LECTURE                                       POWER

In this lecture you will learn about:

Power from fossil fuels - coal, gas and oil
"A fossil-fuel power station is a power station that burns fossil fuels such as coal, natural gas or petroleum (oil) to produce electricity.

Fossil-fuel power station are designed on a large scale for continuous operation. In many countries, such plants provide most of the electrical energy used.

Fossil fuel power stations (except for MHD generators) have some kind of rotating machinery to convert the heat energy of combustion into mechanical energy, which then operate an electrical generator. The prime mover may be a steam turbine, a gas turbine or, in small isolated plants, a reciprocating internal combustion engine.

Byproducts of power thermal plant operation need to be considered in both the design and operation. Sometimes waste heat due to the finite efficiency of the power cycle, when not recovered and sold as steam or hot water, must be released to the atmosphere, often using a cooling tower, or river or lake water as a cooling medium, especially for condensing steam. The flue gas from combustion of the fossil fuels is discharged to the air; this contains carbon dioxide and water vapour, as well as other substances such as nitrogen, nitrogen oxides, sulfur oxides, and (in the case of coal-fired plants) fly ash and mercury. Solid waste ash from coal-fired boilers must also be removed, although some coal ash can be recycled for building materials.


Fossil fueled power stations are major emitters of greenhouse gases (GHG) which according to the consensus of scientific organisations are a major contributor to the global warming observed over the last 100 years. Brown coal emits 3 times as much GHG as natural gas, black coal emits twice as much. Efforts exist to use carbon capture and storage of emissions but these are not expected to be available on a commercial scale and economically viable basis by 2025."
Another problem related to coal combustion is the emission of particulates that have a serious impact on public health. Particulate matter from coal-fired plants can be harmful and have negative health impacts. Studies have shown that exposure to particulate matter is related to an increase of respiratory and cardiac mortality.[18] Particulate matter can irritate small airways in the lungs, which can lead to increased problems with asthma, chronic bronchitis, airway obstruction, and gas exchange.[18]
There are different types of particulate matter, depending on the chemical composition and size. The dominant form of particulate matter from coal-fired plants is coal fly ash, but secondary sulfate and nitrate also comprise a major portion of the particulate matter from coal-fired plants.[19] The size and chemical composition of these particles affects the impacts on human health.[18][19] Currently coarse (diameter greater than 2.5 ?m) and fine (diameter between 0.1 ?m and 2.5 ?m) particles are regulated, but ultrafine particles (diameter less than 0.1 ?m) are currently unregulated, yet they pose many dangers.[18] Unfortunately much is still unknown as to which kinds of particulate matter pose the most harm, which makes it difficult to come up with adequate legislation for regulating particulate matter.[19]"
wikipedia

 
"Green" or renewable resources
"Hydroelectricity is electricity generated by hydropower, i.e., the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy. Once a hydroelectric complex is constructed, the project produces no direct waste.

Dam failures have been some of the largest man-made disasters in history. For example, the Banqiao Dam failure in Southern China directly resulted in the deaths of 26,000 people, and another 145,000 from epidemics. Millions were left homeless. 

Environmental damage

Large reservoirs required for the operation of hydroelectric powerplants result in submersion of extensive areas upstream of the dams, destroying biologically rich and productive lowland and riverine valley forests, marshland and grasslands. The loss of land is often exacerbated by the fact that reservoirs cause habitat fragmentation of surrounding areas.

Hydroelectric projects can be disruptive to surrounding aquatic ecosystems both upstream and downstream of the plant site. For instance, studies have shown that dams along the Atlantic and Pacific coasts of North America have reduced salmon populations by preventing access to spawning grounds upstream, even though most dams in salmon habitat have fish ladders installed. Salmon spawn are also harmed on their migration to sea when they must pass through turbines. This has led to some areas transporting smolt downstream by barge during parts of the year. In some cases dams have been demolished (for example the Marmot Dam demolished in 2007)[15] because of impact on fish. Turbine and power-plant designs that are easier on aquatic life are an active area of research. Mitigation measures such as fish ladders may be required at new projects or as a condition of re-licensing of existing projects."
wikipedia

 

Generation of hydroelectric power changes the downstream river environment. Water exiting a turbine usually contains very little suspended sediment, which can lead to  scouring of river beds and loss of riverbanks.[16] Since turbine gates are often opened intermittently, rapid or even daily fluctuations in river flow are observed. For example, in the Grand Canyon, the daily cyclic flow variation caused by Glen Canyon 
Dam was found to be contributing to erosion of sand bars. Dissolved oxygen content 
of the water may change from pre-construction conditions. Depending on the 
location, water exiting from turbines is typically much warmer than the pre-dam 
water, which can change aquatic faunal populations, including endangered species, 
and prevent natural freezing processes from occurring. Some hydroelectric projects 
also use canals to divert a river at a shallower gradient to increase the head of the 
scheme. In some cases, the entire river may be diverted leaving a dry riverbed. 
Examples include the Tekapo and Pukaki Rivers in New Zealand. wikipedia

SOLAR ENERGY

"Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available renewable energy on earth. Only a minuscule fraction of the available solar energy is used.

