SInRG stands for Scalable Intracampus Research Grid. They operate and maintain many computer clusters, including the Boba cluster which drives the Powerwall. In order to use the Powerwall, you will need a SInRG account.
To get an account, email the Boba cluster administrator, Clay England <sinrg-help at cs.utk.edu>.
For more information on SInRG or the Boba machines, visit http://icl.cs.utk.edu/sinrg/ .