In 2008, total worldwide energy consumption was 474 exajoules (474×1018 J) with 80 to 90 percent derived from the combustion of fossil fuels. This is equivalent to an average power consumption rate of 15 terawatts (1.504×1013 W). Not all of the world's economies track their energy consumption with the same rigor, and the exact energy content of a barrel of oil or a ton of coal will vary with quality.
Most of the world's energy resources are from the sun's rays hitting earth. Some of that energy has been preserved as fossil energy, some is directly or indirectly usable; for example, via wind, hydro- or wave power. The term solar constant is the amount of incoming solar electromagnetic radiation per unit area, measured on the outer surface of Earth's atmosphere, in a plane perpendicular to the rays. The solar constant includes all types of solar radiation, not just visible light. It is measured by satellite to be roughly 1366 watts per square meter, though it fluctuates by about 6.9% during a year—from 1412 W m−2 in early January to 1321 W m−2 in early July, due to the Earth's varying distance from the sun, and by a few parts per thousand from day to day. For the whole Earth, with a cross section of 127,400,000 km2, the total energy rate is 174 petawatts (1.740×1017 W), plus or minus 3.5%. This value is the total rate of solar energy received by the planet; about half, 89 PW, reaches the Earth's surface.
The estimates of remaining non-renewable worldwide energy resources vary, with the remaining fossil fuels totaling an estimated 0.4 YJ (1 YJ = 1024J) and the available nuclear fuel such as uranium exceeding 2.5 YJ. Fossil fuels range from 0.6-3 YJ if estimates of reserves of methane clathrates are accurate and become technically extractable. Mostly thanks to the Sun, the world also has a renewable usable energy flux that exceeds 120 PW (8,000 times 2004 total usage), or 3.8 YJ/yr, dwarfing all non-renewable resources.
Fossil fuels
The twentieth century saw a rapid twentyfold increase in the use of fossil fuels. Between 1980 and 2006, the worldwide annual growth rate was 2%. According to the US Energy Information Administration's 2006 estimate, the estimated 471.8 EJ total consumption in 2004 was divided as follows, with fossil fuels supplying 86% of the world's energy:
Coal fueled the industrial revolution in the 18th and 19th century. With the advent of the automobile, airplanes and the spreading use of electricity, oil became the dominant fuel during the twentieth century. The growth of oil as the largest fossil fuel was further enabled by steadily dropping prices from 1920 until 1973. After the oil shocks of 1973 and 1979, during which the price of oil increased from 5 to 45 US dollars per barrel, there was a shift away from oil. Coal, natural gas, and nuclear became the fuels of choice for electricity generation and conservation measures increased energy efficiency. In the U.S. the average car more than doubled the number of miles per gallon. Japan, which bore the brunt of the oil shocks, made spectacular improvements and now has the highest energy efficiency in the world. From 1965 to 2008, the use of fossil fuels has continued to grow and their share of the energy supply has increased. From 2003 to 2008, coal, which is one of the dirtiest sources of energy, was the fastest growing fossil fuel.
Nuclear power
In 2005 nuclear power accounted for 6.3% of world's total primary energy supply. The nuclear power production in 2006 accounted 2,658 TWh (23.3 EJ), which was 16% of world's total electricity production. In November 2007, there were 439 operational nuclear reactors worldwide, with total capacity of 372,002 MWe. A further 33 reactors were under construction, 94 reactors were planned and 222 reactors were proposed.
Renewable energy
In 2004, renewable energy supplied around 7% of the world's energy consumption. The renewables sector has been growing significantly since the last years of the 20th century, and in 2005 the total new investment was estimated to have been 38 billion US dollars.Germany and China lead with investments of about 7 billion US dollars each, followed by theUnited States, Spain, Japan, and India. This resulted in an additional 35 GW of capacity during the year.
Hydropower
Worldwide hydroelectricity consumption reached 816 GW in 2005, consisting of 750 GW of large plants, and 66 GW of small hydro installations. Large hydro capacity totaling 10.9 GW was added by China, Brazil and India during the year, but there was a much faster growth (8%) in small hydro, with 5 GW added, mostly in China where some 58% of the world's small hydro plants are now located. In the Western world, although Canada is the largest producer of hydroelectricity in the world, the construction of large hydro plants has stagnated due to environmental concerns. The trend in both Canada and the United States has been tomicro hydro because it has negligible environmental impacts and opens up many more locations for power generation. In British Columbia alone the estimates are that micro hydro will be able to more than double electricity production in the province.
Biomass and biofuels
Until the end of the nineteenth century biomass was the predominant fuel, today it has only a small share of the overall energy supply. Electricity produced from biomass sources was estimated at 44 GW for 2005. Biomass electricity generation increased by over 100% inGermany, Hungary, the Netherlands, Poland and Spain. A further 220 GW was used for heating (in 2004), bringing the total energy consumed from biomass to around 264 GW. The use of biomass fires for cooking is excluded.
World production of bioethanol increased by 8% in 2005 to reach 33 billion litres (8.72 billionUS gallons), with most of the increase in the United States, bringing it level to the levels of consumption in Brazil. Biodiesel increased by 85% to 3.9 billion litres (1.03 billion US gallons), making it the fastest growing renewable energy source in 2005. Over 50% is produced in Germany.
Wind power
According to the World Wind Energy Association, the installed capacity of wind powerincreased by 29 % from the end of 2007 to the end of 2008 to total 121 GW, with over half the increase in the United States, Spain and China. Doubling of capacity took about three years. The total installed capacity is approximately three to eight times that of the actual average power produced as the nominal capacity represents peak output; actual capacity is generally from 13-40% of the nominal capacity.
Solar power
The available solar energy resources are 3.8 YJ/yr (120,000 TW). Less than 0.02% of available resources are sufficient to entirely replace fossil fuels and nuclear power as an energy source. Assuming that our rate of usage in 2005 remains constant, we will run out of conventional oil in 40 years (2045), coal in 154 years (2159). In practice neither will actually run out, as natural constraints will force production to decline as the remaining reserves dwindle.[24][25][26]
In 2007 grid-connected photovoltaic electricity was the fastest growing energy source, with installations of all photovoltaics increasing by 83% in 2009 to bring the total installed capacity to 15 GW. Nearly half of the increase was in Germany, which is now the world's largest consumer of photovoltaic electricity (followed by Japan). Solar cell production increased by 50% in 2007, to 3,800 megawatts, and has been doubling every two years.
The consumption of solar hot water and solar space heating was estimated at 88 GWt (gigawatts of thermal power) in 2004. The heating of water for unglazed swimming pools is excluded.
Geothermal
Geothermal energy is used commercially in over 70 countries. In the year 2004, 200 PJ (57 TWh) of electricity was generated from geothermal resources, and an additional 270 PJ of geothermal energy was used directly, mostly for space heating. In 2007, the world had a global capacity for 10 GW of electricity generation and an additional 28 GW of direct heating, including extraction by geothermal heat pumps. Heat pumps are small and widely distributed, so estimates of their total capacity are uncertain and range up to 100 GW. Heat pump capacity factors are low since demand is seasonal.
No comments:
Post a Comment