|Environmental Handbook Volume II: Agriculture, Mining/Energy, Trade/Industry (GTZ, 1995, 736 p.)|
|Mining and energy|
|43. Renewable sources of energy|
In addition to finite deposits of fossil and mineral fuels such as oil, gas, coal and uranium, the earth also offers various natural, auto-regenerative - or renewable - sources of energy that derive from sun insolation, geothermal activity and gravitational forces.
Theoretically, the global supply of energy from such renewable sources by far exceeds the earth's present total energy demand. The supply of energy is subject in part to pronounced technical and economic utility limitations, e.g., the disparity between the temporal/spatial demand for energy and the actually available supply of renewable energies, and the latter's modest power density compared to conventional energy vehicles.
The main renewable energy (RE) sources are:
1. Insolation, i.e., the direct radiant energy of the sun (made useful by collectors, solar cells, etc.)
2. Energy obtained from biomass; biochemical energy of photosynthetic products; made useful by
- burning (of wood, straw, etc.)
- gasification (of wood, etc.)
- anaerobic digestion (= biogas)
- alcoholic fermentation
3. The kinetic energy of wind
4. The kinetic energy of moving water:
- low-pressure systems
- high-pressure systems
- micro-hydropower plants
- tides, waves, ocean currents
- geothermal energy
- thermal energy deriving from differences in seawater temperature
- osmotic energy deriving from concentration gradients between saltwater and freshwater.
With a view to the proper and adequate sizing and, hence, limitation of the environmental consequences of renewable energy systems, the energy consumers' options for the conservation and rational use of energy should always be given full consideration, whereas boundary conditions in the form of prices, tariffs, etc. are major factors.
The environmental impacts resulting from utilization of the following renewable sources of energy are dealt with in this brief:
- solar energy (heat and photovoltaics)
- energy from biomass
- wind energy
- geothermal energy.
To the extent deemed relevant, other renewable sources of energy are dealt with in other briefs.
With regard to the general environmental consequences of energy systems and to the supradisciplinary aspects to be considered in connection with the planning of energy policy and energy economics projects, the reader is referred to the environmental brief Overall Energy Planning.