Light from the sun could provide 1,000 watts of energy per square meter on Earth. Solar Panels, or photovoltaic cells, work by converting energy from the sun into usable electricity. They are made using a semiconductor like silicon. When light from the sun hits the silicon cell, some of the energy is absorbed into it. This energy causes electrons to flow freely in a current. The cells are designed to encourage the flow of electrons in the right direction. The electrons travel to metal conductors at the top and bottom of the cell. This is now usable energy. It can flow directly into powering some device like a solar calculator or highway sign. Solar panels are not economically realistic for all residential uses, as many people cannot afford them. As new technology emerges, however, they will become more affordable and will be used more extensively.
In this lab we tested the photovoltaic voltage generated by a desk a lamp using different colored filters. We placed a small solar panel 6 centimeters away from the lamp, shining light directly on it. We then used a computer program to record the voltages that the panel absorbed. The program recorded 10 measurements and found the averages, which we then graphed, comparing the effects of the filters. All of the filters reduced the voltage absorbed by the cell. Pink was the most effective filter, or least, depending on your use.
danaress
February 21, 2012
In this lab we used mechanically powered flashlights to show how electricity can be generated. The flashlight works like this: along the inside of the handle of the flashlight is a metal coil. Inside of the metal coil is a magnet. When you shake the flashlight the magnet slides back and forth through the coil generating electricity. This is the Faraday Principle of Electromagnetic Energy. The tight coil that the copper wire is wrapped in creates a magnetic field. As the magnet slides through the coil, it induces electron movement in the wire. Electrons change from positive to negative polarity as the magnet passes. As the rate at which the magnet passes increases, the movement of electrons, and therefore the amount of electricity produced also increases. Basically, the faster you shake the flashlight, the more power electricity is generated. The electricity is stored in a capacitor which powers the LED light.
In our experiment we tested different speeds of shaking the flashlight over a fixed period of time and the amounts of energy produced. We connected the flashlight to the computer which took a measurement of the electricity we produced every second. We tested our different speeds as shakes/second for periods of 30 seconds. We recorded the measurement as a single number- the sum of squares of voltages. This allows us to easily compare the measurements from the different rates. First we tested the flashlight held upright without shaking it. The measurement for that trial was .68 volts. Next we tested at a rate of 15 shakes/30 seconds. This resulted in a measurement of .67 volts. This does not seem to make much sense. It is attributed to human error as well as an imperfect experiment. Since the measurement was only taken every 1 second, the computer could be failing to report some of the energy created- basically bad timing. We also shook the flashlight too slowly. Due to other issues we were having with the computer, though, we chose to move on with the lab in order to save time rather than try to correct the mistake. The next test we did was at a rate of 30 shakes/30 seconds (1 shake/second). This resulted in a measurement of 105 volts. Our final test was at a rate of 45 shakes/30 seconds. This resulted in a measurement of 119.67 volts. This can also be seen in the graph below.
danaress
February 14, 2012
Natural Gas Hydraulic Fracturing, colloquially known as Hydrofracking, is a method of extracting natural gasses from beneath the earth’s surface. Put briefly, and hopefully objectively, the process works like this: Steel lined wells are drilled thousands of feet into the Earth’s crust. Eventually, these wells hit a layer of rock called Shale. At this point, the wells change directions and begin digging horizontally through the shale. Since the layer of shale is usually between 50 and 300 feet deep, much more gas can be extracted by extending the well horizontally (for 1,500 to 5,000 feet). Huge amounts of water (more than 1,000,000 gallons) are then pumped through the wells. The water is also mixed with sand and different chemicals before entering the well. The pressure from the water causes the shale to break and form fissures. These fissures, that look like cracks in the shale, then break off into more and more channels- as far as the pressurized water can go. The sand keeps the fissures open so that the natural gas inside can flow back into the well. At the surface the natural gas is collected, refined, and pumped through pipelines to consumers. The recovered water is sent to treatment plants, reused in fracking, etc.
