The capacity to produce a work. For ancient Greeks such as Aristotle, it was a force either in potency (dymanis) or in act (energeia). This idea was formalized in the 19th century by defining the unit of energy the Joule representing a force of one Newton multiplied by one metre. The energy of an object may have multiple forms: potential (its weight multiplied by its height), kinetic (its mass by the square of its velocity), calorific (its temperature), elastic (energy stored in its molecular structure), chemical ((nuclear(Einstein’s E=mc2) etc,… Energy cannot be created (first law of thermodynamic) only changed from one state to another and in the process it gets degraded (second law of thermodynamic). Not all energies are the same, you can produce heat with electricity but cannot run a computer on heat. Gravity produces the highest quality of energy and heat the lowest. When everything will be at the same gravity level and the same temperature, no work can be done anymore. Renewable energies are not creating energy only transforming solar energy into some more useful energy: mechanical, electricity, hot water, or simply food. Today’s source of energy is principally from fossil fuels, often by simply transforming into heat (by burning) the chemical energy accumulated plants and animals over millions of years. This process creates over the long-term three major issues: · It cannot be sustained forever – fossil fuels are getting exhausted. · It is a significant source of air pollution, not only by putting back into the ecosystem CO2 that was captured by these organisms but also by releasing toxic material such as sulphur or mercury. · Two-third of fossil fuel reserves are in developing countries, which are consuming only one third leading to social unrest and geopolitical conflicts. Same as water, energy – the lack of it or its unequal distribution, is a major challenge for the 21st century.
• in detail • see also: Renewable Energy XlnkS623