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Energy development Primary energy sources Electrical energy Fuels Fossil energy oil Natural gas Hubbert peak hypothesis Sustainable development Energy sources
nuclear fuel tidal energy geothermal energy solar energy coal hydrocarbon combustion steam turbine electricity Fossil fuel coal petroleum natural gas power plant renewable energy Mining Oil rig Air pollution
decomposition methane alcohol fermentation pyrolysis air pollution
Flue gas emissions from fossil fuel combustion Biomass to liquid
Unlike the other energy sources in this article, hydrogen fuel cannot be collected or harnessed on earth. Hydrogen fuel must be manufactured with a net loss of energy. As such, it represents chemical energy storage like in other batteries, but it is not a primary energy source. In order to use hydrogen fuel as an energy source, either a) a fuel cell battery is needed to convert the chemicals hydrogen and oxygen into water, and in the process, produce electricity, or b) hydrogen can be burned (less efficiently than in a fuel cell) in an internal combustion engine (e.g. Mazda RX-8 rotary engine).
Pros
edit- Hydrogen is colourless, odourless and entirely non-polluting, the only product of combusting oxygen and hydrogen is pure water. This eliminates the direct production of exhaust gases that lead to smog, and carbon dioxide emissions that enhance the effect of global warming.
- Hydrogen is the lightest chemical element and has the best energy-to-weight ratio of any fuel. Because of this, hydrogen can be economically competitive with gasoline or diesel as a transportation fuel.
- Hydrogen can be produced anywhere, insinuating that it can be produced domestically from the decomposition the most abundant chemical on earth: water. Consequently, countries do not have to rely on OPEC countries for fossil fuels. Hydrogen can be produced from domestic sources and the price can be established within the country.
- Electrolysis combined with fuel-cell regeneration [1] is more than 50% efficient; more efficient than pumped hydro and many other forms of mechanical storage.
- Stationary storage with double-walled tanks is stable over long periods of time; hydrogen which outgases from the interior can be pumped back in.
Cons
edit- Other than some volcanic emanations, hydrogen does not exists in its pure form in the environment, as a gas, because Earth's gravity is not strong enough to hold it at back at the existing temperature (temperature provides the escape velocity. Helium also isn't retained.) There is concern that a hydrogen economy based on nonhydrocarbon or unreacted hydrogen sources would negatively affect Earth's overall hydrogen budget due to leaks into the atmosphere, and then from the atmosphere into outer space.
- It is impossible to obtain hydrogen gas without expending energy in the process. There are two ways to manufacture hydrogen;
- By elecrolysis from water -The process of splitting water into oxygen and hydrogen using electrolysis consumes large amounts of energy. It has been calculated that it takes 1.4 joules of electricity to produce 1 joule of hydrogen (Pimentel, 2002).
- By breaking down hydrocarbons - mainly methane. If oil or gases are used to provide this energy, fossil fuels are consumed, forming pollution and nullifying the value of using a fuel cell. It would be more efficient to use fossil fuel directly.
- By reacting water with a metal such as Sodium, Potassium, or Boron. Chemical by-products would be sodium oxide, potassium oxide, and boron oxide. Processes exist which could recycle these elements back into their metal form for re-use.
- There is currently a lack of infrastructure and distribution network required to support the widespread use of hydrogen as a fuel. It would cost a lot of money and energy to build hydrogen plants and to replace every car and bus with a hydrogen engine and fuel tank.
- Hydrogen is complicated to handle, store, and transport. It requires heavy, cumbersome tanks when stored as a gas, and complex insulating bottles if stored as a cryogenic liquid. If it is needed at a moderate temperature and pressure, a metal hydride absorber may be needed. Transport is also a problem, because hydrogen leaks effortlessly from containers, reducing the efficiency of the fuel. These hassles make hydrogen power very expensive.
- Current efficient fuel cell designs are expensive since they need Platinum as a catalyst, Platinum is not recoverable. If we were to replace every Internal combustion engine with a Fuel cell then we could potetially use all the Earth's Platinum reserves in two years.
- Tidal power
- Solar power
- A renewable energy resource
- Converts sunlight into electricity
- Solar cell
- Parabolic mirror
- No water or air pollution
, because there is no combustion of fuels.
- In sunny countries, solar power can be used in remote locations, like a wind turbine. This way, isolated places can receive electricity, when there is no way to connect to the power lines from a plant.
- Solar energy can be used very efficiently for heating (solar ovens, solar water and home heaters) and lighting.
photovoltaic power station photovoltaic cells
Geothermal Energy
edit- Main article: Geothermal power
Geothermal energy harnesses the heat energy present underneath the Earth. The hot rocks heat water to produce steam. When holes are drilled in the region, the steam that shoots up is purified and is used to drive turbines, which power electric generators.
Pros
edit- Geothermal energy produces air or water pollution if preformed incorrectly but if done correctly, will cause no physical damage.
- Once a geothermal power station is implemented, the energy produced from the station is practically free. A small amount of energy is required in order to run a pump, although this pump can be powered by excess energy generated at the plant.
- Geothermal powers stations are relatively small, and have a lesser impact on the environment than tidal or hydroelectric plants. Because geothermal technology does not rely on large bodies of water, but rather, small, but powerful jets of water, like geysers, large generating stations can be avoided without losing functionality.
