If you count orbiting weapons that just concentrate the sun's energy using mirrors/lenses (like using a magnifying glass to burn ants), there's a 1927 example mentioned on p. 260 of the article "The Historical Death Ray and Science Fiction in the 1920s and 1930s":

The 1927 German novel Flammen aus dem Weltraum [Flames from Space] by Karl August von Laffert describes a space station mounted with huge reflectors that act as a sun gun

(searching a little for this title, I think the article misprinted the name, it should be Flammen aus dem Weltenraum)

The Project Rho page on "Orbital Planetary Attack" includes this section which gives plenty of other examples of stories involving this type of weapon from the early 20th century, though none earlier than 1927.

If you count orbiting weapons that just concentrate the sun's energy using mirrors/lenses (like using a magnifying glass to burn ants), there's a 1927 example mentioned on p. 260 of the article "The Historical Death Ray and Science Fiction in the 1920s and 1930s":

The 1927 German novel Flammen aus dem Weltraum [Flames from Space] by Karl August von Laffert describes a space station mounted with huge reflectors that act as a sun gun, anticipating, or perhaps inspiring, the actual secret German project at Hillersleben mentioned previously.

Searching a little for this title, I think the article misprinted the name, it should be Flammen aus dem Weltenraum. And as for the "actual secret German project" they mention, see here and here for more details.

The Project Rho page on "Orbital Planetary Attack" includes this section which gives plenty of other examples of stories involving this type of weapon from the early 20th century, though none earlier than 1927.

If you count orbiting weapons that just concentrate the sun's energy using mirror/lenses (like using a magnifying glass to burn ants), there's a 1927 example mentioned on p. 260 of the article "The Historical Death Ray and Science Fiction in the 1920s and 1930s":

The 1927 German novel Flammen aus dem Weltraum [Flames from Space] by Karl August von Laffert describes a space station mounted with huge reflectors that act as a sun gun

The Project Rho page on "Orbital Planetary Attack" includes this section which gives plenty of other examples of stories involving this type of weapon from the early 20th century, though none earlier than 1927.

If you count orbiting weapons that just concentrate the sun's energy using mirrors/lenses (like using a magnifying glass to burn ants), there's a 1927 example mentioned on p. 260 of the article "The Historical Death Ray and Science Fiction in the 1920s and 1930s":

The 1927 German novel Flammen aus dem Weltraum [Flames from Space] by Karl August von Laffert describes a space station mounted with huge reflectors that act as a sun gun

(searching a little for this title, I think the article misprinted the name, it should be Flammen aus dem Weltenraum)

The Project Rho page on "Orbital Planetary Attack" includes this section which gives plenty of other examples of stories involving this type of weapon from the early 20th century, though none earlier than 1927.