| Resource extraction and consumption · Pollution · Renewable energy |
Renewable energy is Energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable (naturally replenished). In 2008, about 19% of global final energy consumption came from renewables, with 13% coming from traditional biomass, which is mainly used for heating, and 3.2% from hydroelectricity. The share of renewables in electricity generation is around 18%, with 15% of global electricity coming from hydroelectricity and 3% from new renewables.
Renewable energy flows involve natural phenomena such as sunlight, wind, tides, plant growth, and geothermal heat, as the International Energy Agency explains:
Renewable energy is derived from natural processes that are replenished constantly. In its various forms, it derives directly from the sun, or from heat generated deep within the earth. Included in the definition is electricity and heat generated from solar, wind, ocean, hydropower, biomass, geothermal resources, and biofuels and hydrogen derived from renewable resources.
Renewable energy uses
Renewable energy replaces conventional fuels in four distinct areas: power generation, hot water/ space heating, transport fuels, and rural (off-grid) energy services:
- Power generation. Renewable energy provides 18 percent of total electricity generation worldwide. Renewable power generators are spread across many countries, and wind power alone already provides a significant share of electricity in some areas: for example, 14 percent in the U.S. state of Iowa, 40 percent in the northern German state of Schleswig-Holstein, and 20 percent in Denmark. Some countries get most of their power from renewables, including Iceland (100 percent), Brazil (85 percent), Austria (62 percent), New Zealand (65 percent), and Sweden (54 percent).
- Heating. Solar hot water makes an important contribution in many countries, most notably in China, which now has 70 percent of the global total (180 GWth). Most of these systems are installed on multi-family apartment buildings and meet a portion of the hot water needs of an estimated 50–60 million households in China. Worldwide, total installed solar water heating systems meet a portion of the water heating needs of over 70 million households. The use of biomass for heating continues to grow as well. In Sweden, national use of biomass energy has surpassed that of oil. Direct geothermal for heating is also growing rapidly.
- Transport fuels. Renewable biofuels have contributed to a significant decline in oil consumption in the United States since 2006. The 93 billion liters of biofuels produced worldwide in 2009 displaced the equivalent of an estimated 68 billion liters of gasoline, equal to about 5 percent of world gasoline production.
Mainstream forms of renewable energy
Wind, hydro, solar, biomass, and biofuel are the mainstream forms of renewable energy.
Airflows can be used to run wind turbines, which generate electricity. Areas where winds are stronger and more constant, such as offshore and high altitude sites, are preferred locations for wind farms.
Globally, the long-term technical potential of wind energy is believed to be five times total current global energy production, or 40 times current electricity demand. This could require wind turbines to be installed over large areas, particularly in areas of higher wind resources. Offshore resources experience mean wind speeds of ~90% greater than that of land, so offshore resources could contribute substantially more energy.
Since water is about 800 times denser than air, even a slow flowing stream of water, or moderate sea swell, can yield considerable amounts of energy.
The most popular forms of water energy production are: Hydroelectric dams, micro hydro systems, damless kinetic energy hydro systems, and ocean energy (technologies that harness energy from marine currents and tides.
Solar energy is the energy derived from the sun through the form of solar radiation. Solar powered electrical generation relies on photovoltaics and heat engines. A partial list of other solar applications includes space heating and cooling through solar architecture, daylighting, solar hot water, solar cooking, and high temperature process heat for industrial purposes.
Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.
Biomass (plant material) is a renewable energy source because the energy it contains comes from the sun. Through the process of photosynthesis, plants capture the sun's energy. When the plants are burned, they release the sun's energy they contain. In this way, biomass functions as a sort of natural battery for storing solar energy. As long as biomass is produced sustainably, with only as much used as is grown, the battery will last indefinitely.
In general there are two main approaches to using plants for energy production: growing plants specifically for energy use, and using the residues from plants that are used for other things. The best approaches vary from region to region according to climate, soils and geography.
Liquid biofuel is usually either bioalcohol such as bioethanol or an oil such as biodiesel.
Bioethanol is an alcohol made by fermenting the sugar components of plant materials and it is made mostly from sugar and starch crops. With advanced technology being developed, cellulosic biomass, such as trees and grasses, are also used as feedstocks for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the USA and in Brazil.
Biodiesel is made from vegetable oils, animal fats or recycled greases. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles. Biodiesel is produced from oils or fats using transesterification and is the most common biofuel in Europe.
Biofuels provided 1.8% of the world's transport fuel in 2008.
The major advantage of biofuels emerges from their minor impact on the carbon cycle in nature. While fossil fuels add carbon to the carbon cycle, biofuels recycle the carbon via the path of plants - biofuel - atmospheric carbon dioxide - plants.
Geothermal energy is energy obtained by tapping the heat of the earth itself, both from kilometers deep into the Earth's crust in volcanically active locations of the globe or from shallow depths, as in geothermal heat pumps in most locations of the planet. It is expensive to build a power station but operating costs are low resulting in low energy costs for suitable sites. Ultimately, this energy derives from heat in the Earth's core.
- Event:7th Southeast European Congress on Energy Efficiency and Renewable Energy
- Event:International Trade Fair for Renewable Energy
- Event:Clean Energy World 2011
- Event:Measuring Sustainable Development in the Energy Sector Between Weak and Strong Sustainability
- Event: ASEAN Australian Engineering Congress 2011 (AAEC 2011)
- Event: Hybrid Wind/PV/Systems_and_Micro_Grids_Fundamentals_-_extended
- ↑ 1.0 1.1 REN21. Renewables 2010 Global Status Report. Paris: REN21, 2010.
- ↑ IEA Renewable Energy Working Party. Renewable Energy into the Mainstream. PDF, Sittard: Novem, 2002.
- ↑ Archer, Cristina, and Mark Jacobson. “Evaluation of global wind power.” Journal of Geophysical Research - Atmospheres, 2005.
- ↑ Richard Shelquist (18 October 2005). "Density Altitude Calculator". http://wahiduddin.net/calc/calc_da_m.htm. Retrieved 2010-09-17.
- ↑ Union of Concerned Scientists How Biomass Eneregy Works 2010. Retrieved on 12 February, 2011 from: http://www.ucsusa.org/clean_energy/technology_and_impacts/energy_technologies/how-biomass-energy-works.html
- ↑ "Towards Sustainable Production and Use of Resources: Assessing Biofuels". United Nations Environment Programme. 2009-10-16. http://www.unep.fr/scp/rpanel/pdf/Assessing_Biofuels_Full_Report.pdf. Retrieved 2011-02-11.