Schematic of the global sources of energy in 2006.

Energy production from 1989 to 1999

Energy development is the effort to provide sufficient primary energy sources and secondary energy forms for supply, cost, impact on air pollution and water pollution, mitigation of climate change with renewable energy.

Technologically advanced societies have become increasingly dependent on external energy sources for transportation, the production of many manufactured goods, and the delivery of energy services. This energy allows people who can afford the cost to live under otherwise unfavorable climatic conditions through the use of heating, ventilation, and/or air conditioning. Level of use of external energy sources differs across societies, as do the climate, convenience, levels of traffic congestion, pollution and availability of domestic energy sources.

[edit] Renewable sources

The wind, Sun, and biomass are three renewable energy sources

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.^[1] New renewables (small hydro, modern biomass, wind, solar, geothermal, and biofuels) accounted for another 2.7% and are growing very rapidly.^[1] The share of renewables in electricity generation is around 18%, with 15% of global electricity coming from hydroelectricity and 3% from new renewables.^[1][2]

Wind power is growing at the rate of 30% annually, with a worldwide installed capacity of 158 gigawatts (GW) in 2009,^[3][4] and is widely used in Europe, Asia, and the United States.^[5] At the end of 2009, cumulative global photovoltaic (PV) installations surpassed 21 GW^[6][7][8] and PV power stations are popular in Germany and Spain.^[9] Solar thermal power stations operate in the USA and Spain, and the largest of these is the 354 megawatt (MW) SEGS power plant in the Mojave Desert.^[10] The world's largest geothermal power installation is The Geysers in California, with a rated capacity of 750 MW. Brazil has one of the largest renewable energy programs in the world, involving production of ethanol fuel from sugar cane, and ethanol now provides 18% of the country's automotive fuel.^[11] Ethanol fuel is also widely available in the USA.

While many renewable energy projects are large-scale, renewable technologies are also suited to rural and remote areas, where energy is often crucial in human development.^[12] Globally, an estimated 3 million households get power from small solar PV systems. Micro-hydro systems configured into village-scale or county-scale mini-grids serve many areas.^[13] More than 30 million rural households get lighting and cooking from biogas made in household-scale digesters. Biomass cookstoves are used by 160 million households.^[13]

Climate change concerns, coupled with high oil prices, peak oil, and increasing government support, are driving increasing renewable energy legislation, incentives and commercialization.^[14] New government spending, regulation and policies helped the industry weather the global financial crisis better than many other sectors.^[15]

[edit] Wind

Wind power: worldwide installed capacity 1996-2008

Wind power harnesses the power of the wind to propel the blades of wind turbines. These turbines cause the rotation of magnets, which creates electricity. Wind towers are usually built together on wind farms.

At the end of 2009, worldwide wind farm capacity was 157,900 MW, representing an increase of 31 percent during the year,^[3] and wind power supplied some 1.3% of global electricity consumption.^[16] Wind power accounts for approximately 19% of electricity use in Denmark, 9% in Spain and Portugal, and 6% in Germany and the Republic of Ireland.^[17] The United States is an important growth area and installed U.S. wind power capacity reached 25,170 MW at the end of 2008.^[18] As of November 2010, the Roscoe Wind Farm (781 MW) is the world's largest wind farm.^[19]

[edit] Hydroelectric

The Gordon Dam in Tasmania is a large conventional dammed-hydro facility, with an installed capacity of up to 430 MW.

In hydro energy, the gravitational descent of a river is compressed from a long run to a single location with a dam or a flume. This creates a location where concentrated pressure and flow can be used to turn turbines or water wheels, which drive a mechanical mill or an electric generator.^[20]

In some cases with hydroelectric dams, there are unexpected results. One study shows that a hydroelectric dam in the Amazon has 3.6 times larger greenhouse effect per kW'h than electricity production from oil, due to large scale emission of methane from decaying organic material^[21], though this is most significant as river valleys are initially flooded, and are of much less consequence for more boreal dams.^[22] This effect applies in particular to dams created by simply flooding a large area, without first clearing it of vegetation. There are however investigations into underwater turbines that do not require a dam. And pumped-storage hydroelectricity can use water reservoirs at different altitudes to store wind and solar power.

