Pocster Posted July 2, 2022 Share Posted July 2, 2022 It’s undoubtedly a stupid question ; I just can’t find the answer . A PV 4Kw setup can generate upto 4Kw dc . So 8kw pv 8kw dc Am I correct that in any solar app the PV generation shown is AC? So even if an 8kw was generating 8kw the pv generated app results are ac ?? Or just limited by the inverter ?? i.e ( simplifies confusing question ! ) why doesn’t an 8kw array ever show more than the inverter limit ? If anyone even understands that would be good 🙄🙄🙄🙄😁 Link to comment Share on other sites More sharing options...
SteamyTea Posted July 2, 2022 Share Posted July 2, 2022 The output of the modules are set by a standard test. That test uses lower light levels than even a British summer can produce. Temperatures may also be lower. Link to comment Share on other sites More sharing options...
joth Posted July 2, 2022 Share Posted July 2, 2022 53 minutes ago, pocster said: Am I correct that in any solar app the PV generation shown is AC? It depends on the app, but I believe the solaredge app shows the inverter output not the DC input, so it is clipped if the panes exceed the inverter W capacity. If you have SE optimisers you can also see the DC generation (Wh per day) as the sum of all the optimisers. 1 Link to comment Share on other sites More sharing options...
Pocster Posted July 2, 2022 Author Share Posted July 2, 2022 2 minutes ago, joth said: It depends on the app, but I believe the solaredge app shows the inverter output not the DC input, so it is clipped if the panes exceed the inverter W capacity. If you have SE optimisers you can also see the DC generation (Wh per day) as the sum of all the optimisers. This is what I thought ! 👍 Link to comment Share on other sites More sharing options...
Radian Posted July 2, 2022 Share Posted July 2, 2022 I think it's worth mentioning the First Law of Thermodynamics: "Energy can be changed from one form to another, but it cannot be created or destroyed." The Solar PV modules can't change photon flux into any more energy than the inverter can push out - so it's not like there's 4kW worth of power lurking unused in the array. This is why Voltage is sometimes referred to as Potential. Link to comment Share on other sites More sharing options...
joth Posted July 2, 2022 Share Posted July 2, 2022 21 minutes ago, Radian said: I think it's worth mentioning the First Law of Thermodynamics: "Energy can be changed from one form to another, but it cannot be created or destroyed." The Solar PV modules can't change photon flux into any more energy than the inverter can push out - so it's not like there's 4kW worth of power lurking unused in the array. This is why Voltage is sometimes referred to as Potential. Good point however the piece I'm assuming but wasn't actually stated is there's also some DC coupled batteries, so it's perfectly possible the panels are pumping more power than the inverter is delivering into AC, if the difference goes into charging battery. Link to comment Share on other sites More sharing options...
JohnMo Posted July 2, 2022 Share Posted July 2, 2022 But in the case of a large array say 6kW and a small inverter 3kW or an inverter that can limit export, you could have 6 kW DC, the inverter will waste the rest as heat Link to comment Share on other sites More sharing options...
joth Posted July 2, 2022 Share Posted July 2, 2022 (edited) 6 minutes ago, JohnMo said: But in the case of a large array say 6kW and a small inverter 3kW or an inverter that can limit export, you could have 6 kW DC, the inverter will waste the rest as heat No the inverter is not dumping 3kW as heat through its heat sink, it just won't draw as much current as it could of from the panels. Like if you hook up a 100W load to a PSU or battery capable of delivering 200W, it doesn't automatically mean 100W is being "lost" anywhere. In the example 3kW is being "lost" via reflected and absorbed solar energy in the panels themselves. Just the same as sun hitting a tile roof, or indeed if sunlight is hitting panels with no load connected. Edited July 2, 2022 by joth Link to comment Share on other sites More sharing options...
Pocster Posted July 2, 2022 Author Share Posted July 2, 2022 2 minutes ago, joth said: No the inverter is not dumping 3kW as heat through its heat sink, it just won't draw as much current as it could of from the panels. Like if you hook up a 100W load to a PSU or battery capable of delivering 200W, it doesn't automatically mean 100W is being "lost" anywhere. In the example 3kW is being "lost" via reflected and absorbed solar energy in the panels themselves. Just the same as sun hitting a tile roof, or indeed if sunlight is hitting panels with no load connected. So I guess ; if I am generating more than my inverter can deal with as it’s DC and the SE battery is DC - it will charge at the rate the PV provides ? I.e potentially more than 4kw . Link to comment Share on other sites More sharing options...
SteamyTea Posted July 2, 2022 Share Posted July 2, 2022 1 hour ago, Radian said: First Law of Thermodynamics Second Law comes into play as well. "The entropy of any isolated system never decreases. In a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems increases." Or "You get less out than you put in" Link to comment Share on other sites More sharing options...
Radian Posted July 2, 2022 Share Posted July 2, 2022 1 hour ago, pocster said: So I guess ; if I am generating more than my inverter can deal with as it’s DC and the SE battery is DC - it will charge at the rate the PV provides ? I.e potentially more than 4kw . It depends on the way it's all put together. Hopefully there's a DC path between the PV module array and batteries without going via the inverter's AC output in which case the full power of the array would be available for battery charging - minus any load on the AC output of course. 1 Link to comment Share on other sites More sharing options...
Pocster Posted July 2, 2022 Author Share Posted July 2, 2022 2 minutes ago, Radian said: It depends on the way it's all put together. Hopefully there's a DC path between the PV module array and batteries without going via the inverter's AC output in which case the full power of the array would be available for battery charging - minus any load on the AC output of course. I hope so . It’s hard to test . At some point I might turn the PW off just so I can drain the SE on a solar day . Then ( assuming PV generation is greater than 3.66kw ) I can gauge how fast it charges . Really wish the apps showed ‘real ‘ PV DC generation Link to comment Share on other sites More sharing options...
Pocster Posted July 2, 2022 Author Share Posted July 2, 2022 @Radian so is this showing me my daily amount ( so far ) is 16kwh of DC ?? I.e at source ( pv panel ) generation Link to comment Share on other sites More sharing options...
Pocster Posted July 2, 2022 Author Share Posted July 2, 2022 1 minute ago, pocster said: @Radian so is this showing me my daily amount ( so far ) is 16kwh of DC ?? I.e at source ( pv panel ) generation Actually that’s not correct is it ? ( my understanding I mean ) not the screen grab Link to comment Share on other sites More sharing options...
Radian Posted July 2, 2022 Share Posted July 2, 2022 5 hours ago, pocster said: Actually that’s not correct is it ? ( my understanding I mean ) not the screen grab Not sure. Looks a bit like the display on this app to me: Link to comment Share on other sites More sharing options...
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