Solar Roof

Depending on how your PV array is wired, it can be generating 1000+ volts, but, not much amperage behind it. Say, 10 amps or so, under perfect conditions. My box takes the high voltage DC, reduces it by a wide margin, boosts the amperage by a wide margin (relatively speaking) and feeds that to the inverter on the battery bank terminals.

If the incoming voltage should drop below a pre set threshold where my box cannot provide 48 volts DC to the inverter, my box will provide it nothing instead. Not less, but, nothing. As far as the inverter is concerned, it becomes a 'dead' battery. There are a couple of components inside the box to give the inverter a 'dummy load' for charging purposes, so that the inverter isn't harmed and my box isn't either. But, that's actually being wasted, since it's not storing the current like a real battery would.

My box is simply taking advantage of a series wired PV array for high voltage DC to generate amperage equ to a small battery bank, roughly

100amps or so. I can increase it's amperage output by changing out some of the components. But, nothings for free, in order to run the changed out components, It'll require additional voltage.

If the PV array is parallel and/or a series/parallel combination, addtional changes would be necessary in order for my box to work properly without smoking itself, damaging the PV array and/or the inverter it's tied into.

This is why I said it's VERY specific to the inverter and the PV array configuration it *was* able to provide power to. As the client is using an actual battery bank now, my device has been disconnected and is sitting on a shelf or something waiting for myself and/or boss persons to come get it. As, it's no longer a necessary item.

Essentially what happened was the following:

If the grid goes down, an interlock seperates the inverter AC output from the grid, so that a line man or other personal won't be lit up when they are working on the grid. And, prior to the battery bank installation, my box would take over as long as the PV array is up and running and temporarily continue providing power to the inverter by 'pretending' to be a small battery bank. Now, if it's very cloudy and/or nighttime and the grid goes down, my box isn't able to do anything for the inverter, so, no power is being sent back onto the grid, anyway, and, no power is being provided for the house, either.

At this point, a 30 second delay without grid power or inverter power being detected will cause his generator to start up. The way it was wired, though, if the generator is running, the interlocks will kick in and isolate both the generator as well as the inverter from the incoming mains (the grid); so there's NO chance someone working on the grid will get anything nasty there way and the inverter won't be damaged by power spiking as the generator begins providing power. IE: if the generator is running, the inverter has no access to the 'grid' or the power being supplied by the generator, either. It's isolated from both and doing nothing useful for the client at this point, even if it were able to do something useful. As it's electrically disconnected from the mains that feed the house at that point. And, well, if the generator is running, it's because the inverter and/or grid for whatever reason, couldn't provide power in the first place.

I hope that clears things up.

It depends on what you need/want to use it for...

Reply to
Diesel
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Not if it's a residential solar system, which is what we are talking about here and it complies with the NEC. NEC limits the maximum voltage to 600V. And you claim to be installing these?

The install manual for the hybrid inverter you referenced cleared it up. It shows no examples of using it without a battery bank. And the install instructions specifically say it must be used with a battery bank.

Still waiting for examples of all the solar install companies hawking the capability to power the house during the day with a grid tied system without a battery bank. Still waiting for an app note from one of the eqpt companies that shows using their gear to power houses without the grid or a battery bank.

Show us the case studies. And besides, the whole thread was about what is generally being done, not some fringe users.

Reply to
trader_4

You don't have a commercial installation. You have a bunch of auction acquired stuff cobbled together to make something that works for you. Nothing wrong with a hobby project; I do it all the time. But that's not something you can do with a commercial installation. For general use, you'll find your customers more demanding.

You've described a situation where you have grid tie. You have decided that you can tolerate a 30-second loss of power when the grid is down. You replaced battery storage with diesel LOCAL storage and a generator to convert it to electrical energy. You have not described what happens when the generator is running and the cloud has passed, or the load dropped below what solar can supply, or what happens when a new cloud arrives.

Take a look at the curve here:

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When solar becomes insufficient, the operating point is past the knee of the curve. Small changes in load current can change the voltage dramatically. If the refrigerator starts, the current surge can drop the voltage below your threshold and shut down your system. That lets the panel voltage rise above the threshold. What do you do? With the grid down and insolation low, you will see a lot of those cycles. They can happen way short of 30 seconds apart. They'll probably happen every time you turn on the electric stove or air conditioner when insolation is low. Do you start the generator? Do you let the fridge try to restart every few seconds?

