| Future energy development faces great challenges due to an
increasing world population, demands for higher standards of living, demands for less pollution and a much discussed end to fossil fuels. Failure would result in overpopulation and a Malthusian
catastrophe.
General considerations
All the energy we consume is generated by using the four fundamental forces of nature: Gravity, electromagnetism, the weak nuclear force and the strong
nuclear force to create work. Fission energy and fusion energy
are generated by the strong nuclear force. Many renewables and fossil fuel energy comes from solar energy which comes from fusion
energy. Radioactive decay energy is generated by the weak nuclear force. Tidal energy comes from the gravity energy of the
Earth/Moon system.
Most human energy sources today use energy from sunlight, either directly like solar cells or in stored forms like fossil fuels. The
exceptions are nuclear power, geothermal power and tidal power. Once the stored
forms are used up (assuming no contribution from the three previous energy sources and no energy from space exploration) then the
long-term energy usage of humanity is limited to that from the sunlight falling on earth. The total energy consumption of
humanity today is equivalent to about 0.1-0.01% of that. But humanity cannot exploit most of this energy since it also provides
the energy for almost all other lifeforms and drives the weather cycle [1] (http://www.aims.ac.za/~mackay/oomm.html)[2] (http://www.world-builders.org/lessons/less/biomes/SunEnergy.html).
World energy production by source: Oil 40%, natural gas 22.5%, coal 23.3%, nuclear 6.5%, hydroelectric 7.0%, biomass and other
0.7% [3] (http://energy.cr.usgs.gov/energy/stats_ctry/Stat1.html). In the U.S., transportation
accounted for 28% of all energy use and 70% of petroleum use in 2001; 97% of transportation fuel was petroleum [4] (http://www.spe.org/spe/jpt/jsp/jptmonthlysection/0,2440,1104_11038_1040074_1202151,00.html).
The United Nations projects that world population will stabilize in 2075 at nine billion due to the demographic transition. Birth rates are now falling in most
developing nations and the population would decrease in several developed nations if there was no immigration [5] (http://www.un.org/esa/population/unpop.htm). Still, economic growth probably requires a continued increase in energy consumption.
The Kardashev scale theory is a general method of classifying how
technologically advanced a civilization is, based on the amount of usable energy a civilization has at its disposal.
Fossil fuels
Fossil fuels supply most of the energy consumed today. But fossil fuels
have great problems with pollution, including contributing to global warming and mainly coal causing tens of thousands of deaths each year in
the US alone. [6] (http://www.twnside.org.sg/title/plant.htm) They are also finite. See Hubbert peak for a discussion about the peaking of oil and other fossil fuels.
Energy production usually requires an energy investment. Drilling for oil or
building a wind power plant requires energy. The fossil fuel reserves that are left are often increasingly more 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 reserve is no longer an energy source. This means that a large part of the fossil fuel reserves and
especially the non-conventional ones cannot be used for energy production today. Such reserves may still be exploited in order to
produce raw materials for plastics, fertilizers or even transportation fuel but now more energy is consumed than produced. New technology may
ameliorate this problem if it can lower the energy investment required to extract and convert the reserves.
Oil
Conventional oil
Main article: Hubbert peak
The pessimists predict that conventional oil production will peak in 2007. There are many other predictions, one example is
that the world conventional oil production will peak somewhere between 2020 and 2050, but that the output is likely to increase
at a substantially slower rate after 2020 (Greene, 2003).
Non-conventional oil
Main article: Non-conventional oil
Non-conventional types of production include: tar sands, oil shale and bitumen. These reserves are
estimated to contain three times as much oil as the remaining conventional oil reserves but few are economically recoverable with
current technology [7] (http://www.btinternet.com/~nlpwessex/Documents/DeutscheBankOil.htm).
Oil can also be produced by thermal depolymerization
(TDP) from organic wastes, and by the the conversion of coal or natural gas to liquid hydrocarbon through the Fischer-Tropsch process.
