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Forum Index : Solar : Paralell strings facing different directi
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Tinker Guru  Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Today I bought some second hand 175W panels ($25ea.)and a second hand 2KW Orion grid tie inverter. The idea is to have 1KW of panel string facing west on my roof and another 1KW facing east. Then to connect both strings in parallel to feed the single input Orion grid tie inverter. This is to back charge my battery bank via the stand alone home brew toroid inverter. Is there anything against connecting my two strings (facing in different directions) that way? There also are a fair number of panels facing north, connected for 48V, to feed my battery bank via an outback controller and power the 6KW home brew toroid inverter. Using a grid tie inverter is new territory for me BTW. Klaus |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Not sure how that will work with the single input- We have the same east/west split here, but thats on a dual input mppt inverter, one string per input Be interesting to see the final result! |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I have done it quite a few times with no problems. I have fitted diodes to some to prevent backfeeding through the shaded panels but it turned out that a firmware upgrade fixed the fault I was getting so I never really pinned down if it was a genuine problem. I'm confused, no wait... maybe I'm not... |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
From my mucking around with things solar, it will be fine. Parallel hookups do not seem to matter as long as the strings are even or close to it. I have 2 mismatched strings ( different panel wattages) facing different directions and at different angles just for good measure wired in parallel on a single input nd they work perfectly fine. Around Midday I get exactly the output I would expect for the combined total of the 2 strings. I don't think you'd need a diode, they are built into the panels anyway. |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
When your inverter is running backwards the first time you will be thinking how amazing that is. Have you considered how to regulate it or provide loads to prevent overcharging? There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Been wondering similar things. Hard to match 2nd hand stuff where I am. NE & SW facing gables here are not the best. I've got 2 inputs, both used at the moment, but wonder if a 3rd string could be switched. Morning/Afternoon etc. The SW string of 1.75kW produces 1.2kW well into the afternoon, but that may well change come winter. Phil |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
[quote]The idea is to have 1KW of panel string facing west on my roof and another 1KW facing east. Then to connect both strings in parallel to feed the single input Orion grid tie inverter.[/quote] I have a system like that, 1.2Kw east plus 1.2Kw west, connected in parallel. Both looking 60 degrees above the horizon, and it works very well.  Cheers, Tony. |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
I dare say there will be more questions about this as I progress, first I'll have to make a bunch of brackets for the panel rails. Unfortunately an old concrete tile roof makes putting panels on it a bit of a task. Nice to read the positive comments about this idea too, thanks guys. Mad, at first it might be a solid state on/off control, triggered by the battery bank voltage. More refinement most likely later as I get familiar with this idea of charging. Klaus |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I got a pile of tile roof brackets from the scrap metal dealer, I use them for hanging up stuff in the shed. They are just 40 X 5 mm steel made into a T shape with a few bends and holes. You may even better off buying them as they have all the holes in them including a slot and they are galvanized. The PWM regulation is not hard to build, Oztules code for the Arduino is quite simple. You don't need to learn how to write the code, just upload it from your computer, plenty of youtube videos will step you through that. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Brackets $2.50 each is pretty cheap for these, but the postage @$25 hurts but still only $3.75 each inc post. Comes with screws too. Cheers Caveman Mark Off grid eastern Melb |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I wouldn't bother making them at $3.75 each. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Alastair Senior Member  Joined: 03/04/2017 Location: AustraliaPosts: 161 |
In 2016 we built a house sth of Sydney right on the coast on a limited size block of 800m2 after having lived on 5ac for 30+yrs. I put in a 5KW system comprised of 2 strings each of 8x285W LG panels, One string faces Nth and the other faces W sloped at the roof angle for cosmetic reasons. I do have some roof space facing E which I could have used but had the benefit of living on our neighbour's front lawn in our motorhome whilst the the build was happening. What I realised was that even on good days the coastal cloud effect meant that we rarely had clear sun until ~11am and the solar panels on the roof of the motorhome only started showing good charge about then. From then on we would typically get sun until late afternoon. For this reason I used the N and W aspects on the house and get good results. I have seen 4.8KW in the early afternoon and often just under 3Kw in the late afternoon. I have no shading issues. I have no more space to the N but could sneak another string facing W if I wanted to. I would not bother with E in my location. I plan to put in a battery system this year now the prices have dropped and will go for a 10KWh+ system. At the moment I favour a Tesla or Sonnen system. I do not have the ability to do my own thing like at our last property = Dbl storey house and many neighbours plus my age. I know the price of turnkey systems like the above is high but i can afford it and want reliability with performance. My one self modification will be to put in a diversion once the batteries are charged from the inverter to the electric booster on the HW system. I will do this to get the max benefit as I only get a rebate of 10c/KWh on my grid export vs the ~28.5 I pay on import. It will be worthwhile in winter but in much of the year the evacuated tube solar HW system keeps the water up to temp very well. Just thought a restricted suburban perspective may be useful. Cheers, Alastair |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