Engineering is a process of defining a problem and providing a ROBUST solution that meets the needs of your entire customer base. Sure, you can restrict your customer base to those who want a generator in their back yard and tolerate limit-cycle oscillations in their utility supply. A commercial supplier cannot do that.

Engineering is a process of recognizing, meticulously defining a problem and solving it. You must predict and evaluate the performance of your solution for situations at the limit that most people would not even consider. It requires empathy, putting yourself in the shoes of your target audience. That's something sorely lacking in the engineering community. It's almost non-existent in the newsgroups where everybody talks, few listen and even fewer have a clue. You can't just look at the 10KW on the label and assume it's all good. It ain't.

Many people reading this will conclude that they could tolerate your solution. People over in that other group posting pictures of their cat would find it totally unacceptable. There are way more of them than us.

In summary... You evaded the issues. You DO have grid tie. You DO have local storage, just not batteries. You tolerate interruptions that many would find acceptable in a system that cost them big bux.

Nothing that you have said debunks my assertion that widespread use of rooftop solar without local storage is a fool's errand. Nothing wrong with a hobby project. It's just not a solution for the masses.

One thing that just occurred to me. How does rooftop solar deal with 240V appliances in locations. where 2X 120VAC is the norm, like the USA. Seems like a huge complication to generate two separate 120VAC outputs and try to figure out how to load share a house designed with the ability to use either phase indiscriminately. But, if you don't, the clothes dryer or electric stove won't work. Converting water heating, HVAC, clothes dryer, etc, from electric to gas is not feasible for existing houses.

The hobby project rolling around in my mind would consist of about 17 RV batteries in series. Or maybe an electric car battery. Buck convert it to 170VDC and use that to create 120VAC. Problem is that neutral not directly connected to ground probably violates all manner of safety codes. Existing inverters have solved that problem. On the input side, panel voltage set to something near max battery voltage (~250VDC) at max insolation. MPPT buck/boost controller to charge batteries. May also want a second buck controller to bypass the batteries and feed the 170VDC directly when insolation and load are high. The objective is to keep voltages as high as possible everywhere to minimize current-related efficiency losses.

Depending on usage patterns, it may be cost effective to dump excess back into the grid, but that's not the objective here. The objective is to create a scalable solution to unload the grid without destabilizing their generation and pricing models.

There are lotsa gotchas in the above concept that need to be addressed. That's the fun of engineering. With the 60' trees all around me, the project will never get past the fantasy stage.

Reply to
mike

When this setup was installed, according to a true RMS FLUKE meter, it was generating over a thousand volts, DC. granted, that's with both 'strings' and no load present on either of them.

You obviously have no idea about what I wrote about. Yet, you continue, and call me the troll? Laughable.

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Cripes.. You could be almost anything, such a wide brush...

So, I will ask for my own clarification.. What do you specialize in?

Ahh, I see you've started moving goal posts early. Sorry about that.

Reply to
Diesel

I don't have ANY installation, myself. But, the client does. I shared pics previously of some aspects to its installation. The pics were originally taken for 'promotional' purposes: advertising for one of the companies I work for. I was provided copies.

No, I do not. The home owner doesn't either. The panels, inverter, wiring, etc (except for my 'modbox') are sourced from actual companies, directly purchased from them and/or authorized resellers. Nothing from auction, ebay, etc. Installed by properly licensed electricians. We aren't jake legs.

It wasn't a hobby project...And wasn't my customer, either. I don't own the company I did the work for.

To reduce the clients electrical bill, yes.

I didn't make any of the executive decisions. The client made that decision.

Well, as I said, the generator comes online if no power is detected on the mains, for 30 seconds. As long as the PV array is up, and my box was working (or the battery bank now), that doesn't happen, so, the generator doesn't run. The generator is propane, btw. Not Diesel.

Sorry, I thought some of this was self explanatory. It would be to most other electricians I know. I'll humour you though.

It's done by a few automatic interlock switches. If it detects a load present from the grid and/or inverter for more than a preset amount of time, it disconnects the generator and re-establishes connection to the inverter and/or grid, depending on which unit has resumed providing power. IF the power remains 'stable' for a preset period of time after switch over, the generator is shut down. This prevents unncessary switching and gen shutdown/restart when the power grid and/or inverter is trying to come back up, but continues to fall back out.

