Solar Roof

[mike]

That wouldn't happen if you had battery backup! Classic! ROTFL ;-)

[Diesel]

I find your added condition to be very amusing. Previously, you stated (and quoted several outdated sites as your sources) that without grid power, the system didn't work. So, I asked you what you thought the battery bank(s) were for, and heard crickets as a response. it's no surprise, why, either.

I brought up the usage of battery banks along with what I call the 'modbox' to provide power when the grid is down. You further commented (and again used outdated sites for reference) that the inverter isn't allowed to supply power if it's grid tied while the grid is down, and again, you were wrong. I asked you for the second time when you mentioned that what you thought the battery banks were for. Crickets, again. As expected.

You have no first hand knowledge of this subject, and, evidently, you don't even understand what my modbox is doing, despite devices VERY CLOSE TO IT already on the market, right now! Have you seen the extremely small portable jump starter kits that will fit in your glovebox? They typically run on a 5000MA lithium battery pack producing less than 12volts usually, and, are somehow able (as if it were magic) to provide 12volts DC at 400amps (or more) to jump start your car. Obviously the battery pack they're using doesn't have

400AMPS on it to help you out, but, with some electronics in a very small physical package, it's able to come up with it.

My modbox is very close to one of those in design principle, except that it outputs 48volts DC (under load!) at 120+amps with variable input power from approx 800 to 1200 volts, DC (with approx 3amps!) In other words, it's emulating a small battery bank.

Obviously the more voltage you can feed it, the more amps it can deliver. Anything less than 800 or so volts though will cause it to go into a shutdown condition and it'll provide nothing. It will do it's best to keep the voltage at 48volts, under LOAD. So, it has to have a minimum of 800 volts at approx 3 amps or it will not be able to do it's job, and, rather than risk undervolting, it'll shutdown.

Anything over 1200volts will also cause a shutdown condition, so that it doesn't get fried. Lightning strikes, etc being the exception. Situations like that will cause it's internals to sacrifice themselves, but, no guarantee is made that the inrush current will be stopped as it does so.

Externally, you MUST connect two! 600volt DC PV strings, and, internally it sets them up for series to provide it power. So, at no time, is more than 600volts coming on any lines going to it, or out of it.

[Diesel]

Which is ironic on the face of it, as Trader initially said grid tie can't run without the grid. :) So that would make a battery bank (emulated or real) rather pointless. ROFL, yet, they exist along with the inverters able to run on them, when the grid is down. Without backfeeding into the dead grid. As I wrote, initially.

[Diesel]

You're very welcome. Btw, for NEC code purposes, the series wiring is done on the internals of my modbox. In other words, you run both strings to it. And it's #12 for most of the power input side of the system. PV array strings, etc. The voltage is upto 600volts per string, but the amperage is low. The output on the modbox and the battery bank uses much larger wire as it's carrying lower voltage, but, MUCH higher amperage. The output side of the inverter is also a larger capacity wire, but not as large as the output side of the modbox or a battery bank. Since it's being tied into some switch gear (interlocks, disconnects, etc) and eventually winding up at your panel.

[Diesel]

It's very similar to the 'mini' or glovebox size jump starter packages for your car. But, instead of using a small lithium battery, it uses power from the PV array. It does require a minimum of 800 volts upto 1200volts and can run on a little less than 3amps, but,

3amps keeps it happy. As long as the array can do that, it's golden.

In other words, it requires an array with two strings, each capable of close to 600volts. You bring BOTH strings to it, and, it'll internally treat them as a series connection, to get the higher voltage it requires.

It makes more DC voltage than those devices, but, quite a bit less amperage. And, as long as you can feed it a constant voltage supply, it'll continue to provide the required output. Unlike the mini jump starter kits.

I plan to get a patent on it at some point (if at all possible) and market it to various solar companies, pending they aren't already developing their own versions of it. So, I'm not going to get too specific on it's internals, if that's what you're wanting to know about.

Suffice to say, the modbox will be coming back to my workshop, when I get the chance to visit the client and retake possession of it. They don't need it's services anymore, they have an actual battery bank now, capable of delivering 600amps.

[Stormin' Norman]

I do, but they need to be recharged each night.... ;-)

[trader_4]

It may have passed inspection, but it's not in conformance with NEC code, which almost all jurisdictions use, if it's generating voltages above 600V. What is the compelling reason to go above 600V anyway?

