Photovoltaic direct current hot water production

[eclectron]

Are you expressing yourself to me?
I would love an explanation for your baseless assertions.

Excuse me, as we do not speak the same language and I try to keep answers short, I did not always understand and often misspoke, but I just "said" everything.
Have a good week-end. ;)

No worries, I too have pretty much ... all the time said the same thing.
There may be a problem with language understanding.
I'm going to do my higgins (magnum) but I remember a college teacher that I never understood, yet she spoke French. It's rare, but it happens...

[eclectron]

12 pages to reinvent the photovoltaic inverter from scratch, it is true that personally it annoys me a little

As long as you only have that problem, it's that it must be going pretty well in your life.
Unless you are bored and in this case I understand that screwing up brings a little spice to your life.
What annoys me is having to read and respond to parasitic messages, in a subject that interests me.

[izentrop]

It's true, we can be satisfied with the 95% yield that the technique offers us today, but I always tried to understand. A forum that's it for that.
I have often written stupid things, but at least we are progressing in our understanding. Understanding how it works can also make it possible to better choose from the market offer, to better predict its future installation ... While posting, I am still learning.

It is interesting to understand the difference between an inverter at 50 € advertised 6 Kw and another at 800, advertised 3 kVA. You realize that for the first, it is the maximum peak-to-peak power and that in reality, in nominal power, you should rather rely on 2.5 kVA. In addition with a lower yield and not the essential functionality such as standby on extended idle operation and network synchronization, for example ... Finally, the first, you may not use it ...

The material gains in weight and lifespan, you have to weigh the pros and cons for a second-hand purchase.
The manufacturers do not easily give their diagram, this is normal, given the cost of the research, but just by seeing the inside of the case like the photo of the previous micro-inverter, we see:
- that the papa transformers no longer exist, guaranteeing better performance and less no-load losses ... the absence of a cooling fan testifies to this.
- avoid the chemical capacitors often responsible for breakdowns and limiting the life of the product.
We also understand that the offer with several micro inverters instead of a large one is becoming common. Another advantage, an inverter failure does not prevent the operation of the rest and we can complete its installation without straining the budget ...

[eclectron]

It's true, we can be satisfied with the 95% yield that the technique offers us today, but I always tried to understand. A forum that's it for that.

YES!

avoid the chemical capacitors often responsible for breakdowns and limiting the life of the product.

Indispensable in certain cases but we will not come back to it

[not C]

The prototype 220 V single-phase generator has now been running for several weeks. The connection between the peak power of the panels and the effective power at the output is very good with regard to efficiency. As the component used to perform the function is very recent (marketed by the US manufacturer since February 2019), I hope that it will find its market and that it will not be stopped. The measurement of the conducted spectrum is also very good and the specification for feedback to earth is largely held (EN 55022). I will check the radiated spectrum (30 Mhz 1000 MHz) as soon as I have the broadband antenna which allows the measurement, but I am not worried.

[63fa]

Hello,

I dig up the subject a little bit.

I intend to directly supply a hot water tank with a series of photovoltaic panels. The panels will not cost me much (recovery) and I do not intend to invest (inverter), hence the reason for this choice.

On the hydraulic level I will put the tank supplied by the panels upstream of a second tank connected to the network, the thermostat of the first being adjusted to a temperature higher than that of the second.

On the electrical level, with a ladle (I will refine it later), ten panels in series to have a voltage close to 230V and a maximum power of the order of 2kW.

My question concerns the thermostat of the balloon, which, as I could understand, is not intended to cut off a direct current.
I read here https://www.se.com/fr/fr/faqs/FA19997/ that it was possible to use an AC contactor to switch from DC. Roughly I will have a current of 10A, and if I put the 3 poles of a contactor type LC1D09 in series the rated operating current will be 20A (table page 2, job category DC-1, voltage 250V), so it sticks (?).

If I have good until then, the LC1D096P7 https://docs.rs-online.com/6ec3/0900766b815f7433.pdf might agree. So in the end I feed the coil of the contactor by the network, in series with the thermostat (with rod), and the resistance in DC by the power contacts.

Does anyone have an opinion on this principle?

Goods.

[not C]

Switching direct current is not always very simple from mechanical contacts. A 'collage' quickly arrived and the arc will be powerful with this tension and current ... But hey it can work. Otherwise switching based on a transistor should have a better longevity and a lower cost too.
Do not forget the electrical protection either. A DC device is not equipped with a differential, so you must remain in isolated mode from the earth on the lines of the panels (or with a connection to the strong earth 1 MegOhm for example). We will not see the first insulation fault so this requires checking the insulation periodically before the second fault appears.

[63fa]

OK, well understood.
Thank you!

[not C]

Another aspect to take into account is the configuration of the panels. A 2 KW resistor on the market is a 24 Ohm resistor. So if you want to stay at the maximum power limit delivered by the panel (at a voltage of around 30 V), you need a minimum of solar power:
for a 30 V panel, i.e. 1.25 A
for 2 panels in 60 V series or 2.5 A
for 3 panels in 90 V series, i.e. 3.75 A
for 4 panels in 120 V series, i.e. 5 A
for 5 panels in 150 V series, i.e. 6.25 A

There things can get complicated in the winter because the panels will not provide the necessary current (the point of polarization is no longer the right one). So for winter it is better to configure the panels in serial / parallel modules (2 * 3 panels in series or 2 * 4 or 2 * 5). For mechanical relaying (it's not the one I prefer ...) this will also limit the arc.

[63fa]

OK, I will try it out.
Thank you for the info.