PRO Power? Pipe dream to power generation?

The leader in PRO (pressure retarded osmosis) is Statkraft, a hydro-electric power company in Norway who demonstrated a 4 kw pilot plant in late 2009.  According to Statkraft website:

What is the membrane's efficiency?

The one we are going to test now has a efficiency of less than 1 watt per square metre, but we plan to install membranes that can deliver 2-3 watts after we have run the plant for awhile. The objective is to reach 5 watts.

But with graphene, the flux is theoretically higher and the membrane just 1-atom thick, so mass transfer (internal concentration polarization) should be less of a problem as well as concentration polarization, which plagues the efficiency in current RO membrane architectures.  With orders of magnitude over 100 up to 1,000, the future looks bright for PRO power generation assuming graphene membranes make it to reality.