Tidal energy is not renewable
I'm not sure the author realized this, but they're actually making a statement about how crazy exponential growth is. Not about the sustainability of tidal power. This becomes obvious once you look closer at what that 2% growth rate (as assumed in the post) implies.<p>Our global energy consumption in 2008 was estimated to be 474 exajoules. The total energy received by the earth from the sun during a year is about 5 million exajoules, a fraction of which reaches the surface. 5 million is much more than 474. But at a seemingly modest 2% per year growth rate (as it was between 1980 and 2006), our energy consumption will match those 5 million exajoules in less than 500 years!<p>Think about that: if energy consumption growth continues at the current pace, then in 500 years we'll either be using ALL solar energy received by the earth (leaving none for the biosphere), or we'll have figured out some magic technology to produce 5 million exajoules of energy per year. Assuming the magic technology, where are we going to get rid of all that extra heat? It would effectively be like having a second sun on earth, cooking us in place.<p>edit: I copied the numbers above from a post I wrote in 2010, so it may be a bit out of date. But Sabine Hossenfelder recently made a video where she talked about a similar timescale, i.e. boiling oceans in 400 years: <a href="https://www.youtube.com/watch?v=9vRtA7STvH4">https://www.youtube.com/watch?v=9vRtA7STvH4</a>