Solar powered fan circuit - please help!

[nuttam]

I'm totally new to working with electronics, and have no idea how to achieve what I need. I'm hoping someone here can help.

I'm looking to provide mechanical ventilation to my shed. It's only a shed, and so cost is very much an issue.

Given its position, my best bet is to solar power a small fan.

I'm looking at a small panel (Maximum power voltage: 17.9V, Maximum power current: 0.28A, Open circuit voltage: 22.4V, Short circuit current: 0.3A, Power allowance range: +/-3%) and something like a PC case fan (12v, approx. 4w - open to suggestions).

From my limited understanding, if I wire the panel straight to the fan it'll burn out (or the shed will take off like a helicopter).

Any help on how to make this work would be really appreciated.

Many thanks, Mark

[HackedFridgeMagnet]

rated current for fan = 4W/12v = 0.3 amps

which is uncannily close to your solar panels max output. I'm sure it will be fine.

[Seekonk]

Agree. If you had a bigger panel, there is a way to convert a cheap ebay buck converter into a Linear Current Booster.  Actually, it would also help in this under power situation.  Even though it only takes about 5 parts, it might be above your skill level.  I've been suggesting it for years and no one to my knowledge has ever used it.

[Zero999]

The voltage across the solar panel will drop when the fan is connected. The trouble is, when the sun is shining brightly it might not fall below the fan's absolute maximum operating voltage.

To test this, you could use a constant current sink to draw whatever current the fan draws from the solar panel and measure the voltage.

If the voltage of the solar panels is too high, you could connect the fan via a low drop-out regulator or add a shunt regulator, such as a 12V zener diode  or the TL431 + a few resistors and transistor mounted on a heat sink.