Mohammed Alkhaldi

Final project and Experiment:

The last project of this wonderful course is to create something that relates to the course material that we covered in class. There were dozens of different possible ideas, but since my partners and I were all in the field of electrical engineering, the professor asked us to come up with something more challenging. After multiple meetings with the group we decided to use the wind power as a goal plan. Wind is a natural source of renewable energy and we can use it to generate power by converting the kinetic energy to electrical. According to Ohm’s law, the instantaneous electrical power generated is proportional to the current in the circuit, multiplied by the voltage provided to the system.

Wind power has always interest me, so we came up with the idea of assembling a wind turbine that can actually generate power. Our main idea was to create a wind turbine that we could hook three LEDs to it and have them light up. We started by finding a turbine generator that we could assemble a fan blades to it that can rotate and generate power. Before we began putting the blades together we wanted to test it and make sure it is running and that it could give us enough power to light up the three LED’s attached. So I used my hand to rotate the generator after wiring the LEDs and by doing so I actually had it lighten up, so that gave us a heads up to start the process of assembling.

Unfortunately after presenting the idea to class and having everything sat up, the wind turbine was not giving us enough voltage to light them up. Since doing it by hand gives us much more faster rotation that was why we had them lit. We tried doing the voltage doubler idea which is: an electronic circuit that charges capacitors from the input voltage and switches these charges in such a way that, in the ideal case, exactly twice the voltage is produced at the output as at its input. However, that voltage doubler idea did not work.

In our case when having the fan on high the maximum output voltage we were getting was 250 mV so it was not enough to light up any of the LED’s since we needed at least 1.6 V. We had to quickly change the idea and to find something related with the same concept but with excluding the LEDs. So we decided to prove power efficiency of wind turbines by measuring the output voltage and current that was obtained from the wind turbine after air hits the blades. I personally came up with title of Wind and Math since it is more alluring and it gives a general idea of what we will be experiencing in this specific lab experiment.

If the voltage and current output from a wind turbine are known, the power output can be calculated:

Pout=Current *Voltage

On the other hand, when talking about wind power, the relationship between the air density, the surface area of the blades and the wind speed all determine the input power available.

Pin=12*A*V3=12 *( Air Density) * (Air Speed)3

The efficiency achieved is based on the output, divided by the input, multiplied by one hundred.

Power Efficiency=PoutPin*100

Since we were asked to have other groups within the class to try and test our experiment, we have put together those steps to help the students to simply perform and experience this challenging task. We have followed the assigned rules that was given in the syllabus to make the handout. Part of the handout that we gave to the students was as the following:

Procedure: In order to make this experiment successful we will need you to take a couple of measurements, perform some operations and record all of them in the table below.

1. For the first part of this experiment you will need to calculate the amount of  power  that is generated by the fan on our system. We will call this power the input power and it can be calculated by using the following formula: Pin=12*A*V3=12 *( Air Density) * (Air Speed)3. In order to do this, you need to  the following.

   1. Measure the diameter of the fan in centimeters to determine its radius. radius=d2=diameter of the fan2

   2. With the radius, calculate the area of the fan using Area=*radius 2(Be sure to convert from centimeters to meters before calculating the area. )

1 meter = 100 centimeters

3. With the information calculated in steps A and B,  and the information provided below calculate the input power using the formula that was previously provided .

   1. Air Density= =1.3 kgm3 Air Speed (low)=3.5 meters/second

4. Repeat parts a through c but use Air Speed (high)=3.8 meters/ second as the  new air speed. This corresponds to the air speed coming out of the fan when its set to High

5. Record all your values in the table below.

2. Measure the output voltage (Vout) from the  wind turbine.

   1. Configure the multimeter to the 2000mV position. Connect the leads from the fan to the testing probes of the multimeter. With the fan speed set to Low measure voltage and record this value in the table below.