The inverter has one, the generator has one, too. And, of course, the inverter has a manual switch that the home owner can access which will disconnect it from the grid, whenever they want. I personally wouldn't, since when it's up and running, it's able to save him a power bill, but, that's his decision to make, not mine.

If the refrigerator starts? Well, you see, the problem with your question is this:

It's a propane driven refrigerator. It *DOES* have a small battery to provide power to the internal LED lighting, though. But, that doesn't have anything whatsoever to do with the panel in the house. Infact, it doesn't use *any* power from the house. Not a bit. No way to plug it in, infact.

No, they don't.

Again, no. The stove isn't electric. It's propane, too.

The air conditioner is propane, too. As is the heating system. They do require a small amount of electrical energy to run blowers, but, it doesn't put the drain on the panel you seem to be expecting it to. They have very efficient motors for that...so, you don't even see the lights dim for a second when one switches on.

The fridge is a self contained unit, that has a gas line fed to it. It doesn't make use of household power and could care less if power is even available to the house. It doesn't even need to be plugged in for ignition purposes.

I don't know what they can tolerate or not tolerate. This system along with the house, etc, was custom built to the home owners specifications. They wanted it done this way, they got what they wanted. Would I personally do this myself? No.

I like the grid and all it affords. I'd require a hell of alot more electrical power than he needs to run my computer lab, let alone my work shop, or the house itself. (The shop and house are seperate buildings). It would cost me a fortune, even with the people I know and access to materials I have to be able to harness enough 'sunlight' to power my stuff. I'd have to factor in additional power for my welding equipment, tube benders, etc in the shop.

They aren't exactly gentle when it comes to electrical power consumption. Neither is my computer network for that matter. it wasn't built with tree huggers in mind. It's very kilowatt friendly. And, NONE of my appliances are so called 'off grid' ones. They ALL use electricity. I have gas and electric heat, and, I'm not willing to give up my electric comfy heat.

Then there's battery/generator maintance, additional costs in safe wiring for the interlocks, etc. I see no real benefit to this for my situation. I don't want to live 'off grid'; been there and done that when I was alot younger than I am now. Fuck that shit, I like creature comforts and modern technology and I'm not nearly as financially 'f*ck it all' as the client is. I've got enough tied up in nearly instant on emergency power for this place as it is. And, I only need that because of the computer equipment here. Some of it MUST be able to function 24/7/365 days a year. UPS ensures computers remain online and okay while the backup power switches online, in case you were wondering, in MY house configuration. While there is a small delay in generator coming online for me as well, there's NO waiting for power to resume for these machines; they *never* noticed power dropped out.

And, my generators are more than adequate to run my entire property, at full power if I wanted to do so; without lag, hesitation or strain on them. I planned ahead. Overkill, according to some, but, more amps than you need is ALWAYS better than not enough.

I don't mind electricity at all, but, I have this unreasonable fear personally about gas. I don't like the idea of an explosion.

I recently found the other newsgroup, myself. I was keeping tabs on someone who's dead set on stalking me and punishing me for what he feels are wrongs against him. But, heh, he initiated the problem with me, he's simply bitten off more than he can chew.

This should be fun.

I've evaded nothing of the sort.

I'm personally tied to the grid, yes.

Last time I checked, generators didn't store power. I have generators, no batteries here. You're confusing me for the client. They have both.

The client tolerates an interruption in power, yes. I do not.

It's not a hobby project.

Do you think the inverter is tied into a single leg? :) Think again. It's a 240volt AC output device.

The house was built new with the intention of using gas appliances. So...

That's an issue the client and myself, don't have. OTH, I do have a huge dust problem here. I've planted some grass seeds recently though, so I'm hoping that will become an issue of the past.

Reply to
Diesel

I'll clarify this for you, since you seem to be ignoring things, and, I suspect you're doing so intentionally at this point. The PV array consists of TWO strings. When tested together, in series, they generate a little over 1000+ volts, DC, yes, they most certainly do. The voltage drops by half and doubles the amperage inside the combiner box on the lines which feed the inverter (parallel)

So, it's well within NEC specifications. The other line that comes out of the combiner box keeps them in series to feed my 'modbox'. It's not concerned with high amperage output, it needs the higher voltage, instead. It all passed electrical inspection too. We didn't pull any 'hide the shit' until the inspector leaves and continue wiring.

