Bobster.
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Everything posted by Bobster.
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Solar installed last week
Bobster. replied to dimipiraat's topic in Starting In Solar? Feel free to introduce yourself
They are evaluating a cheaper meter - but it looks like "cheaper" = 5K. The 25c extra per kWh incentive, and the waiver of the net consumer requirement are both time limited. It may be that the City will renew them, but it's also not guaranteed. So, again, understand the offering before taking the plunge. I hate to bash COCT. They have certainly been the most proactive around feed-in tariffs, and they have the best offering, but the devil is in the details. -
I wonder if there can be a single figure for self-consumption. These inverters are actually several devices in one. My Goodwe's internal consumption depends on what it is doing. I know from recent experience that at night, when it's just staying on, not supplying any loads, with the only power source the battery, then it draws about 50W. But during the day when there is PV and it is taking that and converting it to AC then self consumption is higher. There would be other combinations PV AND charging the batteries, PV and not charging the batteries. Point is, self-consumption changes according to what the inverter is doing. Working from diagrams like those you post (neither of which show export to the grid) might also not be an accurate way to work. You need to confirm this, but it seems to me that if the property requires 494W, then the draw from PV and/or battery must be higher than 494 because of the power lost during conversion from DC to AC, or in stepping up the AC voltage. None of those processes are 100% efficient.
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And really I should have just looked at the nice drawing that engineer chap prepared for my registration with COJ and put my thinking cap on. It's all there. Including the placement of the CT between the main breaker and the non-essential DB, and the connections to that three way switch. The third diagram to be found at this page.
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OK... this is a heads up for anybody in the COJ supplied area thinking about pre-paid. WAIT A COUPLE OF MONTHS. There have been questions in my community about recent changes to the municipal statements. A city councillor chipped in to say that he can't reveal any details because the new tariffs are not signed off yet, but that there are big changes coming for electricity tariffs. The speculation is that there will be a fixed connection fee per month. The councillor won't say. I understand this, because is bound from saying anything about tariffs that are not yet finalised. But clearly there are changes coming and so you might not want to apply NOW and then have to deal with whatever the tariff is in 4 months time.
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Solar installed last week
Bobster. replied to dimipiraat's topic in Starting In Solar? Feel free to introduce yourself
How much electricity do you usually use? Your bills will tell you that. Looking at my home as an example, we usually use 13 to 14 kWh per day. I have about half the panel power you do. On a sunny day my system is usually charged by 11:30. You could look at selling your excess BUT check the tariffs that apply where you live, and the accompanying regulations, very carefully. I am supplied by City Of Johannesburg, and as I read the current tariffs that are in the public domain, I won't even break even on feeding back, so I don't. Also I'd have to work my system harder, which is not going to do anything positive for the life of the inverter. I do wish I had more panels. On a sunny day, as I said, the system is charged by 11:30, sometimes 11:00. On overcast days it can take a lot longer, and if I had more panels I would recover more quickly on those days. So (we get to the conclusion eventually), live with this for a couple of of months. Watch how it behaves on overcast days. THEN decide if you want to feed back your excess. A sunny day is a poor test of a system. 2 or 3 overcast days in a row... now THAT is a test. -
OK.... but does it then have some way to send power back to the line coming in from the grid and thus to the DB? And why would that stop happening when the grid goes down? Oh... anti islanding kicks in. Looking at server logs and correspondence I see that there was no loss of grid power for 8 days from the 8th until the 14th. The electrician was actually here in FEBRUARY and so we can remove him from the list of suspects. The flashing of the BMS was done on the 11th. City Power were here on the 6th, and there was load shedding on the 7th which was handled properly (SEMS shows the essential loads still being serviced).
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Yes. It is a manual switch.
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In the last two weeks I have had City Power here testing my system for compliance with safety regulations An electrian who fitted an extra socket connected directly to grid (IE not backed up) for use with the pre-paid meter. He took a feed from the AC sub DB for the solar system. Guys from the installer running some checks on my batteries. They turned the battery off but did not, as I recall, touch that 3-way switch. If they had then the wifi would have gone down, my VPN connection to the office would have dropped, and I would have moaned at them because they said they weren't going to do that. I think it was in that order. I don't recall me having to move that switch in the last week or so. I'm not above that, but I need a good (in my mind) reason. So that "grid" position should bypass the inverter and switch all the essential loads to grid?
