Easy. Use any Canon camera supported by magic lantern. Load it onto the card (plenty of tutorials online, all you have to do is copy some files onto the SD card and run a firmware update on the camera). Once you did that open the ML menu ("Trash" button) and go to the modules tab. Load the lua.mo module by pressing the SET button on the camera.

Save the following script as timed.lua in the /ML/scripts directory on the SD card:

-- Timed shots --
-- take two shots, 15 seconds apart, every hour for 24 hours --

msleep(15000) -- wait 15 seconds to exit menu and setup camera

for i = 1,24
do -- run 24 times
    camera.shoot()
    msleep(15000) -- wait 15 seconds between shots
    camera.shoot()
    msleep(3600000) -- wait 1 hour before taking next shot
end

Put the card in the camera and go to the ML menu, then onto the scripts tab. Select the Timed shots script and run it (press the Q key, then SET to run). You now have 15 seconds to leave the menu and setup the camera the way you want it. Liveview doesn't need to be running. You can increase that time to anything you want.

The script will start after those 15 seconds, if you need it to run exactly at every full hour, take a look at the date class of the ML Lua scripting API, it's possible and easy to implement.

Another even easier idea would be to adjust the 15000 in the fourth line of the script to match the beginning of the next full hour rougly. E.g. if it's 5:56pm rn and you want to start at 6pm, set it to 240000 (milliseconds) and it will take the first shot at 6pm. You should also subtract the 15 seconds between the shots from the 1 hour sleep at the end of the script, so 3600000 would become 3585000.

You don't want a battery for this. Use this instead. (Make sure it's the right battery type)
In case of the above link dying: It's a dummy battery with a connector for an external power supply.