Fossil fuels store energy. Assuming you have extracted enough, you can meet your needs and produce energy on demand by burning them.
Solar is different, The fuel store is the sun, but when it’s cloudy the source dries up until the sun shines again. Wind is different. When the wind drops the source dried up.
That has been the problem for many years. Now clean energy can be stored in batteries. Store today for use tomorrow.
It is the revolution in battery technology that has enabled this.
The United Kingdom, Australia, Germany, and the states of California and Texas in the USA are already doing this on a grand scale.
Nuclear Energy
For years no one has wanted to do a proper calculation of the cost of fission plants. The cost of decommissioning them is huge, and there is the danger of catastrophic accidents.
Fusion is a tantalising goal but it is uncertain.