Generating Electricity by Photoelectric Effect

Generating Electricity by Photoelectric Effect.

Hussain.Q, Uzair. A

January 1^st, 2013

In modern civilization, the need for more environmentally friendly forms of energy has grown to an extent that the use of fossil fuels is now looked down upon. The negative environmental effect of fossil fuels has caused researchers to search for alternative types of energies to generate electricity. A prominent way to generate electricity through a greener medium is through the use of solar panels. Solar panels don’t pollute as much as fossil fuels and in the human timeline, the abundance of solar power will never run out, whereas fossil fuels will eventual run out of supply. Photovoltaic or solar cells in the solar panels convert the solar energy from the sun into usable electrical energy.

Solar panels absorbing solar cells from the sun in order to generate electricity.

The photoelectric effect                                                                                                    

Einstein’s explanation on the photoelectric effect is that it takes a certain amount of energy to eject an electron from a metal surface. This energy is known as the work function (W), which depends on the metal that the electron is being ejected from. Electrons can gain energy by interacting with photons. If a photon has enough energy at least as big as the work function, the photon energy can be transferred to the electron and the electron will have enough energy to escape from the metal. A photon that’s energy is less than the work function will never be able to eject electrons.

Electrons ejected by a metal surface provided that the frequency of the light is greater than the threshold frequency.

The photoelectric effect before Einstein’s explanation was really unknown. Scientists couldn’t really understand why light with low-frequency and high-intensity would not cause electrons to be produced, while light with higher-frequency and low-intensity would. But now it is easy to understand why this happens, since we know that light is made of photons, it is not the total amount of energy that’s important to the creation of electrons but it is the energy per photon that is important.

Problem                                                                                                                                           

A challenge in producing photovoltaic cells is increasing the efficiency as much as possible. The Sun’s rays include the electromagnetic spectrum and no material has a threshold frequency that can relate with the majority of the electromagnetic spectrum. Often the unconverted energy in the cell is given off as heat hence becoming extremely inefficient.

Solution

Scientists have come up with an idea of splitting the sunlight into smaller components and those smaller components will be sent to the different material that is designed to deal with each kind of threshold frequency. Before now, scientist had difficulty directing light at such a fine stage. Recent breakthroughs in optics and lenses have increased knowledge in this area and thus can be used to increase the efficiency of the Solar Panel.

 

Splitting light to increase efficiency of photovoltaic cells

Real life Implications                                                                                                                    

As the growing need for a renewable source of energy drive human beings to search for other solutions, the usage of solar panels can be perfected to produce energy in daily lives. Using the application of photovoltaic cells, energy can be produced to power homes, cars, and even big offices. Photovoltaic cells have come a long way and are now being produced and installed for considerably cheap money. These cells are grouped into frames called Photovoltaic Module also known as, Solar Panels. These Modules are then placed into arrays, which are capable of producing colossal amounts of electricity. However of the efficiency of these cells is sometimes questioned. Recent breakthroughs are allowing these cells to produce fifty percent more energy than before.

Nowadays, solar energy has become extremely popular and ordinary citizens are prepared to mount Solar Panels on the roofing of their houses. These modules sometimes are responsible for creating partial or all of the energy required in the household. Since the cost of manufacturing photovoltaic cells and arranging them into modules has gone down over the years, more and more people are considering solar energy as a way of life. Soon most houses will run on solar energy.

House partially powered by solar panels.

As the production of electric vehicles is rising, it is reducing dependence on gas powered combustion engines, which are one of the leading causes in greenhouse emissions. Since there is now competition in the motor market for producing more and more reliable electric cars, more and more research is being put into solar powered cars.

Vehicle powered by solar panels.

Conclusion:

Since the environment needs to be conserved and burning fossil fuels are prone to diminishing, Solar Energy should be the next frontier since it is a form of renewable energy. The photoelectric effect will enable will enable scientists to harness the energy of the sum into photovoltaic cells which can be arranged into modules and ultimately arrays. Solar Panels will eventually be on top of every home, vehicle and even cities providing green and clean energy.

 References:

http://faculty.virginia.edu/consciousness/images/photoelectric%20effect.gif, retrieved January 1^st, 2013

http://on3dprinting.com/wp-content/uploads/2012/06/20120616-Photovoltaic-PV.png, retrieved January 1^st, 2013

http://why.knovel.com/all-engineering-news/2174-prism-power-solar-cells-could-dramatically-improve-by-splitting-light-into-parts.html, retrieved January 1^st, 2013

http://static.ddmcdn.com/gif/solar-powered-vehicle-possibility-4.jpg, retrieved January 1^st, 2013

http://physics.bu.edu/~duffy/PY106/PhotoelectricEffect.html, retrieved January 1^st, 2013

Hydro-Power

Alternative Energy Project                                                                                                                                                Emily C., Michael Y., Tim M., Tim M.                                                                                                                                                                                                 2012-2013

Hydro-Power

Article:

Hydropower actually brought electricity, jobs and inexpensive power during the Great Depression. Many of the large projects were directed with hydropower, but that all slowed to a halt after the second World War, when the atomic age started. For more information about this, the article below explains the great ideas that were once used, and are starting to be used again. http://www.scientificamerican.com/article.cfm?id=time-to-think-hydropower

 

How it works:

Electrical generation through hydro-power converts energy through several states. First stored energy (water) is converted to kinetic energy (moving the water) then converted to electrical energy. In order to obtain the stored energy, a dam of some sort must be built in front of an elevated water source (lake, river). The dam’s purpose is to build up water behind it, creating a stored energy. Now that stored energy is obtained, it must be converted to kinetic energy. That is obtained by releasing the held water into the dam’s intake via the popular force known as gravity. The water then takes a trip from the intake through the penstock and into the turbines. Water passing through will rotate the massive turbines which are connected to a generator.                                                                                http://save-our-resources.wikispaces.com/Hydroelectricity

 

The generator consists of a number of electromagnets called a rotor, which rotates inside a coil of copper wire. The combination of the spinning magnets and the wound coil of metal create an alternating electric current that can finally be harnessed and transferred to the transformer, stepping up the voltage of the current and passed though power lines and into homes.

The remaining water exits the dam through the outflow and into a lower part of the water source.

 

 

 

 

 

http://users.owt.com/chubbard/gcdam/html/hydro.html

Types:

There are a number of methods and variation in producing hydro-electrical energy.

–          Conventional Dams

• The most common method of using water as an electrical source, see above explanation for electric production

–          Pump-Storage

http://upload.wikimedia.org/wikipedia/commons/9/9a/Pumpstor_racoon_mtn.jpg

• This method uses the exact same format as the convention dam except for a few differences.
• Instead of taking water from the elevated source, running it through the dam, and dumping it to the lower source, where it leaves the system, the water in the lower source is pumped back into the higher source. So water is just being moved from one source to the other. Disregarding water evaporation, this method is extremely efficient in producing energy while using a set amount of water.

–          Run-of-the-River

http://en.wikipedia.org/wiki/File:Chief_Joseph_Dam.jpg

• This method uses the same format of electrical production as the conventional method
• This method contains little to no water storage
• Any water storage is called pondage
• This method takes advantage of the seasonal flow of rivers

–          Tide

http://en.wikipedia.org/wiki/File:SeaGen_installed.jpg

• This method uses the same format of electrical production as the conventional method
• Instead of two water reservoirs (high and low), this method uses the ocean
• This method relies on the periodic tides moving water in and out of the turbines to produce electricity.

History:

Hydroelectricity operates based off of the ancient concept of hydropower – power generated from harnessing the kinetic energy of falling water. It’s a concept that has been around for a very long time, and has been used by people like the ancient Greeks to perform simple tasks such as grinding flour using an invention called the water wheel. The water wheel works by converting the kinetic energy of the flowing water into mechanical energy, causing the waterwheel to spin, much like how a gust of wind can cause a pinwheel to spin. This ancient water wheel acts very similarly to the modern hydropower plant. In the late 19th century, shortly after the invention of the dynamo – the earliest electrical generator that converted mechanical energy into electrical energy via electromagnetic induction to convert mechanical rotations into direct current electricity through a commutator – hydropower became a good way to generate electricity. The first hydropower plant was built at Niagara Falls in 1879, and many other countries soon followed suit including the United States, China, Brazil, and 140+ more. Today, hydro electrical power is the most widely used source of alternative energy production, accounting for approximately 16 percent of global electricity consumption in 2010.

Efficiency:

Hydroelectricity operates based off of the ancient concept of hydropower – power generated from harnessing the kinetic energy of falling water. It’s a concept that has been around for a very long time, and has been used by people like the ancient Greeks to perform simple tasks such as grinding flour using an invention called the water wheel. The water wheel works by converting the kinetic energy of the flowing water into mechanical energy, causing the waterwheel to spin, much like how a gust of wind can cause a pinwheel to spin. This ancient water wheel acts very similarly to the modern hydropower plant. In the late 19th century, shortly after the invention of the dynamo – the earliest electrical generator that converted mechanical energy into electrical energy via electromagnetic induction to convert mechanical rotations into direct current electricity through a commutator – hydropower became a good way to generate electricity. The first hydropower plant was built at Niagara Falls in 1879, and many other countries soon followed suit including the United States, China, Brazil, and 140+ more. Today, hyroelectrical power is the most widely used source of alternative energy production, accounting for approximately 16 percent of global electricity consumption in 2010.

