Solar collector
A solar collector was a large device made of orange material which could be used to collect solar energy for power.
During the USS Protostar's ten years marooned on Ysida, Captain Chakotay used solar collectors to recharge the ship's emergency power cells, having ejected the Protostar's antimatter and proto-core. However, the solar collectors lost efficiency each year. (PRO: "Last Flight of the Protostar, Part II")
When the Protostar was turned into a sailing ship, the solar collectors served the dual purpose of sails and a power source. However, while circling the maelstrom containing the deuterium gas that the ship needed, the solar collectors were torn off by the wind, leaving the Protostar with limited power remaining. Hologram Janeway shut herself down and redirected all of the remaining power to the ship's Bussard collectors as a result. (PRO: "Last Flight of the Protostar, Part II")