   2. Switch the  fan speed to high and record the output voltage in the table below.

3. For the 3rd part of this experiment we will calculate the output power; the power produced by the wind turbine by using Ohm’s Law definition of power. Pout=Current *Voltage For our purposes, the voltage that we will use is the output voltage that was measured on the previous part for each fan speed.

   1. Configure Multimeter to 200mA.

   2. Switch  fan speed to Low; measure the current  and record your values.

   3. Using the formula from above, calculate the output power.

   4. Repeat steps a through c for a high speed  and record your values.

4. Finally, we will determine the efficiency of this wind turbine by calculating the ratio between the input and output power by using the following formula  Power Efficiency=PoutPin*100

   1. Calculate the efficiency for each of the fan speeds and record your values.

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Data:

Analysis:

1. Does the experiment prove the concept of power? i.e. does higher fan speed result in greater power generated?

Yes it does. Air speed is proportional to the output voltage

The Keystone XL extension was proposed in 2008. It is 1,179-mile (1,897 km), 36-inch-diameter crude oil pipeline beginning in Hardisty, Alberta, and extending south to Steele City, Neb. “XL” stands for “eXport Limited”, this pipeline is a critical infrastructure project for the energy security of the United States and for strengthening the American economy. Along with transporting crude oil from Canada, the Keystone XL Pipeline will also support the significant growth of crude oil production in the United States by allowing American oil producers more access to the large refining markets found in the American Midwest and along the U.S. Gulf Coast.

Pros:

1- Building modern infrastructure creates jobs and stimulates the U.S. economy.

2- Taxes paid by TransCanada provide counties much-needed revenue to pay for infrastructure.

3- Supports U.S. manufacturing.

4- Keystone XL Pipeline enhances energy security.

5- Keystone XL supports energy independence.

Cons:

1- Dirty tar sands oil

2- Water waste and pollution

3- Forest Destruction

4- Indigenous populations

5- Pipeline spills

References:

http://keystone-xl.com/?gclid=CjwKEAiAkpCkBRCtstKQo5ia5nESJACsCikRqI9M1hy4NVZ_KeE0yCpVQTu9_4_zi3HbhGuadai7YxoC_afw_wcB#sthash.Y8cLsMhI.dpuf

http://www.mlive.com/opinion/kalamazoo/index.ssf/2014/05/julie_mack_weighing_the_pros_a.html

http://harvardmagazine.com/2013/11/the-keystone-xl-pipeline

“We, the people, still believe that our obligations as Americans are not just to ourselves, but to all posterity. We will respond to the threat of climate change, knowing that the failure to do so would betray our children and future generations. Some may still deny the overwhelming judgment of science, but none can avoid the devastating impact of raging fires and crippling drought and more powerful storms. 

The path towards sustainable energy sources will be long and sometimes difficult. But America cannot resist this transition, we must lead it. We cannot cede to other nations the technology that will power new jobs and new industries, we must claim its promise. That’s how we will maintain our economic vitality and our national treasure — our forests and waterways, our croplands and snow-capped peaks. That is how we will preserve our planet, commanded to our care by God. That’s what will lend meaning to the creed our fathers once declared.” 

— President Obama, Second Inaugural Address, January 2013

Climate change is a definite occurrence, many believes that it could be brutally affective. We the people are going to fight hard to leave the planet clean and undamaged for the future generations. We need to take quick and accurate actions to cut carbon pollution, in order to protect our children’s health and to slow the effect of climate change.

President Obama made a pledge back in 2009 that America is going to work hard to reduce its greenhouse emissions in the range of 17 percent by 2020. The plan that the president had pledged will reduce the amount of energy consumed by families who lives in America; it will cut down on their gas and utility bills. The plan consists of a variety of executive actions and it has three main keys:

1- Cut Carbon Pollution:

Carbon emissions in 2012 fell to the lowest point. The Obama Administration is putting tough rules in place to cut the pollution from power plants. Although the economy continued to grow to build on that progress. The problem with power plants is that there is no federal law that prevent power plants from releasing as much carbon pollution as they want. The goal is to move America towards clean energy sources which will create great jobs and lower home bills.