[edit] Solar

The CIS Tower, Manchester, England, was clad in PV panels at a cost of –5.5 million. It started feeding electricity to the national grid in November 2005.

Solar power involves using solar cells to convert sunlight into electricity, using sunlight hitting solar thermal panels to convert sunlight to heat water or air, using sunlight hitting a parabolic mirror to heat water (producing steam), or using sunlight entering windows for passive solar heating of a building. It would be advantageous to place solar panels in the regions of highest solar radiation.^[23] In the Phoenix, Arizona area, for example, the average annual solar radiation is 5.7 kW–h/(m––day),^[24] or 2.1 MW–h/(m––yr). Electricity demand in the continental U.S. is 3.7×10¹² kW–h per year. Thus, at 20% efficiency, an area of approximately 3500 square miles (3% of Arizona's land area) would need to be covered with solar panels to replace all current electricity production in the US with solar power. The average solar radiation in the United States is 4.8 kW–h/(m––day),^[25] but reaches 8'9 kWh/m–/day in parts of the Southwest.

China is increasing worldwide silicon wafer capacity for photovoltaics to 2,000 metric tons by July 2008, and over 6,000 metric tons by the end of 2010.^[26] Significant international investment capital is flowing into China to support this opportunity. China is building large subsidized off-the-grid solar-powered cities in Huangbaiyu and Dongtan Eco City. Much of the design was done by Americans such as William McDonough.^[27]

[edit] Biomass, agricultural

Sugar cane residue can be used as a biofuel

Main articles: Alcohol fuel, Biomass, Vegetable oil economy, vegetable oil as fuel, biodiesel, Ethanol fuel

Biomass production involves using garbage or other renewable resources such as corn or other vegetation to generate electricity. When garbage decomposes, the methane produced is captured in pipes and later burned to produce electricity. Vegetation and wood can be burned directly to generate energy, like fossil fuels, or processed to form alcohols.

Vegetable oil is generated from sunlight, H₂O, and CO₂ by plants. It is safer to use and store than gasoline or diesel as it has a higher flash point. Straight vegetable oil works in diesel engines if it is heated first. Vegetable oil can also be transesterified to make biodiesel, which burns like normal diesel.

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[edit] Geothermal

Geothermal energy harnesses the heat energy present underneath the Earth. Two wells are drilled. One well injects water into the ground to provide water. The hot rocks heat the water to produce steam. The steam that shoots back up the other hole(s) is purified and is used to drive turbines, which power electric generators. When the water temperature is below the boiling point of water a binary system is used. A low boiling point liquid is used to drive a turbine and generator in a closed system similar to a refrigeration unit running in reverse. There are also natural sources of geothermal ennergy some can come from volcanoes, geysers, hot springs, and steam vents. ^[28]

[edit] Tidal

Tidal power can be extracted from Moon-gravity-powered tides by locating a water turbine in a tidal current, or by building impoundment pond dams that admit-or-release water through a turbine. The turbine can turn an electrical generator, or a gas compressor, that can then store energy until needed. Coastal tides are a source of clean, free, renewable, and sustainable energy.^[29]

[edit] Fossil fuels

The Moss Landing Power Plant burns natural gas to produce electricity in California.

Gas flare from an oil refinery.

Fossil fuels sources burn coal or hydrocarbon fuels, which are the remains of the decomposition of plants and animals. There are three main types of fossil fuels: coal, petroleum, and natural gas. Another fossil fuel, liquefied petroleum gas (LPG), is principally derived from the production of natural gas. Heat from burning fossil fuel is used either directly for space heating and process heating, or converted to mechanical energy for vehicles, industrial processes, or electrical power generation.

Greenhouse gas emissions result from fossil fuel-based electricity generation. Currently governments subsidize fossil fuels by an estimated $500 billion a year.^[30]

[edit] Nuclear

Diablo Canyon Power Plant Nuclear power station.

