Electronic – Mini solar panel not working

Reading here and a couple other places makes it sound like solar panel degradation varies widely. Manufacturing origin doesn't appear to be correlated to longevity or if it is, it may be opposite what we expect (China appears to do well). The general gist is that you'll lose a fraction of a percent every year on average. It's likely due to high energy photons slightly changing the structure over time. Weathering is also a concern. Wind-blown sand scratching the surface and dust blocking light are two other ways cells degrade. Most solar installations appear to be able to handle 20-40 years of use without issue, but some don't appear to handle thermal cycling well. In that case, you can have catastrophic failure of one or many cells causing poor solder bonds to break, delamination to occur, or entire cells to crack. Corrosion of the cell and connectors could be another late game failure mode.

I think more of a concern than the cells degrading is the supporting electronics (inverter) dying. The cost of installing a solar installation these days is largely being determined by peripherals rather than the panels themselves. Power electronics to support the system and their failure mode is really what I would be researching if I were in your shoes as I believe the likelihood of catastrophic failure there is much more likely in a much shorter timeframe.

This looks to give a great rundown of many manufacturers and their lifetimes. I've included a diagram from there below:

After some research I found that I needed a inverter. My question is: do I really need a inverter? if I do what inverter should I get?

You actually need an MPPT tracker also called a solar charge controller. This helps match the voltage and current (that act like a diode) to the load of the motor. The solar panel needs to produce more power than the motor uses. So if you have a 10W panel, it could run a motor using less power than 10W. The controller takes some power (usually 80% to 90% efficient) so that means you could run an 8W motor with a 10W panel. The 10W also assumes that your at the equator (1000W/m^2 of sunlight) and that the panel is pointed directly perpendicular to the sun on a sunny day. At higher latitudes you would get about 600W/m^2. So a good rule of thumb would be 3 to 6 times higher panel than your load.

Source: http://www.solarjourneyusa.com/learn-buy-equipment.php