That highlights how much things can vary from one part of the country to another. We are not far from the coast and there are many times we have clear skies until mid-morning and then it gets cloudy. This I believe is caused by a land breeze at night blowing out to sea and then as the land warms up it reverses and we get a sea breeze. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Alastair Senior Member Joined: 03/04/2017 Location: AustraliaPosts: 161 |
Following on from my last post, I have on my project list to build a solar scanner/logger based on a Micromite, small panel and stepper drives. It will scan across a wide range of angles and give me some real data. Why? Because I can and like projects that combine mechanical and electronic challenges. I am only just starting real thinking and pencil calcs. The issues I am considering before any testing starts are 1. how to 'focus' the sample panel and how narrow to make it 2. how many samples vs scanning time - linked to pt 1 3. size of panel needed 4. how to map the response of my 'telescope' - would a single HP led moved across the field be enough - have not played yet More to come and i will post a separate thread once the ideas have been explored to stage one. I will probably waste lots of time and $ in the end but I will learn a lot and have fun which is the main thing for me now. Cheers, Alastair |
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| Alastair Senior Member Joined: 03/04/2017 Location: AustraliaPosts: 161 |
@Madness Yes indeed. The full story for us is that since we have moved in to our house we have seen the fuller range of weather variations. My previous statement is really a gross simplification and the effects like you stated have often happened for us and last for periods of time. The recent weather pattern has been very different and for the last few weeks we have highly variable cloud cover. In the thread above I have alluded to a solar scanner which would help me to better understand how varied it all is. I started think of a mechanical single small panel which would scan the sky but now I am thinking perhaps and static array of small focused panels would be better or a stepped array so more temporal data will be captured. Once I have a decent database I can scan for the overall maxima and be able to display both the light intensity at any time and normalised to the maximum seen. I have no plans to change my system based of the data just an exercise in knowledge gathering. I will move my thoughts to another thread so I don't highjack this one anymore. Cheers, Alastair |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
One thing to keep in mind is to have panels that perform similarly to the full-size ones. It would be a good comparison to have several fixed panels at different positions to compare. I know the University of QLD have data freely available for all their solar panels located at many different sites, some fixed and some tracking. There may be something similar in your area. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Here in Melbourne, the sun rises and sets well south of due east-west during the summer months, so that even though the days are long, my north facing panels are quite slow to get going in the mornings and quit fairly early in the afternoons. The east west virtual tracker really makes a big difference the first and last hour and a half. At mid winter the sun is mostly in the north, and I expected pretty poor performance from the east west facing array. But in total cloud it works just as well as the north facing panels, taking into consideration their smaller total area. So all things considered it has made a very worthwhile addition, and I am very pleased with the result. Cheers, Tony. |
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| Alastair Senior Member Joined: 03/04/2017 Location: AustraliaPosts: 161 |
@Warpspeed I have always disliked being in direct sun and so tend to now go for walks early in the morning and late afternoon/evening. My inbuilt radiation monitor tells me the same as you that there is a large amount of energy in that partially clouded sunlight. The more I think about my proposed monitor the more I realise that to make it relevant to practical solar PV I need to think through many issues. I will start a new thread and link from here so that you guys with lots of knowledge can steer me back to sensibility. I will also start searching for local authoritative sources starting with the UNSW group. Cheers, Alastair |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Why such a steep angle? Is this for space reasons? Seems others like myself are finding the very shallow angles are working better for them so be interested to know why you have gone so steep? |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Sixty degrees is the optimum angle for a virtual tracker because it gives almost a constant flat power curve over the whole day. Cheers, Tony. |
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