The Beacon can be built after the Decode Signal Project is completed. One the Beacon is built, is must be activated. It costs 1000 
Energy to activate, and "will consume all surplus Energy each turn it is active." However, this effectively sets the Energy per turn to zero, so if the Energy per turn is currently negative, it will be set to zero, a significant advantage.
Images
.jpg "Beacon (CivBE).jpg (109 KB)"){kind=tracking}
.png "Beacon 2 (CivBE).png (1.02 MB)"){kind=tracking}