Societal Implications:

As with all sorts of different energy convention, hydroelectric dams can be useful and efficient but also a setback in other aspects. Hydroelectric dams are useful in Canada as the geography allows for abundance of waterways. But there are hidden, small font price tags that come with the efficient technology. So here are the facts. The dams release fewer emissions and are entirely renewable unlike the common use of oil and gas. However the dams require its water supply to be held back like a reservoir or a steady flow of water must lead towards the dams, and areas where animals reside may no longer have its steady water flow as the water is backed up. Lower water levels will lower the ability for certain water organisms to continue living there. The lower water level also leads to warmer water temperature which could damage certain types of fish such as salmon. Of course in order for the hydroelectric facilities to have a frequent supply of water to run its energy, upstream areas must also be submerged by water coming in from other waterways. This annihilates the ecologically vibrant areas such as lowlands, marshes and swamps. Another notable offense from the use of this technology is the disturbance of fish migrating areas. Fish often need to swim upstream the dams in order to get to their mating locations and reproduce. However, the dams make it impossible for the fish to do so. Therefore, hydroelectric dams must put in place fish ladders or manually catch the fish and release them on the opposite side. The larger the hydroelectric facility the more damage it does environmentally. In order for these large hydroelectric dams to be put in place, areas of nature must be cleared before starting construction. The trees and living organisms become submerged underneath and release methane and carbon into the air. Roads that continue towards the dam from the cities are also needed. It is not just the dam that takes away the environment but everything that connects to it. Construction of these dams must be able to withstand harsh weather conditions, as the destruction of any such dam would cause extreme environmental concerns and danger to nearby living areas. Such was exactly what happened in Banqiao in 1975. The dam built by the Chinese broke under a harsh typhoon that year. Not only were there thousands of causalities and affected, but the environmental damage was difficult to restore. The risk of building these dams and continuing the project, only to have it fail is not a price to pay by the environment. Therefore, using hydroelectricity dams are efficient, but are they worth it? If so, then it is sure hoped that they will consider and find a solution to most if not all the environmental concerns that comes with it.

References:

–          Atlantica Centre for Energy. (n.d.). Hydroelectric. Retrieved December 25, 2012, from   http://atlanticaenergy.org/hydroelectric

–          Bonsor, K. Howstuffworks. (n.d.). How hydropower plants work. Retrieved December 25, 2012  http://science.howstuffworks.com/environmental/energy/hydropower-plant1.html

–          David Suzuki Foundation. (n.d.). Hydroelectricity. Retrieved December 25, 2012, from   http://www.davidsuzuki.org/issues/climate-change/science/energy/hydropower/

–          Lund, K. Agriculture and Rural Development. (2002). Hydroelectric power. Retrieved December  25, 2012, from http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/eng4431

–          Ministry of Energy, Mines and Natural Gas and Responsible for Housing. (n.d.). What is  hydroelctricity?. Retrieved December 25, 2012, from http://www.empr.gov.bc.ca/EPD/Electricity/supply/hydro/Pages/default.aspx

–          Nuclear Technology Exploring Possibilities. (n.d.). Hydroelectricity. Retrieved December 25    2012, from http://curriculum.cna.ca/curriculum/cna_world_energy_res/hydro-         eng.asp?bc=Hydroelectricity

–          Perlman, H. The USGS Water Science School. (2012). Hydroelectric power: how it works.      Retrieved December 25, 2012, from http://ga.water.usgs.gov/edu/hyhowworks.html

–          Practical Action. (n.d.). Micro-hydro power. Retrieved December 25, 2012, from  http://practicalaction.org/energy/micro_hydro_expertise?utm_source=S000&utm_medium=PPC&utm_campaign=C10105&gclid=CN7H66rEtrQCFcN_Qgod2zAA6g

–          Technology and Inventions. (2009). Hydro-electricity. Retrieved December 25, 2012, from   http://www.kidcyber.com.au/topics/hydroelec.html

Global Wave Power

Physics 30 Alternative Energy  Assignment

                                                                                                                                                                                                                                                  Eric K

As the world continues to grow and find new technology, we find ourselves trying to replace fossil fuels with new and improved energy sources.  As we are running out of fossil fuels, researchers are trying to find new energy sources that are clean and renewable to use, and researching whether or not the energy source will be effective in everyday use.  One of the researched sources is wave power, the largest power source on Earth.  Wave power is the transport of energy by the waves in oceans, lakes, rivers, etc, and the capture of that energy to do work, such as generate electricity.  Global wave power is estimated to be 1 terawatt as revealed by previous studies.  Wave-power generation is not a widely employed commercial technology, but there has been attempts to use it since at least 1890.  The major competitor of wave power is offshore wind power.  Please keep in mind that wave power is distinct from the diurnal flux of tidal power and the steady gyre of ocean currents.

Waves are generated by wind passing over the surface of the body of water.  As long as the waves propagate slower than the speed of the wind just above the waves, there is an energy transfer from the wind to the waves.  Both air pressure differences between the upwind and the lee side of a wave crest, as well as friction on the water surface by the wind, making the water go into the shear stress causes the growth of the waves.  Wave height can be determined by wind speed, the duration of time the wind has been blowing, the distance over which the wind excites the waves (fetch), and by the depth and topography of the seafloor, which can focus or disperse the energy of the waves.  A given wind speed has a matching practical limit over which time or distance will not produce larger waves.  When this limit is reached, the sea is said to be “fully developed”  What this means is that larger waves are more powerful, but wave power is not only determined by size, but by speed, wavelength, and water density.  The waves propagate on the ocean surface and the wave energy is also transported horizontally with the group velocity.  The average transport rate of the wave energy through a vertical plane of unit width, parallel to a wave crest, is called the wave energy flux or wave power, which must not be confused with the actual power generated by a wave power device.

Wave power is proportional to the wave period and to the square of the wave height.  When the significant wave height is given in metres, and the wave period in seconds, the result is the wave power in kilowatts (kW) per meter of wavefront length.  In very deep water where the water depth is larger than half the wavelength, the wave energy flux is:

P = (ρg/64π) (H_m0)² T ≈ (0.5 kW/m³•s) (H_m0)² T

Where P is the wave energy flux per unit of wave-crest length, H_m0 is the significant wave height, T is the wave period, ρ is the water density, and ɡ is the acceleration of gravity.  For example, with a wave height of 3 meters and a wave period of 8 seconds, there are 36 kilowatts of power potential per meter of wave crest.  According to linear wave theory, in a sea state, the average energy density per unit area of gravity waves on the water surface is proportional to the wave height squared.

E = 1/16 (ρg (H_m0)² )

Where E is the average wave energy density per unit horizontal area (J/m²), the sum of kinetic and potential energy density per unit horizontal area.  As the waves propagate, their energy is transported.  The energy transport velocity is the group velocity.  As a result, the wave energy flux, through a vertical plane of unit width perpendicular to the wave propagation direction, is equal to:   P = E C_g 

where C_g is the group velocity (m/s).  Due to the dispersion relation for water waves under the action of gravity, the group velocity depends on the wavelength or equivalently on the wave period.  The dispersion relation is also a function of the water depth resulting in the group velocity behaving differently in the limits of deep, intermediate, and shallow depths of water.

There is also a conceptual study focused on using Oscillating Water Columns, which is considered as the most efficient way utilize wave power.  There are 2 variations: onshore and offshore.  Oscillating water columns use a large volume of moving water as a piston in a cylinder.  Air is forced out of the column as a wave rises and fresh air is drawn in as the wave falls.  This movement of air turns a weir turbine at the top of the column.  Deep water wave power resources are enormous.  They lie between 1 terawatt and 10 terawatts, but it is not practical to capture all of this.  The useful worldwide resource has been estimated to be greater than 2 terawatts.  Locations with the most potential for wave power include the western seaboard of Europe, the northern coast of the UK, and the pacific coastlines of North and South America, Southern Africa, Australia, and New Zealand.  The north and south temperate zones have the best sites for capturing wave power.  The prevailing westerlies in these zones blow strongest in the winter.  Countries that are surrounded by seafronts could tap into an alternative source of power generation which could be generated by the waves during the different seasons of the year.  The findings of this study could be adapted to evaluate the capability to generate electricity on shore from lakes and rivers with undulated waves.  Researchers have begun this conceptual study with the derivation of mathematical equations for each component in the electrical generation system after taking into consideration the sea wave as the input to facilitate the workability of the entire system.  The researchers verified the validity of the developed and derived mathematical equations for each stage of the research.  They did this to establish and confirm its workability.  Electrical and mechanical relationships were derived to relate the workability of each component in the system for the purpose of electricity generation.  Numerous experiments were conducted to optimize the results in this study which would eventually lead to the generation of electricity.  The results obtained from the experiments indicated that the proposed model appears practical and could be implemented.

