More Words, Deeper Hole

Oddly enough, this is relevant to a story idea I've been working on. Aliens muck up the sun so its visible-light output drops by a factor of one thousand. The energy goes into near-infrared, above the water absorption band so Earth doesn't get any colder. It doesn't look any darker - human eyes adjust to the dim sun just like they do to artificial light. The problem is that photosynthesis shuts down. The only way to keep people fed is to grow food under artificial lights. With current technology and assuming a strictly vegan diet, how much energy would this require?
Gareth Wilson