Speed up Safari's loading or rendering of background tabs?

I load several Facebook tabs in the background in Safari, using AppleScript. Even if the computer is idle and I wait a minute, these tabs aren’t fully loaded or rendered (they have hardly even started to load or render). OTOH, when I activate such a tab, in loads/renders in a few seconds.

I guess this is because Safari has very aggressive power saving features or similar. Is there some way to disable this? I want my AppleScript to execute in background tabs while I continue to work in Safari as usual.