[trader_4]

No, BS comprehension. Who the hell cares what the combined voltage of a solar array is if it's not INSTALLED THAT WAY? That's like me saying I have 1200V in my house, because I can add the voltage drops across ten 120V loads.

Maybe I missed that part. What exactly "emulates" a small battery bank? Seems logical that one would just use a small battery bank, which by the way is exactly what the install instructions call for. Do you always have to reinvent the wheel?

Still waiting for the examples of all the installs, links to all the app notes from eqpt suppliers on how you can have grid tied solar and power the house with the grid down and no batteries.

Are you sure you know WTF you're talking about? You simply claimed that he had a system that was grid tied, that powered the house without a battery bank when the grid is down. Only now are you bringing up this "emulation" thing. Nuff said. And if this "emulation" thing is true, why emulate a small battery bank instead of just buying one?

I thought I was going to

Some people are incapable of being educated. Still, I've provided you with a lot info here, like the fact that you can't find examples of what you claim, which is eqpt companies or solar companies hawking grid tied solar that powers the house when the grid is down, without batteries. Ever hear of clouds? I also educated you on the fact that

1000V in residential solar systems, which you claim too, is a violation of NEC. Now of course you claim it's not actually wired that way, so then of course it's just a BS number.

[trader_4]

Never mind the algorithms, who emulates a small battery bank? What installer would violate the install instructions of the hybrid inverter that specifically says it must be used with a battery bank? Also the choice of words, used "something" to emulate a battery bank is probative. Also, why didn't we hear about this "emulation" in the beginning of this whole discussion, but instead it comes up now?

[trader_4]

Again, you fail in the concept of CONTEXT. Before I made my remarks, before Mike made his YOU posted this:

"He has no battery bank, so, during the nighttime, and on very cloudy days, he'd require the grid to make up the difference. If he elects to install a large enough battery bank, he wouldn't require the grid during the evenings or when it's cloudy outside. "

Capiche? I was talking about YOUR case, where you said he has no battery bank.

Diesel: I have a car with no engine.

Others: Well then the car can't be driven.

Diesel: You're wrong, you just said that cars can't be driven.

Typical.

So, I asked you what you

No crickets. I immediately showed you that your own link to the supplier of that hybrid converter only shows it being used with batteries. I went further, I supplied the install manual, where it specifically says it must be used with batteries.

Good grief, you're a weasel. You specifically said the system you were talking about HAD NO BATTERIES.

I can read the install manual, read what the supplier of that hybrid inverter says. I can also see that no solar install companies, no suppliers are hawking grid tied systems that power the house with the grid down and no batteries. ABSOLUTELY consistent with what I've been saying.

and, evidently, you

Sure, we all believe you built a "mod box" to emulate a small battery bank instead of just using a battery bank.

Again demonstrating that you're in way over your head here. You don't understand electricity 101.

[trader_4]

Now you're lying. YOU first gave us the specific example you were talking about:

"He has no battery bank, so, during the nighttime, and on very cloudy days, he'd require the grid to make up the difference. If he elects to install a large enough battery bank, he wouldn't require the grid during the evenings or when it's cloudy outside. "

I replied to that, IN CONTEXT. You ruled out batteries and I replied to that. Still waiting for you to show us all the install app notes, all the eqpt suppliers, all the solar install companies offering grid tied solar with no batteries, where the house is powered when the grid is down. It would be one great selling point. Where oh where are they all? Instead, I gave you exactly the opposite, half a dozen explaining why it won't work.

[mike]

I'm not an electrician. I didn't consult the NEC. Regulations can sometimes sound odd to address a particular situation. On the few occasions I've consulted the building inspector, his opinions were different, more lax, than my interpretation of the words written in the NEC.

A few comments: In your house, you have 120V x 1.4 x 2 P-P. But the center of that is near ground. You can never touch more than 120V x 1.4 peak volts relative to ground. This doesn't prevent you sticking both fingers into a 240V socket that runs your dryer...don't do that. Still just as dead, but you never experienced anything greater than ~170 V peak relative to ground.

Dunno how the code is interpreted, but, if you have two 600V panels connected in series inside your box, you have 1200V outside your box and on the panels. You might be able to skirt this like inside your house. Ground the center point of the 1200V where the panels connect together. Then you'll never have more than 600V to ground anywhere on the wiring.

