Numerous aspects of modern life are utterly dependent upon energy in the form of electricity and combustible fuels. Most analysts, however, believe that fossil fuels -- which currently dominate worldwide energy production -- are a non-renewable resource because the rate of extraction far exceeds the rate of formation. This concern has encouraged intense research into technology that can capture energy from the world's fundamental renewable power source: the sun.
Renewable energy originates from self-replenishing natural processes. These energetic processes are generally considered to be inexhaustible because they are governed by chemical reactions and natural cycles that will continue far beyond the foreseeable future. The natural world is teeming with energy of all kinds, but many manifestations of natural energy -- such as lightning and ocean waves -- cannot be conveniently converted into electricity, transportation fuels and other forms of energy required by modern society. The challenge of renewable energy, then, is to identify suitable natural energy sources and develop technology that can use them efficiently.
The Power of Protons
The ultimate source of solar energy is the nuclear fusion that occurs in the core of the sun. This complex reaction begins with two protons that fuse together and ends with the release of large amounts of energy. This energy travels through outer space and arrives at the Earth in the form of electromagnetic radiation. Solar power can be considered the most renewable of all energy sources because it suffers no diminution from human activity and, more importantly, because it will naturally replenish itself for as long as human civilization needs energy -- the Earth will be unable to support life once the sun runs out of fuel.
The energy radiated by the sun is perfectly renewable, and therefore solar power -- which generally refers to electricity generated by solar panels -- is also essentially renewable. But it is nonetheless true that the fusion in the sun cannot continue forever: if fusion converts mass into energy, mass will eventually run out and energy production will cease. In an absolute sense, then, solar energy is not renewable because the sun, like all stars, will eventually lose the ability to support fusion. But this process generally takes billions of years, and scientists estimate that the sun will endure for another 5 billion years. Thus, solar energy is renewable in relation to the Earth because it is impossible to anticipate what humanity's energy needs will be billions of years in the future.
From Non-Renewable to Renewable
It is reasonable to describe solar power as generally renewable, but virtually all sources of renewable energy rely to some extent on fossil fuels or other non-renewable inputs. In the case of solar power, sophisticated technology is required to efficiently convert solar energy to electricity. This technology is manufactured in facilities powered primarily by fossil fuels, then it is transported and installed using equipment powered primarily by fossil fuels. Consequently, it is difficult to affirm that solar power, or any practical form of energy production, is perfectly renewable. Nonetheless, analysts believe that solar power has developed and expanded to the point that the amount of renewable energy it generates is greater than the amount of non-renewable energy required for its fabrication and installation.
- Pennsylvania State University Extension: What is Renewable Energy?
- HyperPhysics: Proton-Proton Fusion
- Cornell University: How Much Longer Will the Earth Last?
- Texas A&M University: What is Biofuel?
- University of Colorado, Boulder: Sun and Climate
- Stanford University News Service: Global Solar Photovoltaic Industry is Likely Now a Net Energy Producer, Stanford Researchers Find
- Case Western Reserve University: Life and Death of Stars
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