It is true that resources of heavy oil, tar sands, and shale deposits exist in large quantities. But the industry will be hard-pressed for the time and money needed to ramp up production of unconventional oil quickly enough to forestall an economic crisis. Renewable energy will play a major role in the energy industry of the twenty-first century and beyond. Industry experts realize that these alternative energy systems not only help reduce greenhouse gas emissions, but they predict that over the next half century, renewables may grow to supply half the world's energy. Successfully generating electricity by harnessing the perpetual power of the Sun and wind is not only technologically feasible, it is already a reality.
Solar power relies on the energy produced by nuclear fusion in the Sun.
This energy can be collected and converted in different ways, such as simple water heating for domestic use or by the direct conversion of sunlight to electrical energy using mirrors, boilers, or photovoltaic cells. The technology is improving and the economics are getting more competitive. Photovoltaic panels don't generate electricity at night, but they can be used to produce hydrogen in the daytime, which can then be stored. Scientists and engineers are continually improving the efficiency of renewable energy systems. Humans have been harnessing the wind for thousands of years, and are now cleanly producing electricity with it.