Our experiment revolved around the effect of pH on the voltage produced by citrus batteries. The point of the experiment was to not only demonstrate how varying degrees of acidity can affect voltage production, but how electricity can be generated by a plain chemical reaction.
The process of conducting the experiment went rather smoothly and the overall process worked well. We were able to generate electricity from the beginning, albeit, it was a very small amount. Initially, we believed we would be unable to produce enough voltage to power anything, however, the use of batteries to supplement the circuit instead of using a dozen citrus fruits really helped the experiment take shape.
Our group reached a problem late into the experiment when we discovered that the orange, the fruit with the highest pH and therefore the lowest acidity, produced the highest voltage. The lemons and the limes produced a fraction of an amount less, but our group was baffled as to why the fruits with a higher concentration of acidity did not produce more voltage. It was only later that we realized that both acid concentration and the quantity of liquid affects how well the solution would help generate voltage. If we had the opportunity to do something different, we would use the juice of the fruits which contain the acid necessary for the experiment. By doing so, we would be able to control the quantity of juice and the fruits with less size would still have the same amount of liquid as an orange.
Our group also found it rather difficult to have the batteries connected in series with the electrician’s tape and copper wiring. If we could have redone the experiment, we would have found a better method than using electrician’s tape to hold the wire and battery in constant contact with each other.
Lastly, it would have been nice to have had more objects that required varying degrees of power to operate. It was difficult to find small, household objects that required small voltages and that were relatively easy to open. With the right objects, this would have further shed light on how little is necessary to generate power given the right materials to create a chemical reaction. In the end, our group and other groups were able to power a TI-30XA with over 6 volts and products with less required voltage to operate would have been a great addition.
The oil industry, with its history of booms and busts, is in its deepest downturn since the 1990s. Earnings are down for companies that made record profits in recent years, leading them to decommission more than two-thirds of their rigs and sharply cut investment in exploration and production. Scores of companies have gone bankrupt and an estimated 250,000 oil workers have lost their jobs.
The cause is the plunging price of a barrel of oil, which has fallen more than 70 percent since June 2014. The question on the minds of many people: why has the oil price been dropping?
Oil prices over the last several years from 2006-present
This a complicated question, but it boils down to the simple economics of supply and demand. Domestic production in the United States has nearly doubled over the last several years, pushing out oil imports that need to find another home. Saudi, Nigerian and Algerian oil that once was sold in the United States is suddenly competing for Asian markets, and the producers are forced to drop prices. Canadian and Iraqi oil production and exports are rising year after year. Even the Russians, with all their economic problems, manage to keep pumping.
On the demand side, the economies of Europe and developing countries are weak and vehicles are becoming more energy-efficient so demand for fuel is lagging a bit. Motorists and home owners that use oil to heat their houses end up benefitting from the plunge in oil prices. However, oil-producing countries and states such as Venezuela, Nigeria, Ecuador, Brazil and Russia are just a few petrostates that are suffering economic and perhaps even political turbulence. Needless to say, the overall oil industry has also suffered as many companies have gone bankrupt and others are struggling to keep their heads above water.
Hydraulic fracturing has helped boost the rate at which oil and gas can be extracted from wells, particularly in the United States. By increasing the current available supply, fracking helps to lower oil prices on a global scale. This is particularly true domestically, since oil does not have a historically strong local market in the U.S. Basic economics states that as the supply of any good increases, its relative cost decreases. The degree to which these decreases occur depend on many factors, including the elasticity of the good. Even though oil is a natural resource, it has no productive economic use unless it is extracted. This means that the real supply, in a productive sense, is limited to what engineers and well technicians can provide. Fracking lowers the cost of oil to the extent that it allows real supply to expand.
What exactly is hydraulic fracking? The term fracking refers to how the rock is fractured apart by the high pressure mixture. Fracking is the process of drilling down into the earth before a high-pressure water mixture is directed at the rock to release the gas inside. Water, sand and chemicals are injected into the rock at high pressure which allows the gas to flow out to the head of the well. The process can be carried out vertically or, more commonly, by drilling horizontally to the rock layer and can create new pathways to release gas or can be used to extend existing channels.
