This was probably the simplest and yet one of the most successful projects I ever made. A Power over Ethernet or PoE Adapter, which allows the usage of Ethernet cable to transmit not only data but power as well for the network equipments.
There are 2 pairs of wires that are not used on UTP cables for communication on 10/100Mbps networks. So these adapters will allow you to use those wires for power transmission.