Is there anything like this in the solar panel array world?

[SolarHead]

Here's a thought I've had but wondered if there's another way to do this and get same (or better) results.

Say my inverter MPPT's are maxed out with what they are rated for voltage/amp wise and I cannot add more panels to my south-facing array as a result.

I have a battery bank but don't want to buy more batteries, but was wondering how get more usable power say in the afternoons from 4pm to 7pm to 8pm , I mean the inverter is there that I paid for, and it can do more work the day isn't over with yet. I see the sun going toward that angle and my incoming power starting to drop as the sun drops.

What if I had another array aimed say SouthWest direction, and have an automated timer/switch of some sort that would turn the south-facing array OFF, and the SW facing array ON? Something like the drawing below. Install some type of timer/switch outside mounted under the array, (or inside the home) , that knows at 4pm to turn OFF one array and turn ON the other array. That would be so my inverters MPPT's wouldn't get overloaded. Basically it would be a tracker but built with solar panel arrays and switches. I know what most people will say, that you point all panels due south and that's the most power. I get that. But what if I want to stretch the curve and have more even power generated throughout the day, is there any merit or need for this? I guess if all panels aimed due south would produce more power, then I'd need to do either ONE - use the power as it comes in, or TWO - store the power and have enough battery bank to store it all. I was thinking having 2 different arrays aimed at different directions and have one array turn on when the other turns off, you could "follow" the sun through the day and get more usable power that isn't necessarily stored in batteries. Either this is a good idea, or terrible one.

I had thought about AC coupling a 2an array but would have to buy a string inverter in order to AC couple. That would fatten the production curve if I aimed those panels southwest (for example). It may be cheaper to NOT buy another string inverter, NOT buy the more panels, just stick with my existing array and get more battery (but then again, more battery is $$$). I was thinking maybe an inexpensive string inverter or even use microinverters on the 2nd array and bring that AC power into my inverter via AC coupling. Either way, I was thinking garner that afternoon sun and stay off my batteries a bit more from say 4 to 7pm, lessening the need for investing in more battery bank.





Some type of DC timer/switch/combiner box, dont know if something like this exists but sure it could be made.

 

[FilterGuy]

There are a lot of ways of doing the type of thing you want.

* I guess a timer like you describe would work.... but I am not aware of anyone that sells such devices so you may have to build it out of timers and relays.

* A lot of people just put the two arrays in parallel, The one in direct sun will dominate and have a higher voltage than the other so as the sun moves the second array will 'take over'. Both arrays need to be set up for the same Voc. It is a bit difficult to figure out if you are going to exceed the Isc or Wattage that many of the AIOs specify for PV, but a lot of people have made this work. Particularly when they have one array that is set up for morning sun and another array set up for afternoon sun.

There is a little debate as to whether blocking diodes are needed for this type of arrangement. I used to think they are a must, but now I am not sure. I would probably try it with and without blocking diode and see what works best.

* The best way from an engineering point of view is to just add an independent charge controller that goes directly to the battery. This allows
both arrays to produce the most amount of energy and in the afternoon, pulling energy from the 2nd charge controller via the battery inputs is no different than pulling energy from the original charge controller.

 

[MisterSandals]

I this thread beat this same horse...

Has really no one ever tested to get power from sunrise till sunset ?

Ok 1st thing I live in the philippines and sunrise here is 6am and sunset 6pm (to make it easier). I installed my system 8x 500W panels now facing sunrise and I see that from 7am it already generates 0.5KWh until 3pm when the roof is in the shade and production drops. What I want to change is...

diysolarforum.com

 

[SolarHead]

this thread beat this same horse

Yes that thread beat the horse pretty well on the discussion of if putting arrays at different directions would be good or not, and so on. I think the final consensus on that thread kind of fizzled. My take on it is, if you have a smaller battery bank, and you can't capture all the energy that a MAX producing all-south-facing array can produce, and you want to use energy throughout the day consistently then yes 2 or 3 different arrays facing different directions (one S, one SE, one SW for example), can product consistent power that you consume and not store, throughout the day since a smaller battery bank can't store but so much. But just a blind thought of how do I get max power, by all means, face ALL panels one direction and you'll produce the most power. But, max power isn't always what someone's situation calls for. It depends on how they use electricity (all at once, or at night, or consistently throughout the day), and depend their battery bank size, and so on. I don't need my power curve to grow taller, I want it to grow wider/fatter so that I can cover loads longer (or at least try to cover more) throughout the day. With a sun tracker mount this would be a mute discussion, but with fixed mounts, there is merit to placing multiple arrays in different directions.