Example of how fracking is done
There are limits on the extent to which fracking can be used to increase supply. Oil is scarce, and hydraulic fracturing is more expensive and complicated than traditional oil extraction. If the global supply of oil increases and oil prices drop far enough, then the high expense of fracking is no longer justified. In other words, the success of fracking eventually imposes a limit on itself, unless technological changes make the technique less costly.
During our discussions, our group was able to come up with various possible experiments that we believe would meet the requirements for the final project. Though these experiments were different in set-up, they were similar because they involved generating energy and possibly how to produce energy in a more efficient way.
The first experiment we discussed involved the use of various fruits to charge or power different types of electrical devices. The purpose of this experiment would be to demonstrate how an electrical current can be generated using citrus fruits (such as lemons or limes) that is strong enough to power a small light bulb or charge a phone.
Electrical current is the flow of electrons (movement) of an electrical charge and is measured using an ammeter. Solid conductive metals contain large population of free electrons, which are bound to the metal lattice and move around randomly due to thermal energy. When two terminals of a voltage source (battery) are connected via a metal wire, the free electrons of the conductor drift toward the positive terminal, making them the electrical current carrier within the conductor. The active ingredient in the fruit are positively charged ions. A transfer of electrons takes place between a zinc nail and the acid from the fruit. The nails act as poles for the battery, one positive and one negative. Electrons travel from the positive pole to the negative pole via the light bulb wire (the conductor), generating enough electricity to light the bulb.
Our second experiment involved the construction of an AC electric generator which lights up a tiny incandescent light bulb. The generator is made from a hollow-ended cardboard box with a nail through the center. The box has many turns of varnished thin copper wire wound around, with four large magnets clamped around the nail. When the nail and magnets are spun fast by hand, the little light bulb lights up dimly.
This project would demonstrate how easy, yet difficult it can be to generate electricity, because it is not extremely complicated to build a generator to power up a bulb, but the steps and materials required are extremely precise and cannot be changed.
Lastly, the final experiment we discussed involved the use of coins, vinegar, paper, aluminum, and salt to create an electrical current to power a light bulb or electrical device. This experiment is very simple to complete, however, it would take a while to prepare. It would be a great way to test a variety of metals and also the number of coins used and how they affect the voltage produced during the experiment.
According to multiple sources, the Obama administration has proposed the most far-reaching climate change adaptation and mitigation measures ever put in place by a U.S. president. The plan includes everything from cutting power plant emissions to boosting the amount of wind and solar energy installations on public lands and buildings as the U.S looks to move into the future conscious of the effects of global warming.
The White House plan includes three main policy tracks. The first addresses emissions of greenhouse gases, chiefly carbon dioxide (CO2), from new and existing power plants. This version of the Climate Action plan would place limits on greenhouse gas emissions from more than 1,000 existing coal-fired power plants for the first time ever. The plan could also include natural gas power plants as well. Thanks largely to the global recession and the displacement of coal by natural gas in the power sector, the U.S. emissions of carbon dioxide (CO2) in 2012 may have been a lowest in a couple decades, but the first quarter of 2013 saw the percentage of electricity coming from coal start to go back up as natural gas prices increased, while U.S emissions rose by at least 4% during that time period.
Emission Rates and other factors 1997-2013
The White House has indicated that without additional measures to reduce carbon emissions from the electricity sector, continued emissions decreases are unlikely to be achieved by market forces alone (i.e., natural gas prices). Their proposal to limit emissions at existing power plants could help drive a continued drop in overall U.S. emissions.
CO2 levels assuming different rates of fossil fuel consumption
The White House has gone as far as recommitting the U.S. to meeting the greenhouse gas emissions reduction goals it established in the Copenhagen Accord in 2009, when the administration agreed to cut greenhouse gas emissions by 17 percent below 2005 levels by 2020. That would be approximately double the reduction the U.S. has seen due to the recession, increase the use of cleaner-burning natural gas, and increase energy efficiency since 2007.
The second track helps prepare the U.S. for the effects of climate change that are already occurring and are likely to occur in the next several decades due to the long-lived nature of CO2 in Earth’s atmosphere. The climate action plan calls for the Department of Energy to make up to $8 billion in loan guarantees “for a wide array of advanced fossil energy projects,” including carbon capture and storage, or CCS. Such technologies, which have not yet been proven to work at the commercial scale, could allow utility companies to continue burning coal for generating electricity, while capturing and burying the related carbon emissions, thus removing CO2 from the atmosphere.
