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Old 10-12-11, 11:52 AM   #51
strider3700
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I'm curious. Have you ever seen how efficient the grid to battery to inverter to appliance path is? with your off peak being 1/3 the cost you probably will still be saving money charging batteries at night but I'm not sure how much.

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Old 10-12-11, 12:31 PM   #52
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Timers work. I use one on my oil burner and save big bucks on oil and a little on electricity.

I have the basic 'default' NStar residential rate, so I'll have to check out their website
and see what they offer for for off-peak plans these days.

The last time I looked, I wasn't using mostly electric heat, and I was using less kW hours..

Have you looked at the actual losses in your system. How many watts of heat are
lost when charging and then converting the DC back to AC later on??
I've heard systems recover 85% of the power used to charge in good systems,
but if the charge and discharge rates are real high, efficiency can drop to 60% pretty quick.

Is your system breaking even? (when compared to grid cost).
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Old 10-26-11, 05:14 PM   #53
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Default Off grid

Hi Xringe, i had read all posts.. Thanks for your investigation and info!

First, excuse me for my not very good english.

I think what happened to your chinese inverter is that the power of the TGI was "regenerated" for the inverter. In other words, current went into the inverter, so the "capacitor" started to acumulate that current and so the voltage was increasing.

What a TGI do is give current at the same frecuency of the voltage of the grid. This means, you can see the TGI as a current source, it doesnt modifies the voltage at all. The current goes in phase with the grid voltage, that means the power is generated (source) and its not consuming.

I think you can use a UPS instead a expensive true sinusoidal inverter. The UPS gives a PMW voltage, this means it have less harmonics than the inverter (is more clean) .

Now im working in a similar idea. The problem of this off-the-grid is when you dont have more energy in your batteries or the solar panel cant give you energy (the night) or simply your system dont have the power to give a load that it needs (a stove of 3000 W for an example). So my idea is to take a system that gives the energy of the PV panels and the batteries, and then if its not enough, it takes energy from the grid. This means a off-the-grid with back-up-grid. All this made with the same equipment (chinese TGI and a UPS). Uhm! in my country send energy to the grid is just give it away (no net mettering for now), thats why the-off-grid is a ver good option. Ill be posting a schematic of what im thinking!

Well thats it, thanks again for sharing your investigation!
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Old 10-26-11, 06:55 PM   #54
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I understand what you want to do, and it sounds like it shouldn't be too difficult.

One method that I was thinking of, was to use an AC current sensor connected to my heating system.
When my heating system was using a lot of power, the current sensor would trigger
a GTI (Grid Tied Inverter) to come on and pull power out of my battery bank.

But, the GTI would be limited, so it would never make more power than I needed for my heating system..
When the heating system power use dropped, the GTI would disconnect.

My DIY circuit breaker design could be hacked to do the switching.

http://ecorenovator.org/forum/applia...r-limiter.html
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Old 10-27-11, 09:21 PM   #55
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Default Off the grid- buck up grid

Interesting, but if you do that youll still getting power to the distributor. I was thinking in the schquematic (attached) i made.

The idea is connect an "UPS online 1000VA (700W)" ( is a type of UPS) before all loads and GTI, this wont let the current goes to the distributor because the rectifier is a bridge of diodes that wont let it happen.

When you connect a load, first this will be supplied from the GTI and if it needs more current, this will be suppliead from the UPS (from the grid throw the rectifier and the inverter). When needs even more power, the UPS will go to the bypass mode (because its overloaded) automatically and then the current flows direct from the grid.

When you dont have a load connected, the current cant goes anywhere, so it will be storage in to the battery of the PV solar panel.

Now my question is: the current really wont go anywhere? maybe the current will goes to the battery of the UPS (voltaje will grow up and then explote (?))
!! I dont know!

If you look this model, when the energy of the distributor goes down. You still can work with the UPS and still can use the GTI. Youll have your own emergency energy system.

