At least, this is due to a patent that has just appeared online. Samsung was supposed to receive it from the USPTO as early as September 16.
The patent describes a fairly standard Galaxy-type watch. What's the change, then? Its strap is equipped with small solar panels. It is not yet known what the performance of such a solution is, but the idea itself is quite interesting, and you can see it in the renderings obtained from the LetsGoDigital website.
How it will be implemented is not yet known. Let's add that Samsung can just experiment with different ideas. After all, we're talking about a patent now, not a leak regarding a specific watch. A feature such as solar power generation would be quite interesting and would significantly increase the runtime of the gadget.