What is our current strategy for future energy security/demands? Is it to prolong the availability of fossil fuels by using renewable sources? Or looking for energy solutions that will replace fossil fuels?

The energy source to replace fossil fuels is already here. It has been here all along; it is the sun, and it is where fossil fuels came from in the first place, via 1% efficient photosynthesis and then millions of years of heat & pressure. Retooling our entire civilization to depend on non-polluting non-fossil energy sources is the only sane, rational voice the humans have. Wind and solar are only the beginning; we need to rethink a civilization currently based on personal transportation infrastructure to a civilization in which mass transit is safe, as fast as airliners, and non-polluting. Heavy manufacturing, shipping and defense applications can continue using the dirty stuff but the civilian and consumer economy must become cradle-to-cradle, at least 75% more efficient, and ultimately wasteless by around 2030 or we will have no civilization left at all by 2100. The business as usual scenario turns the planet virtually unable to support human population, except a few small groups at the poles, by 2150 in the best case: the worst case sees Earth turning into Venus by 2100. Simply put, we are wasteful with the dirty, east energy we have, and not being aggressive enough about the virtually limitless supply of solar income energy that could turn Earth into a Heaven by 2100 instead of Hell.