Pros:

– Wave Power

– Low Maintenance

– No greenhouse gases released

– Renewable energy source obtained by the wind via the Sun’s heating of our atmosphere

– Capable of high efficiency in ideal conditions (60% – 80%)

– Low upfront construction costs

– Minimal environmental impact when properly placed

– Oscillating Water Column

– Moving parts are housed outside for a greater lifetime of the material

– Can be built near shore for easy access to the power grid and for maintenance

Cons:

– Wave Power

– Efficiency drops significantly in rough weather due to safety mechanisms

– Limited locations where waves are strong enough to produce electricity without                         damaging equipment

– Power is only produced near oceans making transmission to inland customers difficult

– Winds can be unpredictable and far from reliable.  Can’t produce electricity at all times

– Improperly placed wave power plants can damage the marine ecosystem

– Initial building cost

– Could be considered an eyesore

References:

– Replacing Fossil Fuels: Utilizing Sea Waves to Generate Electricity                http://www.sciencedaily.com/releases/2012/12/121203080814.htm

Retrieved on January 4, 2013

– Oscillating Water Column (OWC)

http://owcwaveenergy.weebly.com

Retrieved on January 6, 2013

– Wave Power

http://en.wikipedia.org/wiki/Wave_power

Retrieved on January 3, 2013

– Advantages and Disadvantages of Wave Power

http://renewableenergyindex.com/hydro/advantages-disadvantages-wave-power

Retrieved on January 6, 2013

Hydroelectric Dams

Hydroelectric Dams

By Aryan G, and Bayan H

Hydroelectricity is the term referring to electricity generated by hydropower; 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, accounting for 16 percent of global electricity generation – 3,427 terawatt-hours of electricity production in 2010. The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The average cost of electricity from a hydro plant larger than 10 megawatts is 3 to 5 cents per kilowatt-hour. Hydro is also a flexible source of electricity since plants can be ramped up and down very quickly to adapt to changing energy demands.

The theory is to build a dam on a large river that has a large drop in elevation. The dam stores lots of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake. Gravity causes it to fall through the penstock inside the dam. At the end of the penstock there is a turbine propeller, which is turned by the moving water. The shaft from the turbine goes up into the generator, which produces the power. Power lines are connected to the generator that carries electricity to your home and mine. The water continues past the propeller through the tailrace into the river past the dam.

 

Generator:

A hydraulic turbine converts the energy of flowing water into mechanical energy. A hydroelectric generator converts this mechanical energy into electricity. The operation of a generator is based on the principles discovered by Faraday. He found that when a magnet is moved past a conductor, it causes electricity to flow. In a large generator, electromagnets are made by circulating direct current through loops of wire wound around stacks of magnetic steel laminations. These are called field poles, and are mounted on the perimeter of the rotor. The rotor is attached to the turbine shaft, and rotates at a fixed speed. When the rotor turns, it causes the field poles (the electromagnets) to move past the conductors mounted in the stator. This, in turn, causes electricity to flow and a voltage to develop at the generator output terminals.

 

 

 

Pumped storage: Reusing water for peak electricity demand

Demand for electricity is not “flat” and constant. Demand goes up and down during the day, and overnight there is less need for electricity in homes, businesses, and other facilities. Hydroelectric plants are more efficient at providing for peak power demands during short periods than are fossil-fuel and nuclear power plants, and one way of doing that is by using “pumped storage”, which reuses the same water more than once.

Pumped storage is a method of keeping water in reserve for peak period power demands by pumping water that has already flowed through the turbines back up a storage pool above the power plant at a time when customer demand for energy is low, such as during the middle of the night. The water is then allowed to flow back through the turbine-generators at times when demand is high and a heavy load is placed on the system.

The reservoir acts much like a battery, storing power in the form of water when demands are low and producing maximum power during daily and seasonal peak periods. An advantage of pumped storage is that hydroelectric generating units are able to start up quickly and make rapid adjustments in output. They operate efficiently when used for one hour or several hours. Because pumped storage reservoirs are relatively small, construction costs are generally low compared with conventional hydropower facilities.

Cost of Hydroelectric Energy:

Hydroelectric is less than half the cost of fossil fuel derived electricity. It also has no fuel cost.

Advantages of Hydroelectric Energy:

1. Renewable

Hydroelectric energy is renewable. This means that we cannot use it all up. As long as the sun and gravity exist there will be a water cycle and a constant flow of water running the hydroelectrically power plant.  However, there are only a limited number of suitable reservoirs where hydroelectric power plants can be built and even less places where such projects are profitable.

2. Green

Generating electricity with hydro energy is friendly to the atmosphere in the way that it does not pollute the atmosphere. Other forms of energy such as fossil fuels will pollute the atmosphere and increase co2 levels. Hydro electricity is environmentally friendly in the sense of producing a clean form of renewable energy.

3. Reliable

Hydroelectricity is very reliable energy. There are very little fluctuations in terms of the electric power that is being by the plants, unless a different output is desired. Countries that have large resources of hydropower use hydroelectricity as a base load energy source. As long as the sun and water exist electricity can be generated.

4. Flexible

As previously mentioned, adjusting water flow and output of electricity is easy. At times where power consumption is low, water flow is reduced and the magazine water behind the dam is being conserved for times when the power consumption is high.

5. Safe

Compared to among others fossil fuels and nuclear energy, hydroelectricity is much safer.  There is no fuel involved (other than water that is).

 Disadvantages of Hydroelectric Energy:

1. Environmental Consequences

The environmental consequences of hydropower are related to interventions in nature due to damming of water, changed water flow and the construction of roads and power lines.

Hydroelectric power plants may affect fish is a complex interaction between numerous physical and biological factors. More user interests related to exploitation of fish species, which helps that this is a field that many have strong opinions on.

Fish habitats are shaped by physical factors such as water level, water velocity and shelter opportunities and access to food. Draining would be completely devastating to the fish. Beyond this, the amount of water may have different effects on the fish in a river, depending on the type and stage of the lifecycle. Not all unregulated river systems are optimal in terms of fish production, because of large fluctuations in flow.

Also, many species of fish are migratory, using the major rivers as their conduits, and dams cut them off from their spawning areas. Beyond that, the flooding destroys large swaths of habitat, replacing it instead with a new biome. Many animals lose their lives and habitats due to the flooding of the land beside the reservoir.

2. Expensive

Building power plants in general is expensive. Hydroelectric power plants are not an exception to this. On the other hand, these plants do not require a lot of workers and maintenance costs are usually low.

3. Droughts

Electricity generation and energy prices are directly related to how much water is available. A drought could potentially affect this. If there is no water or fluid source there will be no form of electricity generated. So a drought condition is not ideal for running a hydro electric power plant.

 Conclusion:

Overall hydro electricity has its positive and negative effects on our lives and the surrounding environment. It’s a form of renewable energy that runs on the water cycle and gravitational potential energy which causes turbines to spin and generate electricity. This form of energy is much more resourceful than fossil fuels because fossil fuels are non renewable source of energy and is constantly increasing the levels of co2 in the atmosphere whenever it is consumed. Hydro electricity is a cleaner form of energy and it can be used as long as the sun exists. And from the data it is clear that hydro electricity cost much less than other forms of energy. However the negative effects are that the development of hydro electric dams floods the surrounding lands and the animals inhabiting that area loss their homes. This flooding of the land also destroys many ecosystems. Also hydro electrical dams can only work in places where there is water. In extremely dry places where there is drought it is not the ideal condition for a hydro electric generator because it strictly consists of the flow of fluid to generate power. It is also extremely expensive to build and operate. Overall hydro electrical power plants have their ups and their downs, and it’s up to society as a whole to decide whether or not hydro electrical dams are for the good.

Sources:

http://en.wikipedia.org/wiki/Hydroelectricity

http://ga.water.usgs.gov/edu/hyhowworks.html

http://answers.yahoo.com/question/index?qid=20090310133846AATM2VC

http://www.colorado.edu/geolsci/courses/GEOL3520/Hydropower.pdf

http://www.wellhome.com/blog/the-pros-and-cons-of-hydropower/

http://www.worldwatch.org/node/9527

http://www.guardian.co.uk/environment/2010/jan/22/wave-tidal-hydropower-water

http://www.internationalrivers.org/environmental-impacts-of-dams

http://energyinformative.org/hydroelectric-energy-pros-and-cons/

http://en.wikipedia.org/wiki/File:Ren2008.svg

Alternative Energy: Harnessing Solar Energy

Alternative Energy: Harnessing Solar Energy

Katherine L., Alexis F.

Sunlight is a remarkable energy source – but one that can provide challenges to harness. One such challenge that often plagues solar panel installation is misalignment. Installations frequently use pricey solar tracking systems, for example multi-axis platforms that point a solar panel towards the sun, however this uses up electricity and often costs about 25% of a panel’s installation cost. Panels gather two types of light – diffused sunlight (negligible during energy collection) and direct sunlight (makes up about 90% of energy collected). A solar tracker helps to collect that direct sunlight, but its ultimate price proves it not to be a not very profitable solution.

In 2012, two recent Sir Winston Churchill High School graduates, Bruce Gao and Matt Privman, founded SimplySolar, a mobile application that allows people to align solar panels using GPS coordinates, after noticing many solar panel alignment programs required laptops and internet access, which is often hard to access in developing countries where alternative energy is needed the most. To read more, visit http://blogs.calgaryherald.com/2012/10/04/startup-of-the-week-simplysolar/.

The Photoelectric Effect

Solar panels are composed of solar cells, and the phenomenon that occurs in these solar cells is called the photoelectric effect. When light frequency and light intensity are manipulated, it can be observed that if the frequency were to fall below a certain value (different for different materials), nothing happens, no matter what the light intensity is. On the other hand, for frequencies above that certain value, electrons were observed on the surface of the material. In addition, if the intensity of the light were then raised, more electrons were ejected from the material and if the frequency was increased, this would occur with greater kinetic energy. This relationship is shown in Figure 1.

