Unlike the 'kites', the design for Radyr is one that doesn't make Wales a guinea pig for new and unproven technology. The design for Radyr features an Archimedes screw, except instead of needing power to lift water from a lower level to a higher level the water will drive the screw as it descends to a lower level.
Archimedes screws have been used for thousands of years, consequently this makes it far cheaper to implement which should mean a far cheaper price strike in order to pay back investors.
The EBC tells us that the screws will cost £2.6m which is just under ten times cheaper than the £25m the kites off Holyhead will cost. They also tell us that it will power 550 homes, the company behind it tell us that it has the potential for 391kW (compared with the initial 1500kW for the kites).
If these numbers stack up then it means the screws are a far more efficient and cost effective method of generating power than the kites.