Natural gas
Conventional natural gas
The turning point for conventional natural gas will probably be somewhat
later than for oil [8] (http://www.btinternet.com/~nlpwessex/Documents/DeutscheBankOil.htm). The pessimists predict a
peak for conventional gas production between 2010 and 2020.
Non-conventional natural gas
There are large unconventional gas resources, like methane hydrate
or geopressurized zones, that could increase the amount of gas by a factor of ten or more, if recoverable [9] (http://www.naturalgas.org/overview/unconvent_ng_resource.asp)[10] (http://www.naturalgas.org/overview/resources.asp).
Vast quantities of methane hydrate are inferred from the actual finds. Methane hydrate is a clathrate,a crystaline form in which methane molecule is trapped. The form is stable at low temperature and high pressure, conditions that exist at
ocean depth of 500 meters or more, or under permafrost. Inferred quantities of
methane hydrates exceed those of all other fossil fuels combined, including oil, conventional natural gas and coal IEA WEO 2001, pdf, p.395 (http://www.iea.org/textbase/nppdf/free/2000/weo2001.pdf). Technology for extracting methane
gas from the hydrate deposits in commercial quantities has not yet been developed. A research and development project (http://www.mh21japan.gr.jp/english/mh21/02keii.html) in Japan is targeting commercial-scale technology by 2016.
There are several companies developing the Fischer-Tropsch process to enable practical exploitation of so-called stranded gas reserves.
Coal
There are large but finite coal reserves which may increasingly be used as a fuel source
during oil depletion. There are 200 years of proven reserves of coal at the current consumption. Reserves have increased by over
50% in the last 22 years and are expected to continue to increase [11] (http://wci.rmid.co.uk/uploads/RoleofCoal.pdf). Coal is traditionally viewed as one of the
most polluting fuels although this may change with new ways of burning it and cleaning up the exhaust.
Nuclear power
Main article: Nuclear power
The United States would require at least an elevenfold increase in nuclear
power production to replace current fossil fuel use for stationary power generation and transportation all by itself. Nuclear
power may produce hydrogen at a low cost. This hydrogen may be used for enriching hydrogen poor hydrocarbon fuels or precursors
(heavy oil, tar sands, coal, etc) that exist on North American soil.
At the present use rate, there are 50 years left of low cost known uranium reserves [12] (http://www.world-nuclear.org/info/inf75.htm). Given that the cost of fuel is a minor cost
factor for fission power, more expensive, lower grade, sources of uranium could be used in the future. For example: extraction
from seawater or granite. Another alternative would be to use thorium as fission
fuel. Thorium is three times more abundant in the Earth crust than uranium [13] (http://www.world-nuclear.org/info/inf62.htm).
Current light water reactors burn the nuclear fuel poorly, leading to energy waste.
Nuclear reprocessing [14] (http://www.world-nuclear.org/info/inf04.htm), or burning the fuel better using different
reactor designs would reduce the amount of waste material generated and allow better use the available resources. As opposed to
current light water reactors which burn Uranium-235, fast breeder reactors produce Plutonium 239 from Uranium-238, and then fission that to
produce electricity and thermal heat. 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 [15] (http://www-formal.stanford.edu/jmc/progress/cohen.html). Breeder technology has been used in
several reactors [16] (http://www.world-nuclear.org/info/inf08.htm).
The possibility of reactor accidents, like the Three Mile
Island and Chernobyl meltdowns, 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.
Coal and hydropower has caused many more deaths per energy unit produced than nuclear [17] (http://www.world-nuclear.org/info/inf06.htm). 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.