2- Prepare the United States for the Impacts of Climate Change:

Although by taking new steps to cut down carbon emission, we also need to be prepared for the climate change which we are already experiencing some of its impacts. The Obama Administration will help local governments and state to make our roads, bridges, and shorelines more strong. So it can better protect homes, and people from severe weather that could possibly occur.

3- Lead International Efforts to Combat Global Climate Change and Prepare for its impacts:

Climate change is not the United States problem alone. It is very important to look at this worldwide, America must help all other countries to significantly reduce carbon emissions. It should couple action at home with leadership internationally. As well as prepare for climate impacts, and drive progress through the international negotiations.

Museum of Science is an amazing place to visit, it has tons and tons of information about different fields. On the day of Halloween October 31st of 2014 we had the chance to go and visit that awesome place. Our task was to focus on four different exhibits: Catching the wind, Energized, Conserve at home, and Microbiotics takes flight. It was a great opportunity since we had studied most of what we had seen within the exhibits, but not actually had the chance to test our knowledge.

In the Energized section I had the chance to look at the different types of renewable energy that could be generated, such as solar and wind power. I stopped at the solar panels experiment, where they had a shape of a house with a movable solar panels located on the top and a light and some buttons that make you switch from a day time to noon and so on. There was also a sheet of paper where I can calculate my measurements from the given kWs. After doing the experiment I found out that part B is where the panels should be placed to get the maximum power. As shown below:

Catching the wind section was also amazing since it had some data about how much energy that it could produce as well as the different countries and cities that uses it. It also explained how can wind generates electricity as shown below:

Conserve @ home has a lot of different experiments. They had a shape of a microwave with a screen in the middle that shows you what happens to different objects after microwaving them such as CD, or light bulbs. Another interesting thing was about recycling and what could result of recycling different types of plastics. There was also one thing made me stop and try because I have always wanted to know the difference between the light bulbs we use and the amount of watts needed to make them light, there were different kinds bulbs assembled within a box and I had to turn a wheel using my hands to start each light bulb, the idea was to see how much power I needed for each one. I found out that LED one needed the least power to start and the Incandescent needed the most. As shown below:

One of the exhibits had this amazingly incredible idea of a RoboBee, which I have not heard of before:

It is totally not surprising seeing this much of people trying to protest against such a powerful source of energy, due to the impacts it had on societies as well as the disasters it caused. Pandora’s Promise is a weird experience for both supporters and environmentalists. Although I think the main focus of the film is towards the environmentalists despite Republicans whom already in love of the idea of having more nuclear plants.

The film make one intriguing assertion by saying that nuclear power is second only to wind turbines in terms of safety. However, many more people were killed by air pollution from burning coal. Even the making of solar panels are more lethal. Helen Caldicott appears in the film calling the nuclear industry a “death industry” and accusing that the number of people who died from the disaster that happened in 1986 at Chernobyl nuclear plant were up to 1 million people, where the United Nation had said that they were around 50. That’s a big difference in number, and no one in the film appears to reconcile it.

The film also argue about radiation, which is admittedly dangerous. However, there are good reasons to be skeptical of nuclear power. The film had enumerated some of them such as plutonium and byproduct of uranium fission could be used to create weapons. France is another example where 80 percent of its power comes from 50 clean nuclear plants, which is held up as success story.

Another thing attracts my attention during the film was that anti-nuclear activists calling nuclear power “wicked” and “evil”. However, they are not given much opportunity to disprove the arguments that Pandora’s Promise sets forth. At times they sound as surprised to hear their own words. There are also some scenes in the film that are honestly little offensive, especially showing those barefoot children wandering with clear implication that nuclear power is the cause of their poverty. I think nuclear power’s worst enemy is not the anti-activist as the movie imply, but those who made the technology look good and created the attitude of complacency which made accidents happened like the one in Japan. Nuclear power will only be successful if realists acknowledge its issues and work very hard to solve them, not coaxing ideologues like the film maker or the stars of “Pandora’s Promise”.