The status of nuclear power globally:
     Operating reactors, building new reactors
     Operating reactors, planning new build
     No reactors, building new reactors
     No reactors, planning new build
     Operating reactors, stable
     Operating reactors, considering phase-out
     Civil nuclear power is illegal
     No reactors

[edit] Fission

Nuclear power stations use nuclear fission to generate energy by the reaction of uranium-235 inside a nuclear reactor. The reactor uses uranium rods, the atoms of which are split in the process of fission, releasing a large amount of energy. The process continues as a chain reaction with other nuclei. The energy heats water to create steam, which spins a turbine generator, producing electricity.

Depending on the type of fission fuel considered, estimates for existing supply at known usage rates varies from several decades for the currently popular Uranium-235 to thousands of years for uranium-238. At the present rate of use, there are (as of 2007) about 70 years left of known uranium-235 reserves economically recoverable at a uranium price of US$ 130/kg.^[31] The nuclear industry argue that the cost of fuel is a minor cost factor for fission power, more expensive, more difficult to extract sources of uranium could be used in the future, such as lower-grade ores, and if prices increased enough, from sources such as granite and seawater.^[31] Increasing the price of uranium would have little effect on the overall cost of nuclear power; a doubling in the cost of natural uranium would increase the total cost of nuclear power by 5 percent. On the other hand, if the price of natural gas was doubled, the cost of gas-fired power would increase by about 60 percent.^[32]

Opponents on the other hand argue that the correlation between price and production is not linear, but as the ores' concentration becomes smaller, the difficulty (energy and resource consumption are increasing, while the yields are decreasing) of extraction rises very fast, and that the assertion that a higher price will yield more uranium is overly optimistic; for example a rough estimate predicts that the extraction of uranium from granite will consume at least 70 times more energy than what it will produce in a reactor. As many as eleven countries have depleted their uranium resources, and only Canada has mines left which produce better than 1% concentration ore.^[33] Seawater seems to be equally dubious as a source.^[34]

Another alternative could be to use thorium as fission fuel. Thorium is three times more abundant in Earth's crust than uranium,^[35] and much more of the thorium can be used (or, more precisely, bred into Uranium-233, reprocessed and then used as fuel). India has around 32 percent of the world's reserves of thorium and intends on using it for itself because the country has run out of uranium.^{[36] [37]}

Current light water reactors burn the nuclear fuel poorly, leading to energy waste. Nuclear reprocessing^[38] or burning the fuel better using different reactor designs would reduce the amount of waste material generated and allow better use of the available resources. As opposed to current light water reactors which use uranium-235 (0.7 percent of all natural uranium), breeder reactors convert the more abundant uranium-238 (99.3 percent of all natural uranium) into plutonium for fuel. It has been estimated that there is anywhere from 10,000 to five billion years worth of Uranium-238 for use in these power plants.^[39] Fast breeder technology has been used in several reactors. However, the fast breeder reactors at Dounreay in Scotland, Monju in Japan and the Superphénix at Creys-Malville in France, in particular, have all had difficulties and were not economically competitive and most have been decommissioned. The People's Republic of China intends to build breeders.^[40] India has run out of uranium and is building thermal breeders that can convert Th-232 into U-233 and burn it.^[36]

The possibility of nuclear meltdowns and other reactor accidents, such as the Three Mile Island accident and the Chernobyl disaster, have caused much public fear. Research is being done to lessen the known problems of current reactor technology by developing automated and passively safe reactors. Historically, however, coal and hydropower power generation have both been the cause of more deaths per energy unit produced than nuclear power generation.^[41][42] Various kinds of energy infrastructure might be attacked by terrorists, including nuclear power plants, hydropower plants, and liquified natural gas tankers. Nuclear proliferation is the spread from nation to nation of nuclear technology, including nuclear power plants but especially nuclear weapons. New technology like SSTAR ("small, sealed, transportable, autonomous reactor") may lessen this risk.

The long-term radioactive waste storage problems of nuclear power have not been fully solved. Several countries have considered using underground repositories. Nuclear waste takes up little space compared to wastes from the chemical industry which remain toxic indefinitely.^[38] Spent fuel rods are now stored in concrete casks close to the nuclear reactors.^[43] The amounts of waste could be reduced in several ways. Both nuclear reprocessing and breeder reactors could reduce the amounts of waste. Subcritical reactors or fusion reactors could greatly reduce the time the waste has to be stored.^[44] Subcritical reactors may also be able to do the same to already existing waste. The only long-term way of dealing with waste today is by geological storage.