The long-term radioactive waste storage problems of nuclear
power have not been fully solved. Several countries have considered using underground repositories. U.S nuclear waste from
various locations is planned to be entombed inside Yucca Mountain,
Nevada. Nuclear waste takes up little space compared to wastes from the chemical industry which remain toxic indefinitely
[18] (http://www.world-nuclear.org/info/inf04.htm). In the future, fusion or ADS systems could
eliminate waste [19] (http://www.world-nuclear.org/info/inf35.htm). In the meantime, spent fuel rods are stored in
concrete casks close to the nuclear reactors [20] (http://www.wired.com/wired/archive/13.02/nuclear.html).
Advocates of nuclear power point out that it is a cost competitive way to produce energy versus fossil fuels, especially if
you take into account fossil fuel externalities, the same way nuclear
reactors have to pay for their pollution and plant decommissioning costs [21] (http://www.world-nuclear.org/info/inf02.htm). Using life cycle analysis, it takes 4-5 months
of energy production from the nuclear plant to fully pay back the initial energy investment. Nuclear energy gives more energy per
input energy than many other energy sources. If energy becomes scarce, this could be important [22] (http://www.world-nuclear.org/info/inf11.htm). It is possible to relatively rapidly increase
the number of plants. New reactor designs have a construction time of 3-4 years.[23] (http://www.uic.com.au/nip16.htm). 43 plants were being built in 1983, 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 [24] (http://www.wired.com/wired/archive/12.09/china.html)[25] (http://www.world-nuclear.org/info/inf17.htm).
Fusion power could solve many of the problems of fission power (the technology mentioned above) but, despite research having
started in the 1950s, no commercially useable reactor is expected within decades. One estimate is that there will be no
commercial reactor before 2050 [26] (http://www.iter.org/index.htm). Many
technical problems remain unsolved.
Renewable energy
Main article: Renewable energy
Another possible solution to an energy shortage or predicted future shortage would be to use some of the world's remaining
fossil fuel reserves as an investment in renewable energy
infrastructure such as wind power, solar power, tidal power, geothermal power, hydropower and biomass like biodiesel. Before the industrial revolution, they were the only energy source used by
humanity. Solid biomass like wood is still the main power source for many poor people in
developing countries, where overuse may lead to deforestation and
desertification
Hydropower is the only renewable today making a large contribution to world
energy production. The long-term technical potential is believed to be 9 to 12 times current hydropower production, but
increasingly, environmental concerns block new dams [27] (http://www.spe.org/spe/jpt/jsp/jptmonthlysection/0,2440,1104_11038_1040074_1202151,00.html).
Solar cells can convert around 15% of the incoming sunlight to electricity,
solar thermal energy a higher percentage to usable heat and
estimates for biodiesel from algae around 10% to diesel. That means that
theoretically, 1% of the land today used for crops and pasture could supply the energy consumption of today. Or the same area of
land today used for hydropower, the electricity yield per unit area of solar technologies being 50-100 times that of an average
hydro scheme. [28] (http://physicsweb.org/articles/world/14/6/2/1) Wind power is one of the most cost competitive renewables today. Its long-term technical potential is believed
to be up to 1.4 times total current world energy use [29] (http://www.spe.org/spe/jpt/jsp/jptmonthlysection/0,2440,1104_11038_1040074_1202151,00.html).
Geothermal power and tidal power are the only renewables not dependent on the sun but are today limited to special locations. All
available tidal energy is equivalant to 1/4 of total human energy consumption today [30] (http://www.spe.org/spe/jpt/jsp/jptmonthlysection/0,2440,1104_11038_1040074_1202151,00.html).
Geothermal power has a very large potential if considering all the heat generated inside Earth. Other variations of utilizing
energy from the sun also exist, see renewable energy.
Aside from hydropower and geothermal power, which are
site-specific, renewable supplies generally have higher costs than fossil fuels if the externalized costs of pollution are
ignored, as is common. Renewables like wind and solar are cost effective in remote areas that are off grid because the cost of a
grid connection is so high, as is the cost of transporting diesel fuel. The fact that small diesel generators are not hugely
efficiant and the fact that they consume fuel and make noise even when offload also makes renewables seem more desirable in this
situation.
