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Total beginner question on Solar


Justin_A

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Hi all,

Nice to virtually meet you all and also nice to have found this forum. I've been toying around with the idea of solar for a while and was wondering what you experts think of my potential plan. The problem I'm trying to solve is to start reducing my power bill thus freeing up resources for a further build. So essentially what I am thinking of is to put panels and an inverter in and wire it only to certain plug circuits . No batteries at this point as the goal is to try to reduce my "base" operating daytime load as much as possible. So essentially running aircons, and big loads off the grid and computing power of solar with an  automatic switch to Eskom at night.

Now the problem I am having and can't quite figure out is the "base" daytime load I am hoping to cover is around 900w (Yes high I know but I have lots of computing power doing various things). So I guess what I'm interested in is the following:

How many panels would I need to cover the above?  What size inverter etc and what sort of cost range would I be looking at? The long term goal is to use the savings from this to eventually extend the system into batteries etc.

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Hi Justin

Get yourself a smart-grid inverter that can run without batteries. Add 6x 260W panels to begin with which would give you 1.5kw/h roughly. That should be enough to reduce you electric bill to start with. 

Which area do you stay in? Maybe one of the installers on here can lend you a hand.

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1 hour ago, Johann1982 said:

Add 6x 260W panels to begin with which would give you 1.5kw/h roughly

I agree. PV panels don't make that from the second the sun comes up until it sets again tonight. It makes a little in the morning, ramps up to the peak at around 12:30PM (In South Africa) and then ramps down again and by 5PM you're basically done for the day.

So you want to put up enough PV to cover as much of your 900W from as early as possible... but on the other hand, having a large surplus at noon (and nowhere to put it) isn't exactly good either. I mean, that's the lesser problem to have, but a problem none the less :-) So if you can move some loads around so maybe the dishwasher runs at noon, that would be a good idea.

Finally, I see no point in splitting off some circuits. If you're going to run grid-tied, might as well allow the whole house the benefit of the surplus power.

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1 minute ago, plonkster said:

I agree. PV panels don't make that from the second the sun comes up until it sets again tonight. It makes a little in the morning, ramps up to the peak at around 12:30PM (In South Africa) and then ramps down again and by 5PM you're basically done for the day.

So you want to put up enough PV to cover as much of your 900W from as early as possible... but on the other hand, having a large surplus at noon (and nowhere to put it) isn't exactly good either. I mean, that's the lesser problem to have, but a problem none the less :-) So if you can move some loads around so maybe the dishwasher runs at noon, that would be a good idea.

Finally, I see no point in splitting off some circuits. If you're going to run grid-tied, might as well allow the whole house the benefit of the surplus power.

Couldn't have said it better myself. He might want to rather invest in a dual mppt grid tie inverter where he can add a 2nd set of panels for either the early morning sun or late afternoon.

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Once again, depending on how much money you have, I will repeat what I said yesterday: Put in a Fronius Galvo or Primo. The Galvo is the low-voltage model (with a boost stage in the electronics) and starts at 1KW, though for the price difference you might as well take the larger one and just start with less panels. The Primo has no boost stage and you have to add enough panels to get the voltage to above 400V, still a good option, just something to keep in mind. Ballpark you're talking 50k for something like that, but it will be the last PV inverter you buy :-)

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On 12/15/2016 at 9:49 AM, plonkster said:

Finally, I see no point in splitting off some circuits. If you're going to run grid-tied, might as well allow the whole house the benefit of the surplus power.

Aha! Usefull to know now that I actually think this through. Splitting out circuits would only make sense if running of batteries and load spikes would be an issue I guess.

 

I guess now next steps would be to find a decent installer in Jhb / Pretoria and get a quote

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6 hours ago, Justin_A said:

Splitting out circuits would only make sense if running of batteries and load spikes would be an issue I guess.

In my house I have lights and one plugs circuit split off, but that's because I have a hybrid inverter with batteries. It behaves like a grid-tied inverter feeding the whole house, but if there is an outage then only the lights and that one plugs circuit works.

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  • 2 weeks later...
On 12/15/2016 at 9:55 AM, plonkster said:

Once again, depending on how much money you have, I will repeat what I said yesterday: Put in a Fronius Galvo or Primo. The Galvo is the low-voltage model (with a boost stage in the electronics) and starts at 1KW, though for the price difference you might as well take the larger one and just start with less panels. The Primo has no boost stage and you have to add enough panels to get the voltage to above 400V, still a good option, just something to keep in mind. Ballpark you're talking 50k for something like that, but it will be the last PV inverter you buy :-)

Justin says his long-term goal is to add some batteries. Would he be able to do that with the Fronius? 

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You'd need a second inverter to add batteries, the Fronius is a pure GTI. I don't consider that a big problem, the Fronius is at least 10k cheaper than many of the better hybrids. The slightly higher cost will be offset by better equipment and lower entry cost. That's my personal opinion though. YMMV add they say :-)

Editing (from full keyboard now).