Figure 1. During the photoelectric effect, the kinetic energy of electrons increases as the photon frequency increases above a certain value. If the photon frequency is below this value, then a vertical line occurs (indicating the photon energy is too low) and consequently, no electrons will be ejected from the material.

Einstein concluded that this provided evidence that light has the nature of a particle (bundles of light called photons). These photons would bear energy proportional to their frequency. It requires a particular minimum energy, called the ionization energy, to eject an electron fully out of an atom, and a quantity of energy below this ionization energy, called the work function, is needed to free an electron. If the energy of the photon is too low (in other words, the frequency is too low), then no matter how many photons strike the atom, the electron cannot be freed. On the other hand, if the energy of the photon is above the ionization energy level, an increase in the intensity increases the number of photons, which in turn increases the number of electrons ejected from the atoms.

Semiconductors, Bands, and Band Gaps

In a solar cell, the photoelectric effect works in a different way to produce electrons – they do not leave the surface of the material. Because recombination of the electron and ion is instantaneous in most materials, only the exceptions can be used to build solar cells. These materials are called semiconductors.

When atoms are trapped together in a solid, they usually become isolated by regular spacing in all directions, which forms a lattice, also known as a crystal structure. Because the atoms in the lattice influence one another, the electron energy levels of the atoms combine to become “bands.” These bands can either be partially or completely full, or empty. In metals, the band is partially full, and this allows electrons to wander within the material. These materials are called conductors. On the other hand, materials called insulators have all their bands filled. Therefore, since unfilled bands are at a higher energy level, electrons are not able to move unless external energy equivalent to the gap in energy between bands is applied, which is called the band gap (portrayed in Figure 2).

Figure 2. Electron bands in a solid. The valence band exists below the band gap and the conduction band occurs above the band gap. Acceptor states would lie immediately above the valence band, while donor states would sit immediately below the conduction band.

In semiconductors, the filled band, also called the valence band, and the band in which electrons are free to move, or conduction band, are divided by a potential difference of approximately 1 volt. Therefore, incoming light can impel an electron from the valence band into the conduction band if it possesses energy of approximately 1 electron volt. Ultimately, if the electron in the conduction band doesn’t recombine, its energy can be surrendered in an external circuit prior to returning to the material.

Semiconductor Doping

To avoid the recombination discussed above, solar cells use two different types of ‘doped semiconductor’. Pure silicon is developed the presence of silicon vapor that is doped with acceptors or donors to insert layers of p-type or n-type material. For p-type semiconductors, atoms with fewer electrons in the outermost shell than in the rest of the atom are present on intermittent lattice sites, causing holes for electrons. Conversely, n-type semiconductor lattice sites have atoms possessing more electrons in the outermost shells than the rest of the atom. These extra electrons can move around in the n-type material when an external potential is applied, while in the p-type material, it is the holes that move around.

Using n-type and p-type together results in the creation of a p-n junction, where the electrons in the n-type region combine with the holes in the p-type in the region close to the boundary. This eliminates free charges and forms an internal electric field there within the semiconductor that averts the movement of other charges. When an external electric field is applied, it could act in two ways: with or against the direction of the internal field at the boundary. A current can only flow due to an external electric field in the direction that allows the internal electric field to be minimized. Devices that allow this to occur are called diodes.

Connection Between Solar Cells and Photovoltaic Cells

The word photovoltaic is composed of ‘photo’, indicating light, and ‘voltaic’, indicating a potential difference from light. The light directly frees electrons, and the diode action makes certain that if one of the materials composing the junction undergoes the photoelectric effect and produces charges, the electrons can flow in only one direction. The current must pass through an external circuit to reach the other side of the p-n junction and join with the opposite charge.

Therefore, as long as light is incident on the solar cell, charges will be produced via the photoelectric effect and the current will flow. Needless to say, when there is no light, there is no current. This is the main problem with solar energy; when the Sun goes sets, or is covered by a cloud, the cell will cease to produce current.

Solar Cells

Solar cells work to directly transform light into electricity. As described above, when light strikes, electrons are liberated in the p-type region and holes are produced in the n-type region; this lowers the potential energy barrier at the p-n junction. A current flows and establishes an external potential difference. Solar cells act similar to diodes, forcing currents to flow in only one direction.

Standard solar cell cross-sections can be observed in Figure 3b and c. A solar cell from the outside is shown in Figure 3d. The thin lines in Figure 3d represent collectors of charge that have been separated within a solar cell. The ridges cover wires that carry the charge away from the thin strips. Excess energy from the band gap is converted to thermal energy in the solar cell, increasing its temperature. To minimize this, it is required to match the band gap to the available visible light.

Figure 3 a. Solar cell drawing. b. Connections for a p-type solar cell. c. Connections for n-type solar cell. d. Actual solar cell.

 

 

 

 

 

 

 

 

 

Figure 4. Drawing of a photons coming into contact with a solar cell.

 

 

 

The solar cells are single wafers of semiconductor. Each wafer can produce a small amount of power at the potential difference (voltage) determined by its band gap. To use the cells for mass energy collection, they must be assembled into larger structures, and then from into even larger structures.

Societal Implications

The use of solar panels in modern day society is crucial as a source of alternative and renewable energy. The sun (and solar energy) will be around much longer than fossil fuels will be and are much cleaner. In addition to being “clean” (or free of pollution), using solar panels is also much less time consuming and may be used with little maintenance – with the help of programs such as Simply Solar.

Solar panels would be extremely beneficial in rural or developing communities such as South Africa, Nepal, or some regions of China. These often remotes regions have trouble acquiring and utilizing electricity – even if these areas were near urban centers many lack the necessary funds to live sustainable lives when depending on electricity from outside companies. Solar panels after purchase (or donation) require little to no funds to upkeep apart from cleaning and realigning. This would provide many communities with the electricity to help purify water and heat homes. The potential that this technology has to improve the lives of individuals is endless – in just the last year alone over 3.4 million individuals have died from water-disease related deaths, and over 780 million individuals lack access to clean drinking water.

 

Figure 5. A photo of students at the Kopan monastery

in Kathmandu, Nepal standing beside donated solar

panels.

 

 

 

 

On a global scale, solar panels will also help reduce pollution – a great deal of electricity is generated by burning fossil fuels or other methods that create pollution such as smog which are reported to have a multitude of harmful side-effects. In addition, the burning of fossil fuels results in the release of greenhouse gases, which trap heat in Earth’s atmosphere. This increase in greenhouse gases and temperature would result in global warming; the melting of ice caps and the subsequent rise in sea level and flooding.

In conclusion, solar panels though often thought of as expensive and as a high-maintenance technology are actually quite simple to upkeep – it’s benefits outweighing the expenses. With technologies such as Simply Solar, panels can be aligned to generate the greatest amount of electrical energy based on the angle in relation to the sun. On a societal aspect, this technology will also aid in reducing global warming and decrease the number of contaminated water related deaths. Overall, solar panels are an extremely useful and revolutionary piece of technology that can only change our society for the better.

References

Foroudastan, Saeed . Solar Power and Sustainability in Developing Countries. unknown: Engineering Technology and Industrial Studies College of Basic and Applied Sciences Middle Tennessee State University, 2006.

Knier, Gil. “How do Photovoltaics Work?  – NASA Science.” NASA Science. http://science.nasa.gov/science-news/science-at-nasa/2002/solarcells/ (accessed January 1, 2013).

“Solar Cells.” The NEED Project. solardat.uoregon.edu/download/Lessons/Appendix_E_HowSolarCellsWork.pdf (accessed January 1, 2013).

“Solar Energy Facts – Current Solar Energy Information from Solar Online | Solar Content.” Solar Shop – Solar Power, Solar Panels, Solar Systems, Inverters – Solar Online Australia – Solar Online Australia. http://www.solaronline.com.au/content/solar-energy-facts/ (accessed January 2, 2013).

“Solar Power Energy Information, Solar Power Energy Facts – National Geographic.” Environment Facts, Environment Science, Global Warming, Natural Disasters, Ecosystems, Green Living – National Geographic. http://environment.nationalgeographic.com/environment/global-warming/solar-power-profile/ (accessed January 2, 2013).

“Solar cells — the physics behind them.” Solarbotics.net — Home page. http://www.solarbotics.net/starting/200202_solar_cells/200202_solar_cell_physics.html (accessed January 2, 2013).

“The Physics of Sustainable Energy Generation.” UBC Physics & Astronomy Outreach – Home. http://outreach.phas.ubc.ca/phys420/p420_01/james/solarphysics.htm (accessed January 2, 2013).

“Water Facts: Water.” Water.org. http://water.org/water-crisis/water-facts/water/ (accessed January 2, 2013).

Wind Energy as an Alternative

Wind Energy as an Alternative

                                                                                                                                                                                                    Shuainan F., Jing S., Shawn T.

Brief Description of Wind Power

Wind is generated when the sun heats up land, the air around the land will absorb the air and there will be a creation of warmer air. At a particular temperature, the hot air will rise quickly because it is lighter than cool air. Fast air particles will exercise more pressure than the slow moving particles. This means that it will take smaller amounts of hot air particles to maintain the given air pressure at a particular elevation. When the hot air rises due to its lighter mass, the cool air will rush in to fill the gap that the hot air has left. The rush of the cool air is what is known as wind. Using the wind, it is possible to generate electricity that can be used in everyday life as an alternative energy source.

