Any useful interpretation of renewable energy has to do with purely human timeframes as thermodynamics doesn't allow for any energy source to be endlessly renewable. "If I use this source today will more of it naturally be there tomorrow" type consideration, otherwise you end up with a definition which either includes things like fossil fuels as renewable because you can wait millions of years or excludes things like sunlight because it won't be there in 10 billion years.
Well, there is a more important sense in which solar is renewable but not tidal energy. The sun does not burn out appreciably more quickly if we use a larger percentage of the available solar energy, it's there whether we use it or not. This is not the case for tidal energy.
