Another fun “What If” from xkcd:
A Jersey cow presents in the neighborhood of nearly two square meters of usable space to the sun if it stands right. (Cows would have to be trained to stand optimally, but we might not have too far to go; research suggests they already align themselves north-south.
Chlorophyll photosynthesis extracts 3%-6% of the total energy from sunlight. If we figure on any given day the cow gets the equivalent of about six hours of peak sunlight, it works out to less than two million joules of usable energy each day.
