Efficiency check of installed system

Ahir

Hi,
I am from Pakistan and have no knowledge in electronics, I have following system installed and want to check/enhance the efficiency of the currently installed system of following specifications,

6 x 250 watts, Canadian solar CS6P-250P panels, 24 volts.
1 x 3000 watts pure Sine Wave charge controller/invertor, 24 volts
1 PWM Charge controller
2 x 200AH 12 volts lead acid batteries

At the moment solar panels are connected in parallel, distance from panels to charge controller is about 100 feet. through some research i found that i should do following to make the system more efficient
1- Change charge controller from pwm to Tristar MPPT 60 charge controller
2- Re-connect the solar panels in two modules (in parallel) while each module consists of 03 solar panels in series.
2- Change the batteries, current backup is only 2-3 hours.

Please advise me to make the system more efficient. Should i have to change the charge controller or not?

Regards,

stephendv

Re: Efficiency check of installed system

Yes you should change the charge controller to MPPT for 3 reasons:
1. Those panels are not suitable for charging a 24V battery because their voltage is too low, which means they can't reach the absorb or EQ voltage set points needed for lead acid batteries.
2. As you say, with an MPPT controller you will improve the efficiency of the system, but more so in winter than in summer. As you have it connected now the summer efficiency should be pretty good (ignoring point 1. for a second). The MPPT will be able to harvest more power in winter.
3. Depending on the thickness of your cabling between panels and charge controller you might already be losing too much power, changing to an MPPT will help improve this, especially if you put 3 modules in series. Bear in mind that the MPPT controller is slightly less efficient at 3 modules in series vs 2 modules in series, because the conversion down to 24V of the battery is greater. So again, depending on your wire size the most efficient way to wire it will be 3 groups of 2 in series and then using a sufficiently thick cable between panels and charge controller.
If you have thin cables and don't want to change them, then 2 groups of 3 in series.

Cariboocoot

Re: Efficiency check of installed system

Ahir wrote: »

Hi,
I am from Pakistan and have no knowledge in electronics, I have following system installed and want to check/enhance the efficiency of the currently installed system of following specifications,

6 x 250 watts, Canadian solar CS6P-250P panels, 24 volts.
1 x 3000 watts pure Sine Wave charge controller/invertor, 24 volts
1 PWM Charge controller
2 x 200AH 12 volts lead acid batteries

At the moment solar panels are connected in parallel, distance from panels to charge controller is about 100 feet. through some research i found that i should do following to make the system more efficient
1- Change charge controller from pwm to Tristar MPPT 60 charge controller
2- Re-connect the solar panels in two modules (in parallel) while each module consists of 03 solar panels in series.
2- Change the batteries, current backup is only 2-3 hours.

Please advise me to make the system more efficient. Should i have to change the charge controller or not?

Regards,

Welcome to the forum.

You are on the right track in all three regards.

You have six 250 Watt panels - a 1500 Watt array. As-is it's just what Stephen says; insufficient Voltage to charge a 24 Volt system. Reconfigured on an MPPT controller the Voltage problem will be solved and you should have about 48 Amps of peak charge current available, meaning you could increase your battery bank to slightly more than twice its present size. It should manage 3 kW hours to 4.5 kW hours with a battery bank of 450 Amp hours @ 24 Volts.

Ahir

Re: Efficiency check of installed system

Thanks for the time, which MPPT controller should i go for in terms of manufacturer and capacity? i was in favor of Tristar TS MPPT-60, Please share the experience about it.
Here Avg summer Temp in open area remains 43-48 Celsius which some times crosses 50 C.

Regards,

stephendv

Re: Efficiency check of installed system

The TS MPPT-60 is a good controller, comes with an ethernet port to monitor the production from a computer and is passively cooled with no fans.

Bear in mind that on a 24V battery it has a limit of 60A, which translates to about 1440W array- you can install a bigger array, but the controller will only be able to pull 60A from it. So it's a question of what your future plans are, if you're going to install a bigger bank or bigger array then you might want to consider one of the 80A controllers like the Outback FM80 or Midnite classic.

Cariboocoot

Re: Efficiency check of installed system

The TriStar is good, but the display costs extra. Around here that's $500 for the controller and another $100 for the 'digital meter'. At a bit more than that $600 cost you could buy the top-of-the-line MidNite Classic http://www.solar-electric.com/inverters-controllers-accessories/chco/misoclchco/misocl/mnclassic.html which has display built-in and many additional features the TriStar lacks (but you may not need/want) including 80 Amp capacity.

For the same basic $500 cost as the TriStar you can get an Outback FM60 with display http://www.solar-electric.com/inverters-controllers-accessories/chco/ouchco/oupofl60mpso.html Better unit in my opinion.

The least expensive and yet perfectly good quality is the Conext XW MPPT 60 http://www.solar-electric.com/inverters-controllers-accessories/chco/schneider-electric-solar-controllers/xaxwmp60amps.html Less money than the TriStar and has display.

What prices you can get where you are would be the deciding factor. Some of these may not even be available in your area.

Frankly I would not buy a TriStar these days: they are not competitively priced anymore.

Ahir

Re: Efficiency check of installed system

stephendv wrote: »

3. Depending on the thickness of your cabling between panels and charge controller you might already be losing too much power, changing to an MPPT will help improve this, especially if you put 3 modules in series. Bear in mind that the MPPT controller is slightly less efficient at 3 modules in series vs 2 modules in series, because the conversion down to 24V of the battery is greater. So again, depending on your wire size the most efficient way to wire it will be 3 groups of 2 in series and then using a sufficiently thick cable between panels and charge controller. If you have thin cables and don't want to change them, then 2 groups of 3 in series.

I have 10mm copper wire from panels to charge controller and distance is 100 feet.

With Optimum Operating Voltage (Vmp) = 30.1 of each panel
I have planned to buy midnite classic 150 but if we connect 3 groups of panel in series while each group is of 2 panels in series, then total Vmp will become 180.6, will it be handled effectively by classic 150?
what % of less efficiency we can expect from the value written on the label particularly Vmp and Imp?

stephendv

Re: Efficiency check of installed system

Ahir wrote: »

With Optimum Operating Voltage (Vmp) = 30.1 of each panel
I have planned to buy midnite classic 150 but if we connect 3 groups of panel in series while each group is of 2 panels in series, then total Vmp will become 180.6, will it be handled effectively by classic 150?

You should only aim for 2 panels in series. 2 panels in series is called a string. You will have 3 strings. Each string should be connected in parallel. That means that the Vmp will be around 60V.
In winter, the panels could perform at their rating, 30Vmp * 8.3 A = 250W and with an MPPT you could get this full potential (sometimes more depending on altitude, cold and sunshine).

With a PWM controller the voltage will be set by the battery, so when the battery is discharged, say at 25V, then what you can take from the panel is 25V * 8.3A = 207W. As the battery charges up and its voltage rises, you'll get more from the panel.