Lastly, the policy proposals include provisions to work with the international community to address global warming, both from an emissions reduction and climate adaptation standpoint. The climate action plan commits the U.S. to working with international partners to reduce the emissions of not only carbon emissions, but also non-carbon based greenhouse gases such as HFCs. HFCs are used as a refrigerant and is a powerful short-lived climate warming agent. According to Durwood Zaelke, president of the Institute for Governance and Sustainable Development, a phasedown of HFC emissions in the U.S. can deliver a quarter of the administration’s 2020 climate goal. According to a study being published on Wednesday, a global phaseout of HFC use during the early part of this century can avoid a half a degree Celsius in future warming by the end of the century.
The Climate Action Plan also addresses other emissions such as methane emissions by ordering the EPA and other government agencies to develop “a comprehensive, interagency methane strategy” that includes addressing methane emissions from natural gas plants.” As a Climate Central research report found, how much methane emissions are coming from natural gas pipelines and power plants is key to determining how much climate benefits that electricity source provides.
The Obama administration has also looked to increase efficiency in vehicles by enacting the toughest passenger vehicle fuel efficiency standards in U.S. history. It requires hat passenger vehicles have an average performance equivalent of 34.1 miles per gallon by 2016 and 54.5 miles per gallon by 2025, which the White House claims will eliminate 6 billion metric tons of carbon pollution — more than the U.S. emits in an entire year.
Transportation emissions make up about 30 percent of U.S. greenhouse gas emissions, and heavy-duty trucks comprise more than 20 percent of that total. Currently, heavy-duty trucks, which are primarily transport trucks, have an average fuel economy of only 5 miles per gallon, so improving their fuel economy could help significantly lower emissions from the transportation sector. The administration has worked to enact post-2018 fuel economy standards for heavy-duty trucks, buses, and vans, by working with the auto industry.
The four exhibits at the museum of science were concrete proof of some of the laws, theories, and concepts that were discussed in class. Though we have done experiments, written about, and researched wind power, energy, solar energy, and heat conservation, the exhibits were able to offer not only additional, but very specific information that were very interesting.
Catching the Wind:
The “Catching the Wind” Exhibit explained how wind power is a natural and clean resource generated by wind turbines to perform tasks or convert wind into usable electricity. It mentions how humans have been catching the wind for thousands of years, and have continued to perfect wind power technology. the exhibit goes into further detail and explains that wind is actually a form of solar energy. Sunlight hitting the Earth heats the air unevenly which creates a temperature difference. This difference starts moving the air, as warmer air rises and cooler air moves in to take its place. The exhibit also states that wind power is measured in kilowatts (kW), which is equal to one thousand watts. I can also be measured in megawatts (mW), which is equal to one million watts. Wind power can additionally be measured in energy generated per hour using the units kilowatt-hour (kWh) or in megawatt-hour (mWh). The exhibit states that one kilowatt generated at a steady rate for an hour can power 66 energy efficient light bulbs for an hour. The most impressive part of the exhibit was the display of how much wind power is necessary to spin a wind turbine. According to exhibit, a wind turbine only needs wind of speeds of 6-12mph to spin the turbine’s blades. Surprisingly, this is the speed of a gentle breeze! Lastly, I was surprised to find that the MOS uses five different wind turbines on their roof and a display of how much energy is generated by each turbine.
One of the wind turbines used at the MOS and how much energy it generates!
Energized!:
Energized was the second exhibit at the MOS related to topics we have studied in class. This exhibit explains the potential of solar energy. It states that wherever there is sunshines, solar energy could be harnessed to generate electricity. The sun provides the about a thousand times more energy than the world needs, yet solar technology currently generates only about 1% of the world’s energy. This gap exists because sunshine is inconsistent and because it takes large areas to harness useful amounts of power. Despite these challenges, solar energy has enormous potential and is the fastest-growing power-generation technology in the world. It is projected to increase 30-fold in the next 25 years. The exhibit mentions various methods of capturing and using available sunlight. Aside from the regular solar panels, there are solar collectors that do not use photovoltaics. They use mirrors to focus sunlight at a central point and generate heat. From there, the process for creating electricity is essentially the same as a power plant where the heat produces steam and the steam is used to spin turbines. According to the exhibit there are three main types of solar collectors: towers, troughs, and parabolic dishes. Energized! also had an interactive display that showed at what time of day solar panels would be most efficient due to the sun’s movement. At the end of the interactive display, it was clear that solar panels are most efficient in the afternoon where solar energy can be captured for a longer period of time.
