The world energy consumption approximately 12.3 terawatts according to Wikipedia. 1 terawatt equals 1,000,000,000,000 watts. One potato produces a stream of 0.8 watts. However, through the process of boiling a potato for 8 minutes and cutting it into four or five pieces you can increase the output by 10 times, leaving you with an output of 8 watts of electricity for about 40 days. One ton of potatoes is about 2667 potatoes and the world produces about 324,181,889 metric tons of potatoes a year. Which would yield 6,916,744,783,704 watts of energy for 40 days. So to get 12.3 terawatts you would need to increase production by about 1.88 times. 365 days divided by 40 days equals 9.125 so multiply that number by 1.88 and you are left with 17.125. Then multiply the product by 324,181,889 and you are left with about 5,561,340,306 metric tons of potatoes.

So to power the world for a year, you would need about 14,832,094,596,102 potatoes or fourteen trillion eight hundred thirty two billion ninety four million five hundred ninety six thousand one hundred two potatoes.

I am done, I am the greatest potatologist to have ever lived!