Other major contributions came from large hydropower (9 exajoules a year) and from modern biomass (7 exajoules). The contribution of all other renewables 0small hydropower, geothermal, wind, solar, and marine energy was about 2 exajoules. That means that the energy supply from new renewables was about 9 exajoules (about 2 percent of world consumption). The commercial primary energy supply from renewable sources was 27 +/- 6 exajoules (nearly 7 percent of world consumption), with 16 +/- 6 exajoules from biomass.
Renewable energy sources can meet many times the present world energy demand, so their potential is enormous. They can enhance diversity in energy supply markets, secure long-term sustainable energy supplies, and reduce local and global atmospheric emissions. They can also provide commercially attractive options to meet specific needs for energy services (particularly in developing countries and rural areas), create new employment opportunities, and offer possibilities for local manufacturing of equipment.
There are many renewable technologies. Although often commercially available, most are still at an early stage of development and not technically mature. They demand continuing research, development, and demonstration efforts. In addition, few renewable energy technologies can compete with conventional fuels on cost, except in some niche markets. But substantial cost reductions can be achieved for most renewables, closing gaps and making them more competitive. That will require further technology development and market deployment-and boosting production capacities to mass production.
For the long term and under very favorable conditions, the lowest cost to produce electricity might be 0.01-0.02 a kilowatt-hour for geothermal, 0.03 a kilowatt-hour for wind and hydro, 0.04 a kilowatt-hour for solar thermal and biomass, and 0.05-0.06 a kilowatt-hour for photovoltaics and marine currents. The lowest cost to produce heat might be 0.005 a kilowatt-hour for geothermal, 0.01 a kilowatt-hour for biomass, and 0.02-0.03 a kilowatt-hour for solar thermal. The lowest cost to produce fuels might be 1.5 a gigajoule for biomass, 6-7 a gigajoule for ethanol, 7-10 a gigajoule for methanol, and 6-8 a gigajoule for hydrogen.
"RENEWABLE ENERGY FACTS"
Scenarios investigating the potential of renewables reveal that they might contribute 20-50 percent of energy supplies in the second half of the 21st century. A transition to renewables-based energy systems would have to rely on:
o Successful development and diffusion of renewable energy technologies that becomes more competitive through cost reductions from technological and organizational developments.
o Political will to internalize environmental costs and other externalities that permanently increase fossil fuel prices.
o Many countries have found ways to promote renewables. As renewable energy activities grow and require more funding, the tendency in many countries is to move away from methods that let taxpayers carry the burden of promoting renewables, towards economic and regulatory methods that let energy consumers carry the burden.
Renewable energy facts
RENEWABLE ENERGY FACTS
Renewable energy sources have been important for humans since the beginning of civilization. For centuries and in many ways, biomass has been used for heating, cooking, steam raising, and power generation and hydropower and wind energy, for movement and later for electricity production. Renewable energy sources generally depend on energy flows through the Earth's ecosystem from the insolation of the sun and the geothermal energy of the Earth. One can distinguish:
" energy (plant growth driven by solar radiation).
" energy (moving air masses driven by solar energy).
" use of solar energy (as for heating and electricity production).
".
" energy (such as wave energy, marine current energy, and energy from tidal barrages).
" energy (from heat stored in rock by the natural heat flow of the Earth).
If applied in a modern way, renewable energy sources (or renewables) are considered highly responsive to overall energy policy guidelines and environmental, social, and economic goals:
" energy carriers for the production of heat, fuels, and electricity.
" access to clean energy sources.
" the use of fossil fuels, saving them for other applications and for future generations.
" the flexibility of power systems as electricity demand changes.
" pollution and emissions from conventional energy systems.
" dependency and minimizing spending on imported fuels.
Furthermore, many renewables technologies are suited to small off-grid applications, good for rural, remote areas, where energy is often crucial in human development. At the same time, such small energy systems can contribute to the local economy and create local jobs.
The natural energy flows through the Earth's ecosystem are immense, and the theoretical potential of what they can produce for human needs exceeds current energy consumption by many times.
For example, solar power plants on 1 percent of the world's desert area would generate the world's entire electricity demand today.
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