Solar Panel Efficiency in the Afternoon
Investigate:
Investigate was a relatively simple exhibit compared to the others as it involved the conservation of heat through the use of styrofoam and warm water. The exhibit display asks which cup keeps drinks at their starting temperature longest and if blowing on a hot liquid makes it cool off faster. The experiment itself involved pouring hot water in a styrofoam cup and in a plastic cup and gauging the temperature in both. My hypothesis was that the styrofoam cup would keep the water heated longer because styrofoam is widely used to conserve heat in many instances. The result of the experiment were as I expected as the styrofoam cup keep the temperature at 75 degrees Fahrenheit for a longer period of time. The plastic cup’s heat retention was far less and the image below shows that the liquid’s heat was at 74.1 degrees Fahrenheit. Blowing on the hot liquid did also decrease its heat much faster than if it were left alone.
Results of experiment with styrofoam cup and plastic cup. Styrofoam is on the right
Conserve @ Home:
Conserve at Home was an exhibit on the simple changes that can be made at home in order to conserve energy. The interactive display on lightbulbs allowed people to power different types of light bulbs such as LED and incandescent. The LED light bulb was an 8 watt light bulb and it was able to light up a room relatively easily. The 40 watt incandescent bulb was very difficult to light up and barely provided any light. The exhibit also mentioned the importance of recycling and how humans produce 4.4 pounds of daily waste without recycling and 2.9 pounds after recycling. Though these measures do not eliminate waste, they are able to reduce waste by a significant amount when you take the entire population into account.
Pandora’s Promise is essentially a portal into a world that environmentalists, past and present, unanimously fear due to previous incidents such as the Chernobyl disaster and most recently the Fukushima Dai-ichi disaster. The movie is produced in a way that attempts to eliminate the growing concerns that environmentalists, but more specifically, anti-nuclear activists have over the use of nuclear energy. Its central argument is that nuclear power is, in fact, a safe method of generating clean energy and that it can mitigate the global warming problem we face today. The movie’s use of several notable individuals, some of whom were once vehemently opposed to nuclear power but who now speak in favor of it, is a wonderful way to begin the documentary. It offers environmentalists, the target audience, well-known people with a scientific background who shared the same concerns they do. Though once opposed to the use of nuclear power, these people now support it and use modern evidence to dispel anti-nuclear advocate concerns.
Many environmentalists bring up the point that there is not enough safety surrounding the nuclear power plants and use major examples such as Chernobyl, 3-mile Island, and Fukushima Dai-ichi as supporting evidence for these facts. Though the advocates for nuclear power admitted to the failures in the past due human error, negligence, poor safety standards, and lack of a well-designed plant, they claim that these mistakes shall never happen again. The advancement of technology has allowed people to move away from the use of poorly designed reactors, such as Chernobyl, and proper protocol and fail safe measures have been put into place to prevent disasters such as Fukushima Dai-ichi from ever happening again.
Anti-Nuclear Advocates also bring up the point that radiation leaks have a negative effect on people and on the environment. They make strong claims that even if radioactivity is kept under control that the radioactivity surrounding nuclear plants will still be harmful. The environmentalists turned supporters explain how radioactivity is present in many areas of the world where reactors are not found. They are present in small quantities in nature itself. By visiting different locations and testing them, the documentary makes it clear that humans are surrounded by radioactivity and that in small quantities it is not harmful to the body. The documentary shows that radioactivity in U.S cities is roughly the same amount as radioactivity found in reactors. Pandora’s Promise also shows how radiation levels due to cosmic radiation at higher altitudes equal more than that found at plants.
