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Power Demand falls out of Peak sun hours.hmm


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Heya Guys

What to do if you make use of 40Kw per day. But the use is out of peak solar hours. Before 9am and after 3?

1)Adjust lifestyle? Hah

2) Heavily battery based

3) a bit of rocket sicence switch over that uses batteries off sun hours and then grid ties again when sun is up for general offset and battery charging?

4) Net metering in cape town? So you can get a bit back during the day..netmetering in cape town??? Hehe

Eeeyoh too much for my penut.

Thanks

P

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  • 2 months later...

First thing I'd do is try to get that 40kwh down.

 

There are some things you can do. Running geysers during the day and essentially letting them run cold by the time the last person has taken their shower (watch out, if you get this wrong it tends to lead to unhappy females in the household). Run the dishwasher during the day. Freezer on a time switch so it runs more during the day and less at night. Same with pool pump if you have one. Convert all lights to LED so that can run from battery at night. Every load you can move to daytime means savings on battery storage.

 

What you describe is a common problem. I have the same problem really. I can easily get through the day on 7kwh. But then tonight we just suck another 20kwh and more out of the grid...

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To answer one question -- and I know this is a controversial topic with many installers -- but I'd look at a Victron hub system. Perhaps I'm biased because I already bought into the (expensive!) Victron world, but this is the kind of thing at which hub-1 is especially effective.

 

Let me quickly explain the hub systems, because I'm told this isn't common terminology, it's Victron specific.

 

I'll start with hub-2 as this is older and more common. You have two inverters in this setup, one is a Victron Multiplus/Quatro inverter/charger with a battery bank, the other is a GTI (Fronius or Victron). Your solar power is injected onto the grid directly on the AC side. It's injected on the OUTPUT of the Multipus/Quatro. Through some clever software hackery, your Multiplus knows how much power is coming in from the GTI and will use a portion of this to charge the batteries. Whatever remains powers the loads in your house, and/or is fed back into the grid.

 

Hub-3 is similar to Hub-2, except the GTI ties to the grid on the input side of the Multiplus/Quatro. The same software trickery allows you to use that energy to charge the batteries, feed some of it through into your house, boost from the batteries/grid if you don't have enough, and feedback into the grid if you have too much.

 

The difference between hub-2 and -3 is where the GTI ties. With a hub-2 system, if the grid goes out, the GTI ties with your multiplus and continues working. With a hub-3, when the grid goes out, the GTI shuts down and you run purely off battery. One additional upside with hub-2 is that you can program it to avoid grid feedback. You do this by forcing it to disconnect from the grid if consumption is too low. Now your GTI is tied with the Multiplus/Quatro and it can control the GTI using GFPR (Grid Frequency-dependent Power Reduction), that is, by varying the frequency between 50hz (full power) and 53Hz (no power) it can balance GTI with consumption.

 

Now for hub-1. This differs from the other two in that your solar power arrives on the DC-bus through a charge controller. You have no GTI. Once again, through some software trickery, surplus can be fed back into the grid or used directly. It doesn't cost that much less though, as the charge controller plus cabling required to do hub-1 costs about the same as a GTI :-) This system is the most cost-effective one if most of your power will be stored in batteries and used later. The other two hub-systems are better if you use most power during the day when the power is being generated.

 

I like hub-1 a lot, but imho it's still too expensive to setup, and it also isn't an "approved" inverter for grid feed-in, at least not in Cape Town. There is also presently no way to avoid feedback, so people like myself with a prepaid meter can't use it. (Well, there are ways to hack it, but I'm not a great fan of kludges).

 

You could also do what a friend of mine did: He has a SMA Sunnyboy, he runs as much stuff as possible during the day (pool pump) and the rest simply spins his old mechanical meter backwards. He has to be careful not to spin it back too much. Also, this isn't really legal and I would not be surprised if at some point this practice is stopped, possibly by forced replacement of all the old meters.

 

There is a lot of politics involved, and at least in Cape Town the issue is that the higher electricity prices paid by the middle class is used to subsidize costs for the poor. They cannot "pay" a rich man to leave the funding pool (ie buy electricity from him or subsidize his solar setup), and that's why out FIT looks the way it does. Now when you spin an old mechanical meter backwards, you not only "sell" electricity to them, but you sell it at the same rate at which you buy it, which makes this such a good deal that rich people with old meters should all immediately leave the funding pool... which is another reason why I think this practice will be stopped.

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To answer one question -- and I know this is a controversial topic with many installers -- but I'd look at a Victron hub system. Perhaps I'm biased because I already bought into the (expensive!) Victron world, but this is the kind of thing at which hub-1 is especially effective.

 

Let me quickly explain the hub systems, because I'm told this isn't common terminology, it's Victron specific.

