May 27, 20206 yr Hi All, I was pointed here by a work colleague who said he gained many useful hints and advise from the forum. I'm in the very early stages and looking to see what lessons learned are out there and see how I can avoid any not so obvious pitfalls. At this stage my thinking it to install a grid-tie system (I already have a generator in the case of load shedding) with the mission to use Solar/Inverter to supplement my monthly power and thereby reduce my average monthly electricity costs. Ideally looking to do so without significant capital outlay. My average daily consumption ~ 30Kw with a daytime (7am - 5pm) of between 1.7 and 3.2 Kw (Depending if we run the pool and washing machines together) base load ~ 700w. My initial thoughts were along the following: 10 x (250-380w) panels in series connected to a 5KW Inverter, tied into a single phase in the house (0 feedback to grid)
May 27, 20206 yr 1 hour ago, RyanM said: daily consumption ~ 30Kw I assume you mean kWh (units are important, otherwise we don't know if that is a peak power value or an energy value). This is pretty close to my own daily consumption. 1 hour ago, RyanM said: 10 x (250-380w) panels in series connected to a 5KW Inverter, tied into a single phase in the house (0 feedback to grid) Take the peak capacity of the PV modules and multiply by 5. That gives you an idea of how much you can expect to get from the sun. So if you put up 10 x 300W modules, that will make 15kWh per day. In winter it will be lower (closer to 12, way less on cloudy days), and in summer it will be more (could be as high as 18kWh on very good days in October). If you limit grid feed-in, then of course your loads have to use all the power when it is available, or it will simply be lost. So you could probably expect to offset about half the bill (optimistically speaking) if you aggressively move loads to daytime and stagger them appropriately. As an example, I run my pool pump between 08:30 and 11:30. The washing machine starts running somewhere after 10AM (even before lock-down... I'm the stay at home parent, I do the washing), which means the tumble dryer comes on after the pool pump is off. If I ran my pool pump in the afternoon, I'd get more heat from the heat mats on the roof, but then I'd lose a whole lot of early morning energy. In my case I do have batteries so I could employ that, but why do that if you don't have to 🙂 In practice I expect you won't be 100% effective in using all the energy, especially since the peak energy will be around noon when normal people are at work (so that's where you want to set the pool pump and the geyser timer and all those things), so you should probably expect a little less than my estimate above. Edited May 27, 20206 yr by plonkster
May 28, 20206 yr On 2020/05/27 at 12:54 PM, RyanM said: At this stage my thinking it to install a grid-tie system (I already have a generator in the case of load shedding) I'm really interested in how this would work? If your power is cut during the day, would you be using your generator?
May 28, 20206 yr 15 minutes ago, Darknight said: I'm really interested in how this would work? If your power is cut during the day, would you be using your generator? Yes. A grid tied inverter will switch off when there is a power failure. So I would recommend @RyanM to think twice before making the decision for a grid tied inverter. When you want to go without batteries you can also consider an inverter that will run without batteries AND without grid power like this PIP-GK.pdf. The advantage is you can still power loads from the sun during load shedding as long as the load does not exceed the power delivered by the sun at that moment. In a later stadium you can always decide to go (partly) off grid by adding batteries without having to buy a new inverter.
May 28, 20206 yr And this is also a warning; starting with solar and the tech involved can be very addictive! So try to not buy stuff you cannot use when you decide to do everything in a different way or want to expand.
May 28, 20206 yr Author @Darknight ITO of generation during load shedding. I already have my mains feed into a change over so I am able to power up my generator and disconnect mains. This then feeds from the change over, back into by House DB board. As I understand the Grid Tie inverters monitor the "line" for power in order to synchronize and feed power in at a slightly higher level than the main feed thus utilizing the Inverter PV rather than mains. My plan (unless I'm horribly mistaken) is to connect the inverter between my existing Change Over and DB. In the case of Load Shedding, the generator will substitute as the mains and assuming I'm not trying to feedback into the grid, I shouldn't be trying to feed power back into the generator. Edited May 28, 20206 yr by RyanM
May 28, 20206 yr Author @RikH The PIP-GK is this a reasonable alternate to a Hybrid Inverter ? Thanks again for the early warning regarding equipment selection. I have given it some thought and given the hopefully low cost of entry for Grid Tie + panes, I was thinking if I were to rebuild and re-do I will utilize the existing to run my pool & borehole.
May 28, 20206 yr Author In your opinions (Inverter Independent) would you rather run the following system: 1) High Voltage , Lower Amperage with Panels in Series 2) Low Voltage, High Amperage Or a combination?
May 28, 20206 yr 45 minutes ago, RyanM said: The PIP-GK is this a reasonable alternate to a Hybrid Inverter ? Yes. Especially because you don't want to feed back to the grid, it can't. But in terms of a hybrid, it can blend grid and solar. 55 minutes ago, RyanM said: In your opinions (Inverter Independent) would you rather run the following system: 1) High Voltage , Lower Amperage with Panels in Series 2) Low Voltage, High Amperage Or a combination? Nr. 1 is my favorite. No combiner box, no big fat cables, easy and cheap. I have 18 panels with an Uoc of 41,1 Volt. At a freezing 20 degrees below zero that will give a voltage of 874. My inverter (MPI plus 5kW) can go up to 900 so no problem. The PIP-GK goes up to 500 V so dependend on the panelspecs you can make 1 string of 10 or 2 wit 5 panels. Do you know already what panels you're going to use?
May 28, 20206 yr 1 hour ago, RyanM said: (Inverter Independent) Forgot to say, so it is not inverter independant....
May 28, 20206 yr Author Was looking at the JA Solar Solar Mono 380W I understand that it is inverter dependent, but I also know that people have hardware preferences and then propose setups to suite the hardware. Rather than taking a purist view as to: What works better, which (if either) are safer, has cheaper components causes potentially less issues (i.e less strain on an inverter given higher voltages, significant cable sizes associated with high amperage systems) and a bunch of others I'm sure Edited May 28, 20206 yr by RyanM
May 28, 20206 yr 1 hour ago, RyanM said: Those are the ones. JAM72S01-380/PR Ok, yes that's the pdf I posted. Now, in order to calculate the highest Uoc I need the minimum temperature you can expect in winter. Uoc = 48,71V Temp Coeff = -0,3% per degree C
May 29, 20206 yr Author Minimum overnight temp -4 Degrees Celcius, but during daylight hours I do not expect any temperature below zero.
May 29, 20206 yr Ok, at that temp your Uoc is 53,13V. Now 500V (max. inverter Uoc) / 53,13 = 9 panels max in a string. 380 Wp x 9 = 3.240 Wp in total. Or: 5000 W (max inverter DC power) / 380 Wp = 13. You cannot make uneven strings so 12 panels is max. Make 2 strings of 6 and parallel them.
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