Finally, environmental concerns are discussed in the documentary as the storage and nuclear waste is brought up. The advocates for nuclear energy state that the use of breeder reactors instead of light water reactors reduce nuclear waste due to its ability to recycle nuclear material many times over. The unrealistic views of environmentalists concerning solar and wind power are also mentioned. Due to excessive costs required to build, maintain, and use these methods, nuclear energy is still considered a better resource. Nuclear energy advocates mention that nuclear energy may, in fact, be the only way to reduce CO2 levels. The production of nuclear energy produces less CO2 than the production of solar panels and wind turbine components. Ultimately, the nuclear energy advocates bring up France’s nuclear success story and how after its switch to nuclear energy in the 70’s it has enjoyed access to cheap energy and far less carbon emissions than Germany, a leader in the use of solar energy.
Overall, Pandora’s promise makes a clear statement: through trial and error, humanity now has the resource to vastly reduce emissions through the means of nuclear energy. The notable individuals who once opposed the use of nuclear energy put aside their pride and admitted that they were wrong. If the production of safe nuclear energy is indeed the method that will reduce carbon emissions, it is important that environmentalists come to an understanding of how nuclear energy is beneficial and how their concerns have been addressed.
Exactly five years ago today on March 11th, 2011, Japan’s Fukushima Dai-ichi Nuclear Plant went through a series of equipment failures, nuclear meltdowns and releases of radioactive materials at the Fukushima, Nuclear Power Plant, following the Tohoku Tsunami on 11 March, 2011. It is the largest nuclear disaster since the Chernobyl disaster of 1986 and only the second disaster (along with Chernobyl) to measure Level 7 on the International Nuclear Events Scale (INES).
Explosion at the reactor site
Japanese officials are still trying to understand all the factors that contributed to the meltdowns at the Fukushima Dai-ichi nuclear power plant. Officials came to the conclusion that the plant was not designed to withstand the 40-foot tsunami that hit it which was caused by a magnitude 9.0 earthquake. Within days, three of the plant’s six reactors had suffered severe fuel damage—and possibly even melted down—raising fears of radiation dispersal in Japan and around the world. When the tremors rattled the plant, control rods automatically scrammed the reactor as they were designed to do, cutting off the fission process. Then the plant lost electricity from the grid and the diesel generators kicked on, only to be swamped and disabled by a 30-foot tsunami within the hour.
The tsunami caused by the magnitude 9.0 earthquake
With no power to keep coolant flowing, the energy from radioactive decay began to build up, raising the pressure within the reactor vessel. Tokyo Electric Power Company (TEPCO) reported on March 12 that safety valves had been triggered in the reactor vessel, and pressure inside the containment structure had increased to double the design limits. Fearing that the containment structure itself might fail, the utility made the calculated decision to vent it through filters and out to the environment (beyond the support building), albeit at the risk of releasing small amounts of radioactivity—mainly the isotopes created by the decay, including iodine-131 and cesium-137.
Over the next few days, it became obvious that the fuel was damaged. The question became whether it would melt, and if it did, whether it would melt through the reactor vessel and into the containment structure. While all of the specifics are not yet known, the fuel certainly suffered severe damage, and at least part of it likely melted. During this time, the spent fuel stored in pools in the support building surrounding the containment structure was also overheating. This presented a grave dilemma: If that spike in temperature wasn’t stopped, the spent fuel, which wasn’t surrounded by a safety barrier, could release radioactivity directly into the environment.
Despite the failure of the first and second barriers and the venting of radioactive water and steam, a truly major release of radioactivity has been averted—a “major release” being a Chernobyl-style accident in which a large fraction of the fission products escape the plant.
The Chernobyl Nuclear disaster is widely considered to have been the worst power plant accident in history, and along with Fukushima Dai-ichi, is one of only two classified as a level 7 event on the International Nuclear Event Scale.The battle to contain the contamination and avert a greater catastrophe ultimately involved over 500,000 workers and cost an estimated 18 billion rubles.
Results of the explosion in Chernobyl
The Chernobyl disaster was attributed to a flawed system along with human error. The operating crew on the nuclear plant was planning to test whether the plant’s turbines could produce sufficient energy to keep the coolant pumps running in the event of a loss of power until the emergency diesel generator was activated.
To prevent any interruptions to the power of the reactor, the safety systems were deliberately switched off. To conduct the test, the reactor had to be powered down to 25 percent of its capacity. This procedure did not go according to plan and the reactor power level fell to less than 1 percent. The power therefore had to be slowly increased. But 30 seconds after the start of the test, there was an unexpected power surge. The reactor’s emergency shutdown (which should have halted a chain reaction) failed.
