[Strawbale] How to protect/cover windows for heat protection?

[SWallat]

Hello,

our "passive solar" (proper location of the windows in outer walls) 
during autumn/spring time works fine to support heating the house during 
the cooler seasons.
During summer we get heat through the windows inside. Any 
ideas/recommendations what could be installed to the windows of the 
outer walls to protect from "sunray heating"? We have strawbale infill 
walls with wooden panel/cover to protect clay from rain as outer walls.

Regards,
Steffen