A novel, high-efficiency, 
extremely light-weight, 
inflatable refractive 
solar concentrator for 
space power is described. It consists of a flexible 
Fresnel lens, flexible sides, and a back surface, together enclosing a volume of space which can be filled with low pressure gas to deploy the 
concentrator on 
orbit. The back surface supports the energy 
receiver / converter located in the focal region of the 
Fresnel lens. The back surface can also serve as the 
waste heat radiator. Prior to deployment, the deflated flexible lens and sides are folded against the back surface to form a flat, low-volume 
package for efficient launch into space. The 
inflatable concentrator can be configured to provide either a line focus or a point focus of 
sunlight. The new 
inflatable concentrator approach will provide significant advantages over the prior art in two different 
space power areas: photovoltaic concentrator arrays and high-temperature solar thermal conversion systems. Photovoltaic concentrator arrays using the new inflatable lens will be much lighter than prior space concentrator arrays. In addition, for photovoltaic concentrator arrays, the new inflatable lens will eliminate the need for a fragile glass superstrate to support the lens, substantially improving robustness of the lens. Solar thermal concentrator arrays using the new inflatable lens will be much lighter than prior art space concentrators which used parabolic mirrors. In addition, for solar thermal applications in space, the new inflatable lens will eliminate the need for 
high surface accuracy, which has been a significant problem for prior art concentrators.