To utilize, by installing a solar battery, electrical energy not depending on engine power, to increase the fixed area of the solar battery, and to enhance the amount of power generation by allowing the power generation capability of the solar battery to be fully exhibited by making the sunshine strike well thereon irrespective of the position of the sun.

On the surface of a rotary drum 2 rotatively driven by a driving part 30 and holding a fluid concrete there are installed solar battery modules 3 on its whole circumference, and a battery 4 to store the electricity generated by these solar battery modules 3 is mounted. As the solar battery modules 3 there are used flexible solar battery modules whose substrates are formed of a flexible resin. A cleaning mechanism 20 is also equipped which cleans the outer surfaces of the solar battery modules 3 with rotary brushes 21.

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