Astro Solar

Dual-purpose optical device for photovoltaic solar generation and astronomical observation


This dual-purpose optical device allows using the same hardware to be used as a solar photovoltaic generator during the day and astronomical telescope during the night. To achieve the dual-functionality the optical system has a movable secondary mirror that allows switching between the astronomy and energy generation modes. When the system is setup in photovoltaic solar generation mode the secondary mirror is mechanically stowed and creating an unobstructed optical path to the primary mirror prime focus. At prime focus of the primary mirror an image of the sun is created on a high-concentration triple-junction Germanium photovoltaic cell. This cell can achieve up to 39% efficiency conversion. The power arrivijg from the sun is conceptrated 500 times by the optical system.

To enable the astronomical observation mode the secondary flipper mirror is set back on the optical path sending the light to a focal plane on the side of the telescope. At this location an eyepiece can be mounted or a detector to obtain digital images of the sky.

The energy generated during the day is enough to run the motors and control systems to track the sun during the day and charge a sealed lead battery to run the telescope during nighttime. This concept allows utilizing the optics hardware during day and night enabling operation in remote sites and also energy generation that can be injected back to the grid in populated areas.


• Parabolic primary mirror
• Foldable secondary mirror
• Optical Tube Assembly (OTA) or structure to hold mirrors in place
• Triple-Junction high-concentration solar cell
• Heat exchanger to cool solar cell
• Cell holder
• Primary focus structure to hold solar cell and heat exchanger
• Tracking mount to follow the Sun or objects on the sky
• Voltage amplifier
• Control electronics
• Battery to store energy generated during the day
• Camera or eye piece for night observation


Control software to select objects on the sky and track them with telescope. These kind of systems have been designed previously so it is used as an off-the-shelf component.

Control electronics software

The dual application of and optical system for solar photovoltaic generation and also astronomical or day time observation is novel and has been successfully implemented for the first time. The optical system to switch from observation to energy generation modes is also simple and novel utilizing the secondary mirror of the telescope. A key innovation of this concept is placing the solar cell on the primary mirror prime focus preventing damage of the astronomy rated optical components.

Dual-purpose use of an optical system to generate photovoltaic energy and allow astronomical observation.
High-conversion efficiency
Monitoring of:
Cell temperature
Solar irradiance


Opto-mech layout

FIGURE 1. Optical and mechanical drawings of the dual-purpose optical device. The image on the left shows the system in the astronomy/observation mode. The image on the right shows the same systems but in this case configured for solar energy generation


FIGURE 2. The image on the left shows the triple-junction solar cell of 14x14mm mounted on a custom designed structure to hold it. The image on the right shows the electronics designed to amplify the voltage generated by the cell and control the system.


FIGURE 3. The image on the left shows the folding secondary mirror and the mechanism to actuate it. Also behind the mirror the solar cell structure can be seen together with the heat exchanger and cables to operate the system. The image on the right shows the electronics mounted on the OTA.


FIGURE 4. The image on the left shows the system aiming at the sun and generating power. The image on the right shows the electronics reporting the status of the system. Note the efficiency of 32.9%

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