May be useful for recharging small batteries used in the monitoring or control of the a local process. I don't recommend it to use in a large scale to feed back to the main supply. Efficiency of solar panels is not that good. It would be better to use reflective materials (like metallic mylar or plastic mirrors) to direct the light back to the plants.
The light fixture reflective parts should be designed or modified so as to direct the light back to the plants. This could even mean moving the light up and down as the plants grow. A curtain of reflective material could be built over the light and plants so that little light escapes to the sounding aisles or ceilings. Reflective material could be used around the plants roots and between plants to further improve more light reflecting back to the growing areas. Remember carbon dioxide needs to get to the plant so don't restrict airflow. If algae is grown the light would be encased in a sealed plastic or glass tube and put in the center of the tank under water.
Along this line - we should paint the interior of all living and storage areas with as reflective paint as we can. White or some of the florescent glowing white as described in an earlier post by Pat T would work. Takes in the light and glows after the lights are turned off.
Offered by Mike.