Janssen Posted October 23, 2016 Share Posted October 23, 2016 hi to all, can someone explain further what is grid tie renewable and off grid renewable? thnx. Quote Link to comment Share on other sites More sharing options...
___ Posted October 23, 2016 Share Posted October 23, 2016 Grid tie means you have an inverter that carefully injects the power it makes into an existing AC network. It "ties" with the "grid". It is a follower, not a leader, in a manner of speaking. It simply follows the grid frequency. When the grid goes down, it goes down too. Off-grid marches by the beat of its own drum: It makes its own 50Hz signal. It doesn't need a grid connection. Both setups need a way to bridge the variable solar input and match it with the demand. Grid-tied setups push the surplus into the grid and takes the shortfal from the grid. So the grid becomes the battery. Off-grid inverters store the surplus in a battery and takes the difference from the battery. Hybrid inverters are essentially off-grid inverters that can also tie with the grid. This is mostly used when you want a tiny amount backup (small battery bank), but you still want the advantages of taking the shortfall from the grid or selling your surplus to the grid. ibiza 1 Quote Link to comment Share on other sites More sharing options...
Guest Posted October 23, 2016 Share Posted October 23, 2016 Adding onto Plonksters post, grid tie has to be done legally within your local municipal regulations. Turning meters back and all that is not legal. Off-grid does not require same stringent regulations as grid tie, but it is advisable to get a CoC if your off-grid inverters is connected to your DB board. Quote Link to comment Share on other sites More sharing options...
Janssen Posted October 24, 2016 Author Share Posted October 24, 2016 thank you sir Plonkster, the terrible triplett and tinker.. what about this sir... How this hybrid system works? How does it differ with the grid tie inverter or off grid inverter... thank you for helping Quote Link to comment Share on other sites More sharing options...
___ Posted October 24, 2016 Share Posted October 24, 2016 1 minute ago, Janssen said: How this hybrid system works? How does it differ with the grid tie inverter or off grid inverter... The hybrid system does both. It can both tie with an existing grid, or run standalone. You could say that it's got two inverters in one box, though that is an oversimplification. Quote Link to comment Share on other sites More sharing options...
Janssen Posted October 25, 2016 Author Share Posted October 25, 2016 about the smart system, can you discuss further and example sir.. thnx Quote Link to comment Share on other sites More sharing options...
___ Posted October 25, 2016 Share Posted October 25, 2016 7 hours ago, Janssen said: about the smart system, can you discuss further and example sir.. thnx Those two videos does a much better job than I can. It comes down to this: What is your objective? Do you want to save money, have backup when the grid is down, or both? If the grid is stable enough for your applications and you just want to save money, go with a grid-tied inverter. If the grid is unstable or you need backup for critical tasks, go off-grid. If you find that you want to do both, go Hybrid/Smart. GTI is the cheapest, off-grid the most expensive. Hybrids usually sit in the middle as they allow you to get away with a smaller battery bank, and that happens to be one of the most expensive components. Quote Link to comment Share on other sites More sharing options...
Janssen Posted October 27, 2016 Author Share Posted October 27, 2016 if i have money to buy, which is the better to use? why? thnx sir Quote Link to comment Share on other sites More sharing options...
___ Posted October 27, 2016 Share Posted October 27, 2016 20 minutes ago, Janssen said: if i have money to buy, which is the better to use? why? First you have to define "better". What is the most important to you. 1. If the lowest possible bill is what you want and you don't mind the occasional outage, go with grid-tied. 2. If you want a lower bill AND you want to pay as little as possible to get it, go grid-tied. 3. If you cannot deal with the occasional outage or outages are too frequent go with off-grid, preferably a unit that includes a automatic changeover switch so it works like a UPS. 4. If you want to be completely independent (or you have no grid connection), go off-grid. 5. If you want backup for some appliances but your main goal is savings, go hybrid. If you ask my personal opinion, hybrid is the way to go if you live in the city. Gets you the best of both worlds. It costs more than pure grid-tied though. ibiza, superdiy, Chris Hobson and 1 other 4 Quote Link to comment Share on other sites More sharing options...
Chris-R Posted October 27, 2016 Share Posted October 27, 2016 I have been getting quotations and discussions with lots of solar installers in Gauteng and up North. Just about all of them says that the hybrid system is the way to go ?? and also says that one can connect it to the grid without saying anything ( Let sleeping dogs lie !! ) It seems to me that the Western Cape and Eastern cape is just about the only two regions where you could legally connect to the grid? What about all the hundreds of installations I see in Gauteng, knowing that the installers normally would suggest to connect it too the grid. Are they all illegal and aren't this a bomb waiting to explode? Just wondering! Quote Link to comment Share on other sites More sharing options...
Guest Posted October 27, 2016 Share Posted October 27, 2016 3 minutes ago, Chris Rossouw said: Just wondering! It is all very new to SA. Western Cape has only been at it since wot, before 2010 (?) that I became aware of them looking at it. I suspect once Zuma Inc has moved on, the new leaders get in place and start cleaning the SA Inc house, that more municipalities will become aware of the reduction in income from selling power on, necessitating them looking more closely at why. Quote Link to comment Share on other sites More sharing options...
