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SELF CONSUMPTION: Batteries or Eskom


Tariq

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16 minutes ago, Solaris said:

IMHO load shedding is not going to get better, it is only a matter of time and it will get worse. I want to be be ready for when (not if) it gets worse. I also waste about 5kwh to 8kwh of solar per day as the batteries are already full by 10am even after the geyser is hot and all washing loads are done. Adding batteries is the only answer for all the solar going to waste. 

One thing I have learned in this country is that we cannot depend on government. We must not have the mentality of: ”the government must provide for us” We need to provide for ourselves. And the sooner we get off grid, the better for us. 
But like I said; this is just my opinion, feel free to disagree. 😊

I'll see your 5-8Kw, and raise you... Currently I throw away 17-20Kw per day. But yesterday, in Joburg, I only just filled my batteries enough for the night.

Lesson: Have more than more than enough!

I'm going to connect up another 2Kw per hour array (array #5) right now.

(Damn... this drug...)

Edited by PaulinNorthcliff
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8 minutes ago, Solaris said:

IMHO load shedding is not going to get better, it is only a matter of time and it will get worse. I want to be be ready for when (not if) it gets worse.

Agreed.

I have a different approach though.

I have a big enough battery to see me through the night. It costs money and wont last 25 years. I begrudge the expense.

Instead of adding more storage, I add more panels. I don't add them at optimized slopes or directions, I slap them up as cheap as possible.

And what this does for me is this:

I don't care how overcast it is, I can charge those batteries and still have enough to get through the day.

I squeeze my MPPT's so that they have no margin's. I use AC coupling as well. I actively avoid noon day peaks in favour of a long solar day.

This combination of a great deal more sub-optimum panels on an overcast day still gets the job done. 

Every single day, .....40 days of Noah's flood if needs be.

How big would the battery be that could do that?

You'll get a shedload of panels for the price of these fancy batteries.

 

 

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1 hour ago, phil.g00 said:

Agreed.

I have a different approach though.

I have a big enough battery to see me through the night. It costs money and wont last 25 years. I begrudge the expense.

Instead of adding more storage, I add more panels. I don't add them at optimized slopes or directions, I slap them up as cheap as possible.

And what this does for me is this:

I don't care how overcast it is, I can charge those batteries and still have enough to get through the day.

I squeeze my MPPT's so that they have no margin's. I use AC coupling as well. I actively avoid noon day peaks in favour of a long solar day.

This combination of a great deal more sub-optimum panels on an overcast day still gets the job done. 

Every single day, .....40 days of Noah's flood if needs be.

How big would the battery be that could do that?

You'll get a shedload of panels for the price of these fancy batteries.

 

 

 

What about when the sun disappears and there is a power outage for 8hrs? Can you system cope with that? 

The only reason I am adding more batteries is to stay off the grid as much as possible during the night. That's it. 

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16 hours ago, Tariq said:

My question was self-consumption, I already have two 2.4 Pylontech’s, which gives me 3.8 kWh’s per cycle, with my 4.2 kWp of solar panels, I could charge additional batteries, so is it worth adding more batteries or just going with Eskom 

Layman's 2c & thumbsucks. Answer here, as with a lot of things, is that it depends.

In your case you've already sunk the cost of the 4.2kWp of panels and 3.8kWh of storage, that's water under the bridge, horse has bolted, it gets ignored for your next decision, which is: Should you get more storage for self-consumption or not?

Your 4.2kWp of panels can in theory generate around 20kWh per day on average. Of that around 4kWh is put into storage in your existing batteries for nighttime use. That leaves 16kWh. Some of that you're using during daylight hours. How much? Substitute your own value, or shall we just sommer say 11kWh? That leaves 5kWh you could potentially store to use in the evenings, but your panels instead lay idle in the day.

But would you use that power? How long does it take before your 4kWh runs out at night? How much Eskom power are you drawing each day that could have been supplied by your panels?

Let's just say you're drawing daily 2.4kWh from Eskom, or the cycle capacity of one US2000.

20 hours ago, Plaashaas said:

A cycle on a US2000 is 2.4kW
If you DOD to 20% it would supposedly last 6000 cycles
2.4.kW x 6000 = 14400kW

144000x R2.10 =R30240 (Without any Eskom price increases)

Using these costs from Plaashaas (and not accounting for lifetime degradation or installation, etc), the cost of storage is about R1.05 per kWh that you cycle in and out of the battery. It's either that or you spend R2.10 per kWh for Eskom at night. So you make a 100% ROI on the next battery you buy. Rather than let your panels go to waste. Might even be able to add a second battery in this scenario and still see  a benefit.