Solar powered electrical generation relies on heat engines and photovoltaics. Solar energy's uses are limited only by human ingenuity. A partial list of solar applications includes space heating and cooling through solar architecture, potable water via distillation and disinfection, daylighting, solar hot water, solar cooking, and high temperature process heat for industrial purposes.To harvest the solar energy, the most common way is to use solar panels.

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."
wikepedia

WIND ENERGY

"Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, wind mills for mechanical power, wind pumps for pumping water or drainage, or sails to propel ships.

At the end of 2009, worldwide nameplate capacity of wind-powered generators was 159.2 gigawatts (GW).[1] Energy production was 340 TWh, which is about 2% of worldwide electricity usage;[1][2] and is growing rapidly, having doubled in the past three years. Several countries have achieved relatively high levels of wind power penetration (with large governmental subsidies), such as 19% of stationary electricity production in Denmark, 13% in Spain[3] and Portugal, and 7% in Germany and the Republic of Ireland in 2008. As of May 2009, eighty countries around the world are using wind power on a commercial basis.[2]

Large-scale wind farms are connected to the electric power transmission network; smaller facilities are used to provide electricity to isolated locations. Utility companies increasingly buy back surplus electricity produced by small domestic turbines. Wind energy as a power source is attractive[says who?] as an alternative to fossil fuels, because it is plentiful, renewable, widely distributed, clean, and produces no greenhouse gas emissions during operation. However, the construction of wind farms is not universally welcomed because of their visual impact and other effects on the environment.

Wind power is non-dispatchable, meaning that for economic operation, all of the available output must be taken when it is available. Other resources, such as hydropower, and standard load management techniques must be used to match supply with demand. The intermittency of wind seldom creates problems when using wind power to supply a low proportion of total demand, but costs rise as does the proportion."

BIOFUELS

"Biofuels are a wide range of fuels which are in some way derived from biomass. The term covers solid biomass, liquid fuels and various biogases.[1] Biofuels are gaining increased public and scientific attention, driven by factors such as oil price spikes, the need for increased energy security, and concern over greenhouse gas emissions from fossil fuels.

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. Investment into biofuels production capacity exceeded $4 billion worldwide in 2007 and is growing.[2]"

wikipedia


 
Nuclear power
NUCLEAR FISSION

There are different types of particulate matter, depending on the chemical composition and size. The dominant form of particulate matter from coal-fired plants is coal fly ash, but secondary sulfate and nitrate also comprise a major portion of the particulate matter from coal-fired plants.[19] The size and chemical composition of these particles affects the impacts on human health.[18][19] Currently coarse (diameter greater than 2.5 ?m) and fine (diameter between 0.1 ?m and 2.5 ?m) particles are regulated, but ultrafine particles (diameter less than 0.1 ?m) are currently unregulated, yet they pose many dangers.[18] Unfortunately much is still unknown as to which kinds of particulate matter pose the most harm, which makes it difficult to come up with adequate legislation for regulating particulate matter.[19]"
wikipedia

FAST-BREEDER REACTORS
- when U-238 becomes unusable it can be converted to plutonium, another fission source. However, plutonium needs fast, not slow neutrons to get into the nucleus and only liquid sodium is good as a moderator. However, liquid sodium is terribly corrosive and plutonium is not only radioactive, it is also extremely chemically toxic.

Proponents of nuclear energy contend that nuclear power is a sustainable energy source that reduces carbon emissions and increases energy security by decreasing dependence on foreign oil.[89] Proponents claim that nuclear power produces virtually no conventional air pollution, such as greenhouse gases and smog, in contrast to the chief viable alternative of fossil fuel. Proponents also believe that nuclear power is the only viable course to achieve energy independence for most Western countries. Proponents claim that the risks of storing waste are small and can be further reduced by using the latest technology in newer reactors, and the operational safety record in the Western world is excellent when compared to the other major kinds of power plants.[90]

Opponents believe that nuclear power poses many threats to people and the environment[91][92][93]. These threats include the problems of processing, transport and storage of radioactive nuclear waste, the risk of nuclear weapons proliferation and terrorism, as well as health risks and environmental damage from uranium mining.[94][95] They also contend that reactors themselves are enormously complex machines where many things can and do go wrong, and there have been serious nuclear accidents.[96][97] Critics do not believe that the risks of using nuclear fission as a power source can be offset through the development of new technology. They also argue that when all the energy-intensive stages of the nuclear fuel chain are considered, from uranium mining to nuclear decommissioning, nuclear power is not a low-carbon electricity source.[98][99][100]

Arguments of economics and safety are used by both sides of the debate.
 

NUCLEAR FUSION (hypothetical)

Nuclear fusion reactions are safer and generate less radioactive waste than fission. These reactions appear potentially viable, though technically quite difficult and have yet to be created on a scale that could be used in a functional power plant. Fusion power has been under intense theoretical and experimental investigation since the 1950s.