conduit) for about a 50 foot run to an unused PWM controller, which should be fine for this...

diysolarforum.com

 

[SilverbackMP]

Mount them on the trees then...

Interesting tree mount for morning light

Hi all. tall tree to the east of home blocks light until about 10 AM, this is our booster idea that followed some property maintainance. Surplus everything except the pvc box. The buried wire is #2 (in conduit) for about a 50 foot run to an unused PWM controller, which should be fine for this...

diysolarforum.com

Might take a good chunk of a forest to fill out the capabilities of a SB 7.7. It could easily handle 12 370w (ish) panels in series pointed east and two sets of 12 pointed west. Possibly more if you wanted to get into paralleling them and over paneling.

 

[sunsurfer]

What I am testing this year;

Summer time - rotate extra panels towards the west 45deg tilt for a few extra hours of A/C in the evening.

Winter time- rotate same panels east/south 45deg tilt for early morning heating with heat pumps.

 

[the_uglydog]

Here's a question! I'm building a system to run the well and pressure pumps for one of our apartment buildings. The well pump is 3hp and the pressure pump is 1hp. The well pump runs mostly from 5AM till 11AM, sporadically during the day, then from 4PM till 10PM. The pressure pump runs from about 4:30AM till about 9AM, sporadically during the day, then from about 3PM till about 9PM. We will need our battery power early morning and late afternoon mostly and I want a backup system to the utility which often produces power under 160v in the morning. Winter sun here usually starts generating power at about 6:15AM and stops at about 6PM. Summer at about 6:45AM till about 7PM. I'm planning on using a Growatt 12kw inverter, 2 batteries with 16, 280ah cells each. I'm thinking of putting 2 sets of 9, 400 watt panels at very steep angles maybe 60 or 70*, facing ESE and 2 sets of 9 400 watt panels facing WSW (14* toward S from E and same for the W). This might sound nuts but I was thinking of connecting one E set and one W set to each controller in the inverter, connected in parallel so the voltage is the same only increasing the number of strings on each, so that as power dropped off from the E set the power would come up on the W set having it make about the same amount of power all day to charge the batteries, but give a big boost to the AM and PM production. Right now I'm using one of those inverters with 2 sets of 12 400 watt panels and it works great just clipping the excess midday when ever there is full sun all day. I also use 2 extra 100 amp charge controllers for extra power to help charge a very large battery bank. I know I'll be buying a lot of extra panels, but I get them direct from the manufacturer for about $100.+ shipping and I'll already be shipping 24 so it won't be much more. All of your thoughts and comments will be appreciated. the dog

 

[Danke]

Ground mount Bifacials facing south may get more out of E and W sunshine.

 

[RV10flyer]

Ground mount Bifacials facing south may get more out of E and W sunshine.

Mine do because the sun comes up and goes down behind the 180° array. I also have a 155° and 205° azimuth arrays that help after breakfast and fixing dinner. I like over paneling 20% and spreading out the production.