Solar - should work during power outage

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boland

278 posts

Ultimate Geek

# 215426 27-Jun-2017 10:01

One person supports this post

We're thinking to get solar. it's pretty economical to get the panels, so that's great.

however, without battery backup power the system apparently doesn't work during an outage. Additionally, only certain battery systems allow to run during an outage. I've seen one quote of around $8500 for a 5KW Li-Ion battery system that works during an outage.

That's not economical, plus it's quite a lot of money for power during an outage.

I've contacted other solar installers, but none of them so far is able to help with a cheaper option that works during an outage.

Any tips?

Jase2985

8947 posts

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Lifetime subscriber

# 1807435 27-Jun-2017 10:12

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given if solar was to run in an outage, then if you are generating more than you are using and the system then tries to export it to the grid, you have now made the grid live again and could potentially injure anyone working on it.

some of the battery systems detect when the grid is lost and charge the batteries, when the batteries are charged they can shut off.

also check the output the batteries can give you in a power outage, some will have a low (2kwh) output to specific appliances, while others will have much higher outputs and dont require things wired directly.

boland

278 posts

Ultimate Geek

# 1807448 27-Jun-2017 10:42

Jase2985:

given if solar was to run in an outage, then if you are generating more than you are using and the system then tries to export it to the grid, you have now made the grid live again and could potentially injure anyone working on it.

some of the battery systems detect when the grid is lost and charge the batteries, when the batteries are charged they can shut off.

also check the output the batteries can give you in a power outage, some will have a low (2kwh) output to specific appliances, while others will have much higher outputs and dont require things wired directly.

Yep, I understand why a grid tied system is shut down in case of an outage.

The system I've been quoted is a Solax box, which works in case of a power outage. It essentially shuts down the connection to the grid and then we have our own internal grid: https://www.mysolarquotes.co.nz/blog/battery-storage-for-solar/solax-box-what-you-need-to-know-about-this-solar-power-storage-system-

Pretty nifty stuff, although expensive due to Li-Ion batteries.

Stan

929 posts

Ultimate Geek
Inactive user

# 1807598 27-Jun-2017 13:17

The new LG Chem battery's are a tad cheaper now you should be able to pick up the new 6.5 kW version for under 7k inc gst. It's worth noting that the emergency power supply relay on the solax inverter takes a few seconds to click on so the power will go out for a second or so.

Aredwood

3885 posts

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Subscriber

# 1807948 27-Jun-2017 22:21

Stan: The new LG Chem battery's are a tad cheaper now you should be able to pick up the new 6.5 kW version for under 7k inc gst. It's worth noting that the emergency power supply relay on the solax inverter takes a few seconds to click on so the power will go out for a second or so.

It will be a great system assuming it can output the full 6.5KW when running in off grid mode. Although still really annoying that it has a delay in switching between grid connect and off grid modes.

Interestingly, there are inverters at the cheaper end of the market such as Mustpower 5KVA Which has a 10mS transfer time. Although it cant do grid connect. In saying that not supporting grid connect might actually be a feature. As you won't have to get lines company approval to install it, And you could have solar while being signed up to power companies that don't support solar. As it is basicly just a UPS that also supports solar charging of it's backup batteries.

Ge0rge

527 posts

Ultimate Geek

Trusted

# 1807951 27-Jun-2017 22:30

How would you see that working, @aredwood? Power from the lines company supplied to your house that charges your batteries, so you are essentially running from the inverter at all times? I.e. sunny day, batteries are full, so no power used, bad weather period, line power keeps them topped up?

Aredwood

3885 posts

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# 1807959 27-Jun-2017 23:04

Ge0rge: How would you see that working, @aredwood? Power from the lines company supplied to your house that charges your batteries, so you are essentially running from the inverter at all times? I.e. sunny day, batteries are full, so no power used, bad weather period, line power keeps them topped up?

You can configure the inverter to run the whole house by default from battery / solar. And it will switch to mains only if the batteries run out or you try to draw more power than the inverter can provide. This type of setup would be best if the main design consideration was having backup power. (Servers, Tropical fish tanks, Home office ect). Where instead of having to run a generator continuously during a blackout, You would only need to do so if there isn't enough solar to keep the batteries topped up.

It would also work really well if you could integrate a hot water diversion controller with it somehow. So if the batteries are full, excess solar production could instead be used to heat an electric hot water cylinder. Using the cylinder like a battery as well.

In saying that, the perfect solar inverter just doesn't seem to exist.

Ge0rge

527 posts

Ultimate Geek

Trusted

# 1807982 28-Jun-2017 06:36

Yup, that makes sense - thanks.

I imagine that it would work quite well with a heat-pump hot water system - At least that way those people who aren't at home duing the day would benefit from the solar power as well - perhaps integrated with water under floor heating too. New build as opposed to retrofit though.

raytaylor

3416 posts

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Trusted

# 1810561 2-Jul-2017 18:24

I think you could ask a solar installer about a conventional grid-tie system, but have the ability to disconnect the grid, and connect a battery-fed inverter.

To me it seems like your looking for a battery+switching system which has an inflated cost.

If you separate the idea of the batteries and switching into two individual components it might be easier to understand.

Batteries - accepting they can be quite costly, if you only want a day worth of power, and like me you want to use them less so they last longer, and you dont plan on using them in the day-to-day operation of your power supply then they can be for backup only.

Inverter - you could then have a simple switching system that disconnects the grid, and changes it over to the output of a lower wattage dedicated inverter.

When the grid supply is on, use it to keep the batteries charged up with a float charger. When the power goes out, you can manually throw a switch to use the batteries+inverter.

For some extra cost you could also recharge the batteries from solar too while the grid supply is out.

Ray Taylor
Taylor Broadband (rural hawkes bay)
www.ruralkiwi.com

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larknz

284 posts

Ultimate Geek

Lifetime subscriber

# 1810594 2-Jul-2017 20:07

One person supports this post

A system that is going to connect to the power network must comply with as/nzs 4777. This standard specifies anti-islanding requirements.

pchs

144 posts

Master Geek

# 1812860 4-Jul-2017 20:22

Hi - I was after the same thing, I have Solar and an Enatel invertor and wanted to also include 20kVA of batteries plus a LPG Generator so that i could run all (Solar+Batterys+Generator when needed) in a power cut.

I've looking to install a Victron Quattro invertor/charger, this has a UPS type function + can startup the Generator when needed (2 x AC inputs, 2 x DC out/in) and charge the batteries. it also allows the Solar to feed into the supply and either charge the batteries or feed the house or both.

It also allows me to have a larger than needed generator, which will allow for peak load, and charge the battery's at the same time, during say the night i should be able to survive soly off battery's and it would only start the generator when needed.

Using LPG (and with Flick) at some times it might actually be worth starting the generator instead of drawing off the grid, but hopefully the batteries will do a good job at smoothing this out.