Depending on the source different energy return on energy investment (EROI) are claimed. Advocates (using life cycle analysis) argue that it takes 4'5 months of energy production from the nuclear plant to fully pay back the initial energy investment.^[45] Opponents claim that it depends on the grades of the ores the fuel came from, so a full payback can vary from 10 to 18 years, and that the advocates' claim was based on the assumption of high grade ores (the yields are getting worse, as the ores are leaner; for less than 0.02% ores, the yield is less than 50%).^[46]

Advocates also claim that it is possible to increase the number of plants fairly rapidly. Typical new reactor designs have a construction time of three to four years.^[47] In 1983, 43 plants were being built, before an unexpected fall in fossil fuel prices stopped most new construction. Developing countries like India and China are rapidly increasing their nuclear energy use.^[48][49] However, a Council on Foreign Relations report on nuclear energy argues that a rapid expansion of nuclear power may create shortages in building materials such as reactor-quality concrete and steel, skilled workers and engineers, and safety controls by skilled inspectors. This would drive up current prices.^[50]

However, at present, nuclear energy is in decline, according to a report 'World Nuclear Industry Status Report 2007' presented by the Greens/EFA group in the European Parliament. The report outlines that the proportion of nuclear energy in power production has decreased in 21 out of 31 countries, with five fewer functioning nuclear reactors than five years ago. There are currently 32 nuclear power plants under construction or in the pipeline, 20 fewer than at the end of the 1990s.^[51][52]

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[edit] Fusion

Fusion power could solve many of the problems of fission power (the technology mentioned above) but, despite research having started in the 1950s, no commercial fusion reactor is expected before 2050.^[53] Many technical problems remain unsolved. Proposed fusion reactors commonly use deuterium, an isotope of hydrogen, as fuel and in most current designs also lithium. Assuming a fusion energy output equal to the current global output and that this does not increase in the future, then the known current lithium reserves would last 3000 years, lithium from sea water would last 60 million years, and a more complicated fusion process using only deuterium from sea water would have fuel for 150 billion years.^[54]

[edit] Cost by source

The following graph does not include the external, weather-related costs of using fossil fuels.

Large energy subsidies are present in many countries (Barker et al., 2001:567-568).^[55] Currently governments subsidize fossil fuels by $557 billion per year.^[56][30] Economic theory indicates that the optimal policy would be to remove coal mining and burning subsidies and replace them with optimal taxes. Global studies indicate that even without introducing taxes, subsidy and trade barrier removal at a sectoral level would improve efficiency and reduce environmental damage. Removal of these subsidies would substantially reduce GHG emissions and stimulate economic growth.

[edit] Increased energy efficiency

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Energy efficiency is increasing by about 2% a year, and absorbs most of the requirements for energy development. New technology makes better use of already available energy through improved efficiency, such as more efficient fluorescent lamps, engines, and insulation. Using heat exchangers, it is possible to recover some of the energy in waste warm water and air, for example to preheat incoming fresh water. Hydrocarbon fuel production from pyrolysis could also be in this category, allowing recovery of some of the energy in hydrocarbon waste. Already existing power plants often can and usually are made more efficient with minor modifications due to new technology. New power plants may become more efficient with technology like cogeneration. New designs for buildings may incorporate techniques like passive solar. Light-emitting diodes are gradually replacing the remaining uses of light bulbs. Note that none of these methods allows perpetual motion, as some energy is always lost to heat.

Mass transportation increases energy efficiency compared to widespread conventional automobile use while air travel is regarded as inefficient. Conventional combustion engine automobiles have continually improved their efficiency and may continue to do so in the future, for example by reducing weight with new materials. Hybrid vehicles can save energy by allowing the engine to run more efficiently, regaining energy from braking, turning off the motor when idling in traffic, etc. More efficient ceramic or diesel engines can improve mileage. Electric vehicles such as Maglev, trolleybuses, and PHEVs are more efficient during use (but maybe not if doing a life cycle analysis) than similar current combustion based vehicles, reducing their energy consumption during use by 1/2 to 1/4. Microcars or motorcycles may replace automobiles carrying only one or two people. Transportation efficiency may also be improved by in other ways, see automated highway system.