 

I'll start with hub-2 as this is older and more common. You have two inverters in this setup, one is a Victron Multiplus/Quatro inverter/charger with a battery bank, the other is a GTI (Fronius or Victron). Your solar power is injected onto the grid directly on the AC side. It's injected on the OUTPUT of the Multipus/Quatro. Through some clever software hackery, your Multiplus knows how much power is coming in from the GTI and will use a portion of this to charge the batteries. Whatever remains powers the loads in your house, and/or is fed back into the grid.

 

Hub-3 is similar to Hub-2, except the GTI ties to the grid on the input side of the Multiplus/Quatro. The same software trickery allows you to use that energy to charge the batteries, feed some of it through into your house, boost from the batteries/grid if you don't have enough, and feedback into the grid if you have too much.

 

The difference between hub-2 and -3 is where the GTI ties. With a hub-2 system, if the grid goes out, the GTI ties with your multiplus and continues working. With a hub-3, when the grid goes out, the GTI shuts down and you run purely off battery. One additional upside with hub-2 is that you can program it to avoid grid feedback. You do this by forcing it to disconnect from the grid if consumption is too low. Now your GTI is tied with the Multiplus/Quatro and it can control the GTI using GFPR (Grid Frequency-dependent Power Reduction), that is, by varying the frequency between 50hz (full power) and 53Hz (no power) it can balance GTI with consumption.

 

Now for hub-1. This differs from the other two in that your solar power arrives on the DC-bus through a charge controller. You have no GTI. Once again, through some software trickery, surplus can be fed back into the grid or used directly. It doesn't cost that much less though, as the charge controller plus cabling required to do hub-1 costs about the same as a GTI :-) This system is the most cost-effective one if most of your power will be stored in batteries and used later. The other two hub-systems are better if you use most power during the day when the power is being generated.

 

I like hub-1 a lot, but imho it's still too expensive to setup, and it also isn't an "approved" inverter for grid feed-in, at least not in Cape Town. There is also presently no way to avoid feedback, so people like myself with a prepaid meter can't use it. (Well, there are ways to hack it, but I'm not a great fan of kludges).

 

You could also do what a friend of mine did: He has a SMA Sunnyboy, he runs as much stuff as possible during the day (pool pump) and the rest simply spins his old mechanical meter backwards. He has to be careful not to spin it back too much. Also, this isn't really legal and I would not be surprised if at some point this practice is stopped, possibly by forced replacement of all the old meters.

 

A hybrid inverter does very much the same, it is just a all-in-one solution instead of having a few different components. It also combines PV and/or grid and/or battery to supply the load. It can also grid tie, if configured to do, and in the case of the infini you can enable or disable grid export and even specify how much should be exported to the grid. I'm not sure about the possible configuration options on the Imeon, but the infini covers all of the above. Both the infini and Imeon will also still supply the load when the grid fails, unlike standard GTIs.  :)

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A hybrid inverter does very much the same, it is just a all-in-one solution instead of having a few different components. It also combines PV and/or grid and/or battery to supply the load. It can also grid tie, if configured to do, and in the case of the infini you can enable or disable grid export and even specify how much should be exported to the grid. I'm not sure about the possible configuration options on the Imeon, but the infini covers all of the above. Both the infini and Imeon will also still supply the load when the grid fails, unlike standard GTIs.  :)

True. Just be sure it's a real hybrid :-) From what I've read the Infini is, but the Axpert is not. If it's not a real hybrid it can't feed back.

 

As I understand it, the hybrids are really a bi-directional inverter with an mppt controller in the same case, and some clever balancing software. The axpert is a non-bi-directional ( :-P ) inverter with an mppt controller and a transfer switch in the same case, combined with software.

 

With the victron stack, you buy them separately and link them up with cables. Mostly just RJ45. But their high-end MPPTs uses canbus, and imho this is unfortunate, because that bit of translation that is required between busses really pushes up costs. The ve.can<->ve.bus cable costs like 4k. Now the CCGX has canbus ports on the back, but that is in itself on the other side of 5k.

 

Right now I'm watching the Victron guys for hub-4. It's fairly new, but I have a sneaky suspicion this is going to be the answer to the hub-1 drawbacks (though you'll still need to buy the CCGX most likely). Don't quote me on it yet...

 

(Presently I run my Victron in "Axpert" mode :-) )

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True. Just be sure it's a real hybrid :-) From what I've read the Infini is, but the Axpert is not. If it's not a real hybrid it can't feed back.

 

As I understand it, the hybrids are really a bi-directional inverter with an mppt controller in the same case, and some clever balancing software. The axpert is a non-bi-directional ( :-P ) inverter with an mppt controller and a transfer switch in the same case, combined with software.

 

With the victron stack, you buy them separately and link them up with cables. Mostly just RJ45.