Our trip to MIT’s reactor in cambridge was very interesting. However, it took me a little bit of time to get there, since I have decided to meet the rest of the class inside of the facility.  First thing they asked us to do is to attach a simple metal device that could measure the amount of radiation that we might get exposed to from being inside of the laboratory. Thankfully they were running some maintenance inside of the facility so everything was on shutdown. We learned a lot about how does those kind of reactors work and how to maintain their safety.

The MITR-II, is the major experimental facility. The average core power density is about 70 kW per liter. And what making this facility a safe one is as the following:

• The use of anti-siphon valves to isolate the core from the effect of breaks in the coolant piping.
• Having the core located within two concentric tanks
• The design of the core-tank that promotes natural circulation in the event of a lows-of-flow accident.
• Negative reactivity temperature.

The fission process in the nucleus of each atom of Uranium-235 fuel are 92 protons and 143 neutrons. And 92 electrons around the nucleus, which are smaller particles. Fission is when nucleus absorbs an extra neutron, it breaks into two parts or splits. Every time they split, it releases two or three neutrons. The primarily use of the MIT research reactor is to produce neutrons, having neutrons traveling at a very high speed within the core. There are six control blades of boron-stainless steel that control the uranium nuclei, which they are inserted vertically alongside the fuel elements. In order to operate the reactor, we have to slowly raise the blades, so they absorb very few neutrons. Until it reach enough neutrons that causes the split of uranium nuclei, and then sustain a chain reaction. Another essential factor to operate the reactor is  the moderator coolant. Which is very important since uranium nuclei do not readily absorb neutrons that moves really fast, which they leave fissioning nuclei. It is essential to slow them down with a moderator. And because of this problem about one-half the volume of the reactor’s core contains water.

Tom Vales has an incredible amount of information, I have always learned from him something.  His visit to our class was full of new materials, he talked about radioactivity.  He provided us with examples and samples which he had brought.  I learned about the Geiger counter usage. I also learned the difference between the least dangerous alpha, beta, and gamma particles which are the most dangerous particles.  He provided us with some examples of nuclear disasters that had happened and its impact on population like the one in the Three Mile Island.

Raydon, Plutonium, and Radium were also in his presentation. They were not known to have any effects on everyday life. I have learned that radio active elements are currently unstable since they are changing its chemical make up.  Half life is a process where it decays elements into lead, the shorter it is the more dangerous it becomes which make it radio active.

He also talked about Marie Curie, who had won two Noble prizes. Marie Curie’s husband had discovered Polonium and Radium, he died because of anemia. Being around radioactive elements could causes death since it can inter our bodies without noticing.  Around the 1950’s radiation poisoned many things, Tom’s had showed us how a Geiger counter could measure the amount of radiation that an object has, which he have brought. A 10,000 bombs is a Plutonium bomb that caused thousands of people to die from the radiation poisoning that it caused.

On Friday March 11th, 2011 at 2:46 PM an exceptionally powerful earthquake hit the pacific coast of Honshu, the main island of Japan. At 3:36 PM less than an hour after the earthquake, a tsunami swept over the coast, the waves went all the way up to 10 km in land result over 20,000 people dead or missing, destroyed towns, ports, and lands devastated. Nuclear power plants were also affected, one in particular namely the Fukushima Daiichi.

