As I write, the panels on my roof are producing 625 W between them. Soon the swimming pool will kick in and unless there's a sudden change in the weather, there won't be enough PV to support that and the system will draw from the battery (current SOC 41%) for a short while and then switch over to mains.

I am wondering how other solar users in Johannesburg are coping with the overcast weather we've had the last while. I have great respect for Eskom's ability to impose load shedding at short notice, though that seems less likely this time of year, so currently I have a rule on my inverter so that it will charge the batteries from 15:00 to 16:00. Usually this leaves me enough to get through the night, and the inverter will use solar to charge the batteries if there is enough of that available. How are others handling the distinct unsunniness that is being visited upon the fair province of Gauteng?

OK... enough of my moaning.

I also keep a spreadsheet showing how much I use and how much of that is self-generated. I've just updated that for November this year. The reality is that my system produced 79% of the electricity the house used. And we have never lost power because of load shedding. So we're not off the grid, but also that's not so bad is it?

To put all of this in context, as I mentioned in another thread, this house has long been a low consumer. Since I got this system we have never consumed as much as 500 kw/h in a calendar month. Before we went solar we were averaging round about 400 kw/h a month, and I would have considered a 500 kw/h month to be a serious blot on my record and an irredeemable stain on my reputation. So our electricity needs are not excessive.

Because of some quirk in the pre-paid meter we have (Itron) there is a small discrepancy each month between what we actually draw from the grid and the movement of the pre-paid balance. I suspect that the circuitry that handles the latter can't differentiate on the basis of direction, so the small amount that is fed back into the grid reduces the pre-paid credits. But it is a few rands each month, and the cure (getting a proper 2 way meter) would be more expensive than the complaint.

How are other folks in Jhb finding their systems performing of late?

You have 625W more than I do as my Deye inverter was removed to be replaced (fault on the board I'm told) and now stock availability is a real issue. Plus most companies in the building / construction / whatever industries shut shop yesterday so I may go solarless through the festive season. 

(When my system is working) I have a slightly more pragmatic approach to loadshedding preparedness. I drain my batteries to 20% every night and never grid charge. When loadshedding is announced I bump night time reserve to 40%, drop geyser temps and grid charge as a last resort. 

Ask yourself, if you only use 15-20 units a day, how much battery power do you really need to survive a 2-hour disruption? Your 625W may be almost enough not to need any for day-time outages.

 

Edited December 16, 20213 yr by Scubadude

It's a tricky one and each will do it differently.

I have rules set up so that my pool pump doesn't run on low solar production days. The pool has a solid safety cover so it can happily skip a day or 2 because there are no leaves etc getting in anyway to clog it. 

The geyser for the kitchen is also seen as optional for me. I can survive with a day of it not hitting 65 degrees. Obviously if there are a few days in a row of cloudy conditions then eskom has to be called in. 

The same somewhat applied to my main geyser. Get it up to 70 degrees when the solar is good but only 55 when relying on eskom. 

November I was 91% off grid.

Today (in Sandton) I have pulled 23.7kwh from my 8.9kwp array as of 3pm. 10kwh of Batteries are fully charged and now the excess is running the heat pump on the pool. It definitely did not look like it was going to turn out that way this morning so I'm glad the clouds were thin! 

7 hours ago, Scubadude said:

Ask yourself, if you only use 15-20 units a day, how much battery power do you really need to survive a 2-hour disruption? Your 625W may be almost enough not to need any for day-time outages.

The twist in my case is that we have a heat pump on the essential side. That kicks in at 7am and so usually gets some help from solar,  but theoretically it can take 30% of the battery. So the danger period for me is 6 to 8 in the morning on an overcast day. 

But at 6 this morning I had 56% of the battery, so I should just stick it in general mode and leave it there. 

That heat pump should be wired to a geyser circuit breaker ... So easy enough to drop it out if you have to. Or what about a Geyserwise panel with your heat pump? It works a treat and allows you to fine tune hot water production as conditions dictate. Maybe also consider running the heat pump as high as it will go (62°C if I remember correctly from my heat pump days) when you have excess solar to reduce the need for the early morning top-up.

the unsunnyness is resulting in less than expected solar generation, limping through might be an accurate description.

on top of it, my son takes great pleasure in giving me what have become accurate weather forecasts. every now and then a video of flooding somewhere gets thrown in for good measure.

Heat pumps dont like to "just have the power removed" and could result in damage.

I suggest to rather adjust it using the control panel it comes with, unfortunately not easily automated and I have the same problem.

also possibly start it at 8-8:30am, giving you a chance to step in if needed.

i'm sure a bit of digging will allow control via say icc or whatever, emulating the control panel signals.

maybe something to look into once my current solar device project is complete.

this really does bring to topic of to oversize or not into perspective, and exactly how important is it to you not to use the odd unit or 2 on eskom.

do you size to your ave usage and send the excess to eskom, or oversize knowing that even so, you're likely to have to do without the main energy appliances anyway - aka pool pumps, in the event of unsunnyness.

my rule of thumb being to size to your current usage, monitored/recorded first for say 2 weeks, with our of season behavior also thrown in. (read heaters turned on etc)

winter panel performance should also be taken into account, as generation drops, along with reducing power requirements via appliances where possible.

peaks, ave's etc all put together, then add 1.5x (50%) should be enough for most, bringing system size, performance and ROI to acceptable levels, with any shortfall being sent to eskom.

Edited December 17, 20213 yr by Nitrious

On 2021/12/17 at 6:51 AM, Nitrious said:

on top of it, my son takes great pleasure in giving me what have become accurate weather forecasts. every now and then a video of flooding somewhere gets thrown in for good measure.

