270W Solar Panel & 24V Heater for 50-Liter Boiler: Achieving 30°C Water Temp in Summer

I have a 50-liter boiler and I would like to have at least lukewarm water in the summer, i.e. about 30 degrees. How do I buy a 270W panel and a 24V heater and nothing more, no inverter is a chance? The panel can give a voltage of up to 36V, after connecting the heater it will drop to about 24V, the heater 300W? These are my first theoretical considerations about panels.

@lisos Count the efficiency! Why not a collector, even your own design?

According to this, you can combine a Step-down (buck) lowering converter that will give a good voltage for the heater.

fuutro wrote:

Accordingly, you can combine a Step-down (buck) converter, which will give a good voltage for the heater.

See post # 2 - fitness And a small matter - the solar collector absorbs the infrared spectrum, so its efficiency on cloudy days will also be higher than that of photovoltaics (comparatively).

The collector falls off, I would prefer the panel without a converter (simplicity of construction, smaller losses) but will these assumptions pass the exam?

lisos wrote:

I have a 50-liter boiler and I would like to have at least lukewarm water in the summer, i.e. about 30 degrees. How do I buy a 270W panel and a 24V heater and nothing more, no inverter is a chance? The panel can give a voltage of up to 36V, after connecting the heater it will drop to about 24V, the heater 300W? These are my first theoretical considerations about panels.

Take a look at my topic about the boiler, PV and two heaters, there is almost everything about direct connection. The proposed system will not work because a 300W / 24V heater has a resistance of about 2?. The 24V panel works most efficiently at Umpp around 30V, i.e. with such a heater, the power should be:

30 * 30/2 = 450W

Since PV will have 270W, it will give even on sunny days only half the energy it can produce . Not to mention other problems like the risk of burn-out of a 24V heater connected to a 24V PV (actually> 30V).

To have lukewarm (> 30 degrees) water in a 50l bolyler in the summer you need to warm it by about 15 degrees or deliver about 1 kWh per day. If you make a layout with a well-fitted 270W panel, you have

It is GAZ4 instead of combining like a horse uphill and packing an additional panel (which works inefficiently for this), you need to use the MPPT regulator for the heaters and it will squeeze out of the panel or panels as much as possible. (especially when the weather is worse)

Example: The heater has the same parameters as the panel panel = ok super 100% power flies.
Sweet 50%
Power on the heater: 25%
Because the load resistance is the same and the source has 2 times greater internal resistance.

power curve not 45 degrees only 78 degrees ... so wears even higher

Such an example in the photo


And here is a very mismatched panel power / heater power and voltage:
4XGS50 panels (43V Vmpp actually have less) = 200W
Heater 12V 300W

As you can see, the system adjusts the heater resistance to the resistance of the panels at their optimal operating point and the system works with maximum possible efficiency from morning to evening.

And there is no risk of damaging the heater (even if the power of the panels = 300W).

Half measures are not a solution, okay, "a little" works, but I would not be satisfied with this.

That is why this regulator was created and if you do not need hot water, it charges the 12V batteries. A 2-in-1 that makes sense.

Kwazor wrote:

instead of combining like a horse uphill and packing an additional panel (which works inefficiently) you need to use the MPPT heater controller and it will squeeze out of the panel or panels as much as possible. (especially when the weather is bad)

Have you read about the economic aspect of such a procedure? Even the new CIGS calculates more than MPPT. But this is not the end of possibilities because I prefer amorphous ones that are much cheaper (a few years ago I bought new ones for just over PLN 1 / W). I have a very large roof, even if I used low-yielding amorphous I would put over 5 kW on it, if I wash it x2 Do they work inefficiently? For most of the year, 70-80% of Umpp voltage remains on them, i.e. they operate with such efficiency. Sometimes in summer Umpp is exceeded, very rarely the voltage drops below 50%. But only when it is dark even during the day, i.e. sunshine is about 50W / m2. Then from 1 kW you can collect max. 50W, after subtracting the energy consumed by MPPT for heaters, a few watts remain. I doubt that my primitive driver (I've been using it for over a year: https://www.elektroda.pl/rtvforum/topic3223621-90.html#16575602) would have worse effects then. MPPT has an advantage over the heater switch in a narrow range: approx. 100-200 W / m2 and full sunlight when the water in the boiler is cold because it can 100% use it. However, sometimes it is a typical turtle race with a hare: a perfectly matched MPPT will heat the boiler in 5h and turn off, and a switch based on relays in 10h and in the evening we have the same effect in the form of the same hot water in the tap

@ gaz4 exactly. How I bought off-grid stimulants. They have less efficiency than poly or mono, but they work all year and I have always cut off something.

Hello.

Is anyone able to point out a ready-made solution to my problem?

I plan to install a photovoltaic panel of approx. 300W, which is to power the charging of the 12V battery in the first place, approx. 100 Ah, and when the battery is 100% charged, the rest of the PV energy would heat the water in the 10L boiler, heater 300W, voltage 230V. I would not like the boiler to be heated from the battery after sunset (for me, the priority is to have electricity, not hot water - hot water is to be an addition, if the weather permits it). Thanks in advance for your help j

I will not give you the ready one, but I will tell you how to do something like that. Perhaps a PWM controller for the boiler is enough and that's it. Its task is to maintain high heating efficiency, which is equivalent to a constant voltage on PV. If it does not interfere with the operation of the charger, that's enough. So for PV we connect the charger and PWM in parallel, and the rest will be taken care of by physics

Thanks for showing interest ;)

I do not really understand how such a solution is supposed to work, the heater's rated voltage is 230V, and the PV operating voltage is about 32V (I mean PV Model: SR320-60M). Is PWM able to meet such needs? Besides, will the PWM and the charger not "fight" with each other in such a connection system?
gaz4 would you be kind enough and would you like to help and explain it in more detail? I would be obliged

PWM works on the principle that the heater gives "peaks" with a voltage of 230V, so there is no loss. The lower the PV voltage, the shorter these "peaks" are, at 32V the fill will be several%. Looking from the PV side, a good PWM should keep the voltage close to the maximum power point. If a charger is connected in parallel with PWM to PV, it will load the panels. Then a good PWM will consider that the power supplied by the PV has decreased and will reduce the filling of the voltage "peaks" supplied to the heater. As the battery is charged, the PV load from this side will decrease so the PWM will increase the duty cycle. This is probably the simplest description I can provide :)

Practical problems that may arise are poor holding of the point of power. Then the parallel connection of the battery regulator may cause some losses because the voltage will be too low. Another is the fact that PWMs "sow" which may disrupt the regulator's operation. But when the cables are shortened (especially those connecting the PWM with the heater) and if necessary, add a choke and a larger capacitor in the battery regulator, the problem of mutual interference should not occur.