Topic ideas

Main Topic idea: Physics of Wind Power

Sub-topic idea 1: Classical Physics Concepts of Energy, Momentum, and Power

Sub-topic idea 2: Structure of the Turbine and its Significance

Sub-topic idea 3: The Importance of the Generator

Sub-topic idea 4: Inside a Generator

Sub-topic idea 5: Magnetic Force and Electromagnetic Force

Societal Implications

This type of alternative energy is very reliable for energy consumption in the long term, as wind is a resource that will is infinite and renewable. This type of energy generation is much more sustainable than fossil fuels as it does not pollute the environment or produce radioactive or toxic waste. Despite the cost of installation of a wind turbines, wind energy is much more economic than fossil fuels. Wind power may cost a slight bit more than fossil fuel generated power, but it much better for the environment. In more windy areas, there is sometimes so much power generated, that it is possible to sell energy back to the power company!

Wind energy is not only reliable, but it is pollution free, and is cost efficient. It can take as little as one efficient wind turbine to generate enough energy to power an entire household.

Topic 1 Classical Physics Concepts of Energy, Momentum, and Power

Wind Energy is a form of energy that involves using a wind turbine as an electric generator to convert the kinetic energy of the wind to electric energy. Wind turbines consists of a rotor comprised of three blades. These components are placed on a pole with an average height of 20 meters from the ground. Generally, the higher the rotor is placed, the stronger the wind gusts are. In order to optimize the output of the wind, three factors need to be considered. Stronger wind means a wind with higher speed and force; this means that more power will be generated.

 

 

From the formula E_k = ½ mv² , it can be seen that speed and kinetic energy are directly proportional. When there is more speed, there will be a greater kinetic energy. Using the formula: P = E/t, when there is more energy, power (energy/second) will also increase. This is because energy is directly proportional to power. Therefore a higher velocity will result in more power being generated.

Another factor that will increase the output of energy is the size of the turbine rotor and blades. A larger rotor and blades means more mass. Using the momentum formula: p = mv, mass is directly proportional to momentum. This means that the greater the mass of the motor, the greater the momentum of the motor, Ft = p.

Since momentum and time are directly proportional, an increase in momentum would result in an increase in time. Thus, a turbine of more mass would spin for longer even without wind continually driving it.  P = E/t , hence Pt = E.

From this formula, time and energy are directly proportional, the longer the turbine is spinning, the higher its energy output.

 Topic 2 Structure of the Turbine and its Significance

The structure of a wind turbine plays a crucial role in the functionality and workings of wind power. Not only does the wind need to be able to turn the blades, but the whole process must be made efficient, so as to generate maximum amount of energy possible. This way, not only is wind power a clean alternative to coal and other hydrocarbon combustion processes, but it is also at least comparable to, or beats the 40% efficiency of a thermo-electric power plant that runs off of hydrocarbons.

The structure of a wind turbine can be summarized in the following diagram:

Figure 1: Parts and components of a wind turbine

The process of generating power with a wind turbine is identical to the process used by hydrocarbon combustion. They both use a generator, and an external source of energy to turn the generator. The only difference is the type of energy input used. With hydrocarbons, the energy input starts off as the chemical energy stored in bonds between atoms in fossil fuels such as coal and natural gas. When these substances are combusted (reacted with oxygen), the chemical energy gets converted to thermal energy. This energy then is transferred to water molecules, boiling off the water as steam, which in turn drive a steam turbine attached to a generator. At this point, the chemical energy of the hydrocarbon fuel source is now the kinetic energy of the steam turbine, which in turn gets converted to electrical energy via the generator. Wind power however, undergoes less energy conversions, and is therefore a much more simple set of steps.

Simply put, a wind turbine is a generator attached to a set of blades, and a rotor. The blades are angled in such a way that when wind blows on them, the kinetic energy of the fast-moving air molecules is transferred to the blades and rotor of the turbine, causing the turbine to spin. Because the rotor of the turbine is linked to the generator via a system of shafts and gears (as seen in the diagram above), the generator gets spun, converting the kinetic energy of the wind turbine into electrical energy.

 Topic 3 The Importance of the Generator

The generator (structure 7) is the heart of the wind turbine. Without this amazing piece of machinery, the turbine is not much more than a tall, metallic pinwheel. While it is obvious what the generator’s role is, what is it exactly that allows this piece of equipment to operate? The answer requires looking into the inner workings of the generator, and concepts of electromagnetism that contribute to the technology that drives this powerful machine.

 Topic 4 Inside a Generator

A generator has the exact same structure as a motor. The only difference between the two is the input and output energies. Whereas in a motor the input energy is electricity and the output is kinetic energy, a generator requires an input of kinetic energy and supplies an output of electricity. There are two types of generators as there are motors (alternating current, or AC, and direct current, or DC). Typically, when it comes to an application that is as large as electricity generation for a large area (such as big-scale wind farms in the countryside do), the generator type is AC. A personal-sized wind turbine however, such as the ones used by people in their backyard, usually contains a DC generator.

Figure 2: The inside parts of an AC generator.

The generator is composed of a set of magnets to provide the magnetic field and magnetic force required to move electrons (i.e. create a current flow), a set of spinning coils in the magnetic field, where the current is initiated, slip rings, which are linked to wires carrying current out of the generator, and brushes, which allow the slip rings to contact the wires while not disturbing the spinning of the wire coil. A spindle is then attached to the generator along the axis of rotation, to allow the generator to be spun. A DC generator is very similar, with only a minor difference in terms of structure – instead of slip rings, it contains a split-ring commutator:

Figure 3: The insides of a DC generator.

Combining only these relatively simple few structures together (but there may be many of one structure), and an external force to turn the spindle of the generator, large, high-output wind turbines are made capable of cranking out power at rates of  up to 50 kilowatts (50 000 watts)! How is it that these few simple structures allow such a big achievement?

Topic 5 Magnetic Force and Electromagnetic Force

Magnetic force and electromagnetic force are the two principles that allow the generator to perform its task. Imagine the classical experiment from science class of thrusting a bar magnet into a coil of wire that is hooked up to a galvanometer. What do you observe? The needle of the galvanometer suddenly jumps, indicating that there is current flowing through the wire. Hence, this is named the generator effect, and the current is an induced current known as electromagnetic force. The generator of a wind turbine (either AC or DC) operates using the same principle.

Looking back to figure 2 of the AC generator, the open left-hand rule can be applied to the generator. To do this, select one half of the coil that is moving in a specific direction. Then, point the fingers of the left hand in the direction of the magnetic field (from the north pole to the south pole), and the thumb in the direction the wire coil is moving. The outward direction the palm is now facing is the direction of the magnetic force, the force that pushes electrons in the atoms of the wire. Because the wire is made of metal, and metallic atom nuclei have very weak holds on their electrons, the magnetic force can easily push electrons in a certain direction in the wire. Since the halves of the ring are moving in opposing directions, the current induced in the parallel sections are in opposing directions. Because it is connected at the top, the overall current is in the same direction, and an electric current them flows in the wires attached to the slip ring brushes. But where does the alternating current kick in?

Since the generator is obviously not going to keep switching its direction of spin, and neither is the magnetic field, the magnetic force must change in order to create the alternating current. Look closely at the diagram, and use the open-left hand rule. As soon as the generator makes a half-way spin and now the loop halves have switched spots, the magnetic force in each half is in the opposing direction as what it was when the loop was on the other side. This causes electrons to continuously switch their direction as they get pushed around by the magnetic force generated. Hence, alternating current has no fixed direction, and electrons continually flow back and forth in a wire.

So, what prevents the same thing from happening in a DC generator then? During the switch where the two wire coils end up on opposite sides, the split-ring commutator prevents the brushes from contacting anything at all. And when the switch is complete, each brush is contacting the piece of the commutator that the previous brush was contacting. This ensures that the part of the wire coil that is on the right side (magnetic force in a certain direction) at the moment will always contact the wire that is attached to the right side, and the part of the coil on the left side (magnetic field in another direction) always contacts the wire attached to the left. Therefore, no such reversal in current occurs, and a direct current is generated.

Topic 6 Why Alternating Current?

A common question is, why is alternating current used for large-scale electricity generation, if most appliances use direct current? The answer is related to the efficiency of transporting a current over a long distance. Since it is obvious that the energy is going to be lost due to resistance of the wire it is transported over, it is desirable to minimize this loss as much as possible. To maximize efficiency, the voltage of the electricity must be stepped up. A property of alternating current that direct current lacks is its ability to be stepped up or down in terms of voltage. This is not only useful to make transporting over long distance efficient, but also allows the voltage to be adjusted accordingly before it is used.

 Conclusion

Clearly, wind energy is advantageous in terms of eco-friendliness and in terms of costs, due to its relative simplicity and its rather high output. Of course, there are drawbacks with wind energy, as there are with anything, but there are many more advantages than there are drawbacks. So why not choose it over other forms? Converting to wind energy is a breeze!

 References and Citations

• Alternative Energy. (2009, July 24).What factors affect the output of wind

turbines? Retrieved December 29, 2012, from http://www.alternative-energy-news.info/what-factors-affect-the-output-of-wind-turbines/

• howstuffworks. (n.d.).  How Wind Power Works. Retrieved December 29, 2012,

from http://science.howstuffworks.com/environmental/green-science/wind-power.htm

• The Electricity Forum. (2012). Wind generated electricity. Retrieved December

29, 2012, from http://www.electricityforum.com/wind-generated-electricity.html

• The Marsmen Website. (2005). How do Wind Turbines Work? Retrieved

December 29, 2012, from http://marsmen.webs.com/windpoweronmars.htm

• Tutor Notes. (2011). AC Generator – Electromagnetism. Retrieved January 2,

2013, from http://www.tutornotes.com.hk/ac_generator/

Mars? Possible?

