The "Power curl" is NOT a biceps exercise. It's a curl grip power clean. Al Oerter (the 4 time O champion in the discus) ppularizd it. What you do, it to grab a bar off the rack, with a curl grip, lower it down past mid shin or on the floor, and whip the bar up to the shoulders. We did these back in High School, because they did not require the technique of a power clean, but used the same posterior chain movements. Look over at Dan Jo0hn's site. He has a couple of articles on this.
I think it can be utilized as a biceps exercise though if done like the way i mentioned. It allows you to take your max concentric curl weight or even a little more, use all the force to curl it up...then perform negatives with it.