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Just installed 8kw system - notes


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Hi all

Thought I’d introduce myself and take you through my current experience with solar. We have moved into a new house and the family is big - 8 people and the electricity bill was getting completely out of control - in winter we were doing in excess of 80kW per day. I live in Johannesburg and City Power’s tiered electricity costs hurt bigger households. Borrowed money out of the mortgage at 7% interest and figure I can make the money back with interest.

I didn’t do enough analysis up front, but just decided to go with
8kW Deye inverter
18 x 540W JA Solar = 9720W 
3 x 4.8kW LifePO4 (80% DOD) 

The whole household and two cottage are on 4(!) solar EVT geysers. I bought these first and then got more ambitious. In retrospect, I’m wondering whether they I needed them with proper timing (not running all at same time) - maybe I could have got away with just using the solar panels to heat the water (see load graphs later). We have LEDs and gas stove.

Bought the whole set up from SolarAdvice and their installers did a great job, no complaints.

They flicked the switch on on Monday. I think my night time load is a problem because we don’t get through the night - mostly because the household still thinks cooking is for night time. We have a fish pond pump that may be an issue.

It’s a bit desperate to see all the power after 12pm going to waste because COJ doesn’t want our electricity or won’t pay for it. And I can’t see it on the graph as it has nowhere to go, so I don’t know the potential... Natural answer is to spend more money on batteries. 

Also some lifestyle changes required.

I’m setting the battery to discharge to 25% leaving 5% for early morning load shedding.

My questions

  • Have I sized the solar too large? It made sense to me to max out the inverter. 
  • How bad is winter in Johannesburg (% difference in solar production in your actual experience)? 
  • Were the solar geysers a waste of money? I feel I should have got these second and not first as everyone says... I see geysers as batteries (rather poor performing) as they store energy for later use
  • I’m thinking of allowing the excess solar power I have during the day to contribute to the heating of water, to guarantee max temp at sunset. Anyone doing this?
  • What is the current situation with grid tied in Johannesburg with City Power. Does it exist? Anyone done it and is it worth it?
  • What should I do with this extra electricity from 12pm-5pm? Bitcoin mining?

I will attempt to answer these questions over time on this thread, but appreciate any input.

 

Typical sunny day in JHB

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Congrats, I can't see a single problem. My reasoning for maxing out the panels is they are the cheapest part of the system and on cloudy and rainy days and winter that high peak comes in handy.

A few weeks ago we had terrible weather and long power outages and this happened once but it was useful. Due to rain we barely had enough power to power the TV then around midday the sun came out briefly for a couple of hours and almost fully charged the batteries. 

Again congrats. 

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@RichardZA good system I think it's good you maximized they solar arry. Maybe try a little lifestyle change like cooking, heating the geyser up before sunset so make the most of the sun energy while available vs more batteries as they are expensive just my opinion.

Edited by John2
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Rough thumbsucks from the graph are that 15kWh of electricity is failing to be generated during the day even though the opportunity/capacity exists. And around 10kWh is being purchased from Eskom each evening until just after breakfast. One, maybe two more batteries almost certainly worth it. Could try running loads like dishwashers & laundry on timers from 12 noon onwards. Slow-cooker running all day? Arb thought: Selling electricity to your neighbour is not legal, but I wonder if pumping hot water or a running a pool pump's pipes across boundaries is okay? 

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@RichardZA Sounds like you bought a great system

I have 3 geysers that I heat as well as a pool, pressure pump and a borehole. You can never have too much power 🙂  

I agree with maxing out the panels, as they are cheap in comparison to batteries, have been looking for a way to make methane gas for cooking after hours using electrolysis,  would be a HUGE win. 

I have 12740Watts of panels on my Sunsynk 8kw so WELL over paneled. Batteries are usually charged by 12:00 and my loads have all finished running by 13:00, I think I am going to put in a pool heater this summer as I have LOADS of spare power on Sunny days.  Overcast days are usually still giving me enough power to get everything done that needs to. 

