Portable solar system to run electric fans

[idelphic]

I'm rather late to this but the o2Cool 10inch fan works on both Dcell batteries and 12v adapter.

[surfivor]

I'm rather late to this but the o2Cool 10inch fan works on both Dcell batteries and 12v adapter.

 I have had those types of fans for years. This 12 volt setup allows me to run a more powerful fan but I still use those other types sometimes also

[antsyaunt]

  I am back from the dead....

So good to hear, Carl!  Hoping you are feeling better every day. 

And thanks to those who are providing good explanations.  Knowledge from college physics hasn’t stayed with me, unfortunately.    Refreshers are needed!

[Carl]

  I find that effecting air motion ,as with air temperature,that more power is needed than often planned for. I find favor with the 8 inch ,12 volt fans in the 15 watt class that require about ONE AMP to give motion to air and as there is little innovation in propeller...one can well judge the average fan with the power consumed. Being able to recognize the need to oil bushings can add to the useful life of these fans as they are  simple and fairly tough. Also keeping the moving and non-moving parts free from dust will greatly effect their usefulness. 

  I have used 120 volt fans in the 8 to 10 in (about 30 watt) table top size and will use them with an inverter as I have good supply of solar to power stuff and while an inverter driven fan does work well,they are less efficient than a directly driven 12 volt fan . Of the battery operated fans I like best are thee one or two speed 12 volt ,with cigarette plug...often advertised as 15 to 20 watt and often requiring ONE AMP or there abouts of power. I will link one or two below with the fact that brand name offers little in decision here as cost is my guide....most appear to be made to the same quality anyway.

  A final note is the OH 2 COOL battery fans is that they are good fans ,though they lack the power to move as much air as the 12 volt ,plug in fans and would not be my first suggestion unless battery only (internal batteries) is a requirement as they tend to not move as much air...though they are quite effective...I like the more common looking dash board fans as below.

https://www.amazon.com/gp/product/B01BFLQKLK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B0719JVTW4/ref=oh_aui_search_detailpage?ie=UTF8&psc=1


Note that COST,not brand name,is more my guide to purchase these and I also look at options as speed,and oscillating to be good to better aid motion in a somewhat larger than 'personal' room.

[idelphic]

Small... but if you can pull them from old Server Power supplies - or old Servers period,.. try looking for something similar to this:

https://www.sager.com/9crb0412p5s201-3676235.html?utm_source=googlemerchant&utm_medium=click&utm_campaign=sager-brand&gclid=EAIaIQobChMIkr2Gsqiu3QIVB9bACh3TTgw6EAQYBCABEgKWv_D_BwE

I have a San Ace 40, it's a two stage fan that runs at 12v 1.1a.. It's a pretty powerful fan for the size...  but they do have a bit of a bite on cost.

[fratermus]

> most 60 watt panels will only output 50 watts

The difference usually has more to do with voltage suppression due to cell temp above lab conditions (25F, about 0F ambient).

>  with the charge controller

Even without a controller.  A panel attached to a battery the panel will be run at battery voltage.  This is why PWM is said to "waste power" and the secret to how MPPT controllers maniupulate panel voltage (and therefore power).


> as the panel is usually rated at maximum current TIMES Maximum voltage

The panel is rated at Vmpp:  voltage at which the panel puts out max power under lab conditions.  This is usually far away from Vmax (max voltage, open circuit) but generally in the neighborhood of Imax (max current) because current is usually pretty flat across the power curve.


> and as we use 12 volt batteries with 20 volt panels

Hence MPPT. 


>  ,,,the math will always be FUZZY....  they still don't add up.

A look at the panel's power curve will clarify the situation greatly. 

OP:  non-controller or pwm controller scenarios work best when the panel's Vmpp is close to Vbatt (battery voltage).  A mono panel (higher than usual voltage) and lithium pack (lower than usual voltage) are not matched very well.   This is one of those situations where more expensive (or more mindshare) is actually counterproductive.*

related info: 

• matching panels to PWM (or no controller)
• Is my solar working?

* that and AGM charged by solar, but don't get me started

[fratermus]

This time of year you should get about 4.5 hours of optimum sunlight per day in Maine.

This idea is correct;  the unit of measurement is Hours of Full Sun Equivalent (FSE).   It's the amount of light a flat-mounted panel will receive n a given location at a given time of year on average.  IOW, the amount of sun received throughout the day will be equivalent to 4.5hrs of sun under perfect/lab conditions. 

I point this out because it might help people predict the amount of average sun available where they are.  It also allows us to see how much gain we can get from tilting/tracking. Here's one example of FSE data by month:

http://solarinsolation.org/wp-content/uploads/2012/01/Solar_insolation.jpg <-- having troubles inlining images from this browser

say a 60W 12 volt panel 60/12=5 Amps so roughly 5 amps per hour [of course it is not that clear cut usually it will be round 4 amps per hour with a 60 watt panel

Temperature derating can be calculated here. 

Controller losses will be:

• ~5% for MPPT (see product specs)
• variable for PWM.  Tiny losses under the right conditions (poly panels, high ambient temps, low altitude, Absorption stage), huge losses under the wrong ones (mono panels, low ambient temps, high altitude, Bulk stage while deeply discharged)

. 

This means that in special cases PWM can actually put more power into the bank than MPPT.   

I've started a gentle intro to solar for beginers on this wiki page.  It's proving harder than I thought.  I welcome corrections and additions.