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Objective

I would like to power single 49 inch TV (LG 49LF6300) using only solar panel without a battery. I am aware that this will only keep the TV running for a few hours each day but this is not an issue for me. The following is the schematic I've devised for this setup.

enter image description here

Solar Panels

I plan to use two RSPRO 100W Monocrystalline solar Panels connected in series. The specifications for the panels are as below: (https://docs.rs-online.com/4e4d/0900766b815873ae.pdf) enter image description here

DC-DC converter

The Voc of each solar panel is 23.15VDC so the total combine voltage of two solar panels will be 46.3VDC. As they are connected in series, the current Isc remains as 5.45A.

With this in mind, I choose Mean Well RSD-300E-12 DC to DC converter. (https://www.farnell.com/datasheets/2547994.pdf)

enter image description here

The maximum voltage at the input of DC-DC converter will be 46.3VDC and maximum current, 5.45A. So, it is within the specs of RSD-300E-12 converter.

Inverter

Lastly, the Mean well NTS-300-212 inverter (https://www.farnell.com/datasheets/3212202.pdf) is used to convert the DC to AC for powering the TV.

enter image description here

Based on this inverter specifications, it could take in 12VDC/ 30A. So, it should be compatible with the output from DC-DC converter 12VDC/ 25A.

The AC output from inverter is then to be used to power the TV.

Question

Is the above plan feasible? Are there any other areas that I should consider before proceeding to buy each components?

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  • \$\begingroup\$ I can only find an average power consumption for the TV, which is around 70W. Did you ever measure peak power draw? I also think some kind of buffer battery between the Panels and Inverter would greatly reduce the risk of the Inverter shutting down due to input voltage drops that result from passing clouds or other shadow on the panels. \$\endgroup\$
    – S_G
    Commented Nov 9, 2023 at 7:55
  • \$\begingroup\$ @S_G LG only provides the power consumption in the form of Kwh/year. Based on this info, I worked out the power consumption of TV to be around 50w. I have not yet measured it myself to confirm it. I agree on the battery point, but I have to avoid using any kind of batteries due to some restrictions at my current premise. \$\endgroup\$
    – Chris Aung
    Commented Nov 9, 2023 at 8:02
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    \$\begingroup\$ I then recommend you measure the actual consumption, before you invest. Even if you are at ~50-70W average, I expect peaks beyond 100W. And with some clouds or on a hazy day, I'm relatively sure you will reboot that thing a LOT. You need to consider losses in the inverter and DC/DC plus don't expect your panels to provide even close to 200W continuously. \$\endgroup\$
    – S_G
    Commented Nov 9, 2023 at 8:16
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    \$\begingroup\$ Your proposed system will suffer from several things: double DC-DC conversion, 12 V intermediate voltage and lack of MPPT. \$\endgroup\$
    – winny
    Commented Nov 9, 2023 at 8:39
  • \$\begingroup\$ @ChrisA Keep in mind that the nameplate capacity is at the equator with clear skies and the sun at some angle to the panel (so-called STC -- standard test conditions.) You have to derate for actual operating temperature of the interior of the panel during high-sun conditions, derate for your latitude, derate for non-ideal atmospheric conditions, derate for dust accumulation on the panel surface, derate for age, and derate for still more. And all panels are rated using the MPP with equator-like insolation. Not running open-loop. \$\endgroup\$
    – periblepsis
    Commented Nov 9, 2023 at 9:19

1 Answer 1

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Quick observations: looks to be pretty well designed, though you haven’t put in didoes to protect the PV panels (not sure if they’re in the PV panels, they may be already fitted). You haven’t looked at doing maximum power point tracking (often called MPPT) which would make the system a lot more reliable. Then there’s the question: why haven’t you included a battery?

Why you should include a battery: solar panels give out the amount of power they have. If a cloud passes in front of the sun, if a shadow moves over the panels, the power can drop dramatically. This means that you need to massively over spec your panels to make sure you have enough power to drive the TV, and you will also need to add protection to dump the power the solar panels are generating more than you need. A small simple battery would make life so much easier and you wouldn’t be so worried about current peaks as you are without one. It wouldn’t need to be a big battery, I’d probably got for the smallest which can take 200W from the panels so that no power is wasted.

I’ve no idea what your panels will be able to produce, but we know it’ll be no more than 200W. In my experience, most of the time you’ll be getting less than 50% of their rated power because it isn’t always perfectly sunny. So if we run the numbers: you’ve got 100W coming in, a DC-DC which claims up to 90% efficiency, but it does drop to 85% even in it’s advertising, so that’s the figure to use, so now you’ve got 85W. Then you put it into an inverter, which again claims 90% efficiency, so now you’ve got 76.5W. Which is worryingly close to the 70W needed by the TV. And that's with using the good numbers from the datasheet, not real world numbers due to what you're using.

In summary: look at adding MPPT and add a battery, that would make everything so much better and more reliable. Don’t forget to protect your DCDC converter/inverter from power spikes when the PV panels are providing more power than you’re using.

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