There are only a hand full of hybrid inverters that can run without batteries (like a GTI). I think it pretty much restricts you to a Infini or a Goodwe, right? Nothing wrong with that, but my Meyers-Briggs indicator (aka MBTI) ends in a P: Such a lack of alternatives makes me feel very anxious.

But that's not the only way to add batteries later, so my Fronius answer doesn't completely ignore that part of the question, it merely postpones the decision to later. Granted, at slightly higher overall cost, but I think there is a rule about that somewhere in finance, that money spent now is always a bigger problem than money spent later :-)

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2 hours ago, plonkster said:

You'd need a second inverter to add batteries, the Fronius is a pure GTI. I don't consider that a big problem, the Fronius is at least 10k cheaper than many of the better hybrids. The slightly higher cost will be offset by better equipment and lower entry cost. That's my personal opinion though. YMMV add they say :-)

Editing (from full keyboard now).

There are only a hand full of hybrid inverters that can run without batteries (like a GTI). I think it pretty much restricts you to a Infini or a Goodwe, right? Nothing wrong with that, but my Meyers-Briggs indicator (aka MBTI) ends in a P: Such a lack of alternatives makes me feel very anxious.

But that's not the only way to add batteries later, so my Fronius answer doesn't completely ignore that part of the question, it merely postpones the decision to later. Granted, at slightly higher overall cost, but I think there is a rule about that somewhere in finance, that money spent now is always a bigger problem than money spent later :-)

Interesting, thanks. 

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Hi Guys.

Great thread.  I know on the very pricey inverters such as the shnieder units,  they have a output for essential loads only.

Thus when the grid fails  heavy load item do not kill your batteries. 

I am interested in how this gets done on other inverters and still offsetting the homes entire consumption and not just selected circuits,  to avoid the above situation. 

Very interesting would love to know.

Sincerely 

Jay

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You can split your db and have the heavy items on the grid feed side and the lighter items on the inverter load side. So if the grid fails you only loose the heavy items.

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3 hours ago, Energy said:

I am interested in how this gets done on other inverters and still offsetting the homes entire consumption and not just selected circuits,  to avoid the above situation. 

In the deep technical sense, what they do is sync the internal oscillator with the grid frequency, using (as far as I know, correct me if wrong) a Phase Locked Loop (PLL for short). This is why it is so important that the frequency is clean and stable and why they refuse to tie with some generators. So then it connects the input and output of the inverter together (as it would in bypass mode) and simply feeds the power in like a GTI.

If the grid fails, it has to do a few things pretty quickly. No need to worry about the frequency, even though the grid is gone, we have our internal oscillator tuned to the same frequency so we can keep going without the grid. But we have to disconnect the input (aka grid) very quickly, not only because we don't want to feed back and kill someone on that side, but also because we can't power the whole neighbourhood.

Once the grid is disconnected, the circuits on the output side remains powered by the inverter and all it has to do is adjust to the current power levels, precisely as it would after a large load turns off.

Here I used the Victron terminology. The "Critical circuits" part is what is normally the output side on these inverters.

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1 hour ago, Energy said:

Super interesting.  When splitting the db are we still able to offset the use of the heavy items?

Yes. I have my Multiplus set up this way. The grid meter is used to ensure that I don't push back too much, thereby avoiding grid feedback. In my setup all my PV is connected via MPPT, I don't have PV inverters... but you can mix and match... which is totally awesome.

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I run my setup the same way. Any inverter can do it. In my case I did not split the DB, too much work to do as the people who wired my house had no clue. If I want to split the DB I will have to rewire the house. So I left the DB as is and I have a manual switch over switch that will move the load from the grid feed side to the Inverter side and back again. Depending on if the gird is there or not.

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16 hours ago, Energy said:

Hi Guys.

Great thread.  I know on the very pricey inverters such as the shnieder units,  they have a output for essential loads only.

Thus when the grid fails  heavy load item do not kill your batteries. 

I am interested in how this gets done on other inverters and still offsetting the homes entire consumption and not just selected circuits,  to avoid the above situation. 

Very interesting would love to know.

Sincerely 

Jay

If you don't want to split the DB you can always install an external contactor with the heavy loads connected to it and Eskom power connected to the coil.  When there is no Eskom power the contactor opens and all the heavy loads disconnect and the batteries last longer.  This works well when you have excess generation from the PV panels and set the pool pump to run during that time. The pool pump will not drain the batteries if you are not at home to switch it off during a power failure.

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11 hours ago, DownTime said:

If you don't want to split the DB you can always install an external contactor with the heavy loads connected to it and Eskom power connected to the coil.  When there is no Eskom power the contactor opens and all the heavy loads disconnect and the batteries last longer.  This works well when you have excess generation from the PV panels and set the pool pump to run during that time. The pool pump will not drain the batteries if you are not at home to switch it off during a power failure.

Give this man a bells! This sounds pretty effective solution!

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