But what about starting from scratch if you've not yet sunk any costs? Depends on the cost of the inverter and panels, you would have to factor in the generation costs. Some grid-tied kits advertised on the internet promise a cost per kWh of around 95c, but realistically you need a battery inverter too, or at least a hybrid inverter, or consider your specific setup. Anyway, working on that 95c per kWh generation costs over 15 years, the total cost of generation and storage amounts to 95c+R1.05=R2. If you're starting from scratch, the return is just 5%, which hardly covers the cost of capital, it basically just pays for itself, and is hardly worth pursuing for investment return purposes. But it's basically free insurance against Eskom, and for that I think it's priceless.

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10 hours ago, PaulinNorthcliff said:

fCurrently I throw away 17-20Kw per day

Now you are just making me jealous. 😂 

10 hours ago, phil.g00 said:

Instead of adding more storage, I add more panels. I don't add them at optimized slopes or directions, I slap them up as cheap as possible

I have been reading your many posts the past few months and wondering why nobody else thought of such a brilliant idea. Extract every last watt out of the sun throughout the +/- 9 hours of daylight. I have just started my east facing array with 3 x 330w panels and have space (not the funds) for another 3. I will then start my west facing array, and also plan to use different orientations. 

 

10 hours ago, phil.g00 said:

I don't care how overcast it is, I can charge those batteries and still have enough to get through the day

Maybe a silly question, but what is your output like when it is raining? 
 

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51 minutes ago, Solaris said:

Maybe a silly question, but what is your output like when it is raining? 

I have two systems, with two different goals, one is there for load-shedding and one is to save money on the bill.

I don't really remember how many panels there are, but lots, around 25kWp maybe slightly more, but completely unoptimized.

The highest peak I have seen from my these is about 14kW on the larger save-money system.

That is over and above what the off-grid system is drawing.

(The 2 systems are on the same battery bank and only the save-money system has online monitoring).

When it is raining all those panels (now at a much lower % yield), prop up the smaller off-grid system.

The second bigger save-money system gets ditched (sort of like non-essential loads).

From a paper I've read, a flat panel yields about 50% more than an optimized north-facing panel when it's overcast.

Mine aren't flat, but at many combinations of mainly E-W at flatter that the optimum slope. ( Whatever slope that piece of roof happens to be).

The night-time demand on this off-grid system is very low, but the daytime demand fluctuates between 0.5kW and 3kW'ish.

The battery bank although theoretically large, is absolutely shot, and I mean absolutely shot.

5 year old Lead acid car batteries.

All I know is if the available solar doesn't meet my off-grid demand during the day the system will go down and it doesn't.

Because the system still trundles on those batteries remain, they are really more of a system buffer/dampener than a battery at this stage.

So all I have is a educated guess out of that +/- 25kWp in the rain, I am getting maybe 5 to 12%'ish.

But as I say the offgrid system doesn't the fancy VRM Victron monitoring that the save-money system has, so I can't give you definitive values.

Edited by phil.g00
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On 2020/09/01 at 3:19 PM, Plaashaas said:

Just 2 more panels babes then I am done

Jup, but with me it is the other way around, she wants now extra panels after seeing the saving we have. 

I run my system with 3 panels in 1 string and am already saving on units. 

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On 2020/09/01 at 5:12 PM, Gerrie said:

Just be warned! During load shedding babes is going to watch her favorite program, and you might end up running around like a serious operator monitoring battery view, inverter, watchpower, ICC and whatever to try and not look like the fool who spent that bucks on the rabbit hole😁

That is so true, but not movies. She like her sport and wwe. I'm the one monitor everything. 

 

On 2020/09/01 at 5:18 PM, Plaashaas said:

I'm pretty much off grid. The only way we know its loadshedding is the messages on the community group. That's why it is becoming more difficult to expand the system. 

I'm almost the same. Just my geyser and oven will be off then I know something is wrong or like you said - Community group.

 

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On 2020/09/02 at 7:11 PM, phil.g00 said:

I have two systems, with two different goals, one is there for load-shedding and one is to save money on the bill.

I don't really remember how many panels there are, but lots, around 25kWp maybe slightly more, but completely unoptimized.

The highest peak I have seen from my these is about 14kW on the larger save-money system.

That is over and above what the off-grid system is drawing.

(The 2 systems are on the same battery bank and only the save-money system has online monitoring).

When it is raining all those panels (now at a much lower % yield), prop up the smaller off-grid system.

The second bigger save-money system gets ditched (sort of like non-essential loads).

From a paper I've read, a flat panel yields about 50% more than an optimized north-facing panel when it's overcast.

Mine aren't flat, but at many combinations of mainly E-W at flatter that the optimum slope. ( Whatever slope that piece of roof happens to be).

The night-time demand on this off-grid system is very low, but the daytime demand fluctuates between 0.5kW and 3kW'ish.

