Solar Controllers PWM MPPT Temperature Performance

It is not whether or not NOTC works for you, it is that NOTC info shows that panel get hot as you know, they get hot even with 80% 'sun'.

The biased white paper shows when PWM=MPPT, this is a large range, bigger than the blue shaded area, I'll suggest 40-100C

NOTC does not work for me. I would get full Isc when conditions seemed to be more NOTCish. I assumed when I got full Isc that meant it was like Standard conditions. You don't know how much air pressure is compared with temperature and light. To get all of those variables to line up per NOTC would be difficult. One component will be ahead of the other in real life.

With MPPT, to check it, you first check Isc of the panel, get rated Isc in the prevailing conditions, then connect up and see what amps to the battery are when the battery is low enough to have the MPPT in Bulk. That will be as good as it gets for amps to the battery except for edge of cloud events

My Tracer has a setting for temperature but I just leave it at 25C. Not sure what that is about.

Here is how I had the panel when I was doing the temp meaurements with the IR gun at the back of it. Lots of breezeway. As mentioned, the temp is not the same everywhere so it would be hard to get each cell's temp and do its voltage calculation from the coefficient and add up all those voltages to get your "panel voltage". It sort of works as an average using the middle of the panel. (Not showing are the bungee cords I had all over the back of that to stop it blowing away)



My Eco-Worthy has a funny program for seeing how much better it is doing than PWM would be. It is sort of bogus, but it turns out that its PV amps reading is the same as the Isc reading by meter, so you don't have to disconnect the panel to get that figure with the Eco-W.

Many panels have published NOTC.
This test is @ 80% or 800 watts per square meter vs 1000.
20C air blowing on the panel @ 20C.

45C temps in these conditions! with a breeze and space behind the panel for air flow.

"Both conductive and convective heat transfer are significantly affected by the mounting conditions of the PV module. A rear surface which cannot exchange heat with the ambient (i.e., a covered rear surface such as that directly mounted on a roof with no air gap), will effectively have an infinite rear thermal resistance. Similarly, convection in these conditions is limited to the convection from the front of the module. Roof integrated mounting thus causes higher operating temperature, often increasing the temperature of the modules by 10°C."

https://www.pveducation.org/pvcdrom/modules-and-arrays/nominal-operating-cell-temperature

Lwiddis wrote:
Interesting article.

“The MPPT controller will harvest more power from the solar array. The performance advantage is substantial (10% to 40%) when the solar cell temperature is low (below 45°C...”

I don't camp much when the temp exceeds 113 degrees F for me or my panels.

Typically panel temp is about 20C above ambient, which I can confirm from my measurements. So when it is nice out at 25C, panel is 55C and down 10% in watts at around 50C

I cannot understand the way they do panel specs at panel 25C which would mean ambient is just above freezing. Sort of weird.

The MPPT guys all talk about power but PWM could care less about power--just the amps. So all that power being wasted by PWM is bogus, since you still get the rated Isc so the power does not matter.

The main thing is that you need the buck converter in the MPPT to do 24-12 with 24v panels, which PWM controllers cannot do. They can do 12-12 or 24-24, while an MPPT can do either 24-12 or 12-12 or 24-24 so you have a choice between series and parallel with 12v panels.

the full white paper is informative although I believe biased as one can see in the graph fig 15 (chapter 7). The problem is their comparison includes series connected panels for MPPT! Well additional voltage above batt from somewhere!
"Let us now assume that the MPPT controller is connected to a solar array with sufficient cells in series to achieve an MPPT voltage several volts higher than the highest battery voltage."

Full white paper

It is hot here! All I need to do is look at fig 15 and see that PWM is above the 90% line in the temps of concern. The MPPT line should mimic PWM when Vmp is less than batt voltage as seen in chapter 5. Vmp drops with heat!
"Most MPPT controllers cannot transform a lower voltage to a higher voltage, as that’s not what they are made for. If the MPPT voltage Vm becomes lower than Vbat, they will therefore operate like a PWM controller, connecting the panel directly to the battery."


to me the 90% line represents the bucking eff. With regular controller limiting power in abs and float it just don't matter much then you go series (wiring. light and heat) and ya need MPPT.

No idea who often claims that.

It is a fact that panel heating lowers the panel voltage so that typically, you lose 10% of the power because voltage which drops with heat is such a big component of watts compared with amps which go up a bit with heat. So you lose watts for using MPPT which has a buck converter that uses watts in and watts out.

Meanwhile PWM gets the prevailing panel amps to the battery up to and sometimes over the Isc value no matter what the panel heating is.

So for instance with my three 100w panels aimed at high sun each panel rated 6.3 Isc, I got 18.6 amps to the battery with PWM as seen on the Trimetric.

Nostalgic photo--those three are now on top of the Class C in sig.



Swapped out the PWM real quick, no change in the sky, for the MPPT controller set to 12-12, no change in wiring and Ta Da! 18.x amps not even 19. So same amps.

I did all kinds of measurements of temperature with my IR gun and tried different things with different panels and measured it all, did all kinds of math with the temp coefficients . I reported a lot of that on here back then. Most of my notes from then are now gone.

Anyway despite those studies that showed (one was Dutch ISTR) that what I was seeing was impossible, I got what I got. Everyone is invited to go out there and do the same thing, swapping controllers, etc, and see what you get.

I have now got a mix of MPPT and PWM controllers in parallel set to the same voltage on my roof arrays and they all behave adding their amps to the right amounts (as expected by me) so I do not have a dog in this race anymore.

I will stick with what I saw with my own eyes for real, never mind what I am supposed to see according to the MPPT enthusiasts, Dutch or not :) .

Note--I do not have the controller efficiencies for my PWM and MPPTs. the wiring was good for 12v and both controllers were 12-12. Panel temps taken on the back of the tilted panels aimed at the sun showed variations in temp with location on the panel--not the same everywhere, but more to where the sun was and up higher too. So panel temp must be taken as some sort of average and the voltage of each cell is added to get panel voltage remember. Anyway, it was all good fun playing scientist and seeing what was really going on.

Interesting article.

“The MPPT controller will harvest more power from the solar array. The performance advantage is substantial (10% to 40%) when the solar cell temperature is low (below 45°C...”

I don't camp much when the temp exceeds 113 degrees F for me or my panels.