Not so. Sea Solar Power (use of ocean thermal gradient) is the cheapest way to generate electricity from the Sun.
See this site:
Sea Solar Power
Much of the details of the heat exchangers is secret until the patents are granted. What I can tell you is that heat transfer efficiencies of eight times the standard book values have been achieved in actual tests. I have held this miraculous heat exchanger material in my own hand. The surface area is incredibly large when compared to ordinary heat exchanger surfaces.