PV power optimization

maks_sm · Aug 22, 2015

Hi Folks,
I am looking for some way to optimize my home PV system of 4 panels 235Watts each sitting in sequence and connected throug MPPT charge controller (960Watts or 40 amps) to two batteries 12V connected in sequence also. I have also two inverters 600W and 1600W. Easy 'stand alone' or 'off grid' system. As you all know SOMETIME we have cloudy days, I would say cloudy weeks also. Have two questions:

1. Do we have some sort of automatic solution to plug my PV panels through smaller charge controler I have 780W 30Amps? If charging current reach 28 amps that automatic would unplug 4th panel and plug it back when current is less than 20 Amps. I have expansion plans for that 960Watts charge controller to be connected to two strings of panels by four panels 960Watts each in parallel. And plan is to connect second string directly to water heater if direct solar light. That will need very similar automatic solution.

2. I have no constant power consumption in my house. Original plan was to plug 600 W inverter to the refrigerator and enjoy free electricity. Plan collapsed because pump of the compressor of the refrigerator is eating about 780Watts and my pure inverter automatically turns off supply. What I am looking for is automatically energised second inverter 1600W when consumed power is over 500W. That may be as current from batteries is over 22 Amps. Also required with swich AC delay of 3 sec, as second inverter does not give energy instantly.

Sure it s easy for some one familiar with game. Thank you

uksparks · Aug 22, 2015

This isn't my area of expertise, anything is possible with enough money thrown at it, but at a guess I'd say it's not going to be very straight forward and the costs involved in creating such a setup would probably be significantly greater than the saving it would give you.

4 Panels is a very small system as you know and in reality isn't going to generate a great deal, I can only have a guess and say it's connected into the grid etc so you are already using the free power from it? If this it not the case I cod only have a guess and say your best bet would be to simply connect it to feed the grid as that's more likely to work best for you.

Like I say I don't know much about PV and may be totally wrong but I feel I'm probably along the right lines.

Gavin A · Aug 22, 2015

1. depending on the MPPT charger it could well be that the charge controller will regulate the output anyway by adjusting the tracking point to a less efficient voltage.

1a - beware that the thermostat may stick when DC current is run through it, unless you have a DC specified immersion (not actually experienced this, but it's an issues I've seen mentioned before).

2. it's doable with the correct inverters that are designed to work in that way, but I doubt that applies here.

your second inverter would need to be capable of synchronising with the first, which most cheap end offgrid inverters aren't.

maks_sm · Aug 22, 2015

uksparks said:
This isn't my area of expertise, anything is possible with enough money thrown at it, but at a guess I'd say it's not going to be very straight forward and the costs involved in creating such a setup would probably be significantly greater than the saving it would give you.

4 Panels is a very small system as you know and in reality isn't going to generate a great deal, I can only have a guess and say it's connected into the grid etc so you are already using the free power from it? If this it not the case I cod only have a guess and say your best bet would be to simply connect it to feed the grid as that's more likely to work best for you.

Like I say I don't know much about PV and may be totally wrong but I feel I'm probably along the right lines.

Thank you for reply. I would say nowdays in PV solar off grid more entusiasts than businesmen. The cost of 30Amps charge controller less than 40Amps and it is less power consuming. Averagly we may have 3 hours direct sun fall per week excluding summer. That system is totally separate off grid including zero and earth

maks_sm · Aug 22, 2015

Gavin A said:
1. depending on the MPPT charger it could well be that the charge controller will regulate the output anyway by adjusting the tracking point to a less efficient voltage.

1a - beware that the thermostat may stick when DC current is run through it, unless you have a DC specified immersion (not actually experienced this, but it's an issues I've seen mentioned before).

2. it's doable with the correct inverters that are designed to work in that way, but I doubt that applies here.

your second inverter would need to be capable of synchronising with the first, which most cheap end offgrid inverters aren't.

I have chineese Tracer 3215 and 4215. They look after batteries charging point. To say over 27Volts they hit flat rate something like 10 Amps. No automatic swich inside, just fuse burns off in midday of four panels plugged to Tracer 3215. Simple time relay would be a help, but it does not know if we have sunshine in midday. I think Panasonic has proper relay to swich off a solar panel or string of panels (see my expansion project). But I would fancy to swich them to other power supply, not off. Anwer is close.

Sinchronize chineese and tailand inverter? If you see my original postage I mentioned '3 sec delay'. For that time big inverter would be ready for power suply and small would be still running.

Gavin A · Aug 23, 2015

sinchronise as in sinch the frequency and voltage between the 2. You can't just wire 2 inverters together into the same circuit if they're not set up to sinch with each other in that way.

Unless you're talking about actually changing over from 1 inverter to the other via a changover contactor, though I'm not convinced that's a great plan either.

maks_sm · Aug 23, 2015

Gavin A said:
sinchronise as in sinch the frequency and voltage between the 2. You can't just wire 2 inverters together into the same circuit if they're not set up to sinch with each other in that way.

Unless you're talking about actually changing over from 1 inverter to the other via a changover contactor, though I'm not convinced that's a great plan either.

I understand that idea, but what I want always 'on' small inverter and large inverter activated when load is becoming high (deactivateing small inverter).All other time large inverter can be left off. |Every inverter eating energy as you know even not producing power.

Gavin A · Aug 23, 2015

maks_sm said:
I understand that idea, but what I want always 'on' small inverter and large inverter activated when load is becoming high (deactivateing small inverter).All other time large inverter can be left off. |Every inverter eating energy as you know even not producing power.

depends if the inverters have the capability to be remotely triggered / switched off.