Fukushima Daiichi  is 250 km north east of Tokyo, the nuclear power plant has six reactors. Each reactor successively commissioned during the 1970s. Units one, two, and three were operating at full power. The core in unit four was unloaded, units five and six were in cold shutdown. Fukushima reactor’s have a different technology than the pressurized water reactors built by the French operator EDF, they are boiling water reactors called BWRs. They called reactor because the heat in the core is produced by fission reactions. Boiling water, because the water that removes the heat from the core turns into steam and the steam goes directly to the turbine, the turbine drives the generator that produces electricity, afterwords the steam is condensed with the help of a sea water cooling system and returns to the core. A boiling water reactor has only one single system combining feed water and steam. The core is composed of few assemblies containing uranium it is controlled by control rods introduced from the bottom that can stop the fission reactions in case of an emergency, fission of uranium nuclear produces radioactive atoms that intern produce heat and this continues to occur even after reactor shutdown, this is called “Residual Heat” keeping the fuel cool is a major safety issue.

The fuel is isolated from the environment by different containment barriers just like the famous Russian dolls. The first barrier the fuel cladding of zirconium alloy , a second barrier the steel reactor vessel in combination with steam and water cooling systems. Finally, the third barrier the containment building in concrete with the leak tight steel liner. The fuel is kept under water in the reactor as well as in the adjacent pool where the spent fuel is unloaded a the pool is located at the top of the reactor vessel to facilitate the transfer fuel underwater.

When the earth quick hit the coast seismic sensors trigger the insertion of control rods. although fission reaction stopped, the residual heat had to be removed. the offside power supply was lost in the emergency diesel generators took over automatically. They supply electricity to the backup systems needed for core cooling. In reactors two and three it is a turbo pump. the steam generated by the reactor operates the turbopump which feeds water into the reactor vessel the steam is condensed in the wet well suppression pool within the containment. In reactor one there was no turbo pump but a heat exchanger which condensed steam from the reactor vessel, the condensed water was reintroduced into the reactor vessel by gravity. This heat exchanger provided core cooling by natural convection for more than 10 hours until then everything seems under control. However reactor one due to excessive cooling force the operators to temporarily isolate the heat exchanger in compliance with operating procedures. the tsunami wave arrived less than an hour after the earthquake. The waves went over the seawall flooding over the lower parts of buildings and disable the emergency diesel generators, on reactor one the operator was unable to reactivate the heat exchanger, the core was no longer cool it would be the first to melt. On units two and three the batteries were still operational. They operated some of the valves the turbine driven palms ran for nearly 24 hours and then stopped.

The cores were no longer cooled. the meltdown scenario is almost the same at all three reactors only the dates change. The water in the reactor vessel evaporated the fuel became un covered heated up to a temperature of 2300°C, the fuel melted and mixed with the materials from the structured to form a magma called corium. the corium flowed down to the bottom of the reactor vessel. according to Japanese officials it pierced the reactor vessel before falling on the concrete base mat inside the containment.

At the same time still in the reactor vessel, the steam is loaded with radioactive elements and hydrogen. Heated at high-temperature the fuel cladding is oxidized and cracks releasing volatile radioactive elements. In addition to this, the zirconium of the fuel clad created a reaction with the steam by absorbing the oxygen and by releasing hydrogen. Normally, when mixed with air  hydrogen catches fire and explodes. However the containment building was filled with nitrogen and an inert gas that avoids the presence of oxygen, at this stage there was no risk. as the steam pressure rose to a dangerous level in the reactor vessel the depressurizing valves opened, gas was forced into the wet well suppression pool by inventing line, the water acted as an efficient filter by trapping much of the radioactive elements. But the water was no longer cooled because the emergency diesel generators were out of order, and it’s soon began to boil thereby reducing it’s filtration capacity.

The wet well suppression pool in the communicating containment began to enter into an over pressure situation, to avoid containment rupture the operator decided to release the gas into the atmosphere. Normally the venting line should have led all the gas outside the building but hydrogen was escaping through uncontrolled leakage pathways it was released into the reactor building. Hydrogen reacts violently with oxygen in the air, the explosion part of the frame at the top of the building apparently without damaging the containment building. Radioactive elements not yet trapped in the wet well suppression pool were released into the environment. Due to the absence of usable freshwater on the side, the operators decided to inject seawater water into the reactor vessel, this solution far from ideal since salt is chemically active had at least the advantage of cooling and stabilizing the corium.  In the four days following the tsunami the four reactors were damaged by explosions and three of them with core melt, although it has kept its structure intact, reactor two is the current source of the most important radioactive releases into the soil as well as into the sea. The explosion took place inside the building operators encountered difficulties depressurizing the containment in the wet well suppression pool broke. This loss of leak tightness led to the discharge into the atmosphere of unfiltered radioactive elements into the spreading of highly contaminated water in the buildings leading to highly polluting discharging into the sea.

