Solar power has begun to transform the world’s energy system

good article I just don't know why author prefer to spell all numbers using words rather than digits. It's very mentally taxing for me to read, e.g:

>> of twenty-one thousand respondents in twenty-one countries, found that sixty-eight per cent favored solar energy, “five times more [...]

could be just:

>> of 21,000 responders in 21 countries, found that 68% favored solar energy, "5x more [...]