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421 posts

Ultimate Geek
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Topic # 222774 28-Aug-2017 10:35
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"Grid tied" / "on-grid" is normal for 99.9% of homes in NZ. It means a power company connection to your home.

The opposite is "off-grid", which means no electrical company connects to your home.

Grid-tied solar: using large solar panels to reduce your home's electricity bill.

Why Grid Tied Solar SUCKS For Emergencies

In emergencies when you lose power from your electrity company. This short video explains why having solar panels on your home won't work, unless you have a fairly complex (and expensive) set up.



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  Reply # 1853860 28-Aug-2017 10:36
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Perhaps you could add a bit more text into your post, to make your point, rather than relying on everyone watching a video.





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Ultimate Geek
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  Reply # 1853921 28-Aug-2017 11:35
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Also, it's not exactly news, the reason why anti-islanding is required is to make sure you don't kill electrical workers when there's an outage and the supposedly safe wires are actually live.

 
 
 
 


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  Reply # 1853954 28-Aug-2017 12:23
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For the odd outages I have UPS's and a generator. Solar is to save money not to make me independant. It works fine for what it is.

 

In the future I could add something like a tesla battery, which is basically a big UPS, but that isnt needed as vector have managed to get the previously terrible north shore power network that used to have many long outages over winter into something quite reliable.





Richard rich.ms

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  Reply # 1853983 28-Aug-2017 13:20
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The abilty for a house to switch over to battery power will come.

I believe there's a lot of work going on re regulations and standards in the industry, consultation etc

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  Reply # 1854165 28-Aug-2017 15:58
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its not much more expensive these days to get an inverter that will cut the grid off when it looses power so you can still run off solar


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Uber Geek
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  Reply # 1854187 28-Aug-2017 16:39
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richms:

 

For the odd outages I have UPS's and a generator. Solar is to save money not to make me independant. It works fine for what it is.

 

In the future I could add something like a tesla battery, which is basically a big UPS, but that isnt needed as vector have managed to get the previously terrible north shore power network that used to have many long outages over winter into something quite reliable.

 

 

Freshy this weekend made use of one. First in the country with the Vector/Tesla agreement since 2015 (of a Gen II)

 

http://www.voxy.co.nz/business/5/291424 


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  Reply # 1854446 28-Aug-2017 23:01
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I will be setting up a solar + battery system on my own house soon. I will be designing it so it will never be able to export power on purpose. (Both normally and under fault conditions). As Flick Electric don't support solar. And being able to operate "off grid" Is a mandatory feature I want.

 

I will probably start just by using an old but working 1.2KW (2KVA) UPS that I have. And adding solar panels to it along with disabling it from charging the batteries from the mains. It just uses 48V SLA batteries. So easy to add some bigger deep cycle batteries. Hopefully putting it into battery test mode will allow me to operate it off the batteries with the mains still connected, and have it switch to bypass mode if it gets overloaded.

 

It managed to start a fridge compressor no problem, and run a 1KW heater. And it will happily start up and provide output without first needing to connect the mains. So it will work "offgrid", I just don't know if it will survive running continuously. As it's internal transformers got really hot. Output stage is iron core transformers running at 50Hz in a tank circuit, so they probably have high iron losses.






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Ultimate Geek
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  Reply # 1854458 28-Aug-2017 23:25
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You might be thinking of the copper losses. Iron losses would probably show as a loss in efficiency.

 

EDIT; Suggest you soak test your UPS / inverter before relying on it !


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  Reply # 1854459 28-Aug-2017 23:28
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regardless, UPS"s are not made for efficiancy in their inversion, since it will seldom operate there is little point spending more just to get another 10-20% runtime when the same cost could go towards a larger battery and get considerably more runtime.





Richard rich.ms

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  Reply # 1854482 29-Aug-2017 00:15
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elpenguino:

 

You might be thinking of the copper losses. Iron losses would probably show as a loss in efficiency.

 

EDIT; Suggest you soak test your UPS / inverter before relying on it !

 

 

Due to the tank circuit, the transformers will be constantly charging and discharging energy between themselves and the tank capacitor. And the drive circuit is a MOSFET H bridge operating from the battery supply.

 

Interestingly, it outputs a pure sine wave. But when you first connect a load (both good and poor power factor loads), the output waveform gets really notchy, then a second later it goes back to a pure sine wave. So I suspect that the H bridge is sticking a really complex high frequency waveform into the transformers, and using the Tank circuit and transformer inductance to turn it into a pure sine wave. My understanding is that laminated iron transformers have quite high losses at high frequencies. I do agree that there will be copper losses as well. I should start it up with a very low load on the output, and see if those transformers start heating up. (annoyingly, it turns itself off if there in no load connected).

 

Even if I do destroy it, it only cost me $35, so no great loss. And since it uses a nice standard battery bank voltage (48V nom), It will be easy to swap it out with a better inverter later.

 

I have found some well priced 20Amp MPPT buck converters on Aliexpress which are adjustable from 14V to 70V or so output, at 56V output they are rated at 1.1KW. So extremely good value for the price. I have ordered one, which I will test with a 270W panel to charge my current 12V backup power system. The only annoying thing is their max input voltage is 100V, it would be better if they could handle 120V. So I could wire 3X 39V open circuit voltage panels in series on each converter.








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Ultimate Geek
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  Reply # 1854514 29-Aug-2017 07:37
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Looks like Telsa Powerwall uses a "Backup Gateway" which isolates the home from the grid during a blackout so that the PV+battery system can keep the house energised without violating anti-islanding.

https://www.tesla.com/sites/default/files/pdfs/powerwall/powerwall-welcome-guide.pdf



421 posts

Ultimate Geek
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  Reply # 1854519 29-Aug-2017 08:04
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Here's a link to some competitors comparisons for Tesla Powerwall here in NZ. Range from $2,500 upwards to $16,000

https://mysolarquotes.co.nz/about-solar-power/residential/solar-battery-storage---product-comparison/

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Ultimate Geek
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  Reply # 1854536 29-Aug-2017 08:37
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As per the topic: Solar power in emergencies....

 

A few solar panels with micro-inverters and you are good to go.





Gordy

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  Reply # 1854659 29-Aug-2017 11:42
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Gordy7:

 

As per the topic: Solar power in emergencies....

 

A few solar panels with micro-inverters and you are good to go.

 

 

Have you @Gordy7 tried using micro-inverters with out a grid tie?
I believe micro inverters need the 50Hz AC reference signal from the grid to function. I also think they have built in anti-islanding function to stop them functioning when there is no mains supply.
For micro inverters to work off grid I think some other controller would need to introduced to keep the inverters functioning in the absents of the 50Hz grid signal.

 

I would love to be proven wrong.
If they could function standalone it would make it easy to put together a simple system. As long as you had good sunlight.


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  Reply # 1854894 29-Aug-2017 16:55
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I've been told that the enphase will not even feed back into a panel fed by a generator because of unstable frequency so not sure how they would go trying to invert with no grid at all.




Richard rich.ms

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