It is only connected to solar power.
This is a stand-alone server. It is not connected to the internet. What I mean is that we can not connect a smartphone or laptop to the router. When you look for the wifi network from the AR150, nothing appears. If we restart the router, then we can find the network again and connect.
Interesting point on the USB model. The reason that we chose the AR150 is that it has an external antenna. We need to get maximum signal strength to be accessible from multiple classrooms. You are right that it would be less wires, possibly less power consumption also.
In your opinion, does the USB version have a comparable reach for the network?