Very interesting development for the chosen application of water purification in the developing world requiring nothing more than the equipment and sunlight to sterilise water effectively, however...

A direct comparison with photovoltaic cells is not appropiate as the solar cells convert directly to electricity and requires no turbine to generate the electricity with a working fluid.

When you factor in the losses (and expense) for a traditional turbine system on such a small scale you will probably be getting less than 50% efficiency for the turbine system.

An electrode boiler is around 99.9% efficient and requires Alternating Current (AC):

http://en.wikipedia.org/wiki/Electrode_boiler

So a photovoltaic cell with some kind of inverter from DC to AC will produce steam, as well as user switchable DC and AC power output:

http://www.photovoltaic-cells.net/

The people behind the nano solar technology know this (I think) and are avoiding power generation for these reasons, so the direct comparison with photovoltaic cells is dishonest for this reason. However, most people would not know this so they would get away with it for sensationalisation purposes.

Still a good development though and I am impressed, just wish they had told the whole truth, and not a selective version relying on peoples ignorance of the facts.