Hydrofracking has its share of fans as well as those who appose it. I will try and provide the some basic reasons behind each side’s position, but do not claim objectivity in this section.
Benefits of Hydrofracking:
Hydrofracking will move us closer to energy independence. By satisfying more of our energy needs with resources within U.S. we will be less dependent on unstable regions/MIddle East
Job creation. The fracking industry employs about 1.2 million in the U.S.
Cons of Hydrofracking:
Water pollution. This can come in several forms. The first 1,000 or so feet of the well is lined with cement outside of the steel to prevent water leakage. However, there are concerns that water leaking from other places in the well could contaminate drinking water- especially since aquifers are often close to the layer of shale. Once the water returns to the surface it is pumped into large pools before treatment. There are accusations that the pools leak into groundwater, or that the water is directly pumped back into streams.
May cause earthquakes. Although these are probably minor seismic events, there have been reports in the U.K. and U.S.
Companies are not required to disclose which and how much chemicals are added to the water. This is a complicated issue. The mixtures are often made uniquely for each well based on the geological makeup of the ground underneath. This would make it impractical for the companies to disclose the contents of each well, each time it is used. However, there are reports of toxic chemicals being used. Since the wells require millions of gallons of water, there would undoubtedly be thousands of gallons of these chemicals added. The mere fact that the companies are not required to disclose this information, coupled with the accusations of contamination, is discomforting in itself.
In Conclusion: while researching this issue I read an article titled “Fracking Pros And Cons: Weighing In On Hydraulic Fracturing,” on the Huffington Post ‘Internet Newspaper.’ They explained one of the cons of Hydrofracking: “Leaks more emissions than coal.” It states, “Compared to coal, the footprint of shale gas is at least 20 percent greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years.” They also explained one of the pros: “Burns cleaner than other fossil fuels.” It states, “Researchers at MIT found that replacing coal power plants with natural gas plants could work as part of a plan to reduce greenhouse emissions by more than 50 percent.”
I think that this sums up the issue in a broader context (and perhaps says something about the H.P.) That is: People need to be more educated. After reading this article I found myself more confused than anything else, and needed to look elsewhere. The United States Environmental Protection Agency (EPA) released a report stating, “EPA’s analysis of samples taken from the Agency’s deep monitoring wells in the aquifer indicates detection of synthetic chemicals, like glycols and alcohols consistent with gas production and hydraulic fracturing fluids, benzene concentrations well above Safe Drinking Water Act standards and high methane levels.” This is the information I am basing my personal opinion on, though, I recognize the complexities. Yes, it seems there are great health risks. Yes, this industry is providing much needed jobs. If a company were trying to begin Hydrofracking in my community I would certainly oppose it.
http://yosemite.epa.gov/opa/admpress.nsf/0/EF35BD26A80D6CE3852579600065C94E
http://gothamist.com/2011/12/11/epas_report_on_hydrofracking_in_wyo.php
http://www.huffingtonpost.com/2011/11/10/fracking-pros-cons_n_1084147.html#s524124
danaress
February 13, 2012
In class, we performed a series of experiments testing the relationship between mass, acceleration, and power. We designed the experiment using a pulley, strong, set of weights, and motor. The string attached to a motor on one side of the pulley, wrapping around it as a wheel turns. On the other side of the pulley the strong is attached to a hook that can hold weights.
For the first experiment we tested a fixed mass vs. modified power levels. We kept the mass constant at .19 kg for 4 trials. The power level began at 25%. The motor turned on, causing the string to wrap around the wheel and pull up the weights. There was an acceleration of 2.57 rpm/s. We conducted 3 more trials, increasing the power level by 25% each time. The results can be seen in the graph below:
For our second experiment we tested a fixed power level vs. modified masses. We kept the power level constant at 75%. We first texted this power level pulling a mass of .25 kg. The acceleration was 48.49 rpm/s. We conducted 3 more trials with masses of .21 kg, .17 kg, and .13 kg, respectively. The results can be see in the graph below:
danaress
February 7, 2012
