I cant seem to beat it, creeper gets in too fast and there is just not enough energy to run all the shields i need a spoiler, thanks
How many shields do you use and when do you build them? Using less shields and building them later (after most reactors are complete) often helps.
The central building is protected from the slip emitter (ie it can't dump creeper there). So there's no point building any shields inside it.
Not to advertise, but I made a video of my speed run of this map... :) http://www.youtube.com/watch?v=RfM74fNsmOg Though most players wouldn't be able to beat this as aggressively as I did in the video.
As for tactics...
Spoiler
What is likely the best way is to simply build a chain of shields to the emitter it and nullify it, without waiting too long for your energy to deplete. It only takes a single line of shields from your base to the emitter (the creeper is very thin). And if you know how to do it, you can grab the shield key at the very beginning of the map (you can see me do this at the beginning of my video).