I think that thread was the initial poster asking how to do something, but the discussion turned into trying to figure out IF placing panels was wise or not. The guy had already made up his mind to do it, he was asking how. I think the original poster left the discussion after he discovered he wasn't getting the help he desired. I think in my situation, starting out with a very small battery bank has taught me a lot about how my home consumes power, when the system is maxing out and so on. Once I get a larger battery bank I can more-or-less be more stupider than I am already, because I can store a lot of power and use it at night and not worry about late after noons, or early mornings when I could be covering loads using multiple arrays and staying off the grid more. I'm drawing from the grid more than I like due to my small battery bank. My batteries last about half the night, pooping out around 3 or 4am usually. That's with discharging 500 watts starting at 9pm each night. Looking at prices of batteries, I can see where multiple arrays of panels at different directions would fatten the power curve (fatten, not flatten, eek), would be cheaper than buying more battery.

 

[SolarHead]

* The best way from an engineering point of view is to just add an independent charge controller that goes directly to the battery. This allows
both arrays to produce the most amount of energy and in the afternoon, pulling energy from the 2nd charge controller via the battery inputs is no different than pulling energy from the original charge controller.

This is a great idea, but with a small battery bank (or no battery bank), this idea is deflated. I do like the idea because it shields the SCC from having to over-work or be risking overload. With a larger bank this would work, but even with a larger battery bank what happens if your main inverter has already topped the bank off at 100% by 2 or 3pm? That late sun in the day via 2nd array facing SW wouldn't get stored (but I guess the right inverter could take the power from the battery as fast as it's going in kind of like a buffer). So, back to the drawing board kind of. My real only goal for wanting to have a SW facing array is to garner more power from the sun that covers loads at that time (from say 3pm to 8pm) so I don't pull from the grid, and my battery is sitting there at 100% waiting for darkness to start discharging and carry me through the night. The battery bank size (or some people with no battery at all) is what it seems people are not taking into consideration when discussing max power you can get out of facing all panels due south. If you are looking to cover loads without battery or grid, then multiple arrays seems like a wise idea. I was just trying to figure out how would someone best wire multiple arrays so that you don't over power your inverter and cause damage. I suppose facing them really far apart say one array SE and one array SW, you could rely on the suns movement to "switch" over from one array to the other and not over-power your equipment. I was thinking a mechanical or digital type of timer or switch but its not the same time of day year-round that it would need to switch from one array to the other. I guess it may be better to have and use multiple MPPT (some inverters have 2 or 3 MPPT's), or use multiple inverters , or do AC coupling by adding a string inverter to your existing inverter configuration and bring the 2nd array power in that way.

 

[FilterGuy]

This is a great idea, but with a small battery bank (or no battery bank), this idea is deflated. I do like the idea because it shields the SCC from having to over-work or be risking overload. With a larger bank this would work, but even with a larger battery bank what happens if your main inverter has already topped the bank off at 100% by 2 or 3pm? That late sun in the day via 2nd array facing SW wouldn't get stored (but I guess the right inverter could take the power from the battery as fast as it's going in kind of like a buffer).

The All-in-one inverters can be modeled like this:



When looked at this way, you can see that the energy flow through an internal charge controller is really no different than through an external charge controller.

I guess it may be better to have and use multiple MPPT (some inverters have 2 or 3 MPPT's), or use multiple inverters ,

You can always just add a stand-alone charge controller instead of multiple AIO inverters I really like the Victron line of charge controllers, but they tend to be pricy

or do AC coupling by adding a string inverter to your existing inverter configuration and bring the 2nd array power in that way.

In concept, the string inverter (Or micro inverters) would work, but you have to make sure the main inverter and the string/micro inverters are both designed for AC coupling.

 

[12VoltInstalls]

There is a little debate as to whether blocking diodes are needed for this type of arrangement. I used to think they are a must, but now I am not sure. I would probably try it with and without blocking diode and see what works best.

I have MC4 diodes on hand somewhere because they are quick and dirty but I haven’t used them.
I’ve watched my own stuff be fine for a long time but at the price? I don’t think the diodes harm anything.

 

[FilterGuy]

I don’t think the diodes harm anything.

No harm, but the ~.6V drop reduces the power output of the array by a tiny amount.

I would only use blocking diodes if the strings are not all getting the same sun angle and shading. Even then, I would test the system with and without the diodes.

 

[12VoltInstalls]

~.6V drop reduces the power output

That much?! sorta kills a bit of the low light harvest. Didn’t even think about it

I would only use blocking diodes if the strings are not all getting the same sun angle and shading. Even then, I would test the system with and without the diodes.

