Assuming naively: A serving is 665 kilocalories, or1/3 RDA, worth of starch, 1 serving needed per day per human, and capture, synthesis, and storage is 100% energy efficient, .86 kcal per watt hour of energy conversion rate, then you need 775 watt hours of energy per serving per day.
Assuming a standard solar panel and conditions, a 1sq meter panel captures about 700 watt hours per day.
I'd guesstimate the creation is less than 10% efficient, meaning you need 10-11 square meters of solar panels per serving produced per day.
Processing plants or fungus or bacteria from bioreactors is orders of magnitude more efficient.
