Wide Acceptance Angle, High Concentration Ratio, Optical Collector

Technology Opportunity

Wide Acceptance Angle, High Concentration Ratio, Optical Collector

           his solar energy concentrator provides a way to focus the solar rays coming from the sun onto a small area using two mirrors. The first mirror has a spherical shape and focuses the solar ray onto a second mirror. The second mirror has multiple curvatures, which allow it to focus not only the solar rays coming in aligned, but to also include those that may be coming in slightly out of alignment, onto a small area. In this small area where the solar energy is concentrated, one can then place a device to convert the solar energy into a useful form, by using solar cells (photovoltaics) to generate electricity, or a heat exchanger (photothermal converter) to generate heat.

Potential Commercial Uses

This solar energy concentrator (mirrors) can be used in either a photovoltaic or photothermal concentrator system, or both. As an integral part of a photovoltaic system located on the roof of a building, it can assist in producing electricity, which can be used in parallel with the local utility providing electrical energy to augment and share the load. The photovoltaic cells, used with this concentrator and located at the focal point of the secondary mirror is likely to get hotter than is tolerable by the cells, requiring cooling. If cooling is required, the thermal energy removed from the solar cells during the cooling process can be used to augment the heating of a building during winter months. When used with a photothermal converter, the solar radiation is converted into heat, from which electric power can be generated, or used in heating and cooling the space in a building, as well as in desalination plants and other industrial applications which require heat or steam.

Benefits

The concentrator provides both a high-concentration ratio and a wide acceptance angle. It is capable of tolerating a small amount of misalignment, which makes it easier to install, thereby eliminating the need for special training of the installer. It captures a greater amount of off-axis light than the currently available cassegrain collectors. 		     




          

The Technology

The collector is capable of improved collection of off-axis radiation at high- concentration ratios. The primary concave mirror receives and reflects the incoming radiation on to the secondary mirror. The secondary mirror is aligned coaxially and spaced in relation to the primary mirror. The secondary mirror redirects and concentrates the radiation received from the primary mirror onto a photovoltaic or photothermal converter. The secondary mirror has three different zones: inner, central, and outer. The central zone has a hyperboloid cross sectional shape, which reflects on-axis radiation from the primary mirror. The inner and outer zones of the secondary mirror have paraboloidal cross sectional shapes, which reflect the off-axis radiation from the primary mirror onto the photovoltaic or photothermal converters.

Options for Commercialization

This solar energy concentrator device is part of the NASA Technology Transfer Program available to industry. A patent for the system has been issued to Marshall Space Flight Center and is available for licensing. 		     

Patent Number

5,062,899

Contact for Licensing Information

Technology Transfer Office
Patent Licensing Information
Mail Code LA20
Marshall Space Flight Center, AL 35812
Phone: 1-800-USA-NASA
          

Key Words

Concentrator
Solar Heating
Wide Acceptance Angle
Solar Energy





National Aeronautics and
Space Administration

George C. Marshall Space Flight Center