Cons
edit- Geothermal energy is only sufficient as source of power in certain areas of the world. These regions require the presence of hot rocks near the surface to warm the water. The depth of these rocks must be enough so that one can drill down to them. The type of rock also plays a role because it must be easy to drill through.
- A geothermal site is prone to running out of steam, meaning that the water is not heated at a high enough temperature to generate enough steam pressure. This makes the site useless, in terms of energy production, for decades.
- Drilling holes underground may release hazardous gases and minerals from deep inside the Earth. It can be problematic to dispose of these subsidiary products in a safe manner.
Hydroelectric energy
edit- Main article: Hydroelectricity
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. An electric generator, when there is excess energy available, can be run backwards as a motor to pump water back up for later use.
Pros
edit- Hydroelectric power stations can promptly increase to full capacity, unlike other types of power stations. This is because water can be accumulated above the dam and released to coincide with peaks in demand.
- Electricity can be generated constantly, because there are no outside forces, which affect the availability of water. This is in contrast to wind, solar or tidal power, all of which are far less reliable.
- Hydroelectric power produces no waste or pollution.
- Hydropower is a renewable resource; oil, natural gas, and coal reserves may be depleted over time.
- Hydroelectricity secures a country's access to energy supplies.
Cons
edit- The construction of a dam can have a serious environmental impact on the surrounding areas. The amount and the quality of water downstream can be affected, which affects plant life both aquatic, and land-based. Because a river valley is being flooded, the delicate local habitat of many species is destroyed, while people living nearby may have to relocate their homes.
- Dams are expensive to build, making the start-up costs of a hydroelectric power station very high.
- Hydroelectricity can only be used in areas where there is a large supply of water.
- Flooding submerges large forests. As the vegetation decays, it releases methane, a potent gas, thus contributing to global warming.
Nuclear Energy
edit- Main article: Nuclear energy
Nuclear power stations work similar to fossil fuel power plants, except for the fact that the heat is produced by the reaction of uranium inside a nuclear reactor. The reactor uses uranium rods, which are split in the process of fission, releasing a large amount of energy. The process continues as a chain reaction with other nuclei takes place. The heat released heats water to create steam, which spins a turbine, producing electricity.
Pros
edit- The process of nuclear fission allows for the production of tremendous amounts of energy from a small amount of fuel, a pound of uranium or thorium being equivalent to 3.5 million lbs of coal in energy content.
- The cost of making nuclear power is about the same as coal, which is considered very inexpensive.
- Nuclear power plants are heavily guarded with the nuclear reactor inside a reinforced containment building, and thus are relatively impervious to terrorist attack or adverse weather conditions.
- Nuclear power does not produce any air pollution or release carbon dioxide and sulfur dioxide into the atmosphere. Therefore, it does not contribute to global warming or acid rain.
Cons
edit- The waste produced from the nuclear fission of uranium is poisonous, and extremely radioactive, requiring constant and costly maintenance and monitoring at the storage sites. Moreover, the long-term disposal of the long-lived nuclear waste causes serious problems, since (unless the spent fuel is reprocessed) it takes from one to three thousand years for the spent fuel to come back to the natural radioactivity of the uranium ore body that was mined to produce it.
- The operation of an uncontained nuclear reactor near human settlements can be catastrophic, as shown by the Chernobyl accident in the Ukraine(former USSR), where large areas of land were affected by nuclear fallout. Members of the public are hesitant about the safety of nuclear power.
- Building a nuclear power plant requires a huge investment, and the costs of safe disassembling after it becomes obsolete (called decommissioning) must be included into the budget.
- There can be connections between nuclear power and nuclear weapon proliferation, since both require large-scale uranium enrichment facilities.
- Nuclear fuels are non-renewable energy sources, with limited high concentration ore reserves. There is a large amount of trace concentration nuclear material in seawater and most rocks, however extraction from these is not economical.
- See also the problems related to Uranium mining
- 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. Refined hydrocarbon fuels such as gasoline and LPG may also be delivered via aircraft.
- Electric grids
- 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.
- In the week of 3 August 2003, the US set an all-time national record for electricity use of 90,000 gigawatts. 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. This network's service provision and its administration is an ongoing issues for that states politicians.
Energy storage
edit- Main article: Energy storage
While most fuels can be stored, electricity in itself cannot. For that reason, many methods of energy storage have been developed, which transform electrical energy into other forms of energy. A method of energy storage may be chosen based on stability, ease of transport, ease of energy release, or ease of converting free energy from the natural form to the stable form.
- 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, batteries and explosives such as cordite and dynamite.
- Gravitational
- Dams can be used to store energy, by using 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. :[2].
- Another example of gravitational energy storage is the counter-weight on elevators.
- Electrical capacitance
- Electrical energy may be stored in capacitors. These are often used to produce high intensity releases of energy (such as a camera's flash)
- Mechanical
- Pressure:
- Energy may also be stored pressurised 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.
- Flywheels and springs
- Energy can also be stored in mechanical systems such as springs or flywheels. Flywheel energy storage is currently being used for uninterruptible power supplies.