Electricity distribution may change in the future. New small scale energy sources may be placed closer to the consumers so that less energy is lost during electricity distribution. New technology like superconductivity or improved power factor correction may also decrease the energy lost. Distributed generation permits electricity "consumers," who are generating electricity for their own needs, to send their surplus electrical power back into the power grid.

[edit] Transmission

An elevated section of the Alaska Pipeline.

While new sources of energy are only rarely discovered or made possible by new technology, distribution technology continually evolves.^[57] The use of fuel cells in cars, for example, is an anticipated delivery technology.^{[citation needed]} This section presents some of the more common delivery technologies that have been important to historic energy development. They all rely in some way on the energy sources listed in the previous section.

[edit] Water

This section requires expansion.

[edit] Fossil fuels

Shipping is a flexible delivery technology that is used in the whole range of energy development regimes from primitive to highly advanced. Currently, coal, petroleum and their derivatives are delivered by shipping via boat, rail, or road. Petroleum and natural gas may also be delivered via pipeline and coal via a Slurry pipeline. Refined hydrocarbon fuels such as gasoline and LPG may also be delivered via aircraft. Natural gas pipelines must maintain a certain minimum pressure to function correctly. Ethanol's corrosive properties prevent it from being transported via pipeline. The higher costs of ethanol transportation and storage are often prohibitive.^[58]

[edit] Electricity

Electric Grid: Pilons and cables distribute power

Electricity grids are the networks used to transmit and distribute power from production source to end user, when the two may be hundreds of kilometres away. Sources include electrical generation plants such as a nuclear reactor, coal burning power plant, etc. A combination of sub-stations, transformers, towers, cables, and piping are used to maintain a constant flow of electricity. Grids may suffer from transient blackouts and brownouts, often due to weather damage. During certain extreme space weather events solar wind can interfere with transmissions. Grids also have a predefined carrying capacity or load that cannot safely be exceeded. When power requirements exceed what's available, failures are inevitable. To prevent problems, power is then rationed.

Industrialised countries such as Canada, the US, and Australia are among the highest per capita consumers of electricity in the world, which is possible thanks to a widespread electrical distribution network. The US grid is one of the most advanced, although infrastructure maintenance is becoming a problem. CurrentEnergy provides a realtime overview of the electricity supply and demand for California, Texas, and the Northeast of the US. African countries with small scale electrical grids have a correspondingly low annual per capita usage of electricity. One of the most powerful power grids in the world supplies power to the state of Queensland, Australia.

[edit] Storage

Methods of energy storage have been developed, which transform electrical energy into forms of potential energy. A method of energy storage may be chosen on the basis of stability, ease of transport, ease of energy release, or ease of converting free energy from the natural form to the stable form.

[edit] Chemical

Some natural forms of energy are found in stable chemical compounds such as fossil fuels. Most systems of chemical energy storage result from biological activity, which store energy in chemical bonds. Man-made forms of chemical energy storage include hydrogen fuel, synthetic hydrocarbon fuel, batteries and explosives such as cordite and dynamite.

[edit] Gravitational and hydroelectric

Dams can be used to store energy, by using pumped-storage hydroelectricity, excess energy to pump water into the reservoir. When electrical energy is required, the process is reversed. The water then turns a turbine, generating electricity. Hydroelectric power is currently an important part of the world's energy supply, generating one-fifth of the world's electricity.^[59]

[edit] Thermal

There are several technologies to store heat. Thermal energy from the sun, for example, can be stored in a reservoir or in the ground for daily or seasonal use. Thermal energy for cooling can be stored in ice.^[60]

[edit] Mechanical pressure

Energy may also be stored pressurized gases or alternatively in a vacuum. Compressed air, for example, may be used to operate vehicles and power tools. Large-scale compressed air energy storage facilities are used to smooth out demands on electricity generation by providing energy during peak hours and storing energy during off-peak hours. Such systems save on expensive generating capacity since it only needs to meet average consumption rather than peak consumption.^[61]

[edit] Electrical capacitance

Electrical energy may be stored in capacitors. Capacitors are often used to produce high intensity releases of energy (such as a camera's flash).

