Hi,

Abstract:
I am going to design and build a portable solar powered device which is able to charge a USB device and drive a 4w fan. It also includes lithium ion batteries to store energy in case the direct illumination is not present.
Objectives:
*Portable ( foldable pv panel)
*Efficient ( combination of MPPT and PMW)
*keep the fan running in full speed and charge USB devices at the same time.(Ideally)
* Prevent the battery from getting over-charged and over-discharged.
*Satisfy USB devices charging specifications.(assuming be able to charge a mobile phones 3500mah battery within 1 hours in full illumination)
*relatively low cost.

I would appreciate it if you guys help me to find out where should I start in calculating . what steps should I take. what information's do I need. Components have to carefully calculated so u have to keep assumption minimal. In the end of the day this is a device that I eventually need to build and it has to work.
P.S: attached a diagram of the system.

 

There is a lot to take into consideration when building such project.

• What solar panels will you be using, are they sufficient in size to provide enough power?
• What efficiency solar power panels have? 5%? 10%? 20%?
• How much solar radiation are you getting in your location? http://www.solarpanelsplus.com/workspace/uploads/solar-insolation-us.jpg
• Is there anything blocking your panels from sun? Trees? Buildings? Cloud cover?
• Will the panels be always facing south or are they gonna be rotating and auto-tracking the sun?
• Have you calculated the power loss when converting power from solar panels to 5V USB?
• Have you considered the price of such project? it may cost you more that you assume.

Walmart already has something in your parameters, much cheaper.

https://www.walmart.com/ip/12000mAh...0510&wl11=online&wl12=160592533&wl13=&veh=sem