The battery bank although theoretically large, is absolutely shot, and I mean absolutely shot.

5 year old Lead acid car batteries.

All I know is if the available solar doesn't meet my off-grid demand during the day the system will go down and it doesn't.

Because the system still trundles on those batteries remain, they are really more of a system buffer/dampener than a battery at this stage.

So all I have is a educated guess out of that +/- 25kWp in the rain, I am getting maybe 5 to 12%'ish.

But as I say the offgrid system doesn't the fancy VRM Victron monitoring that the save-money system has, so I can't give you definitive values.

After a while with my panels all facing north. I think I'm heading in the same direction. Face some east for the morning sun then face some west for the afternoon. Are you running an axpert? I am. but I think I must get another 2x mppt charge controllers to supplement the one mppt in the axpert. 

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6 hours ago, Dani said:

After a while with my panels all facing north. I think I'm heading in the same direction. Face some east for the morning sun then face some west for the afternoon. Are you running an axpert? I am. but I think I must get another 2x mppt charge controllers to supplement the one mppt in the axpert. 

Not running an axpert, I have two Victron systems with 4 Outbacks with a Solis and ABB PV inverters downstream.

3 solar thermal geysers and a small array dedicated to a borehole pump.

 

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On 2020/09/04 at 9:11 PM, phil.g00 said:

4 Outbacks

Thx @phil.g00 I want to add another mppt to my setup in looking at the below. Seems to work with my Canadian solar 400w panels in sets of 2. And it is very reasonably priced when compared to the Outbacks. 

https://thepowerstore.co.za/products/epsolar-tracer-5415an-50a-mppt-150v-charge-controller-12v-24v-36v-48v?_pos=24&_sid=33ffe7842&_ss=r#downloads

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23 minutes ago, Dani said:

Thx @phil.g00 I want to add another mppt to my setup in looking at the below. Seems to work with my Canadian solar 400w panels in sets of 2. And it is very reasonably priced when compared to the Outbacks. 

I don't have any experience with that controller, but if it can take the same settings as any existing controller I think it will work.

All my controllers function independently, they don't need to function as a collective (within reason).

 

 

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25 minutes ago, phil.g00 said:

All my controllers function independently, they don't need to function as a collective (within reason).

I'd better add the caveat that I don't use Lithium batteries. Lithium batteries do require that all Charge controllers do switch off together for high voltage battery protection.

This is easily implemented with a contactor on the solar side of the MPPT.

Break the PV side, as most manufacturers recommend you switch off PV input before the battery.

In practice, I find it doesn't matter if you have your Voc ratings right, but you may as well do it the way they say.

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I'm guessing I'm one of the lucky ones. We live in a estste in CPT who allows us to feed back. We get 75% of the normal per kwh fees we would pay back in rebate and on a nice sunny day I feed back around 24kwh. An added bonus is that the same smart meter is used for water and electricity so the credit goes to both on my account.

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1 hour ago, Heinds said:

I'm guessing I'm one of the lucky ones. We live in a estste in CPT who allows us to feed back. We get 75% of the normal per kwh fees we would pay back in rebate and on a nice sunny day I feed back around 24kwh. An added bonus is that the same smart meter is used for water and electricity so the credit goes to both on my account.

You are lucky indeed, if the rest of the country twigged on this could be a good thing.

There are many opinions about safeguard limits and potential power gluts if that is done though.

I say SA starts to manage the problems it has and not deal with the problems it could potentially have.

It would actually be nice to have to deal with the issues we could maybe develop in the future, if we relaxed domestic solar restrictions.

I have had 5 x 2 hour load-sheds between 10:00 and 14:00 in the past 7 days. That means at peak solar production times ESKOM couldn't meet the national demand.

That's today's problem.

Edited by phil.g00
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On 2020/09/03 at 9:15 PM, Solaris said:

I have been looking for this paper as it sounds like an interesting read. Please tell me where I can find it. 

@Solaris Here's the link Phil shared:

https://www.researchgate.net/publication/241076784_Increasing_the_solar_photovoltaic_energy_capture_on_sunny_and_cloudy_days

In this thread: https://powerforum.co.za/topic/6581-mixing-solar-panels/?do=findComment&comment=79657

 

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9 hours ago, Dani said:

 it is very reasonably priced when compared to the Outbacks. 

 

I am now weary of the cheaper MPPT controllers after having just replaced the last fongkong one with a Victron. I certainly have peace of mind not wondering how long it will last.

Here is a decent one for a few bucks more:

https://www.weable.co.za/power/battery-equipment/mppt-charge-controller/victron-energy-bluesolar-mppt-100-50-vic-bluesol-mppt-100-50.html

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