Well done him. Every weather app I have is suddenly useless for forecasting and instead seems to have switched to a reactive mode IE they confirm what you just saw when you looked out the window two minutes ago. 

Yesterday goodwe, Google, accuweather and BBC all forecast a bright summer day for Jozi, this morning it's raining cats and dogs, and surprise! All the apps on my phone now tell me it's going to rain. 

What app is your son using? 

On 2021/12/16 at 9:34 AM, Bobster said:

this house has long been a low consumer. Since I got this system we have never consumed as much as 500 kw/h in a calendar month. Before we went solar we were averaging round about 400 kw/h a month, and I would have considered a 500 kw/h month to be a serious blot on my record and an irredeemable stain on my reputation. So our electricity needs are not excessive.

Everything is so fragile. We bought a 2nd hand fridge/freezer combo. This unit has problems. The compressor runs all the time and there is condensation around the door and inside the freezer compartment. It took a day and a half to get up to temperature and nearly doubled my daily usage in doing so. 

The shop I bought it from is showing concern and made a site visit and some adjustments, but it is still using a lot of juice and my batteries no longer last the night. 

What has happened here, I think, is that our system was sized for our then current usage. Now that usage is up, the system is under stress. Some overspeccing would have been good, but hindsight is a wonderfully clear thing. 

The fridge is is being swapped out today. Ironically if I wasn't on solar I probably wouldn't have noticed the increase in load. 

Then there is the enemy within who got various gadgets for gifts, all of which involve a motor, and who has developed an idea that we have all this free electricity so we may as well use it. 

Villainy! Treachery! The foul finger of fate! 

54 minutes ago, Bobster said:

What app is your son using? 

I have not idea, he gets his phone and device (ps) time every day, at which point the weather reports starts coming in, for a few days ahead.

give pv solar forecast (google play store) a try, its by no means perfect, but does an adequate job.

we also have a channel from a local guy - does weather in entertaining ways.

I've been playing around with the idea of tying something like this into inverter management, Youshiko YC9466 Radio Control Full Colour Weather Station  with 7-in-1 Sensor, while not forecast really, at least current solar irradiance could be tied in, and lower than optimum values (rain) could cause switching to grid, once values are back up to speed, it could switch back to solar.

as for household inverter sizing, like it or not but a 8-10kw (deye/sunsynk) solution seems to be the perfect fit for just about anybody. you could sell your growatt (at least it has value) and just pay in the difference, or cough cough, buy 2x 5kw axperts, here your financial input would be substantially lower, but then you'd have axperts.

the thing is solar is about to dive in prices, from copper instead of silver being used in panels (australian breakthough), to perskavites actually becoming feasible (german crowd) 1400 hours, 1% degradation (read another dive in panel prices), to battery tech moving to cheaper than li ion alternatives rapidly. the worlds scientists all seem to be focused on one thing atm, improving the energy equation. 

actaully another nice "innovation" are solar panels that replace roofing, and are colour coded (italian lot), look really nice.

the snag is investing now in panels or batteries could lead to capital loss as the newer cheaper products make their way to market.

Edited December 23, 20213 yr by Nitrious

39 minutes ago, Bobster said:

What app is your son using?

Try https://www.yr.no/en  or the YR app.  Works very well for me (Stellenbosch).

Having said that, current weather patterns are very disrupted and I think all the forecasters are struggling a bit.

51 minutes ago, Calvin said:

Try https://www.yr.no/en  or the YR app.  Works very well for me (Stellenbosch).

Having said that, current weather patterns are very disrupted and I think all the forecasters are struggling a bit.

By far the most accurate weather app I've used.

2 hours ago, Nitrious said:

as for household inverter sizing, like it or not but a 8-10kw (deye/sunsynk) solution seems to be the perfect fit for just about anybody. you could sell your growatt (at least it has value) and just pay in the difference, or cough cough, buy 2x 5kw axperts, here your financial input would be substantially lower, but then you'd have axperts.

It's a goodwe. What you suggest is still feasible, but I'd need somebody to do the install and setup for me. I ain't going to do that myself (I'd have a fool for a client). And most players in the solar arena are only interested in installing complete systems that they have sold to you.

Also it wouldn't solve my problem. I'd still have the same amount of battery and the same loads to service. So the battery will still run down quicker than it used to.

Edited December 23, 20213 yr by Bobster

most "installers" do seem to have issues as you have mentioned, along with preferring unknowledgeable clients they can push any old thing onto no doubt, although as more people have solar already installed, I think in time it will change.

well depending on the route taken ie, the deye, sunsynk route, it should be as simple as swap out/swap in.

the 2x axpert setup would take a bit more effort, but not much more.

Depending, the 7.2kw axpert might be a good fit as well. 

Then its check trip switch, circuit breakers, ac wiring capacity to/from the db box, along with all the other checks before commissioning.

I'm sure the swap can be arranged one way or another, even if its a knowledgeable member in your area willing to help out.

I would offer but on 2 week quarantine atm, 2x fevers in the house atm and although not me I have to be careful. 

warranties on remaining equipment would need to be checked to ensure full compliance first, I'm thinking batteries here.

Perhaps the first step should be a usage assessment, so you know which of the 3 routes to take. This is a device fitted which monitors your grid usage for around 2 weeks, unless you already have an idea of grid peak and ave usage, in which case it can be skipped.

It may seem unnecessary, it may well be but is a good precautionary first step. Going deye/sunsynk would no doubt make it a mute point but advisable all the same. 

Future proofing an installation while keeping costs and roi acceptable should always be first in mind imo

Edited December 23, 20213 yr by Nitrious

Best description of a weather forecaster: the person with whom the weather very seldom ever agrees.