Chris-R Posted October 27, 2016 Share Posted October 27, 2016 Tinkerboy, what happens if the meter does not reverse? Do you still feed into the grid, but just receive no credit for it? By the way, I did not refer to an actual explosion, but rather the day when someone wakes up and found the hundreds of illegal installations. Hope you are right on this one! Quote Link to comment Share on other sites More sharing options...
___ Posted October 27, 2016 Share Posted October 27, 2016 33 minutes ago, Chris Rossouw said: Tinkerboy, what happens if the meter does not reverse? Do you still feed into the grid, but just receive no credit for it? Mechanical meters sometimes have a reverse lock-up, so with those you simply receive no credit. The electronic meters generally have two kinds: Those that bill you for the electricity you feed back (because they cannot sense direction) and those that trip. So with the electronic meters you usually have to invest in a grid-limiter. Quote Link to comment Share on other sites More sharing options...
PaulF007 Posted October 27, 2016 Share Posted October 27, 2016 So with the electronic meters you usually have to invest in a grid-limiter @plonkster does this prevent feedback into the grid? Quote Link to comment Share on other sites More sharing options...
___ Posted October 27, 2016 Share Posted October 27, 2016 29 minutes ago, PaulF007 said: @plonkster does this prevent feedback into the grid? With some inverters it is built in and with others it's an external unit. However you look at it, it only works if the inverter supports some form of communication (with the external unit) or internal setting, and not all inverters have this feature. They all operate on the same principle. They measure the consumption at the point of consumption and aims for zero. It communicates with the inverter and adjusts the power level to balance it close to zero. There are some things you have to know: because it takes time to measure the current/voltage, communicate that to another system/subsystem, and then make an adjustment, it usually means that sudden changes in load results in short periods of feedback (a few seconds) and this is sometimes enough to trip prepaid meters. In these circumstances, the ones that bill you are much easier to live with: The momentary billing events usually won't add up to much. Also, just to avoid confusion: Grid-limiting isn't the same as anti-islanding. Anti-islanding has to do with disconnecting if the grid goes down (whether you feed back or not), grid-limiting has to do with not spinning meters backwards. Might be old news in this forum, just mentioning it for completeness. Quote Link to comment Share on other sites More sharing options...
PaulF007 Posted October 28, 2016 Share Posted October 28, 2016 5 hours ago, plonkster said: it usually means that sudden changes in load results in short periods of feedback (a few seconds) and this is sometimes enough to trip prepaid meters @plonkster I remember I saw a thread somewhere about this but cant find it , were there a solution to the prepaids that tripped? Quote Link to comment Share on other sites More sharing options...
___ Posted October 28, 2016 Share Posted October 28, 2016 3 hours ago, PaulF007 said: a solution to the prepaids that tripped? There are ways to reduce the tripping. One way is to tell the grid-limiter to aim for some non-zero value, for example for 50W. Since the prepaid meter works on some kind of average (the Conlog meters uses a 15 seconds window) that gives you a bit of credit. The second way is to limit the feedback to some value that won't skew the average too badly over that time window. But @Jaco de Jongh also pointed out to me that you can guy these Rhomberg relays (SP510) that detects reverse flow and switches very quickly. So no official solution yet, but I have an idea to use that relay to switch on a load for a second or two (but the load will be powered from the grid BEFORE the measurement point so the grid limiter doesn't see it). Jaco De Jongh 1 Quote Link to comment Share on other sites More sharing options...
Chris-R Posted October 28, 2016 Share Posted October 28, 2016 So in my case where I have a meter which is about twelve years old and still got the old ring turning, it might work. ___ 1 Quote Link to comment Share on other sites More sharing options...
___ Posted October 28, 2016 Share Posted October 28, 2016 You can calculate the limits, say for example you have a Conlog meter like I do: 40W reverse power over 15 seconds will trip it according to the manual. 40W over 15 seconds is 600Ws (watt seconds). So if the inverter takes two seconds to respond, the maximum push-back I can do 600/2 = 300W. If I aim for 50W rather than zero, then my two second window becomes 13 seconds at -50W (choosing negative here for consumed power) and two seconds at some positive value of x which we have to determine, of which the total must remain under 600Ws. -50*13 + x*2 = 600 x*2 = 600+650 x = 1250/2 = 625W. As you can see, it remains problematic for anything more than a few hundred watts. Just note that I sucked the value of two seconds out of my thumb. I have no idea how fast or slow your average inverter is. Given the time it takes to take a reading (easily 0.2 seconds), some comms time between the various units inside/outside the inverter (optimistically another 50ms), the soonest the inverter might know of a change in power is a quarter of a second after it's happened, so I have a feeling the best inverters will track this at best 0.5 seconds to 1 second. This is a gut feeling, I have no empirical facts behind this. I know that the Victron Multiplus is "very slow", this is what I was told. I don't know how slow yet, but I will find out soon. Quote Link to comment Share on other sites More sharing options...
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