Many renewable energy systems produce intermittent power. Other generators on the grid can be throttled to match varying
production from renewable sources, but most of this throttling capacity is already committed to handling variations in load.
Furthur development of intermittent renewable power will require simultaneous development of energy storage systems like compressed air energy storage or pumped storage to provide steady power.
On the other hand, nuclear power has been subsidized by 0.5-1 trillion dollars since the 1950s with nothing comparable in
renewable energy. The technology is improving rapidly, with for example solar
cells a hundred times less expensive today than the 1970s. Large scale production would also decrease costs. They may be
especially suitable for developing countries with abundant sunlight. They allow great decentralization, decreasing the cost and
energy loss from distributing energy. And they are usually small scale, allowing a single unit to be rapidly built and
decommissioned.
More efficiency in using available energy
New technology may use already available energy better, examples being more efficient lightbulbs or engines. Better insulation another one. It is possible to recover some of the energy in waste warm water and air, for example to
preheat incoming fresh water. Mass transportation increases
energy efficieny while air travel usually reduces it. Thermal depolymerization could also be in this category,
allowing recovery of some of the energy in hydrocarbon waste. Note that none of these methods allows perpetual motion, some energy is always lost to heat.
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 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.
Energy storage and transportation fuel
There is a widely held misconception that hydrogen is an alternative energy
source. As there are no uncombined hydrogen reserves on Earth (what there is resides in Earth's outer exosphere), hydrogen is itself not a source of chemical energy. Hydrogen-based energy always involves
conversion of an upstream energy source. Typically, this energy source is natural gas or electricity (generated by fossil fuels,
nuclear or renewables). Biomass or coal gasification, photoelectrolysis, and genetically modified organisms have also been proposed as means to produce
hydrogen.
It is as a means of storage of energy for intermittent power sources, like solar power, and as transportation fuel for
vehicles that hydrogen may play a very important role. (See Hydrogen
economy). However, the idea is currently impractical: hydrogen is inefficient to produce, and expensive to store, transport,
and convert back to electricity. New technology may change this in the future. Other alternatives to hydrogen as energy storage
are discussed in renewable energy. Some energy will be lost when
converting to and from storage and the storage systems will also add to the cost of the intermittent energy sources requiring
them.
There are also other alternatives for transportation fuel. The Fischer-Tropsch process converts coal, natural gas, and low-value refinery products into diesel.
This process was developed and used extensively in World War II by the Germans, who had limited access to crude oil supplies. It
is today used in South Africa to produce most of country's diesel from coal. [31] (http://www.eere.energy.gov/afdc/pdfs/epa_fischer.pdf) This technology could be used as an
interim transportation fuel if conventional oil were to disappear. Coal itself has
historically been used directly for transportation purposes in vehicles and boats using steam engines.
Liquid biofuel like methanol, ethanol and biodiesel can be used in internal combustion engines
with minor modifications. Oil from thermal
depolymerization are also usable in vehicles. Compared to hydrogen, they have the advantage of already existing technology
for diesel and gasoline engines and in place distribution infrastructure.
Boron has been proposed as a better alternative to hydrogen [32] (http://www.eagle.ca/~gcowan/boron_blast.html). Nuclear power could be used in large ships [33] (http://www.world-nuclear.org/info/inf34.htm). Some mass transportation systems can use electricity from a power plant and do not need transportation fuel.
Electric vehicles and electric boats not using hydrogen are other alternatives.
Speculative
Abiogenic petroleum origin and cold fusion has been proposed as very controversial future sources of energy.
Space exploration could yield energy sources from satellites (see
solar power satellite), from the moon (see helium-3), from other planets (see abiogenic petroleum origin for a list of planets with hydrocarbons), and from a Dyson sphere. The accretion
disc of a black hole can convert about 50% of the mass energy of an object
into radiation, as opposed to nuclear fusion which can only convert a few percent of the mass to energy.
External links
References
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