Hi all,
I have a new installation of a H1-3.7-E-G2-WL hybrid inverter and a EP12 Plus (w) battery. The system has 2 strings covering two sides of the roof, each with 3 x 515W panels. It all seems to be working as expected. I have the inverter linked to Home Assistant, so handy for logging the data.
A couple of days after it was all commissioned, during the first break in the clouds, the system generated 3.1kW peak for a while, but was generally up around 2.8kW while the sun was out during the day. Since then, it seems the max has dropped to 2.3kW max. Even though we have had wall to wall clear skies. I've checked and the scaffolding isn't causing any shadows during the peak of the day, but the solar PV output seems to be some 40% down on the max. The inverter can supply 3.7Kw from the battery, or as a combination of battery and solar PV. It just seems the PV output isn't where I'd expect it to be.
Our previous installation, on the same roof, didn't show any where near the same percentage difference. It had developed a fault after 12 years, so we took the opportunity to replace it and add a battery.
The system has produced what, in theory, the maximum is it can produce. But it seems to be slowly declining. I know temperature plays a part, but I can't see it causing this much of a drop. The installer is back next week, as the bi-directional meter is backwards. The Net value is getting ever more negative, even though we are just charging the battery from the PV. To maintain the FIT payments, this needs to be solved. It was a nice surprise to find out we can keep receiving FIT payments, they just pro-rata the payment down to the old capacity, so 3.09kW to 2.57kW.
The inverter is running Manager 1.33, Master 1.47 and Slave 1.04 firmware. The integrated manager is on 2.09, as I could update that. I see no option to update the firmware on the inverter itself. I did e-mail Fox support, got a case number, but heard nothing since.
Anyone have any suggestions as to what could be happening with the PV?
Don't underestimate how the heat can affect the output.
I have 6.16kWp worth of panels, and during the high heat, I lose around 25-30%.
So getting around 4.2-4.5kW at best. With a sunny day, and cooler weather and a decent breeze, you can exceed for short periods above the 6.16kW output.
I have 6.16kWp worth of panels, and during the high heat, I lose around 25-30%.
So getting around 4.2-4.5kW at best. With a sunny day, and cooler weather and a decent breeze, you can exceed for short periods above the 6.16kW output.
OK, I guess just keep an eye on it when the temperature returns more to normal.
Just surprised it is as high a loss as it is.
Just surprised it is as high a loss as it is.
Heat really does sap the output, but long term you will see the seasonal patterns.
I see similar behaviour to what MB reports. Despite my panels having a nominal Temperature Coefficient of Power of -0.26%/ °C (with a datum of 25°C) I see 3.6kW on a cool sunny day and 3kW if I'm lucky on a hot day.
There's obviously something about the temperature effect beyond the quoted performance coefficient that I don't understand - but it is what it is, and that's the real world performance.
There's obviously something about the temperature effect beyond the quoted performance coefficient that I don't understand - but it is what it is, and that's the real world performance.
I think what happens, is the temperature of the glass is the real temperature used for calculations, not the air temp.
I don't have a value, but if you touched the glass on a hot day... it wouldn't be 30°C on a 30°C day.
Maybe someone has measured this, and can give a reading?
I don't have a value, but if you touched the glass on a hot day... it wouldn't be 30°C on a 30°C day.
Maybe someone has measured this, and can give a reading?
I think you're right about that.
In my case if we assume the temperature performance coefficient is right the panels have to be about 60C hotter on a 30C day than a 15C day to explain the loss of efficiency.
That seems probably too high, but I assume it's in the right ballpark.
Thinking back to my heat transfer studies of 50 years ago radiation and convection are going to be the dominant cooling mechanisms in the heat balance, and a windless hot day would be the real enemy of efficiency according to my rough sums. On such a day convective heat transfer coefficient would be low and radiation would have to dominate in maintaining equilibrium, driving a significantly greater temperature increase and loss of conversion efficiency than on a windy hot day.
I'm sure someone else will have done a proper analysis, but I've strained my brain on enough back of fag packet sums in the past couple of hours to persuade me that my choice of inset panels has caused an unnecessary hit to warm day efficiency. They do look prettier though.
In my case if we assume the temperature performance coefficient is right the panels have to be about 60C hotter on a 30C day than a 15C day to explain the loss of efficiency.
That seems probably too high, but I assume it's in the right ballpark.
Thinking back to my heat transfer studies of 50 years ago radiation and convection are going to be the dominant cooling mechanisms in the heat balance, and a windless hot day would be the real enemy of efficiency according to my rough sums. On such a day convective heat transfer coefficient would be low and radiation would have to dominate in maintaining equilibrium, driving a significantly greater temperature increase and loss of conversion efficiency than on a windy hot day.
I'm sure someone else will have done a proper analysis, but I've strained my brain on enough back of fag packet sums in the past couple of hours to persuade me that my choice of inset panels has caused an unnecessary hit to warm day efficiency. They do look prettier though.
Using a thermal camera, the roof next to the panels was 60°C just now. The panels appeared cooler, but they may not irradiate well, as they have an anti-reflection coating on them. I was tweaking the camera settings, but the battery has run out, typical.
The ambient air temperature is 31°C.
Have to wait for the heat to subside and look at the data then. The system is getting checked next week anyway.
The ambient air temperature is 31°C.
Have to wait for the heat to subside and look at the data then. The system is getting checked next week anyway.
Good to see some measured temperatures of the panels, I have been and touched them in the Sun before, and can confirm they are above 50°C easily.
6-8 Weeks ago, I would get above 4.5kW sustained, now it's closer to 4.2kW in this extreme heat.
6-8 Weeks ago, I would get above 4.5kW sustained, now it's closer to 4.2kW in this extreme heat.