Regards!
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Old 10-27-11, 10:42 PM   #56
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Nice, you are putting your whole house on an UPS..

The problem I see with your method, is the UPS's inverter is connected to the GTI inverter.
In my experiment, my GTI was connected to a PSW inverter (like your UPS inverter)
and when the load was too light, the AC voltage from the GTI, climbed very high.
Soon, smoke was coming from my new PSW inverter..
If seems like my Chinese 1200w GTI can't use another inverter as a load.
It really needs the grid to allow it to work correctly.

~~~


If I was going to use a GTI without putting any of my power on the grid,
I would use a current sensor to measure the power being used by my main loads.
That would be my two Sanyo heat pump/AC systems.

If the heat pumps were using more than 450 watts,
I could connect a 400 watt GTI to the house grid.

At that time, the grid would be supplying 50w and my GTI would be
supplying the heat pumps with 400 watts. No power lost to the grid..

When heat pump power dropped lower than 450w, the current sensor would quickly turn off the GTI.

Easy to do, with a small amount of extra hardware.

~~~

One of the posters here did make use of an UPS, but he was using his solar
panels to charge up the UPS's battery. He replaced the small UPS batteries with larger AH batteries.

I think that system would be good to use with this PC, since it's on so much!

Cheers,
Rich
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Old 10-30-11, 03:31 PM   #57
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Yes, your idea sounds good, but i want a generalized system that works in all cases. I mean, for every load, not just for the big ones. Let me ask you a question. What was the configuration when the inverter burn? then why does the system of depdevil1 ( youtube video) works?

MVL.
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Old 10-30-11, 05:43 PM   #58
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depdevil1 is using a MSW inverter + batteries. But, I'm not sure what kind of waveform his MSW inverter is generating.
It might be a small step type waveform that looks very much like a sine-wave.



Plus, his Island grid might have a pretty large load on it, most of the time.
That solid load might be what's keeping his GTI's from putting out high voltage.


IIRC, In my test configuration, I had a 1200 PJ GTI connected to a light load(300-500w),
and a 48v 1500w TSW inverter to simulate the grid.
Not sure what happened, but my guess is the high voltage came from the GTI.
It was working great, then I saw some smoke and heard a pop from the TSW unit and shut down the test.
I think the PJ GTI was connected to the 800w PV array.

~~~

The way I think of GTIs, is a large one might able to provide all the power needed for your loads.
But, if it is connected to a large battery or PV, it will try to run at full power, to it's max rating!
How does it get rid of that excess power (that your loads aren't using)???
It tries to dump it out on the grid.. That's what it was designed to do..

But, how does it dump to the grid? There is only one way it can make
current flow into the grid. It increases it's output voltage. slightly.
Because the GRID is so powerful, it only needs to raise the voltage a small amount.

BUT, if you are running an Island, with limited loads..?. Well, that's a difference story.
The GTI will pump up it's output voltage! It wants to move some kWh onto the grid.. (The real grid)!
My old 1200w PJ tried to smoke my tiny grid!! My loads were too light.
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Old 10-31-11, 01:04 PM   #59
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There is a small step (between the modified and the true sine wave): The PMW sine wave ( the UPS usually use that voltage). I was thinking, and its more simply than i thought. If you send your energy to the distributor grid. The power metter will go back so its the same as you use that energy with your loads. The hibrid system has no sense.

Your inverter burns because the current from the GTI was accumulated in ther internal capacitor (of the inverter). The increasing current produces a increasing voltage (in the capacitor) until it blows up.

I think the key is the inverter that ddepvil1 uses (Xantrex XPower 3000) that doesnt allows that the current goes inside. I know that system has a load detector, when there is no load the inverter turns off. Weve get to open one of that and see what is in there Maybe a diode (in the DC line) is the solution..maybe.
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Old 11-04-11, 08:23 AM   #60
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Here's some new EnPhase info..

Are Enphase microinverters grid tie only?

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