 

Yes, the infini is a true hybrid, the Axpert is not. Different Axpert models are available though, some with PWM and some with MPPT.

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  • 11 months later...
On 8/25/2015 at 0:37 PM, superdiy said:

 

A hybrid inverter does very much the same, it is just a all-in-one solution instead of having a few different components. It also combines PV and/or grid and/or battery to supply the load. It can also grid tie, if configured to do, and in the case of the infini you can enable or disable grid export and even specify how much should be exported to the grid. I'm not sure about the possible configuration options on the Imeon, but the infini covers all of the above. Both the infini and Imeon will also still supply the load when the grid fails, unlike standard GTIs.  :)

Can you please tell me if the Sunny Boy can also be configured as a "hybrid" inverter. My scenario is a follow. I stay in JHB (were grid tried is not an option yet) and I do not want to run the risk of doing "anything illegal" such as reversing the meter when the municipality does not allow it. So my question is ... can the Sunny Boy be configured not to feed into the Grid, but still switch to Grid to supply my load if the Solar is not enough (during cloudy days) to carry the load.

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Sunny Island, or a GTI? The GTIs have an RS485 port and as far as I know they speak Sunspec over modbus RTU, so in theory a grid limiter is possible, but I'm not aware of one that exists other than the ExSolar one made by chtech.co.za.

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If I understand you correctly? I would need a Sunny Island, and if the load demands more power than the solar can supply via the Sunny boy, then the Sunny Island will provide power from the battery and the grid if necessary to supply the load (during high load demands) ? 

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No, I just wanted to be sure. As far as I know the SunnyBoy (no batteries, just grid tied) can be throttled down using the RS485 port. I don't think they can do it on their own (like the hybrid systems loved by some members on this forum :-) ). If I missed something I would love to be corrected :-)

http://www.sma.de/en/products/monitoring-control/modbus-protocol-interface.html

I think there are two ways to make it happen. The one is to add a Sunny Island inverter. Then you avoid feedback by disconnecting from the grid and forming a Microgrid. That's expensive of course.

The other way is to throttle back the GTI. It's been done for the Fronius (by ExSolar). I suspect, though cannot prove, that the process will be similar for the SMA. I am not aware of existing implementations.

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Ultimately it will be much cheaper to cut your usage in half, rather than to try and replace with solar (which doesn't help at night anyway as you point out). What's the point in complicated solar grid tie and battery solutions, if all your usage is at night?

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You could blow some money on a Tesla battery with a Solar Edge inverter. Those work quite well in damping the early evening consumption and the efficiency is not too bad... but you're going to "cough" (jy gaan hoes!) to afford that combo :-)

That makes me think. The SMA Sunnyboys are "transformerless", in other words high 450VDC input from the solar array, switched directly into AC, no boost step. The SolarEdge is ALSO transformerless, it uses "optimizers" (MPPT tracking boost converters) under each panel, feeding the inverter with 450VDC from the roof, so the topology is similar. The Tesla is "hacked" in there by adding a boost converter to the battery pack so it can feed the inverter with the high DC voltage it wants.

So... technically it would be possible to take that same solution, slap it onto the SMA, and it should "just work" (tm). :-)

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18 hours ago, SBBS said:

... I do not want to run the risk of doing "anything illegal" ...

FWIW:
If your power comes direct from Eskom, they are so far behind, I read somewhere it is not allowed at all.
If your power comes from the municipality, then you need to follow their rules and regulations.

Bottom line, by connecting to the grid, even with a grid limiter, you are still connecting "illegally" unless you have all the paperwork in place from the relevant authority.

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5 hours ago, Carl said:

You can use a Sunny Home Manager directly with a Sunny Boy to limit active feedback to 0 Watts.

A cheaper option is the Suntrol management devices.

Both these solutions require external energy meters as well. 

I have manged to get the following extract from the installation manual of the Sunny Home Manager.

"The grid operator may demand the permanent limitation of the active power feed-in for your PV plant,
this means limiting the active power fed into the utility grid to a fixed value or a percentage of the
installed nominal plant power. If need be, ask your grid operator whether a permanent limitation of
the active power feed-in is necessary and whether you are allowed to use the Sunny Home Manager
for this purpose. The Sunny Home Manager monitors the active power being fed into the utility grid via a feed-in meter.
If the active power feed-in exceeds the prescribed limit, the Sunny Home Manager limits inverter
PV generation via Bluetooth or Speedwire"
.

This answers my question on limiting the Sunny Boy to feed back into the Grid. But my next question is if the Load demands for example 5 Kwatt, but the solar power can only provide 2 Kwatt (due to low radiation and cloudy day), will be Sunny Boy (or Sunny Home Manager), then automatically provide the additional 3 Kwatt from the grid to supply the 5 Kwatt to the load?  

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