The worldwide energy systems are not sustainable! The economies of industrial countries, as well as the economies of rapidly developing third-world countries, are completely dependent on fossil fuels, specifically coal, oil and natural gas.
Coal, oil and natural gas are non-renewable natural resources that we will exhaust one day. In fact many predictions made decades ago stated that these natural resources would even be in short supply by the year 2000.
Now, as we know, that gloomy scenario hasn't materialized. However, many who have followed this situation closely for decades believed that they would have witnessed the transition to renewable energy resources - away from the dependence on fossil fuels - by now.