There is no magic. You can't get more instantaneous power out of the emulator than you can get out of the panels WITHOUT STORAGE of some kind. Capacitors are a form of storage. The energy stored in a cap is proportional to the square of the voltage. You can store 400x the energy in a cap at 1000V than you can at 48V. Problem is that high voltage capacitor banks big enough to be useful are expensive...probably more expensive than a 48V battery. You could make an argument that a 1200V panel will put out 48V at lower insolation than a 600V panel. But, at low currents available, it won't do you much good. And component expenses for the higher voltage and increased losses will probably exceed any gains.

I've had many discussions over the years with people who took a concept they didn't fully understand, extrapolated it into a region where it didn't apply and believed they'd invented something. In every case, they hadn't invented a new branch of physics. They were just plain wrong. They'd neglected something very important and their system didn't do what they thought.

Under conditions of high insolation, you certainly can run your house without a grid or storage, until the peak load exceeds the currently available power. Then it's over in an instant. Let me rephrase... The peaceful consumption of energy is over in an instant. The thrashing of the voltage coming out of your 120VAC socket can continue until the sun goes down or something catches fire.

You can't build a practical solar house that most people would accept without the grid or local storage or some other energy source, like diesel or natural gas or pumped water or... Energy out of a system can never exceed the energy in. Without storage, instantaneous power out can not exceed power in. Solar is ill-suited to applications without storage or replacement (the grid).

[mike]

You're making a guess and extrapolating it and it still doesn't make the argument.

If your car is in good shape and the battery is good, it will start in a second or two. If you left your lights on and ran the battery down slightly, the jump starter can replenish the surface charge in a few seconds to the point that much of the starting current is will still coming from the car battery, not the jump starter.

If your battery is DEAD, you probably won't start most cars from the handheld battery.

No, there aren't electronics that manufacture 400Amps out of thin air.

But that's irrelevant. It's a battery; it's storage. Your system doesn't use either.

48V x 120A = 5760W out 1200V x 3A = 3600W in

My math disagrees. And when a cloud goes by, the system will crash as soon as the output power required exceeds the input power available from the panels because you have no storage.

Your box adds cost, losses and does nothing to fix the power problem. System reliability goes down as the voltages go up. You are NOT emulating a battery bank because you have no storage. You have a presumably regulated power supply at 48V output that still has all the issues that comes with unreliable solar. You have gained cost and complexity. You may have reduced wiring losses, but that's a whole different argument that doesn't address the unreliability of solar without storage.

There is no free lunch.

[trader_4]

This is simple. In the beginning of this thread, Diesel told us that the install he was talking about, the one that was grid tied, no batteries, but provided power to the house when the grid was down, used a Conext-XW hybrid inverter. I already provided a link to the install manual that says it must be used with a battery bank, which is contrary to what Diesel was claiming. So now, let's see what Conext says about the specs for the input voltages:

file:///C:/Users/Int1/Downloads/Schneider-Electric-Conext-XW-60hz-inverter-charger-datasheet_eng.pdf

The nominal input voltage is 25 volts for the small one, 50 volts for the larger ones. Max input voltage is 32V, 64V respectively.

It's typically used with the solar charge controller that goes between the inverter and the solar panels, so, let's look at that:

Max DC solar panel input votage, operating: 140V Max , open circuit 150V

Yet Diesel claims to have a residential system that's feeding at least 600V into a solar system using at least the hybrid inverter from that company. Go figure.

Nuff said, but if that's not enough, how about this:

DC-to-AC Inverters for Your Solar Equipment - dummies

"In your solar power system, you need inverters to take the low-voltage, high-current signals from the PV panels and convert them into 120VAC or 240VAC, which is directly compatible with grid power. "

It would have to be one hell of a cap. And what's the point when storage batteries are readily available?

The energy stored in a cap is

Which it seems the eqpt manufacturers and installers understand, so they don't offer solar house power systems that power the house without batteries when the grid goes down.

[trader_4]

First problem there is it doesn't take anywhere near 400A to start a car. Typical car starter is ~1000 watts, so less than 100A will do. These new jump starters, AFAIK, are relying on lithium batteries, which pack a lot of power into a small size. You only need to supply 1000W for a second to start a car with no other issues. If a lithium battery pack can power a handheld shop tool for it's job over a long period, what's so special about providing 1000W for a second or two?

+1

Looks like it doesn't use 600V either.

