https://www.entrepreneur.com/article/342714

As Greta Thunberg, the 16-year-old activist environmentalist, said recently after trying in vain to be heard by an international audience at the United Nations, “I will not beg the world leaders to care for our future. I will instead let them know change is coming, whether they like it or not.” 

As awareness of climate change grows, one thing has become exceedingly clear: Using energy generated by renewable sources is crucial to reducing harmful greenhouse-gas emissions. And while energy sources like wind and solar are increasingly valuable in this effort, they can be unpredictable and intermittent. How much energy will any single panel or solar plant contribute to the grid on any particular day? The answer to that question has historically been tricky to answer.