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On the AC sub DB for my system there is a three position switch. Top position is labelled "Solar" and this is the position that would usually be selected. Middle position turns off all power to the property - no grid, no solar. The inverter and battery stay on. Bottom position is labelled "Grid". OK... so yesterday morning we had load shedding schedule from 4:00 to 6:30. I woke up about 5:45 as I had to get dressed and shaved earlier than usual as I would be commuting to Centurion that morning. I decided to have a cuppa. I walked into the kitchen, hit the light switch and ... nothing. What? I took a peek at the inverter. All the lights one would expect to see on were on and in their usual state. Except for the wifi indicator which was flashing - because it couldn't connect to the wifi in the house. So it must be earth leakage. What a nuisance at this time of the morning. Only it wasn't. Every switch on the DB was where it should be. So now I go and check the sub DBs for the solar system and I find that this three way switch has been left in the "grid" position. Hmmmm.... throw that up to "solar" and everything in the house starts switching on. How that switch got to be in that position is a mystery to me, but that's not really why I'm posting this. Suffice to say that I didn't change this switch from "solar" to "grid" sometime the previous evening. Here's yesterday's graph from the Goodwe portal You can see everything going quiet at 4 am. Until then, the system had been behaving as expected. Loads (yellow line) are serviced by the battery, and the SOC (green line) is slowly dropping. At 4:00 the loads drop to almost nothing (actually about 50W, which I assume is self consumption by the inverter). Then just before 6:00 the loads come up again. That's when I put that three way switch back into the top ("solar") position. So now my question: What is the "grid" position on that three way switch for? As I've said, the property was running off of battery until the load shedding started. If look at the graph for the day before (when I had no need to touch that switch) the system is working usually: house running off battery until solar starts coming on line, then solar takes over the loads and starts charging the battery. Once the sun goes down, the battery takes over. So everything ran just as usual until there was a load shed. Then despite the inverter being on and the battery having better than 50% SOC, no power is supplied to the property. I had thought that "grid" position switched the property to grid and bypassed the inverter, but clearly it does something else. But I'm not sure what.
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Advice on Solar setup
Bobster. replied to Qbom1990's topic in Starting In Solar? Feel free to introduce yourself
OK... if you are using 9kWh during the night, then you are going to deplete a 10kWh battery. But are you sure it's going to be 9kWh? You're talking about putting the geyser on a timer and that will mean it doesn't run at night. My way of looking at these systems is that the batteries give you protection against outages, and the panels reduce your bill. So you want to minimise night time draw from the batteries so that if the sun isn't shining the next morning and there's an early morning shed then you have some protection. One way to do this is be setting rules on the inverter that limit how much can be drawn from the battery. On my system this is set so that the battery cannot be discharged past 40% remaining when there is grid power. So that's the minimum I will have in the bank, so to speak, when there's an outage. Because we manage our loads overnight we very seldom hit that 40% remaining, and often have over 50% (of a 10kWh battery) when we start getting useful PV in the morning. But this depends on choices and the routines of the household. We are just two adults, one retired and one working from home. So it's been quite easy for us to set things up so that we maximise the free power from the sun during the day and use little at night. I don't have a Sunsynk inverter (nor a Deye) so I can't tell you how to set your inverter to behave like mine, but there will be some way to do this. -
My thoughts are that you shouldn't wait. No matter who wins the forthcoming election, load shedding is not going to go away any time soon. My system has been in over 4.5 years now. When I got it the wife thought this was just a midlife crisis sort of thing. Two days later load shedding started up, and we were in the only house in the street that kept the lights on, that had fridges still working etc. She was then very appreciative. Ever since we have had a largely uninterrupted routine in our house. Lights always on. Wifi always on. Beer always cold. Milk never going off. Etc etc. Do it now. Get a 48V system. You will have a much better choice of batteries, and won't have to scale up again in a couple of years time and sell your 24V inverter at a loss. There is always some better kit just over the horizon. If I were to start today, with the benefit of experience and with what I have learned from helpful folks here, I would not go for exactly the same setup I have now. But I would do it, and I am not sorry that I have what I do have.