+1 It doesn't add up. Funny coming from the guy who made the alleged "mod box".

And something converting power from one source to another is very different than a BATTERY. A battery stores power, what's described above does not.

+1

+1

But a battery bank would. Why would some install company screw around with a "mod box", instead of just using some batteries? He did claim that he installed this working for a company for a client, didn't he?

System reliability goes down as the voltages go up.

Bingo.

+1

[Diesel]

My apologies, I confused you for another poster:

MID:

Does he know that most grid tie inverters will NOT function without the grid.

What that means in practical terms, he cannot use the electricity from solar during a power failure.

I think that is a travesty and the rules re inverter designs should be changed.

Right now this behavior is REQUIRED by the rules to prevent the possibility of backfeeding power to a dead power line.

At the time I wrote the post, I was not aware of any configuration changes in the clients setup. IE: As far as I was aware, they did not have a battery bank and were still using my modbox. My information wasn't accurate. Simple as that.

[Diesel]

That it did.

Using both strings in a series wiring fashion, it can, yes.

Already explained.

[Diesel]

Nope, 1200 isn't flowing outside the unit. Circuitry inside the unit prevents that. I'm not new at this, nor am I an idiot.

I don't disagree.

Yes they are. I wasn't aware Capacitors was considered cheating? They aren't batteries...

Well, considering that the client didn't pay for the modbox, not a single dime, they aren't out anything. And, I already covered this possible issue with a reply to Trader sometime ago; when he/she asked why the solar companies weren't doing this, already.

Interesting.

I didn't claim to have invented any new branch of physics.

Do you often make such assumptions?

Unless the peak load of the house will most likely, never exceed the systems capacity. You seem to be quick to forget, the appliances are GAS, not electric. The 'load' for the house is essentially LED based lighting and some home entertainment gear, oh, and a laptop and a few tablets that for the most part, ONLY use the HOUSE to recharge.

That's quite alright. You've made enough assumptions and rolled with those assumptions.

It's very interesting to me how we go from, it doesn't work if the grid is down, to, you can't do it without such and such additional conditions. Fact is, yourself nor Trader have one of these 'Solar' houses or wired one, and you both seem to have a problem with the idea in general.

I've read enough, thanks.

[Diesel]

Nope. I'm going by first hand experience testing several of them on the market. I don't work for any of those companies, either. Despite occasionally getting free gear to test and report back on. While I'm not paid in money, I do get to keep the gear, even if the report is a terrible one.

Actually, you can disconnect your cars battery and run the jumper cable clamps to your wires, directly. It will start your car if the car can be started on the amps it can provide.

See above. The reason it may not (I noticed you used the word probably) if connected to a dead battery is because a dead battery is like a black hole to incoming electricity. It's a heavy load while dead/very low. Little electricity will be passed along so long as it remains connected in those cases.

I didn't say it did it out of thin air.

Caps are storage (not for long term in this case), unless I was taught incorrectly. And, It certainly does use some.

Well, no, it won't. It possibly could have if left in it's original configuration, but, as I wrote, a few days back now, he's on an actual battery bank. The modbox is no longer wired into the system.

My box is designed to keep the inverter going via PV array (if PV array permits it) in the event of temporary grid failure. I didn't say it would do anything more than that.

I have no longterm storage options in the modbox, correct. However, as long as the PV array is up and going, It is as far as the inverter is concerned, a small battery bank. If the grid temporarily goes down, the inverter won't care, it can use the power provided by the modbox to keep the client going. Which was the intention behind it.

Complexity, slightly, cost increase? No. The modbox cost me, but, not the client. And, no there's no free lunch. Be it solar, wind, nuclear, whatever you prefer. Nothings for free.

[mike]

It's not rocket science. Draw a schematic with two 600V battery symbols representing the solar panels. Connect them in series inside your black box. Inside the box, place an X on two points attached to the panels that have 1200V between them. Convince me that you can't find two points outside your black box that have 1200V between them. It'll be two of the four wires attached to the black box. If you can't they're not in series.

Yes, I do. If they can't explain the phenomenon using known laws of physics, there has to be something new, previously unknown going on.

Ok, so you've moved the battery to the device. That works. But it's storage nonetheless. If you have adequate distributed storage in devices to run them without grid tie, you don't need grid tie and you're off the grid. Good job. Just don't try to tell me that it's a typical residential rooftop solar system for the masses.

You're welcome.

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