The explosion of reactor four was due to hydrogen even though the core was completely unloaded the hydrogen came from reactor three via a joint pipe. The reactor storage pools were also a great concern because they had lost their cooling systems and in addition to this, they were not protected by any containment. Very little spent fuel was stored in pool one, however there was much more in pools two, three, and four. Especially pool four which contained the equivalent of the three cores. In all three pools the water started to boil and without the help in extremis of cold water from helicopters and from a firehose the spent fuel would’ve caused considerable radioactive release into the environment. Gradually, the situation began to stabilize by the end of March 2011, freshwater had replaced seawater. In July the reactor cooling system was again in operation in closed circuit, thereby avoiding discharges of contaminated water into the environment. In December 2011 Japanese authorities officially declared that the nuclear power plant reached the cold shutdown state, an expression used when the cooling water does not evaporate anymore and remains liquid below 100°C.  This nuclear crisis was managed by men working under extremely difficult conditions, cut off from the rest of the world with no news from their families after the tsunami without any power supply threatened by radiation they fought with all their force to cool the reactors trying to make invade the backup systems work again or by using improvised means. After this race against time to cool the plant followed a year where about 20,000 workers succeeded each other trying to regain control of the plant by the following:

• Enhancing the dyke against another tsunami.
• Mapping the site contamination.
• Clearing every access to the site.
• Immobilizing radioactive dust.
• Treating and disposing of contaminated water.
• Avoiding further radioactive release.

In the years ahead the challenge will be to remove the spent fuels from the pools for final storage and radioactive waste repositories. Eventually on the long term under the critical eye of international experts the issue will give way to a challenge, namely to remove the melted fuel from the three damaged reactors and to dismantle the site. As we can see a huge task awaits the Japanese, a task that started in March 2011 and that will last for several decades

References:

http://www.world-nuclear.org/info/Safety-and-Security/Safety-of-Plants/Fukushima-Accident/

http://time.com/worlds-most-dangerous-room/

http://www.techtimes.com/articles/13316/20140818/fukushima-disaster-show-effects-of-radiation-in-animals-plants-study.htm

http://www.hiroshimasyndrome.com/fukushima-accident-updates.html

Geothermal energy has been used for many years in some countries for heating and cooking.  It is derived from the Earth’s internal heat which is mostly contained in the rock and fluids beneath the Earth’s crust. A geothermal heat pump system can take advantage of the stable temperature of the upper zone of the Earth’s surface. Iceland in this case has at least 25 active volcanoes and many hot geysers and hot springs.

The Icelandic geothermal energy has been used for a quite long time. The people in Iceland have used this kind of energy for multiple purposes such as heating their greenhouses or even washing their clothes as in the early 20th century. Arnarsson was the first permanent settler in Iceland people have figured out many ways to use this energy. When he came to Reykjavík, he saw smoke coming out of the geothermal zones which are in Laugardalur. Which made Icelanders translate Reykjavík to “Smoky Bay”.

In the middle of 18th century was the first experiment of using geothermal energy for house heating. The steam of the hot water is used to heat up ground water and that water is pumped into pipes which go into people’s houses and provide them with heated water. Geothermal heat is also used by many companies to dry some products, like fish heads and wood. The heat is also used for some other things for example to bake bread and heat up footpaths, streets and parking places.

Advantages:

• No need of burning a fossil fuel to extract.
• Much less carbon dioxide produced.
• Always available unlike solar or wind energy.
• Inexpensive.

