Every day the Sun radiates some 15,000 times more energy onto the Earth than is used by all forms of human activity, and this supply is assured for billions of years into the future. For this reason alone, we can no more run out of energy than a fish in the ocean can die of dehydration.
But solar energy is diffuse, covering the whole disk of the planet, and only a small fraction is harvestable as sunlight, wind, and as the gravitational energy released by the hydrological cycle (hydro energy). During the last hundred years, it has been much easier to feed on the neonatal supply (that birthed humankind into our present levels of comfort and technology) of fossil fuels from the Earth, than to harvest the ambient energy of the Sun. We are witnessing the beginning of the end of that era, and how we choose to adapt is the key determinant of human futures. The challenge is to capture ambient energy, and to store and distribute it in quantities sufficent for transportation, industrial and heating needs.
Important constraints are imposed by the basic energy budget of activities on Earth. For example, at present the total energy capture per year by all forms of photosynthesis is only about ten times greater than the total energy consumption by humans. Since our technology is unlikely to ever surpass the efficiency of nature, we would have to utilize one-tenth of all plant growth on the planet to sustain current consumption from bioenergy alone. A much greater amount of solar energy goes into evaporating water and driving weather systems. But the challenge of collecting, storing and reusing these energies is not trivial.
It is safe to assume that any sustainable energy supply places strong limits on growth, and perhaps more importantly, what kind of growth is even possible. You don't want to be in a city of 10 million people when the lights go out. Rural and small communities have the best chance of efficiently using the diffuse sources of renewable energy.
Are our politicians listening? Are they even aware?
Energy in British Columbia
"If you canít do it without fossil fuels, by definition it isnít sustainable." - Richard Heinberg
"Running the global economy on hydrocarbons is like driving your car
Ashore & Afloat