Mars? Possible?

                                                                                                         Alternative Energy Project                                                                          January 2^nd, 2013

By: Christine K, Sarah E, Esther C

                                                   (ESA, 2012)

Have you ever thought about life on Mars? Stephen Johnson, director of INL’s Space Nuclear Systems and Technology Division, did. For years, NASA has gathered research and data on a sufficient way to produce energy for potential Mars missions. In 2008, the team had began to develop the idea to provide a power system that can run continuously for many year that provides about 110 watts of electricity. The team started to build the mission in the year 2008, by creating a rover called Curiosity, which was ready to lunch by 2009. However, scientists have come across the problem of sustainable energy usage in order to prevent any fuel declines out in space. The latest space battery that can reliably power a deep space mission for years on end is the Multi-Mission Radioisotope Thermoelectric Generator. Curiosity successfully landed on August 5^th 2012, and will carry out the mission for another 23 months. 

This amazing device can provide a continuous stream of heat and power for the rover, Curiosity. How can it do this? The rover, Curiosity, is a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), which is designed specifically to operate on the planetary body of Mars, and as well as in the vacuum of space. The nuclear battery that consistently converts heat into electricity by transforming it from the natural decay of radioisotope materials into electricity, this electricity creates the power for the rover to function on Mars. Natural decay is when the nucleus of unstable radioactive isotopes break apart. A nucleus is composed of positively charged protons that are compacted together in an extremely small volume of space. When the protons start to become unbalanced duo the external force, the protons loose control and start to repel like as the Law of charges states it. This causes the protons to repel each other inside the nucleus. When the forces holding the nucleus together can no longer sustain the energy of the particles the nucleus ruptures.  In this way energy is given off which is captured to fuel the Thermoelectric Generator. Due to this energy, the rover is able to be in fulltime communication with regarding where it lands, and can go farther, travel to more places, and last longer. On Mars, the rover will investigate the life of the organisms and the different craters for clues about whether there is microbial life.

The generator consists of two major elements: a heat source, and a set of thermocouples that convert the heat energy to electricity.  The heat source contains plutonium-238 dioxide, this is a radioactive isotope of plutonium that has an extreme half-life of 87.7 years. It emits powerful alpha particles but no other significant amounts of harmful radiation.

One gram of this heat source generates approximately 0.5 watts of power. The heat that this radioactive isotope produces is surrounded by a solid-state thermocouple that converts the plutonium’s heat energy to electricity. A thermocouple has two conductors of different materials that produce a voltage and thereby, a current. These thermocouples are widely used as temperature sensors but can also be used to convert a heat gradient into electricity.

(“Diagram of a MMRTG” 2012)

Missions targeting outer space require reliable and long living power systems that will provide electricity and heat for not only science instruments, like rovers, but also entire spacecraft. The radioisotope thermoelectric generator is capable of such a feat. This nuclear battery can sustainably convert heat into electricity for long periods of time. A German scientist named Thomas Johann Seebeck first discovered the principles required to convert heat into electricity. In 1821, Seebeck found that circuits made with two dissimilar metals, that have junctions at different temperatures, deflect a compass magnet. Seebeck originally believed this deflection was due magnetism and later on, realized that an electrical current was induced from the temperature difference. Today, this effect is known as the Peltier-Seebeck Effect.

Although this sounds like a very good idea there are many set backs that the scientists have had to address to ensure the safety of space missions. For starters the radioisotope fuel can be a health hazard when broken into fine particles that can be inhaled or ingested and then retained in the body. The scientists dealt with this by using a ceramic form of radioisotope fuel know as plutonium dioxide. This form has material properties similar to a coffee cup: it tends to fracture in large, none inhalable chunks and is highly insoluble; this means that it does not easily mix or become easily transportable in water, nor does it react easily with other chemicals.

The plutonium dioxide is also encased is a strong, ductile metal that does not corrode or react chemically with the radioisotope fuel. These changes made have increased the safety of the use of a radioisotope thermoelectric generator. Intensive testing and computer modeling has also been conducted over the past five years to ensure malfunctions do not occur. The MMRTG (Multi-Mission Radioisotope Thermoelectric Generator) has undergone a series of experimental and real life tests. Before 1971, three space missions were conducted with the help of MMRTG. These missions were subject to mechanical failures and human errors that did not affect the performance of the radioisotope power system. Experimentally, the mechanical design of the fuel source has undergone a series of tests, and through each mission, the generator performed as it was designed. Testing such as fires, blasts similar to launch vehicle explosions, submersion in water, and impacts designed to stimulate pieces of metal shrapnel, helped to create the final model of the MMRTG. In these ways, the credibility and reliability of the MMRTG has been held in great respect by space institutions the entire world.

The MMRTG has a minimum lifetime of fourteen years, which long space missions are guaranteed a reliable fuel source. Furthermore, although there are varying models of this generator in different space institutions around the world, the weight of all of these models individually are less than thirty-two kilograms, the minimal weight ensures that small devices such as the rover Curiosity can move around with the MMRTG as its main fuel source. The rover Curiosity landed on August 5th of this year and is currently collecting data on the surface of the red planet. Because of the reliable Multi-Mission Radioisotope Thermoelectric Generator Curiosity uses, it is able to function at night and winter seasons of the planet Mars. Also, this fuel source model is extremely more flexible than other models because it is capable of meeting the needs of a wider variety of missions through the MMRTG producing electrical power in small increments that are slightly above one hundred watts. In this sense, it is capable of fueling different types of space equipment, no matter how small or large.

In conclusion, this Multi-Mission Radioisotope Thermoelectric Generator has becomes one of the leading fuel sources in almost all of the current space missions happening in our solar system. The vigorous testing it has undergone as well as the impeccable performance of the generator itself in real life missions has made the reliability of this technology skyrocket. Thus, space exploration has come to a new level of possibilities.

Bibliography

Caponiti, A. U.S Department of Energy, The Office of Nuclear Energy. (2006). Space radioisotope power systems multi-mission radioisotope thermoelectric generator. Retrieved from website: http://nuclear.gov/pdfFiles/MMRTG.pdf

Moore, J. T. (June 2011). The process of natural radioactive decay. (Chemistry For Dummies ed., Vol. 2nd Edition). John Wiley & Sons. Retrieved from http://www.dummies.com/how-to/content/the-process-of-natural-radioactive-decay.html

Alpha particle. In (2012). Wikimedia Foundation Inc. Retrieved from http://en.wikipedia.org/wiki/Alpha_emitter

Graham. (2011, 12 02). [Web log message]. Retrieved from http://www.thenakedscientists.com/forum/index.php?topic=42323.0

Thomas johann seebeck. In (2012). Wikimedia Foundation Inc. Retrieved from http://en.wikipedia.org/wiki/Thomas_Johann_Seebeck

DOE/Idaho National Laboratory (2011, December 13). Reliable nuclear device to heat, power Mars Science Lab. ScienceDaily. Retrieved January 3, 2013, from http://www.sciencedaily.com­ /releases/2011/11/111121142455.htm

National Aeronautics and Space Administration. (n.d.). Safety of radioisotope power systems. Retrieved from website: http://solarsystem.nasa.gov/rps/docs/FINAL_APPRPSSafetyFactSheet052112.pdf

Curiosity. (Photographer). (2012). Mars science laboratory. [Print Photo]. Retrieved from http://solarsystem.nasa.gov/rps/msl.cfm

(2012). Diagram of a mmrtg. (2012). [Web Graphic]. Retrieved from http://en.wikipedia.org/wiki/Multi-Mission_Radioisotope_Thermoelectric_Generator

ESA. (Photographer). (2012). Mars . [Web Photo]. Retrieved from http://www.stfc.ac.uk/News and Events/3376.aspx

The Generator Effect: Hydro-electric Dam

The Generator Effect: Hydro-electric Dam

Author: Ricky B.

The origins of the Hydro-electric dam: The dam was first used for fishing but when they found out they could use it to do work, they integrated it to grind wheat into flower. Then in the 1700s they started making the water wheel turn a series of gears to turn a large blade to cut lumber and also for pumping irrigation water.

Then in 1882 in Appleton, Wisconsin  they made the first hydro-electric dam that generated a total of 12.5 kilowatts of power, this was a revolution to their former knowledge. It could provide enough energy to power 250 lights at maximum. At this point they still used a simple engine but 20 years later they came up with the hydraulic reaction turbine, which created large advancements in the hydroelectric energy field. So much so the in the early 1900s hydroelectric dams were producing 40% of all the electricity in the USA. In 2001 90,000 mega watts of power could be produced from hydro-electric dams.

 

Hydro-electric power: It is the power generated from a spinning turbine that is spun when the water falls onto the turbine or passes around the turbine to spin it creating electricity. As you can see in the photo potential energy from the weight of water falling through a vertical distance is converted to electrical energy. The amount of electric power P that can be generated is given by the equation below, where Q is the volume flow of water, h is the height through which the water falls, and k is a constant equal to 0.102 when Q is in cubic meters and h is in meters (SI units). The formula for electricity of the hydro electric dam is P = Qh/k (kW units).  This unit is a key part to how they know how to build the dam and how to operate the wicket gates to make sure that the turbine gets enough water and not too much Water so that the damn floods. It is also used to calculate the amount of power they can achieve with a certain amount of water or how much water they need to create the required power.

