So we're going to shoot these precious entropy differentials away into space?
The earth already emits massive amounts of energy back into space. Nearly all the energy received from the sun is reemitted back into space, if this didn't happen the earth would quickly burn up. Adding reflectors won't make a huge difference as this energy would go back into space anyway.
EDIT: Of course, we would have to significantly alter the albedo, which is probably not possible with rooftop panels alone.
From the article, it doesn't look like increasing albedo is the researcher's goal for these devices. It looks like they're doing this to reduce air conditioner energy usage, which would reduce CO2 emissions from fossil fuel burning power plants.
Also, the earth's temperature is never really in equilibrium in the first place, as it's always heating or cooling due to the day-night cycle or seasonal axis tilt.
Delete "per hour". The watt is already a unit of energy per unit time (1 joule per second, specifically). So 12 trillion watts is the same as 12 trillion joules per second.