An Austrian company, Heliovis, has developed an inflatable cylindrical thermal concentrator which concentrates sunlight onto a central thermal receiver, similarly to a parabolic trough, but at a much lower cost.
The concentrator is made of three plastic films: a base film, a transparent film and a mirror film. The mirror film divides the concentrator into two air-tight chambers running lengthwise through the tube. Small pressure differences between the top and bottom chambers arch the mirror film downward. This creates a mirror channel that concentrates the sun rays onto a thermal receiver containing a fluid in the upper chamber. The fluid within the chamber can reach temperatures of 400 to 600° C.
Each 220 meters long HELIOtube can output 1 megawatt of thermal energy. The tube, which is 9 metres in diameter, is held in place by standard steel pillars and circles which are modular in design. Every circle is equipped with a motor, thus allowing the HELIOtube to rotate up to 340° degrees around its own axis.
Heliovis says that its technology costs less than half as much as conventional trough systems and reduces CO2 emissions by 40% because the materials are much less resource intensive and can be recycled at their end of life.
The system can be “rolled up” and transported in a standard shipping container, and then inflated once on the site, which represents a significant advantage over other trough systems in logistics costs.
A pilot system is currently undergoing testing in Spain.