 

The Hydro power generator: The water flows through the dam then hits the turbine turns a shaft which rotates a series of magnets past copper coils and a generator to produce electricity. There is a part of the turbine called the Kaplan Head which is the part associated with the adjustable blade which improves the efficiency of the pump to counteract the variations in water flow and energy demands.

The rotor is a series of magnets that is turned by a shaft that spins inside the stator (which is the stationary coil of wires) which is where the magnetic field is created. This is all controlled by a series of gates called the wicket gates that provide the water flow to the turbine with gets everything to go.

 

 

 

 

The key Aspects to the Hydro-electric power:  The key aspects to the hydroelectric dam are the water cycle and the force of gravity. Water that evaporates from a river or lake turns into clouds. The water in these clouds that came from a water source will then fall back down to earth. Some of the water that evaporated from a lake or the ocean will fall onto a higher elevation than the lake or ocean that it originally was in. This increase in elevation is directly related to the energy that is created through hydro-electric power. Water evaporates and rises in altitude, while the whole hydroelectric process relies on water falling, and losing elevation.

The second major aspect is gravity because the water is falling onto the turbine to cause it to spin. A hydroelectric dam capitalizes on gravity. In order to subtract the gravitational force from the water and cause an energy transfer, a hydroelectric dam blocks the flow of water from a higher elevation to a lower elevation. The physical dam actually lets a small amount of water pass through the dam, but this amount is blocked by a turbine. The turbine is the primary object that utilizes the gravitational force of the water. This is the only reason that the hydro-electric dam works to create a load of electricity.

Advantages of Hydropower:

1. Electricity can be produced at a constant rate.

2. If electricity is not needed, the sluice gates can be shut, stopping electricity generation. The water can be saved for use another time when electricity demand is high.

3. Long lasting energy because dams do not break easily.

4. The lake that forms behind the dam can be used for recreation activities.

5. The lake’s water can be used for irrigation purposes.

6. The buildup of water in the lake means that energy can be stored until needed, when the water is released to produce electricity.

7. It is not bad for the environment.

Disadvantages of Hydropower:

1. Dams are extremely expensive to build and must be built to a very high standard.

2. It blocks the river for decades at a time and blocks the environment for very long time.

3. The flooding of large areas of land means that the natural environment is destroyed.

4. People living in villages and towns that are in the valley to be flooded, must move out. This means that they lose their farms and businesses. In some countries, people are forcibly removed so that hydro-power dams can be made.

5. The building of large dams can cause serious geological damage. For example, the building of the Hoover Dam in the USA triggered a number of earth quakes and has caved in the earth’s surface at the Hoover Dam.

6. Although modern planning and design of dams is good, in the past old dams have been known to be breached (the dam gives under the weight of water in the lake).

7. Dams built blocking the progress of a river in one country usually means that the water supply from the same river in the following country is out of their control.

8. Building a large dam alters the natural water table level. For example, the building of the Aswan Dam in Egypt has altered the level of the water table.  This has also happened in many other places were the dams mess up the water flow so then many minerals are not displaced which leads to problems for farmers.

References:

http://library.thinkquest.org/17658/hydro/hydphysicsht.html

Think quest, (unknown ), used Jan 3, 2013

http://ga.water.usgs.gov/edu/hyhowworks.html

Howard Perlman, (2012), used Jan 3, 2013

http://curriculum.cna.ca/curriculum/cna_world_energy_res/hydro-eng.asp?bc=Hydroelectricity

Unknown, (2007), used Jan 3, 2013

http://science.howstuffworks.com/environmental/energy/hydropower-plant.htm

Kevin Bonsor, (unknown) used Jan 3, 2013

Wind Farms, It’ll blow you away.

Alternative Energy Project

            Wind Farms, It’ll blow you away.

                                                                                                            Daniel T, Matthew B

                                                                                                                                                                      2012-01-06

In society today, fuel has become less desirable due to its harmful effects on the world. It now leads in alternative energy sources by two common methods : electricity by generator effect as well as electricity by photoelectric effect. Some examples of electricity by generator effect involve hydroelectric dams, wind farms, or nuclear power plants, compared to electricity by photoelectric effect which involves solar panels. A key element for an alternative energy source that is being currently being improvised world-wide is wind farms.  As the utilization of wind energy has increased in recent years, there has been an annual increase in installed capacity of around 20%. For example, the 38 GWe (GWe is the gig watts of electric energy produced by wind turbines in the location) increment in 2010 represented an investment of EUR 47 billion, which is equivalent of 65 billion in US dollars, and was followed by 41 GWe increase in 2011. Which brought  the total world wind capacity up to 238 GWe, with tens of thousands of turbines in operation? Currently, wind turbines of up to 6 MWe are now functioning in many countries around the world. China leads the field with over 62 GWe installed, US with 47, Germany with 29, Spain with 21.5GWe, and India with 16 GWe at the end of 2011. The largest wind farm is that of the Forewind for the Dogger Bank in the North Sea, producing around 7.2GWe, which will supply the UK with some 25 billion kWh/year. Today, Denmark is the most intensely wind-turbined part of the planet with 1.74 per 1000 people- 4700 turbines totaling 2315 mWe, 1800 MWe of which have priority dispatch and power .

Figure1. Graph showing the increased purchase of wind turbines in Denmark

(http://energy.saving.nu/windenergy/history.shtml)

Wind turbines ranges from class 1 which are the lowest to class 7 with are the highest. Wind turbines consist of a few basic components: a rotor( the part that rotates in the wind), an electrical generator, a speed-control system, and a tower.

Figure2. Wind farm with several hundred wind turbines in motion

(http://blogs.telegraph.co.uk/news/files/2012/02/wind-turbine-2.jpg)

Figure3. Parts of a wind turbine

(http://www.therockatbc.com/wp-content/uploads/2012/02/Wind-Turbine-Diagram.gif)

(http://www.canadiangeographic.ca/magazine/oct12/nwt_diamond_mines_wind_power.asp)

In the above electronic article “Wind Power, energy gem”  wind power is fueling the push to green diamond minds in the Northwest Territories. In the Northwest Territories there are currently four towering wind turbines which are 99 m tall, these wind turbines were installed by a mining corporation known as Rio Tinto at the Diavik Diamond Mine and are scheduled to be operational near the early fall. This is the first industrial use of wind power in a mining operation in the world as stated by Wade Carpenter, the territorial government alternative-energy specialist.

Figure 4. Rio Tinto Diamond Mines in Canada

(http://www.bdlive.co.za/world/americas/2012/12/04/news-analysis-cleaner-power-for-a-dirty-industry)

Societal Impact: The societal impact of the wind turbines is that prior to the creation of the wind turbines in the Rio Tinto at the Diavik Diamond Mine, the mine was being powered entirely on diesel fuel. Many problems came from the use of such fuel, as they had to be trucked up with winter ice and then driven to the roads of the mine; but when the warm temperatures melted the roads, the mines had to fly in fuel, increasing the greenhouse-gas emissions given off by the Northwest Territories by a staggering amount of 60 percent since the onset of diamond mining which had occurred 20 years ago. To solve this issue, the Diavik’s wind-diesel hybrid system was incorporated as the system would reduce the carbon dioxide emissions by approximately six percent. The wind turbines reduced the annual diesel consumption by four million litres, or 100 truckloads as stated in the article- which would save the Diavik $6 million a year at today’s fuel prices. Among the Rio Tinto at the Diavik Diamond Mine, wind turbines allowed people to avoid external or societal costs associated with conventional resources, namely, the trade deficit from importing foreign oil and other fuels, less pollution to the environmental cost of pollution, and the cost of depleted resources. Wind powered turbines offer renewable energy forms, as well as it having no cost and being a renewable resource, there will always be the same amount in the future as it is as stated renewable, as it is a clean source.

Among that, many countries that have implemented wind turbines like the UK , Germany , and Denmark have seen abundant amounts of energy produced , for example in  Germany, it was reported that between 6 and 8% of the total capacity of the wind was usable, resulting in a total of 14.5 GWe of energy for Germany. Keep in mind that one megawatt or MW can supply electricity to approximately 240 to 300 households per year, so the amount of households that could be supplied by 14.5 GWe of energy form wind turbines is immense.

Also the pros of wind turbines as stated are that wind energy is a free, renewable resource, clean non-polluting, they emit no air pollutants or greenhouse gases for example, in the U.S department of Energy in 1990, California’s wind power plants offset the emission of more than 2.5 billion pounds of carbon dioxide and 15million pounds of other pollutants that would’ve produced otherwise if California had used fossil fuels. Remote areas that are not connected to the electricity power grid can use wind farms to provide for their own energy, and wind turbines play a role in both the developed and third world. Wind also compares more favorable with the costs saved on fuel from fossil generators.

Some cons of the wind turbine are: that the strength of the wind is not constant and it varies from zero to an abundant force via a storm, the amount of energy produced will vary, wind turbines are noisy, and may cause harm to the animals that live in the location. But most of these cons are not being solved.

As wind turbines are located in areas that experience high average wind speeds, and that are distant from areas of electricity demand. New technology has improved to diminish the noise created from wind turbines. Under most conditions, modern turbines are quiet.