Max daily usage is around 65kw of which I buy bought in 8.6kw, doesn't make sense to spend R40k in extra batteries to save R20 a day

Monthly usage last month was 1.61Mwh of which I purchased 309kw/hr from Eskom

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@RichardZA, you certainly did not oversize, it's not wasted. This week we are in for a cloudy and rainy week in Jhb, let's talk again next Monday, you may even consider adding a panel or two 😉

Winter may be slightly lower if your panels are North facing, but if East<-->West, the effects will be more pronounced. Mine are just off North and at 26 degrees pitch, and I actually had my best production this last Winter (then again I had learned how to optimise my usage far better than in Summer). Keep educating the household members on their usage patterns and get them to change habits, get their eyeballs on the daily and monthly graphs, motivate them by setting targets and you will see small, quick wins. Success breeds success. At the same time, don't become a Power Nazi, don't nag, but rather encourage and reward good behaviour.   

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Thanks for the advice everyone.

On 2021/10/25 at 9:29 AM, YellowTapemeasure said:

@RichardZA, you certainly did not oversize, it's not wasted. This week we are in for a cloudy and rainy week in Jhb, let's talk again next Monday, you may even consider adding a panel or two 😉

This week is teaching me a lesson! But I am impressed even in cloudy overcast conditions solar does help take the "edge" off and I'm VERY glad I went for some more panels.

On 2021/10/24 at 5:36 PM, Sc00bs said:

Are you on prepaid @RichardZA?

 

No I'm not should I be? Network charge currently is R498 excl and a Service Charge of R169

I'm considering some more batteries, but the payback feels very long!

I'm still hunting down why I have a base load of 1kw during the night, it seems too high - my guess is a couple of really old fridges are hurting me. If I can get it to 0.5kw I won't have to buy batteries - new A+++ fridges may be a better investment than batteries.

 

 

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3 hours ago, RichardZA said:

No I'm not should I be? Network charge currently is R498 excl and a Service Charge of R169

I would definitely recommend changing to pre-apid if you are on solar. 

I did a spreadsheet of my payments as a 3-phase user (only use single phase but anyway) and there was no point where it was cheaper for me to be on post-paid vs pre-paid, even at the top usage - 3000kw/hr a month + 

There is no connection charge from CityPower on pre-paid at the moment, that may change after the elections but who knows. 

Eskom do charge a connection fee on pre-paid so mileage may vary but pretty sure it will still be cheaper. 

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Thanks for the advice I'm on City Power and will definitely investigate - since I intend 80% of my electricity to come from solar, the slightly more expensive prepaid tariff is not an issue. It looks like they will be charging a prepaid network fee of R200 per month soon.

 

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@Sc00bsgoing to your earlier point. Just checking a couple of things, because I like your oversizing idea - these panels are very cheap comparable to the rest of the system. I'm currently on 9720W. Are you saying going to 12kW won't hurt my inverter on a super sunny day? And that the extra e.g 2kW for maybe R15,000 is the best long term spend (25 year life) and gives me more oomph during overcast weather? And then just let go of the fact that sunny days there is a lot of unused power.

 

 

 

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@RichardZA Yu have had pretty much the same thought process as I had. I have 12,740W of panels now and average generation is about 55kw, I reckon that I could probably make about 70kw on a sunny day if I had somewhere to put all that energy.  On partly overcast days I will still make 55kw and last few days with totally overcast days was in the region of 30kw. 

How are your panels configured? I have an East/West split which works really well, am making 3kw of power at 07:00 in the morning.

Just make sure you stay well away from the MPPT Voltage limits. 

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I would say I have a NE (12) / NW (6) configuration.

Production at 7am is 0.4kw :( - NE gets killed early morning by some trees that prevent early morning sun - I may have to do some trimming :). Today at about 9.30am it will ramp up and by 12pm it will be producing so much power the inverter will clip it at 8.99kW (see second screenshot)

How do you use 55kW. My graph is tragic, it's like whenever it's the complete worst time to use electricity, we use it and when it's the best time, the family does not use it. And of course I've got the latest energy efficient products and actually don't want to use electricity, but my municipality wants to make it hard and expensive to sell back to them (I really don't mind a low rate, but to jump through 10 hoops to do it is too much.) 

I've attached my graph from yesterday and the day before.

I may run 5 heaters in the garage today to actually know my system capacity.