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Question around feeding back into the grid and battery discharge
Bobster. replied to munchies's topic in General Discussion
10kWh of battery. I've got that much. We run the house on battery at night. The heat pump runs around 6:30 in the morning. Sometimes I might have as much as 55% left when the pump has run. Sometimes it's down to 45% left. My system is set up so the battery will not discharge past 40% remaining whilst there is grid. So that's the reserve I will always have in place. Most days that reserve is a non-issue. The sun comes up and the system starts charging. But on overcast days when the power goes down at 6 or 7 or 8? So I could maybe give up 1.5 kWh at best to support Eskom. It's not a lot, and I won't get much back for my trouble. OK... I could sell a bit more, but then I'm eating into that amount I've reserved for safety, for the bad set of circumstances. How much could you actually feed back? And how much do you want in hand to CYA on an overcast, gridless morning? Which City do you live in? If Cape Town then your feed-in helps to charge up Steenbras. -
OK, then a change of immediate subject: There's a running discussion about whether or not it makes financial sense to sell back. There is no one answer, because different municipalities offer different re-sell tariffs with different admin fees attached to them. So would you care to share who supplies you with power and what sort of saving your are acheiving. From my POV as a client of City Power in Johannesburg, the potential savings are very small, and the cost of converting to the feed-in tariff is non-trivial, so I can't see way to make it work for me.
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OK... this is a different, newer model Goodwe then mine, so take this where it comes from. I can't help you with the economical mode settings. Firstly because I don't truly understand economical mode on my own, older ES. Secondly because mine doesn't work with the "modes" that you refer to. I had a problem recently with strange behaviour on my Goodwe. This was resolved with a firmware update. So check the firmware version on your inverter (SolarGo will show you this), record that number, then get whoever is supporting your inverter to upgrade to a newer version (I said to record the current version number in case you want to roll back). This can be done remotely and without needing to restart the inverter. You don't say where you are and what time of day those screen shots were taken. They don't show a lot of PV coming in, so your batteries are not going to charge quickly. Your battery is not fully charged, but you are getting just 300W from the panels. You might try this: Just set up a discharge "mode" as you already have. Do not specify times for charging. The inverter should behave as if it's in general mode if there are no time based rules that apply. Whatever you change, change one thing at a time and then allow time to see if it works. Otherwise you will never know what the problem was and may fall back into the same hole in the future.
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But this is why COCT are an outlier - they have somewhere to store that power they get during the day. Steenbras gives them options that other metros don't have. Though you'd think that COJ (to pick my home town) would have been able to take some of the sting out of stage 2 during the day today, which would have helped businesses
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I posted a link to an article that compares feed-in tariffs for three metros in SA (the 4th, COJ, says they don't have tariff information at this time). I see nothing to change my old suspicion that they don't want us feeding in. Maybe because of some technical issue that they haven't resolved, or maybe for political reasons. Which makes it even more interesting that COCT are making such a thing of this (though a strictly time limited thing, folks need to read the small print). Durban, for example, has a better per unit rate than Cape Town, but they charge R120 odd per month per rated kWa of your inverter, so you have to sell back a lot just to break even. Tshwane say they pay 13c a unit that you sell back - that's just flat out insulting.
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Thanks. But there is something going on here. There's too many complaints about the meter showing more useage than the amount drawn from the grid. I had this problem - the prepaid credit would run down faster than the total used went up. But I didn't complain about it because it was costing me a couple of rand a month and I calculated this was cheaper than being on the feed-in tariff. With this meter (Itron) the hand held unit that we use for loading purchases would be tripping almost constantly if plugged into a backed up socket. If it stayed up long enough you could capture that long number representing the purchase or get accurate (IE corresponds with the main meter) readings from it. The new meter I got a couple of months ago after the Itron went pop does not show this behaviour. The total use moves by the same amount as the pre-paid credit.
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https://mybroadband.co.za/news/energy/527805-cape-town-vs-pretoria-vs-durban-best-electricity-feed-in-tariffs.html
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It's my observation that a lot of meters don't do well with power fed back into the grid. They can sense the current, but they don't know which way it is flowing. They weren't designed to deal with a situation where power can be flowing from the property to the grid. This is a problem in COJ. People get solar, they set their inverter to feedback, then they find out that the meter doesn't behave as they expected. So I don't think we can just set the inverter to export and expect to automatically get a credit. This may depend on the specific meter that you have. There is a reseller's tariff. I don't find it very attractive, because I'm on pre-paid. If you're on the post-paid tariff then it may be a better deal. I am in the process of registering my system with the City (they did the technical inspection yesterday), so I hope to have a chat with them soon about tariffs.
