Use 20W DC power output from PVs in a useful way

[Danielv]

Hello,

I have 4 PV cell chips producing 20W of DC power. I had a few ideas about how to use this power, and a few questions.
1. Use the 20W to power a strip of LEDs to the light the room the PV cell chips are in.
Here are the options I've picked out.
**broken link removed**
OR
the first one this link
**broken link removed**
OR
**broken link removed**
Also, will I need to use some capacitors or resistors to limit the power to the load?

2. Use a micro-inverter to convert the 20W DC output to an AC output for use. Is 20W enough power to do this? Also what would be a good option for a micro-inverter?

All Suggestions welcome.
Thank you!

 

[D.A.(Tony)Stewart]

Why do you need LEDs when you have sunlight?

- unless you store the energy to use later.
- what is Voc on PV, optimum is ~80% of Voc for battery or PMMT charger.

How many Watthour (Wh) do you need? Then assume battery efficiency ~50% and size storage needs then comes converter needs to match load.

 

[Danielv]

Why do you need LEDs when you have sunlight?

- unless you store the energy to use later.
- what is Voc on PV, optimum is ~80% of Voc for battery or PMMT charger.

How many Watthour (Wh) do you need? Then assume battery efficiency ~50% and size storage needs then comes converter needs to match load.

Yes, the energy is stored for later use. The room has no sunlight. Having the LEDs would replace the conventional lighting already used in the room, and provide use to some excess power being generated(20W). I believe I need 200Wh, if I need them to be on for 10 hrs at a time? Is this correct? Wh = 20W *10hrs? I am unsure of the Voc though. If I connect the LEDs to the output, will I need to store the voltage in a battery, or charger first?

Sorry new to a lot of this stuff.

 

[D.A.(Tony)Stewart]

Yes, the energy is stored for later use. The room has no sunlight. Having the LEDs would replace the conventional lighting already used in the room, and provide use to some excess power being generated(20W). I believe I need 200Wh, if I need them to be on for 10 hrs at a time? Is this correct? Wh = 20W *10hrs? I am unsure of the Voc though. If I connect the LEDs to the output, will I need to store the voltage in a battery, or charger first?

Sorry new to a lot of this stuff.

No you need 40W array and more if you dont guarantee 10hrs/day of direct sun, not oblique sun or cloudy day. Then you need more Wh capacity in battery too.

 

[Danielv]

So, Ive decided to build my own LED system. Here's my preliminary idea/design, correct me anywhere/add suggestions along the way.
With 20W produced DC power, I can wire 5 1W LEDs in series, and connect 4 rows of these in parallel. I understand the an important part in this is limiting current, but at the same time, the goal is to lose as little power as possible. So I was thinking of using a switching mode power rectifier like this:
https://www.onsemi.com/pub_link/Collateral/MBR20100CT-D.PDF
and have it wired in series before each row of 5 leds. Also, I will wire a current sensing resistor in series right after the switching mode regulator, which should produce a feedback signal that controls the duty cycle of the transistor that is being switched on or off.
I plan to mount this on a Heatsink + Fan, something like this,
**broken link removed**
For the LEDs, I was thinking of getting something like this,
https://www.amazon.com/LOHAS®-White-Power-Energy-Saving/dp/B00D13DQHM

Any foreseeable problems/issues? Any suggestions?

Thank you.

 

[red_alert]

PV panels are current sources.. Try to match your LED array current with PV panels current. This way, you won't need any converter at all nor a limiting resistor - just your LEDs.

PS: I presume you want to use PV panels directly (during the day), as your room has no direct sunlight.