 

 

Screenshot 2021-11-01 at 07.36.04.png

Screenshot 2021-11-01 at 07.37.20.png

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I would also say that although you may have alot of spare capacity now to charge extra batteries, when winter comes the solar production will drop and consumption increases, especially if you use electrical heaters during the day like me cause the electricity is free, this is when you realise that you dont have the spare capacity for more batteries anymore.

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@De0n19 what has your experience been in winter (I assume you are in same Gauteng region as me?) - just so I have the data for sizing any additional batteries if at all. What does your production look like mid summer vs mid winter?

I do intend using electric heaters during the day in winter for work stations and at night we'll light the fire!

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On 2021/11/01 at 6:20 PM, RichardZA said:

@De0n19 what has your experience been in winter (I assume you are in same Gauteng region as me?) - just so I have the data for sizing any additional batteries if at all. What does your production look like mid summer vs mid winter?

I do intend using electric heaters during the day in winter for work stations and at night we'll light the fire!

In winter my 6.5kwp panels peak at about 4kw at around 13h30, i have north and west facing panels. The west panels production really takes a dive in winter. Currently at 10h30 i can already produce 5kw. In winter i can just about charge up a single us3000 from 20%, I'm sure i could even charge up like 4 of these batteries with my current production

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Thanks all appreciate the insights. I've now found half my problem - the CT has not being working correctly - I noticed when my meter carried on ticking upwards when it shouldn't be. So basically my solar has not been supplying all my electricity while there has been abundant solar.  The installer says it's because it's more than 25m away from the inverter. We're going to try make a plan to get the CT working via a lan cable which apparently has better results. 

Edited by RichardZA
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On 2021/11/04 at 2:06 PM, RichardZA said:

Thanks all appreciate the insights. I've now found half my problem - the CT has not being working correctly - I noticed when my meter carried on ticking upwards when it shouldn't be. So basically my solar has not been supplying all my electricity while there has been abundant solar.  The installer says it's because it's more than 25m away from the inverter. We're going to try make a plan to get the CT working via a lan cable which apparently has better results. 

Have you tried changing the CT ratio under Advanced setting?

Also don't run the wires parallel to mains wires in trunking, and when crossing mains wires, cross at 90 deg. The extension wire must be twisted pair too.

 

Edited by TimCam
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On 2021/10/30 at 6:41 AM, RichardZA said:

Thanks for the advice I'm on City Power and will definitely investigate - since I intend 80% of my electricity to come from solar, the slightly more expensive prepaid tariff is not an issue. It looks like they will be charging a prepaid network fee of R200 per month soon.

 

They have tried this 3 years running. 

2019 the city said it was edited into the budget after sign off and then did not impose the surcharge. 

2020 it was proposed then dropped as a part of a packet of relief measures. 

2021 proposed again with some twists. No surcharge where average property value for the neighbourhood was under a limit and the homeowner opted for a 20A main breaker. First 150 units per month would be increased at half the %age increase Eskom got. This was all dropped for reasons not explained. No surcharge, but also no discount so everybody gets the full 15% increase. 

Run the numbers. At present it is still cheaper to be on prepaid, especially if you don't draw a lot from  City Power. You pay more per unit, but all the fixed fees fall away. Even with the R200 you could still save. 

BUT

1) there is a cost for switching and you bear that (City Power will give you a quote for this) 

2) for a couple of months you are going to be feeding the meter and paying off the arrears on your post-paid account. 

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  • 3 weeks later...
On 2021/10/29 at 6:06 AM, RichardZA said:

Thanks for the advice everyone.

This week is teaching me a lesson! But I am impressed even in cloudy overcast conditions solar does help take the "edge" off and I'm VERY glad I went for some more panels.

No I'm not should I be? Network charge currently is R498 excl and a Service Charge of R169

I'm considering some more batteries, but the payback feels very long!

I'm still hunting down why I have a base load of 1kw during the night, it seems too high - my guess is a couple of really old fridges are hurting me. If I can get it to 0.5kw I won't have to buy batteries - new A+++ fridges may be a better investment than batteries.

Swich to CoJ pre-paid - cheaper than post paid upto about 3000 kWh per month.

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