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AIUI COCT currently has permission from NERSA to waive the net consumer requirement. There is surely no impediment to COJ seeking the same waiver? The other part of their current package is an extra 25c per unit incentive over and above the NERSA rate. Maybe they take that off some other part of the bill. But I'm open to offers. The guys who came out today were technical and in a hurry, so they weren't going to talk tariffs. I'd hoped they would.
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It would make a difference here I believe: City Power customers get a unified bill for rates, electricity, water, sewage & pikitup. The way I see it, R100 back under any heading is R100 off the total. For private homes anyway. Or am I missing something?
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I don't see that it makes a difference. No matter what heading the credit is under, the total of my bill is reduced. What COCT are doing is making a lot of noise about how fantastic it can be. So they're advertising that you can sell back and save some money. And they have a more attractive tariff than COJ do. So they are getting uptake. Whilst some googling I have done shows that COJ have had their regulations and a registration process in place for at least five years, they have not made a song and dance about it, so nobody thinks about selling back and so nobody does. Well not nobody, but not a lot of folks. And they also need to work on their offerings. Last time I looked at their tariffs it was going to cost me about ten grand for a new meter, and about a grand a month in admin fees to get maybe twenty bucks credit per month. So no thanks. COJ trapped themselves years ago. Their per unit cost is lower than a lot of other municipalities, but they compensate for that with high admin fees. Probably a good idea at the time (at least 20 years ago), but now a problem for them because they have to impose those same admin fees on the reseller's tariff, and that now becomes a discouragement. Unless you're still on the post-paid tariff in which case the admin fees are the same and you can make some money back each month - but there's still the meter and the cost of that. I hope to have these conversations in the next while. I was actually hoping to have them today, but the guys from the City had to get going to do another inspection.
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There's so many rules! It's worse than rugby. So far it's all been technical and safety. There's been no discussion about tariffs, and under the current tariff structures as published, in Johannesburg I have no interest in selling back because it will cost me money. I hope they can come up with a set of tariffs that will change my mind. Qualifier: If the new meters that they are installing can cope with two way transmission and so don't have to be replaced at the householder's expense, and if one is on the post-paid tariff at time of install, then there may be a small win to be had.
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Whilst we were waiting for the installer to arrive, I asked the City's engineer about the stories going around about arbitrary disconnections. He said this is not City Power policy. He said that the most common means of finding out about a PV system is that the meter is misbehaving (according to the householder) or that they go out to check why your meter readings have dropped off. They may advise you on the process to register your system, to get your installer to check the installation, or they may suggest that you switch to the reseller's tariff, but there should be no disconnections just for having PV.
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OK… so the City Power engineers were just here (in a hybrid vehicle). They require a representative from the installer to be present at inspection time. The engineer who did all the work until now may be present, but doesn’t have to be As far as I could see and ask whilst they were busy, they checked That the inverter is as described on the documentation the engineer submitted. This includes the serial number. They had already checked that the inverter (as described) was on the approved list That all the necessary safety labels were in place. On the outside box that houses the main breaker, on the main DB, on any sub DBs for the PV system. I chatted to them about this. They said that there have been cases of City Power electricians thinking the house was dead because they had thrown the main breaker outside on the street, then getting a surprise. So the labels alert any electrician to the presence of a second power source. They had the installer rep demonstrate that the inverter is connected as described in the line drawing. He didn’t have to open up the whole thing and take them up into the roof, he did have to answer any questions they asked him: “Please show us [whatever]” They checked the functioning of a three way breaker that was installed so that the house can be suppplied by the PV system, by the grid, or get no supply at all. They measured the time taken to reconnect after grid power returns. They are looking for 60 seconds or greater. They will now take the test results back to their office. They don’t liaise with me or with the installer, they deal with the engineer. They said that they were happy with what they had seen but pointed out to me that the actual certificate was not yet issued, and the system is not deemed registered until the certificate is issued. They also told me I shouldn’t change anything because any certificate that will be issued will be for the system as tested.