The reactor’s fuel elements ruptured and there was a violent explosion. The 1000-tonne sealing cap on the reactor building was blown off. At temperatures of over 2000°C, the fuel rods melted. The graphite covering of the reactor then ignited. The graphite burned for nine days, churning huge quantities of radiation into the environment. The accident released more radiation than the deliberate dropping of a nuclear bomb on Hiroshima, Japan in August 1945.
Workers during the clean up of Chernobyl. Many were irradiated 650 times the annual limit
With events such as these, society will demand increased safety standards, more rigorous planning, careful checklists, and increased transparency in the whole nuclear political system.
Nuclear security is the most essential element of safe nuclear. According to the International Atomic Energy Agency (IAEA) nuclear security plan can be achieved through “prevention, detection of and response to malicious acts, and Information coordination and analysis. The Fukushima incident has called for increased transparency in the public and private sector, as the plant’s operator Tokyo Electric Power (TEPCO) received severe scrutiny from the international community because of the problems at the reactor. Aside from these two important measures, it is also important to have specific protocols and fail proof designs that will hedge or completely eliminate the risk of nuclear disasters occurring from malfunction or unexpected natural disasters.
Normally, geothermal energy is hard to come across due to the amount of drilling is required to reach the required heat and steam to produce geothermal energy. There is, however, one country whose geographical positioning makes it perfect for extracting geothermal energy.
Iceland is a young country geologically. It lies on either side of one of the earth’s major fault lines, the Mid-Atlantic ridge. This is the boundary between the North American and Eurasian tectonic plates. The two plates are moving apart at a rate of about 2 cm per year. Iceland’s location is a hot spot of unusually great volcanic productivity.
During the course of the 20th century, Iceland went from what was one of Europe’s poorest countries, dependent upon peat and imported coal for its energy, to a country with a high standard of living where practically all stationary energy is derived from renewable resources. The main reason for this enormous change in the country’s energy resource is due greatly to the volcano activity.
Iceland is currently a pioneer in the use of geothermal energy for space heating and the generation of electricity. Generating electricity with geothermal energy has increased significantly in recent years and geothermal power facilities currently generate 25% of the country’s total electricity production.
In 2014, roughly 85% of primary energy use in Iceland came from indigenous renewable resources and 66% was from geothermal resources. The use of geothermal energy has many direct utilizations from bathing and recreation to snow melting to space heating. Many pools in Iceland are heated using geothermal energy. Most of these pools are public, but many school pools are also heated by these means. Only about 8% of these pools are heated using electricity or fossil fuels. Geothermal energy is also used to heat fish farms as the fish raised in these farms require the water to be in a specific temperature range for them to survive.
A fish farm in Iceland
Some of the other direct utilizations of geothermal energy include space heating and snow melting. After World War II, Iceland carried out a lot of research and development , which has led to the use of geothermal resources for heating in the 89% of households in the country. The relative share of energy resources used to heat households has changed since 1970. The increase in geothermal energy is clear, but after 1985 it has been relatively small. The proportion of the population using geothermal energy is, however, still increasing. Overall, the share of oil for heating continues to decrease and is at present at about 1%. The share of electric heating is about 10%.
Consumption of Oil, Electricity, and Geothermal from 1970-2010 for Space Heating
Snow melting with geothermal water has also increased during the last two decades and now most new car parking areas in regions enjoying geothermal district heating are provided with snow melting systems. Interestingly enough, the water used in space heating does not go to waste, but is actually used to deice sidewalks. The water used in space heating returns at roughly 35 degrees Celsius and is sometimes mixed with hotter water to melt the ice or snow found on streets and sidewalks.
The pipes found under sidewalks and streets that help melt snow and ice
Generating electricity with geothermal energy has increased significantly in recent years in Iceland. As a result of a rapid expansion in Iceland’s energy intensive industry, the demand for electricity has increased considerably. The use of geothermal power plants in Iceland has helped reduce the amount of fossil fuels to produce electricity by a huge magnitude. The geothermal power plants are able to harness the steam produced through the geothermal process to spin steam turbines which ultimately produces electricity.
Due to its geographical positioning, Iceland has been able to make use of its access to geothermal energy. They continue to improve on and decrease the amount of fossil fuels they use to generate heat or electricity and are on their way to becoming self sustaining energy wise.