Physics Implication: The use of wind turbines in wind farm incorporates the physic concept of kinematics. Wind energy is the kinetic energy of moving air generated by high winds, the kinetic energy of a mass m and the velocity of that mass, v, can be summarized in the formula:  “ Ekin=1/2mv^2” . Since air mass , m, can be determined from the air density , p, and the air volume, v , according to m=pV, then Ekin,wind=1/2Vpv².

Power is the energy divided by time, time which is used as (delta) t, travels a distance which is velocity multiple by time, v (delta) t, which is then multiplied by the distance with the rotor area of the wind turbine, resulting in the volume ((∆V=A(∆t)(v)  which drives the wind turbine for the set period of time.  Since we know

we can  determine the power generated by wind.

With this formula we can see that wind power increases with wind speed, for example, doubling the wind speed gives eight times the wind power. This is why locations where wind occurs more frequently are prime locations for wind turbines to be set up at, but the effective useable wind power is less than indicated by the equation.

This is, because given that the wind speed behind the turbine cannot be zero, since no air can follow, the result is that only a part of the kinetic energy being able to be extracted.

Given this diagram:

Figure5. Diagram of two turbines, http://uni-leipzig.de/~energy/ef/15.htm

It is indicated that the wind speed in the second turbine is larger compared to the wind speed in the first. This is because the mass flow must be continuous, resulting in the area of the second turbine to be bigger than the first. The effective power is the difference between the two wind powers, which can be deprived using

In the case that the difference of both wind speed is zero, there is no net efficiency, and where the difference is too big, the air flowing through the rotor is too greatly hindered.

Wind turbines located too close together would be driven only by slower air. Therefore wind turbines would need a minimum distance of eight times the rotor-diameter for them to work with an efficient amount of air.

Turbines have lost one blade and now use three blades, due to the rotor power, which is proportional to the torque (M) acting on the shaft, and the rotation frequency (n).  The torque (M) increases with the number of blades, however, every blade, as it rotates, reduces the wind speed known as the wind shadow. The wind shadow increases with the number of blades, which means the optimal tip speed ratio is achieved when three blades are used.

Figure6. Four bladed wind turbine                                                             Figure7. Three bladed wind turbine

(http://www.chegg.com/homework-help/questions-and-answers/physics-archive-2011-april-06)

(http://indianapublicmedia.org/amomentofscience/wind-turbines-have-three-blades/)

Wind Turbines continue to prove to be a successful and efficient alternative energy source in today’s society. Given the successes of wind turbines in countries like the U.S, Denmark, U.K, and Germany, it can be said that wind farms and wind turbines can essentially become an important source of energy in the world. As the wind turbine industry continues to be fastest growing power source worldwide. “http://www.nature.com/news/the-trouble-with-turbines-an-ill-wind-1.10849

References:

Websites:

. 2013. . . . [ONLINE] Available at: http://windeis.anl.gov/documents/docs/WindFAQ21Jun05.pdf. [Accessed 07 January 2013].

Renewable Energy and Electricity | Sustainable Energy | Renewable Energy. 2013. Renewable Energy and Electricity | Sustainable Energy | Renewable Energy. [ONLINE] Available at: http://www.world-nuclear.org/info/inf10.html. [Accessed 07 January 2013].

What are the Benefits? – Wind Energy and Wind Facts – CanWEA. 2013. What are the Benefits? – Wind Energy and Wind Facts – CanWEA. [ONLINE] Available at: http://www.canwea.ca/wind-energy/index7_e.php. [Accessed 07 January 2013].

Advantages and Disadvantages of Wind Power. 2013. Advantages and Disadvantages of Wind Power. [ONLINE] Available at: http://www.technologystudent.com/energy1/wind8.htm. [Accessed 07 January 2013].

Main Article:

An energy gem – Canadian Geographic. 2013. An energy gem – Canadian Geographic. [ONLINE] Available at: http://www.canadiangeographic.ca/magazine/oct12/nwt_diamond_mines_wind_power.asp. [Accessed 07 January 2013].

Images:

Physics Archive | April 06, 2011 | Chegg.com. 2013. Physics Archive | April 06, 2011 | Chegg.com. [ONLINE] Available at: http://www.chegg.com/homework-help/questions-and-answers/physics-archive-2011-april-06. [Accessed 07 January 2013].

Why Do Wind Turbines Have Three Blades? | A Moment of Science – Indiana Public Media. 2013. Why Do Wind Turbines Have Three Blades? | A Moment of Science – Indiana Public Media. [ONLINE] Available at: http://indianapublicmedia.org/amomentofscience/wind-turbines-have-three-blades. [Accessed 07 January 2013].

Physics of Wind Turbines; Energy Fundamentals by R. Snurr and D. Freude, . 2013. Physics of Wind Turbines; Energy Fundamentals by R. Snurr and D. Freude, . [ONLINE] Available at: http://uni-leipzig.de/~energy/ef/15.htm. [Accessed 07 January 2013].

. 2013. . [ONLINE] Available at: http://www.therockatbc.com/wp-content/uploads/2012/02/Wind-Turbine-Diagram.gif. [Accessed 07 January 2013].

2013. . [ONLINE] Available at: http://blogs.telegraph.co.uk/news/files/2012/02/wind-turbine-2.jpg. [Accessed 07 January 2013].

Energy Saving Now!. 2013. Energy Saving Now!. [ONLINE] Available at: http://energy.saving.nu/windenergy/history.shtml. [Accessed 07 January 2013].

Alternative Energy

Alternative Energy Assignment

Jonathan L, Andy C, Wai Miu A

2012-06-08

 Nuclear energy has shown itself to be a rising alternative energy source that is already being used heavily in countries such as France, where it provides for 80% of France’s electricity energy. Nuclear power is produced through the generator effect with uranium-235 being its primary fuel. Uranium-235 is used because unlike its predominant isotope, uranium-238, uranium-235 is fissile (can undergo a fission reaction). Since uranium-235 typically only takes up around 0.72% of uranium-238, it needs to be enriched to about 2-3% before it can be used in a nuclear power plant.

Enriched uranium pellets. These pellets are arranged into long rods and bundled up before being placed in water in a nuclear power plant

As mentioned above, uranium-235 is fissile, and it is this exact fission reaction that creates a majority of the nuclear energy. uranium constantly undergoes spontaneous fission, making it a very good fit for nuclear power plants. The natural alpha decay that U-235 experiences can be explained through this formula:

As the above equation shows, when a neutron is introduced into a uranium-235 atom, the newly formed uranium-236 is unstable and thus undergoes fission, splitting into Krypton and Barium and releasing more neutrons. These newly released neutrons then strike other U-235 atoms, creating a chain reaction that theoretically should never end since neutrons are always being released (though uranium fuel rods will eventually run out).

Uranium-236 fission chain reaction

The actual energy is created through the splitting of the atom, which not only produces massive amounts of beta and gamma radiation, but also causes the release of an incredible amount of heat. This heat energy heats the water that the uranium is submerged in, creating steam that in turn drives a turbine. The spinning of this turbine is what generates the power.

Nuclear power today provides approximately 15% of the world’s electricity supply. The top 3 nuclear energy producers in the world are currently the United States, France and Japan. Nuclear power plants can be potentially very dangerous, preventing this method of energy production from being more popular. Aside from being one of the most efficient energy production methods out there, there is a potential risk when it comes to nuclear plants. It is impossible to build a nuclear plant that is guaranteed to be 100% accident free. If there happens to be an accident inside a nuclear power plant the destruction that it causes to humans and natural world is far greater than any other energy production method. Many countries are not willing to take this risk and that is why the popularity of nuclear power is still relatively low.

Nuclear power plant accidents such as the ones at Chernobyl (Ukraine) and Fukushima (Japan) are partially the reason some individuals are against this method of energy production. Although gases such as carbon dioxide and sulfur dioxide are produced at a minimum, nuclear power plants still produce radioactive waste. This waste is damaging to almost all ecosystems and their organisms and must be stored until its radioactivity is depleted to a lower safe level. There seems that in the present day that no one method of energy production is clearly more advantageous than another. Scientists are continually trying to improve the efficiency of nuclear power plants as well as decrease the amount of radioactive waste that they produce. Radioactive waste is stored underground and the more radioactive it is, the deeper into the ground it had to be placed. One day, these efforts will give countries more confidence to use nuclear power plants as one of their major energy producing industry.

The Fukushima power plant explosion

Sources:

Thinkquest Team. “Basic Nuclear Fission” 2012-06-08 <http://library.thinkquest.org/17940/texts/fission/fission.html>

http://www.world-nuclear.org/education/uran.htm

science.howstuffworks.com/nuclear-power.htm

http://www.technologystudent.com/energy1/nuclear1.htm

http://www.epa.gov/cleanenergy/energy-and-you/affect/nuclear.html

http://timeforchange.org/pros-and-cons-of-nuclear-power-and-sustainability

http://www-formal.stanford.edu/jmc/progress/nuclear-faq.html

http://nuclearpowervillainorvictim.engr.wisc.edu/

Highly enriched uranium, 8 June 2012 <http://theforeigner.no/images/pages/2010/12/22/HighlyEnrichedUranium-large.jpg&gt;

Uranium fission, 8 June 2012 <http://www.dummies.com/how-to/content/nuclear-fission-basics.html>

Fukushima power plant explosion, 8 June 2012 <http://www.davidicke.com/images/stories/March20119/fukushima-explosion.jpg&gt;