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Just before I start description my question, I would like to let you know that I am new at this.

I am working on a solar air heater for one of my window. I've been researching and reading up on a lot of things but I am not sure if I understand how this whole thing works.

I have a computer 120mm fan that I want to run on solar power. I recently bought a solar panel thinking it was more than enough to run the fan. As it turns out that it was not putting out enough power. So, here is the specification for my fan.

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I would like for someone to point me in the right direction as to what I need to buy in terms of volts and current level or the type of and size of solar panel to run my computer fan with solar panel.

UPDATE: solar panel I purchased as follows: Moultrie 12 Volt Solar Panel

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UPDATE I recently purchased a new solar panel 2.5W 12V NOCO BLSOLAR2 Battery Life Black 2.5W Solar Battery Charger and Maintainer. When I connect my CPU fan directly, it fails to run. In fact, there is an indicator light on the Solar panel connector and it came on right away as soon as I opened the solar panel. However, every time I connected my CPU fan to the wire, the indicator light went off. I believe it has built in safety that is preventing the flow of DC power to my CPU fan. I just want your thoughts before I decide to bypass its safety circuits by splicing the wire.

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  • \$\begingroup\$ It is important to remember that solar cell specifications are given for the best ever conditions. You are extremely unlikely to get the maximum output at all times in 99% of the world. \$\endgroup\$ – David Oct 11 '14 at 20:00
  • \$\begingroup\$ it's a 2W fan, so get a 20W solar panel just in case haha. \$\endgroup\$ – KyranF Oct 11 '14 at 20:07
  • \$\begingroup\$ What solar panel did you try. Why did you expect it to work. What happened. To run on a sunny day you need 12V 150 mA or about a 2 Watt panel IF PROPERLY MATCHED. Often nominally 12V panels are higher voltage and lower current and when loaded to 12V do not make enough power. | Even with an OK panel the fan may need more current to start. On less than a sunny day you need a larger panel. To run in anything down to "very bright cloud that hurts eyes but sun position uncertain" you need about 5x as much or a 10W panel!. A small 12V battery charged by a 12V panel would work and start OK. \$\endgroup\$ – Russell McMahon Oct 12 '14 at 6:45
  • \$\begingroup\$ As this is for a solar air heater then fan only needs to run when sun is reasonable. Thermoflow should work well enough if hot outlet duct is level or rising. \$\endgroup\$ – Russell McMahon Oct 12 '14 at 6:46
  • \$\begingroup\$ @KyranF While there is some merit in your comment it is not at all helpful in isolation and the 'haha' risks causing problems (such as attracting my attention :-) ). A 20W panel would work in most conditions - down to bright overcast) but is liable to be too costly. \$\endgroup\$ – Russell McMahon Oct 12 '14 at 6:48
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The fan requires 12V, 150mA (0.15A). About 1.8W as listed. That is for standard power. You can provide less volts, for less powerful blowing, at a relatively lower current draw.

As such you need a solar panel that can provide 12V and 0.15A, again 1.8W, in regular light. Unless you have 100% unobstructed direct sunlight, no clouds or anything, you will need a solar panel that can provide alot more than just 1.8W. So you need to over size it.

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  • \$\begingroup\$ How much do you need to overpower it by? Assuming the solar panel will indeed be outside. I'd be very interested in the experience of anybody who has actually got this to work. \$\endgroup\$ – tom r. Jan 8 '19 at 23:39
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Aside from the rated wattage of the solar module, there's the matter that it includes a battery maintainer. The module may not be outputting power if it doesn't sense at least a minimal voltage on the output. Note the "short circuit protection". The windings on your fan are quite effectively a short circuit. They certainly don't look like a battery to a battery maintainer circuit.

Putting a small 12V sealed battery between the solar module and your load (fan) may be required in order to use that particular solar module. This provides the added benefit of permitting your load to continue to function even when the sunlight isn't directly hitting the module (for how long depends on your battery and load). A module which is rated at a higher output will allow you to recharge the battery at a higher rate than your load discharges it.

PV solar modules operate most efficiently when pointed towards the sun. Systems seeking to extract maximum power utilize "solar trackers" - a relatively simple circuit to angle and rotate the module to track the position of the sun. While such a system out of necessity consumes some of the generated power, the actual stepping is in very small increments.

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