Thermoelectric devices, such as generators, take a temperature difference and are able to turn it into electrical power. Amazingly, thermoelectric devices can also be run in reverse! If power is put into a thermoelectric generator a temperature difference is created. Small mini-fridges, for just a few sodas, use thermoelectric generators to efficiently cool a few drinks.
To understand how thermoelectrics generate the electricity from a temperature difference, it is important to know how electrons move in a metal. Metals are good conductors because electrons can move freely within them, similar to a fluid in a pipe.
The best way to explain thermoelectrics is imagine a pipe full of water and you raising one end. The water will flow down the pipe from the high end to the low end. This is because when the pipe was raised the potential energy was increased and the water wanted to flow to the lower point. In a thermoelectric material the same general concept applies where fluid-like electrons want to move from one point to another.
Heating one end of a thermoelectric material causes the electrons to move away from the hot end toward the cold end. When the electrons go from the hot side to the cold side an electrical current is formed. The larger the temperature difference, the more electrical current is produced and therefore more power generated.
The movement of atoms and creation of electrical current
The tricky part about thermoelectric devices, such as generators is that as one side is heated, the other side, or the cold side of the generator heats up too. In order to generate power with the a thermoelectric generator it is necessary to have both a heat source and a way of dissipating heat in order to maintain a temperature difference across the thermoelectric materials.
An example of a thermoelectric device is known as the power pot. It essentially is a generator that creates electricity with water and a variety of heating sources, such as fire or propane. The power pot is essentially able to limit how hot the cold side can get because water itself cannot get any hotter than 212 degrees Fahrenheit, the point at which it boils. Because the power pot has no moving parts and only requires a heating source and a cold source, it is a great way to provide electricity to communities or people that do not have access to it through a grid. Essentially, it is yet another step to providing power for everyone.
A Power Pot with its connector cables charging a phone
The purpose of this Solar Energy Experiment is to understand the relationship between light intensity and the voltage output of the solar cell used. To change the light intensity, we must change the distance between the solar cell and the light source. The second part of this experiment is to understand the relationship between the wavelength of light and the voltage output of the solar cell by using different colored filters on the light source when the light source is held a constant distance from the solar cell. At the end of these experiments, a graph and bar chart will be created to show both relationships.
Hypothesis:
I believe that the closer the light source is to the solar cell, the stronger the voltage output will be, while a lightly colored filter would offer the best voltage production.
Equipment:
One solar cell
One voltage probe
One NXT adaptor
NXT with light sensor
One light source
Labview VI
Ruler
Colored film filters
Excel sheet
Example of the solar cell
The NXT Intelligent Brick
Procedure:
Experiment 1:
Connect solar cell, voltage probe, NXT adaptor, and light sensor together
Open Tabview VI program
Using a ruler, choose a small distance to place the light source from the solar cell
Turn on the light source and run the experiment for 10 seconds
Record your results
Choose 4 more distances and repeat steps 3-5.
Experiment 2:
Connect solar cell, voltage probe, NXT adaptor, and light sensor together
Open Tabview VI program
Choose a filter and place it on top of the solar cell
Place the light source on top of the solar cell with the chosen filter
Turn on the light source and run the experiment for 10 seconds
Record your results
Run the experiment 3 more times choosing a different filter each time and repeat steps 4-6
Results:
Distance vs Voltage:
0 cm
5 cm
10 cm
15 cm
20 cm
0.521604
0.281683
0.21625
0.205986
0.172628
Filter Color and Affect of Voltage:
Green
Pink
Red
Purple
0.461303
0.456171
0.488246
0.471567
The numbers found in the both the charts and graphs are an average of the 10 data points taken over the 10 second span each experiment was run.
The average can be taken by adding all data points together and dividing by the number of data points.
Conclusion:
The distance of the light source and the voltage were directly related as the further away the light source got, the less voltage was produced by the solar cell. This makes perfect sense as less light was able to reach the solar cell from a longer distance. I was surprised to find that a dark filter color, such as red, was able to create more voltage than the lighter colored filters. The light source was held at a constant 0cm away from the solar cell with the filter and the .488 average we got from the experiment using the red filter was very close to the .521 average we got when testing the voltage produced by the solar cell at a distance of 0cm without a filter.