[edit] Hydrogen

Hydrogen can be manufactured at roughly 77 percent thermal efficiency by the method of steam reforming of natural gas.^[62] When manufactured by this method it is a derivative fuel like gasoline; when produced by electrolysis of water, it is a form of chemical energy storage as are storage batteries, though hydrogen is the more versatile storage mode since there are two options for its conversion to useful work: (1) a fuel cell can convert the chemicals hydrogen and oxygen into water, and in the process, produce electricity, or (2) hydrogen can be burned (less efficiently than in a fuel cell) in an internal combustion engine.

[edit] Vehicles

Energy flow in the U.S., 2008

[edit] Fossil fuels

Petroleum and natural gas is used to power most transportation.

[edit] Batteries

Main articles: battery, battery electric vehicle

Batteries are used to store energy in a chemical form. As an alternative energy, batteries can be used to store energy in battery electric vehicles. Battery electric vehicles can be charged from the grid when the vehicle is not in use. Because the energy is derived from electricity, battery electric vehicles make it possible to use other forms of alternative energy such as wind, solar, geothermal, nuclear, or hydroelectric.

[edit] Compressed air

Main articles: Compressed air vehicle, Air car

The Indian company, Tata, is planning to release a compressed air powered car in 2008.

[edit] Sustainability

Energy consumption from 1989 to 1999

The environmental movement emphasizes sustainability of energy use and development. Renewable energy is sustainable in its production; the available supply will not be diminished for the foreseeable future - millions or billions of years. "Sustainability" also refers to the ability of the environment to cope with waste products, especially air pollution. Sources which have no direct waste products (such as wind, solar, and hydropower) are seen as ideal in this regard.

Fossil fuels such as petroleum, coal, and natural gas are not renewable. For example, the timing of worldwide peak oil production is being actively debated but it has already happened in some countries. Fossil fuels also make up the bulk of the world's current primary energy sources. With global demand for energy growing, the need to adopt alternative energy sources is also growing. Fossil fuels are also a major source of greenhouse gas emissions, leading to concerns about global warming if consumption is not reduced.

Energy conservation is an alternative or complementary process to energy development. It reduces the demand for energy by using it more efficiently.

[edit] Resilience

Energy consumption per capita (2001). Red hues indicate increase, green hues decrease of consumption during the 1990s.

Some observers contend that the much talked about idea of 'energy independence' is an unrealistic and opaque concept. They offer 'energy resilience' as a more sensible goal and more aligned with economic, security and energy realities. The notion of resilience in energy was detailed in the 1982 book Brittle Power: Energy Strategy for National Security.^[63] The authors argued that simply switching to domestic energy would be no more secure inherently because the true weakness is the interdependent and vulnerable energy infrastructure of the United States. Key aspects such as gas lines and the electrical power grid are centralized and easily susceptible to major disruption. They conclude that a 'resilient energy supply' is necessary for both national security and the environment. They recommend a focus on energy efficiency and renewable energy that is more decentralized.^[64]

More recently former Intel Corporation Chairman and CEO Andrew Grove has touted energy resilience, arguing that complete independence is infeasible given the global market for energy.^[65] He describes energy resilience as the ability to adjust to interruptions in the supply of energy. To this end he suggests the U.S. make greater use of electricity.^[66] Electricity can be produced from a variety of sources. A diverse energy supply will be less impacted by the disruption in supply of any one source. He reasons that another feature of electrification is that electricity is 'sticky' ' meaning the electricity produced in the U.S. is more likely to stay there because it cannot be transported overseas. According to Grove, a key aspect of advancing electrification and energy resilience will be converting the U.S. automotive fleet from gasoline-powered to electric-powered. This, in turn, will require the modernization and expansion of the electrical power grid. As organizations such as the Reform Institute have pointed out, advancements associated with the developing smart grid would facilitate the ability of the grid to absorb vehicles en masse connecting to it to charge their batteries.^[67]

[edit] Future

World energy consumption.

An increasing share of world energy consumption is predicted to be used by developing nations. Source: EIA.

