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esawyja
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Hi all,

I have 3-phase on a plot in Kyalami, I want to convert it to single phase at some stage as I do not use the 3 phase at all. I have the Engage Clip on system, one for each phase, that produces a graph like this for the year

image.png.1024ef1e026b83e75a871f42fda3a2b3.png

My question is and I do know it is very generic, how big of a solar solution will be enough for my needs? To get as close as possible to go off grid. As I want to convert to single phase, do I add all the phases together? But what then, how do I calculate what is needed, any advice please?

 

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Welcome

(Correct me if I'm wrong.) If you take like Jul and sum them up 1316.77+738.26+233.16=2288.19/31=73.813kW a day/24= 3.08KWh, is high.

You need to go look what using all the power, what is your budget, there is lots of ways to do it, split the system.

You can start small and build up from there.  I like the King Inverters and others like other types.

image.thumb.png.b1065a188039a2eecd65d15eff362962.png

But like I say(correct me if I wrong)

image.thumb.png.ac1340586d922305efe59320c0fafae4.png

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2 hours ago, esawyja said:

how big of a solar solution will be enough for my needs?

Your situation is very similar to mine - I had 3-phase Landrate (with a fixed charge of about R2000 per month, plus about R1.60/kWh).  I am now essentially off-grid, using ESKOM (Landlight, no fixed charge, R5/kWh) as my standby supply.

I have put in 12.5kW of panels, 15kW of inverter capacity and 28kWh (25 usable) of storage, and it seems to have been about right.  I have an energy management system controlling my geysers and air conditioners to ensure that the 15kW inverter capacity is never exceeded.

My ESKOM usage has decreased from R50000 p.a. to about R5000.  The total cost (DIY) was about R320k.

 

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36 minutes ago, Vassen said:

ive used a geyserwise thermostat and replaced the sensor with a sonoff th16. I then heat the water to 80 degrees in my 200l geyser if I have excess solar power. This then feeds into a 150l geyser with geyserwise controller. 150l geyser is also heated to 65 degrees (max allowed by geyserwise controller) at mid day. These geysers don’t come on after sunset. 

How are  you controlling the excess power fed to the geyser? Is this automated?

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Thanks so much for all the answers, I think I'm understanding this better. Is there any thing in favour keeping a 3 phase system? My understanding is that you only need 3 phase for big pumps etc, is this still valid for modern day designs? Am I making a mistake in converting to single phase? I think I'm going to tackle the geysers 1st, convert them to solar and then rethink my consumption

Thanks again for the advice

 

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51 minutes ago, esawyja said:

My understanding is that you only need 3 phase for big pumps etc, is this still valid for modern day designs? Am I making a mistake in converting to single phase?

Generally you only need 3-phase for large motors.  The obvious advantage of single phase is that you do not need to try and balance your loads across the 3 phases, meaning that you can get away with lower total inverter capacity.

I actually do have a few 3-phase motors, but they are driven by inverters that make 3-phase from a single phase input.  A further advantage of these is that they can remove the huge start-up currents associated with large motors by slowly ramping them up to speed.  Best of all, they are surprisingly affordable.

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1 hour ago, esawyja said:

Am I making a mistake in converting to single phase?

One other thing to consider is, that a single phase system will severely restrict the maximum possible feed in power. If we follow the rest of the world (which i sincerely hope so), it will soon be possible and viable to completely cover our roofs with PV and export the surplus to the grid 🙂.

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22 hours ago, esawyja said:

I do know it is very generic, how big of a solar solution will be enough for my needs? To get as close as possible to go off grid.

Do you want to back up everything in your house, or can you lose some circuits? At my house when Eskom goes down we lose the swimming pool and the out buildings. Many people don't back up geysers (I keep the guest geyser turned off, and the main geyser is heated with a heat pump, so I get away with it). Point is that if you want to back up EVERYTHING ALL THE TIME then you need a bigger system (can handle greater loads, has more batteries) and you will have to size it for your high winter usage. If you can give up some heavy loads then you can have a smaller solar system. 

You're in Gauteng, so think of the weather we've been having. Today my system took a lot longer than usual to charge up, and yesterday it didn't charge all the way and I had to draw from the grid. 2 or 3 consecutive days like yesterday and a hybrid system like I have is struggling, so if you want to go all the way off grid you will need a source beyond solar - probably a generator.

Factor in the cost of getting the wiring in your house recertified. 

Before I started with alternate/backup power I found that we could make useful savings in use and thus billing by exercising some discipline (EG not boiling a full kettle multiple times and eventually making one cup of coffee) and generally adopting the mindset that we could assert some control. This process is still useful to you now because it help you make your solar system go further.

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2 hours ago, Vassen said:

Honestly, if you are planning on going full inverter / solar install, I wouldn’t worry about solar geysers. 
 

It’s easier to just over spec your pv array and use the excess power to heat your water.  Depending on your hot water usage, I would rather install a second geyser inline with the first to increase your hot water storage. 
 

I have a solar geyser and on a day like today in jhb, my evacuated tubes have so far increased the water temperature from 40 degrees this morning to 46.8 degrees currently. Ignoring the fact that the entire tank is not at 46 degrees because of stratification and the sensor being at the center, heating 200l of water from 40 degrees to 46 degrees, required around 1.5kwh of equivalent power. 
 

My solar PV array has however produced 9.4Kwh and my batteries are full. So once my 150l geyser is heated to 65 degrees, I will turn on the element in the solar geyser to get the water to 70+ degrees unless the weather turns really bad. 

So on overcast days my PV is still generating enough power. On clear days my batteries are full around 9AM so I still have more than enough excess solar power  

Bottom line, for me the solar geyser is a bit of a waste. I did learn a lot by installing it and I didn’t have to pay installation as I did a self install, but it’s not as efficient as I expected and takes a lot more place on my flat roof. 

That does make sense, let me start to shop around and see what I can afford...

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