I found a great way on abyss:
While your energy generation is only 8, Dark beam can be only used a little. Get all chips and upgrade the following:3*Energy Storage,2*Beacon Range and Decrease U.Cost by 20%.
Then light up dark beam and let it hit gate directly. Build a microrift in that empty area, so happy building several nullifiers! :) :D
In many maps you can put liberation ship in danger and nullify the emitters which has a field surronding.