Solar Powered Fans

[Chris L]

I recently bought some SPFs from eBay (mistake-they were cheap non-functionion items) to replace the solar panels that had stopped working. I am looking to replace them, even though I think they will work if I give them a good clean - I want to boost the number of fans running in any case.

The SPs I have now run a computer fan each, but only very gently. I think I need a much bigger SP to make the fans spin faster. This time I am going to look at Amazon, but there seems to be a confusion of limited products and I have no idea which will be the best one to get.

Any recomendations (or even a non-amazon product/company) would be gratefully appreciated.

As a side note is there a way to connect (safely) more than one SP to a fan without resorting to complex electronic solutions.

Thanks.

ETA - I am wondering if it would be better to buy the SP and fans seperately......

[el48tel]

A simple question. A simple concept. But the answer is complex.
Even on a sunny day my fan will stop while the battery in the solar panel tops up. On a bright day like today the fan is non stop.
There's a minimum level of brightness required to top the battery up by pushing the charge into it. That needs force or voltage. Below that the battery will not charge any further. Similarly there's a minimum level of battery charge required to push the motor around. Even a digital motor has a required amount of force (voltage) to push the blades. As the blades turn they consume the charge as current.
And .....
That's the simplified answer. Think of it as the battery being a domestic bath. The solar panel is a tank running into it via the tap. The fan is on the outlet drain .........
You'd need to balance the current and voltage supply from the solar panel with the charging characteristics of the battery and then match the discharge characteristics with the demands of the fans ....

[peter831shaw]

I am also doing the same thing, and have tried a few fans. I tried a 9" automotive 12V fan with a decent CFM but was really, really loud.

I dont think you need much of a battery, it only needs to go on when the sun is up and pounding on the roof. However, during our sunny cool days of winter and spring I dont want it on, so I need a 12V temperature sensor and controller (make one from a strawberrypi or Arduino). I do have a small battery because from what I understand its better to have one using the controller that came with the solar panel.

The key is the fan, I want the blades to be large but spin moderately fast so the noise is low. My greenhouse is very close to my house and my neighbors back patio.

There is one manufacturer here in the states. Here is a link, but way too much $$$ for me.
https://snapfans.com/solar-greenhouse-f ... hobby-kit/

I used the motor from my purchased auto fan and tried to mount it to a box fan blade ... hard to get balanced and it wobbled and came loose.

I will try again, but thinking about using a motor and fan belt to turn an old car fan (If I can find one).

Then again, we installed a large solar array on the house this spring so it might be worth using the electric fan......

[Chris L]

My fans are connected directly to the solar panels. Very low tech.

[Phil_SK]

Can you not just use a mains-powered fan? Or use a transformer to power your PC fans? Solar seems a bit complicated and expensive.

[el48tel]

Can you not just use a mains-powered fan? Or use a transformer to power your PC fans?

Mains power is easy.
Solar driven is free electricity ..... but high tech

[Chris L]

Can you not just use a mains-powered fan? Or use a transformer to power your PC fans? Solar seems a bit complicated and expensive.

I got the solar panels so that I wasn't using any electricity in the GH (only the heater in winter) - the original SPs must have paid for themselves by now.

[peter831shaw]

Can you not just use a mains-powered fan? Or use a transformer to power your PC fans? Solar seems a bit complicated and expensive.

I got the solar panels so that I wasn't using any electricity in the GH (only the heater in winter) - the original SPs must have paid for themselves by now.

Did a single computer fan have any impact on cooling? I looked at some for sale but reporting CFM's is not easily found, I guess they are interested in other things.

My greenhouse is small, 9 x 12 and averages 8' tall, making for 865 cubic feet so to cool the house properly I need a fan or multiple fans with 900cfm to keep the greenhouse cool.

I have aluminet shade cloth on the inside with roof vents on the leeward side to aid in natural ventilation.

My goal is to use my solar panels and battery along with some fan to do this for me.

Additionally, I will attempt to build a temperature controller to keep the fan from turning on when the greenhouse is below my set point.

With summer on the way (our maximum temperatures are usually in late summer and into our "Indian summer" I will spend some of my recent retirement time on this later this summer.

[Chris L]

Can you not just use a mains-powered fan? Or use a transformer to power your PC fans? Solar seems a bit complicated and expensive.

I got the solar panels so that I wasn't using any electricity in the GH (only the heater in winter) - the original SPs must have paid for themselves by now.

Did a single computer fan have any impact on cooling? I looked at some for sale but reporting CFM's is not easily found, I guess they are interested in other things.

Cooling - not really, but it does provide a modest amount of air circulation. I think I need a bigger solar panel and then connect a few fans to it - the trouble is knowing how to do that correctly/safely.

I do have a bigger 12 inch fan as well powered by solar and that does move the air quite a bit (but granted not as much as a mains powered desk fan would).

[Tina]

What roughly is the prices for a decent solar panel, I've wondered about them before as my 2 larger greenhouse have quite a few fans in them.