With a combination of scripts Domoticz can be configured to operate your sunscreen considering several weather conditions. These scripts help you to get this working.
With some cheap hardware you can measure the sunlight. Your Domoticz software can check the values. This board is available in several webshops. I bought it here: https://www.tinytronics.nl/shop/nl/communicatie/rf(id)-wifi-bt/esp8266-12-board-met-batterijhouder?search=esp8266