Extrapolations from current knowledge to the future offer a choice of energy futures.^[68] Some predictions parallel the Malthusian catastrophe hypothesis. Numerous are complex models based scenarios as pioneered by Limits to Growth. Modeling approaches offer ways to analyze diverse strategies, and hopefully find a road to rapid and sustainable development of humanity. Short term energy crises are also a concern of energy development. Some extrapolations lack plausibility, particularly when they predict a continual increase in oil consumption.

Energy production usually requires an energy investment. Drilling for oil or building a wind power plant requires energy. The fossil fuel resources (see above) that are left are often increasingly difficult to extract and convert. They may thus require increasingly higher energy investments. If the investment is greater than the energy produced, then the fossil resource is no longer an energy source. This means that a large part of the fossil fuel resources and especially the non-conventional ones cannot be used for energy production today. Such resources may still be exploited economically in order to produce raw materials for plastics, fertilizers or even transportation fuel but now more energy is consumed than produced. (They then become similar to ordinary mining reserves, economically recoverable but not net positive energy sources.) New technology may ameliorate this problem if it can lower the energy investment required to extract and convert the resources, although ultimately basic physics sets limits that cannot be exceeded.

Between 1950 and 1984, as the Green Revolution transformed agriculture around the globe, world grain production increased by 250%. The energy for the Green Revolution was provided by fossil fuels in the form of fertilizers (natural gas), pesticides (oil), and hydrocarbon fueled irrigation.^[69] The peaking of world hydrocarbon production (peak oil) may lead to significant changes, and require sustainable methods of production.^[70]

[edit] History of predictions

Ever since the beginning of the Industrial Revolution, the question of the future of energy supplies has occupied economists.

• 1865 ' William Stanley Jevons published The Coal Question in which he claimed that reserves of coal would soon be exhausted and that there was no prospect of oil being an effective replacement.
• 1885 ' U.S. Geological Survey: Little or no chance of oil in California.
• 1891 ' U.S. Geological Survey: Little or no chance of oil in Kansas or Texas.
• 1914 ' U.S. Bureau of Mines: Total future production of 5.7 billion barrels (910,000,000 m³).
• 1939 ' U.S. Department of the Interior: Reserves to last only 13 years.
• 1951 ' U.S. Department of the Interior, Oil and Gas Division: Reserves to last 13 years.

(Data from Kahn et al. (1976) pp. 94'5 infra)

• 1956 ' Geophysicist M. King Hubbert predicts U.S. oil production will peak between 1965 and 1970 (peaked in 1971). Also predicts world oil production will peak "within half a century" on the basis of 1956 data. This is Hubbert peak theory.
• 1989 ' Predicted peak by Colin Campbell ("Oil Price Leap in the Early Nineties," Noroil, December 1989, pages 35'38.)
• 2004 ' OPEC estimates it will nearly double oil output by 2025 (Opec Oil Outlook to 2025 Table 4, Page 12)rashi

The history of perpetual motion machines is a long list of failed and sometimes fraudulent inventions of machines which produce useful energy "from nowhere" ' that is, without requiring any energy input.

[edit] See also

	Sustainable development portal
	Energy portal

[edit] References

[edit] Sources

• Serra, J. "Alternative Fuel Resource Development", Clean and Green Fuels Fund, (2006).
• Bilgen, S. and K. Kaygusuz, Renewable Energy for a Clean and Sustainable Future, Energy Sources 26, 1119 (2004).
• Energy analysis of Power Systems, UIC Nuclear Issues Briefing Paper 57 (2004).
• Silvestre, B. S., Dalcol, P. R. T. Geographical proximity and innovation: Evidences from the Campos Basin oil & gas industrial agglomeration ' Brazil. Technovation (2009), doi:10.1016/j.technovation.2009.01.003

[edit] Journals

• Energy Sources, Part A: Recovery, Utilization and Environmental Effects
• Energy Sources, Part B: Economics, Planning and Policy
• International Journal of Green Energy

[edit] External links

• Hidden Health and Environmental Costs Of Energy Production and Consumption In U.S.
• RECaBS REcalculator Interactive Renewable Energy Calculator ' compare renewable energy to conventional energy sources