Iceland is generating 25% of the country’s total electricity production. In the 20th century Iceland has increased its use of geothermal energy, which moved the country’s from being one the poorest among Europe to a country with a higher standard of living. Most of the countries energy now is derived from renewable resources.

In the next several years IDDP is expected to drill down in number of boreholes in Iceland that will penetrate supercritical zones. It will require a drilling of almost 5 km in depth in order to reach hydrothermal fluids at temperatures that range from 450°C to around 600°C.

A feasibility study completed in 2003 indicates that relative to the output from conventional geothermal wells, which are 2.5 km deep, a ten-fold increase in power output per well could result if fluid is produced from reservoirs hotter than 450°C . A typical 2.5 km-deep geothermal well in Iceland yields power equivalent to approximately 5 MWe. Assuming a similar volumetric inflow rate of steam, an IDDP well tapping a supercritical reservoir at temperatures above 450°C and at a pressure of 23-26 MPa may be expected to yield ~50 MWe.

References:

http://environment.nationalgeographic.com/environment/global-warming/geothermal-profile/

http://www.nea.is/geothermal/

http://waterfire.fas.is/GeothermalEnergy/GeothermalEnergy.php

Robert Stirling in 1816 had invented an engine called the Stirling engine.  It is way more efficient than regular engines like what we have in cars. They are mostly used in yachts, or submarines. The Stirling engine uses the Stirling cycle, which is different than the one used in internal-combustion engines.

In gasoline or diesel engines, gases could leave the engine unlike Stirling engines where gases never leave. As well as they are very quiet and are explosions-free. In the Stirling cycle an external heat source is used, which it could be from gasoline, solar energy or heat produced by decaying plants. There are a lot of ways where you can build up a Stirling engine, and the key source of doing so is to focus on the amount of gas that is sealed inside the engine. And for the Stirling engines to operate, there are some properties of gases that are critical; if you have a fixed amount of gas in a fixed volume of space and you raise the temperature of that gas, the pressure will increase. And if you have a gas and you compress it, the temperature will increase.

For the engine to operate it requires a temperature difference between the top and the bottom of the cylinder. Similarly the difference between your hand’s temperature and the room’s, it is enough to run the engine. There are two pistons which the engine mostly depends on for it to work:

• The power piston: is the smaller one which is located at the top of the engine and it moves up as the gas expand.
• The displacer: is the larger one which is very loose inside of the cylinder and it allows the air to flow easily between the cooled and the heated sections of the engine.

There are also two positions for the displacer to control whether the gas in the engine is being heated or cooled:

• When it is near the top, most of the gas is heated by the heat source causing it to expand. Then pressure is build and the piston goes up.
• When it is near the bottom, most of the gas cools and contracts causing pressure to drop which makes it easy for the piston to move downward and compress the gas.

Peltier Devices:

There are also called Thermoelectric coolers (TECs). They are basically heat pumps that utilizes movement of heat.

The way they work is by placing two conductors in an electric contact, where electrons flow out of less bounded one and move to the more bounded one. And to represent the demarcation in energy within the conduction band of a metal there is something called Fermi level. When two conductors with different Fermi level make contact, electrons flow from the conductor with the higher level until the change in electrostatic potential (contact potential) becomes on the same value. Temperature gradient is caused by the current passing across the junction in a forward or reverse bias. If the temperature of the hotter junction (heat sink) is kept low by removing the generated heat, the temperature of the cold plate can be cooled by tens of degrees.

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Thermoelectric cooler (Peltier devices) have the following advantages:

• Little or no maintenance since there are no moving parts.
• Low noise operations with a great cooling power
• Lightweight
• Long life
• Small size

References:

http://auto.howstuffworks.com/stirling-engine.htm

http://www.activecool.com/technotes/thermoelectric.html

http://espressomilkcooler.com/how-thermoelectric-power-generation-works/