Well ? I’ve been running without for a year or so and it’s been fine. Well other than the blotches on my skin and that buzzing sound. . .

 

[kanelr]

hey I also have a beat the same horse thread going here somewhere. my summary and take away
Regarding the multi directional panel catch sun all day long discussions, it seems that consensus on the forum is;
There is disagreement on whether diodes are needed between panels
There is disagreement as to whether collecting through diagonal atmosphere (morning/ evening) affects the harvest enough to avoid it.
There is agreement on using mixed panels as long as they are sorted and semi well matched and in parallel (less agreement when series is used)
There is agreement that relays can be used, and agreement that they can be a nuisance.
There is agreement that any morphs of a configuration can not use DC output charge controllers on the roof due to voltage drop issues
And more among other things I forgot to list
___________________________________
I think- Since the sun can't be in two places at once you can use more panels (facing in dif. directions) than the charge controller is rated for. (but still use some good math). If you have the panels and the wire, why not?
At home we can't use more panels facing south without more charge controllers, each one requiring 65' of 6/3 romex at the price of about 65 gallons of us gas this month plus the price of the controller, and I have extra panels, so up they go, just in a way that can't blow up my system. I am continuing an upgrade beginning today which will add panels facing a different direction and using the position of the sun as the only device that dictates which panels get the "heat".,
And they can tie to the same home run cabling without increasing the size up from #6 because again, just like with the charge controller, they will not overload unless we got a second Sun.
Also on clear days we already produce more than we need in the daytime for just lights, fans, computers, and sump pump, so I am adding a relay to transfer the refrigerator circuit only when we are at float voltage. At night when we drop below float, the fridge stays shut mostly anyway, so it's a good fit for that time to be on the grid, if any time is good. The wiring is easy once you see it mentally. A member found the right relay on amazon for less than 30 USD. I have the link. If you had a power failure you can set the relay voltage lower to run the refrigerator longer I suppose.
SO IN TRADITIONAL SOLAR SPEAK, you can set up your main refrigerator as your diversion load this way. (I think I'll post that idea too)

 

[12VoltInstalls]

There is disagreement on whether diodes are needed between panels

They should be there. But a calculated risk and math and some of us deal with it no problem

There is disagreement as to whether collecting through diagonal atmosphere (morning/ evening) affects the harvest enough to avoid it.

If one is focused on max watthours then no- bi-directional facings aren’t worth much. If one needs to improve time of use harvest, then yes! your batteries will remain fully charged much later in the day or into the evening. I’ve proven that myself.

 

[kanelr]

They should be there. But a calculated risk and math and some of us deal with it no problem

If one is focused on max watthours then no- bi-directional facings aren’t worth much. If one needs to improve time of use harvest, then yes! your batteries will remain fully charged much later in the day or into the evening. I’ve proven that myself.

Yes

 

[Hedges]

They should be there. But a calculated risk and math and some of us deal with it no problem

My measurements say PV panel in the shade (not total darkness) has Voc similar to Vmp of a panel aimed at the sun. So under MPPT operation, the shaded panel doesn't drag down the producing one.

I've also put a panel in total darkness and applied voltage to it. Applying Voc didn't cause enough current to be interesting. I had expected Isc of a sunny panel, instead of just leaking through PV cell diodes of itself, to split and put half into dark panel. Had to connect two illuminated panels in series, wired parallel to one panel in darkness, to get any interesting current. It carried < 50% of Isc.

I don't think anti-backfeed diodes are needed when paralleling strings of different orientation/shading. But do use fuses if more than two in parallel.

Overpaneling with multiple orientations could have higher Isc when in direct sun plus reflected light edge effect of clouds. Various SCC have ways of dealing with over-current and over-voltage. I think a quality SCC with a correctly connected array than never exceeds allowed voltage will be OK, because it will limit current draw to what it wants and will not have to crowbar or clamp the PV inputs. Incorrect conditions or poor SCC design could result in failure.

Keep your SCC cool, since extended high-power, high-temperature operation will shorten its life. The warranty for my GT PV inverters is given in terms of years or kWh, whichever comes first. Heating of transistors goes as the square of current, and lifespan decreases exponentially with temperature. Heating of capacitors also occurs due to current (presumably also squared?) and current is a function of ripple voltage, which is proportional to power.

 

[12VoltInstalls]

Overpaneling with multiple orientations could have higher Isc when in direct sun plus reflected light edge effect of clouds. Various SCC have ways of dealing with over-current and over-voltage

Thank you for the overview.

FWIW I have the diodes. Just never installed them. I didn’t see a way of my system amplifying voltage and overcoming circuit integrity.