Reply to
Diesel

I am curious, which make and model of panel was used in this array? How many panels?

Reply to
Stormin' Norman

I would want to see what conductors he was using.

Reply to
gfretwell

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18 panels, total. Two strings, 9 per.

Reply to
Diesel

Thanks, that is interesting.

Have you wired all panels in series to get your approximate 1kv? Does your step down transformer then bring it down to 220-240v?

What is the length of your run at 1kv? What size conductors? Are you using a Teflon insulated cable?

Is the array roof or ground mounted?

Reply to
Stormin' Norman

Thanks

Yes, to run my modbox. Otherwise, they are parallel for the controller that runs the inverter. 1kv is too much for the controller or the inverter. But, my modbox needs that additional voltage to be able to emulate a small battery bank. It reduces and converts the 1kv to 48volts dc with a higher amperage than the PV array can provide. It was tied into the battery bank terminals.

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You have your choice of the control panel...

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Or this version of the control panel that requires either a laptop or Android device.

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They're sold seperately.

The inverter does, yes. It's transformerless, though. And, a controller board keeps the PV array from overloading it. I figured you might ask about that, so here's the board specifics. [g] It also maintaines the battery bank (formally my modbox)

Less than 50ft total run per string. #10, the cable is rated specifically for this work. This is one of the suppliers we used, for the cabling...

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We opted for #10 because our strings exceeded 7 by 2. :)

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roof mounted. And the metal support structure is grounded for safety.

I do not work for either company, I'm just one of several people very pleased with the products they sell.

Reply to
Diesel

Even residential customers can't. So far, Diesel hasn't provided us with examples from all the solar installers that offer a residential grid-tied system that also supplies power to the house when the grid is down, without a battery bank. If this was possible, practical, it would be a powerful selling point. But it isn't, with the cloud problem, the rainy day problem, etc, being the major, insurmountable problem. Like you say, customers aren't going to tolerate brown outs, total outages, from passing clouds. And during a power outage, when do you need power the most? Typically at night, when the sun isn't shining. That's why you don't see installs that offer power without the grid or batteries.

Reply to
trader_4

Well then it's in violation of the NEC.

Still waiting for those examples of grid tied solar that powers the house with the grid down and no batteries. If it was possible, all the solar install companies would be hawking it. So far, you can't produce one. And I provided you the install manual for the hybrid inveerter that you cited, where it only shows installs with a battery bank and where it specifically says it must be used with a battery bank.

Reply to
trader_4

More gibberish. If they are wired in series and installed that way, then it's a violation, because 600V is the max permitted voltage between any two conductors. If you wired them in series as an experiment, which sounds rather bizarre, then who cares what the voltage is? And we are talking about real residential solar systems, installed to code, not a hack job, are we not?

Reply to
trader_4

It's #12, my apologies. Confused this one for another job I was looking at.

Amperage is well within limits:

Reply to
Diesel

No, it's not. It's a two string array. I was measuring the combined voltage from both strings. I did say BOTH strings and no load present on either of them, Didn't I. Why, yes, Yes I did...

Reading comprehension, right? :)

Don't wanna tell me? Are you still in college to become an electrical engineer or something?

I already answered that for you. While it wasn't using batteries, it was using something which emulated a small bank, as long as the PV arrays were up and going.

Already discussed that too. Perhaps you should consider switching over to a real usenet client so you can keep better track of replies?

OR! A device which can use the arrays to emulate a battery bank. :) Are you sure you're an electrical engineer? I thought I was going to be able to learn something useful from you, but, so far, I've learned nothing new from you. I'm not impressed.

-- I would like to apologize for not having offended you yet. Please be patient. I will get to you shortly.

Reply to
Diesel

Are you sure you're an electrical engineer?

It *IS* installed to code, passed inspection just fine. Not a hack job, no. Far too much money spent in equipment alone to justify a half assing installation.

Reply to
Diesel

Thanks very much for taking the time to put all this information together, tomorrow morning when I have more energy, I will scour all of it.

Reply to
Stormin' Norman

On Friday, May 12, 2017 at 10:38

The lights are just tied t the grid. the power company charged X per connection......

if its a light that varies depending on season, they calcuate that too.....

Reply to
bob haller

I'd like to hear more details about how it works and the algorithms for dealing with changes in insolation.

Reply to
mike

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