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# Solar power conditioning unit

Discussion in 'The Projects Forum' started by Roadrunner, Feb 14, 2013.

Feb 14, 2013
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I have four 250W PV panels in parallel, connected to a power conditioning unit(PCU). At the input of PCU, I have 20.08V and 32.8A going in, i.e. 658.62W.

Taking the efficiency of the PCU to be 85%, I have an output power of 560 W.
What I do not understand is, what is the reason for this loss? Is it voltage drop, or current loss, or both?

Feb 14, 2013
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Here is what I think:
There can be two cases here
1) PCU charges the battery
In this case , V and I both will be changed if we have an MPPT controller.
I think losses will be very low in this case.

2) PCU supplies power to AC load
Here, we need to invert the PV output to power the loads.
What kind of losses will take place here?

3. ### praondevou AAC Fanatic!

Jul 9, 2011
2,935
491
Any voltage/current conversion lossy. The energy lost is mostly transformed into heat.
Actually, when a current flows through a non-ideal conductor, there will be loss.

What do you not understand? The efficiency of 85%? It's not that bad.

Feb 14, 2013
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Thank you for responding.
My doubt is, in the output power, will there be voltage loss, current reduction, or both, as something has to decrease right?

5. ### tindel Well-Known Member

Sep 16, 2012
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You don't lose power or current, per se... your power decreases because it has gone into your PCU. In other words, your PCU has consumed 100W to be able to deliver your 560W to your system.

What's the PCU doing is controlling battery charge, producing AC voltage, powering your a micro-controller, and probably some other smaller functions. Your power conditioner won't do these things for free, it takes power.

85% efficiency is very good.

6. ### praondevou AAC Fanatic!

Jul 9, 2011
2,935
491
If you assume the unit to be a voltage source then total available current will be less. Power is just the product of voltage and current.

7. ### ErnieM AAC Fanatic!

Apr 24, 2011
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What I do not understand is where did this number of 85% come from?

What is this PCU? Do you have a link to the manufacturer's data sheet?

Feb 14, 2013
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ErnieM,
I just assumed the 85% efficiency, as in general the efficiencies of commercial conditioning units are in that range.