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HeatStorageforSolarHeating - Ch 9 Objectives Heat Storage...

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9-1 Ch. 9 Heat Storage for Solar Heating Objectives To learn about solar thermal energy and heat storage devices To learn about a technique called calorimetry To measure the heat of fusion of sodium thiosulfate pentahydrate, Na 2 S 2 O 3 5H 2 O To evaluate the feasibility of using this salt for heat storage Introduction Fossil fuels account for approximately 90% of all the energy used in the United States and petroleum, coal, and natural gas are expected to be the dominant energy sources for the United States and the rest of the world through the 21 st century. An optimistic report published by the U.S. Geological Survey in 2000 estimates that there is 20% more oil to be discovered in the world than was predicted in 1994. In this scenario, the world’s oil production will peak in 2050. The current estimate of coal reserves indicates that the supply of coal is sufficient to meet our energy needs for the next 200 years. Although fossil fuels will be able to meet our energy needs for most of the 21 st century, the increasing environmental burdens of these fuels have Figure 1: Projected global primary energy production by energy type. (C. Starr, M. F. Searl, and S. Alpert, “Energy Sources: A relative outlook”, Science , 256 , 981-987.)
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Chapter Nine 9-2 sparked an interest in developing a variety of cleaner and renewable energy sources. Figure 1 shows the projected global primary energy production by energy type. In the future, a greater fraction of energy will be derived from nuclear energy and renewable sources such as solar power. Energy conservation is predicted to be the largest “energy source” after 2020 by reducing requirements due to increased efficiency. In this experiment, you will explore a chemical method for storing solar energy. I. Solar Thermal Energy The annual energy deposited by sunlight on the continental United States is about 500- 700 times greater than the total annual U.S. energy consumption. However, problems arise with harnessing the sun’s radiation to meet our energy needs. Sunlight is diffuse and intermittent, and many of the technologies to utilize and store solar energy are relatively inefficient and expensive at present. The two main methods for converting solar radiation into energy useful for humans are photovoltaic cells and solar thermal heat. Photovoltaic cells are made of silicon alloys and convert sunlight directly to electricity. Solar thermal heating utilizes solar collectors to heat a fluid. The major application of energy harnessed from this technology is heating water for domestic use, but larger power plants have also been developed. For example, Solar One in California began operation in 1982 and was the world’s largest solar tower plant, producing 10 Megawatts of electricity. Figure 2 shows a simple schematic of the tower plant design. These plants operate by focusing sunlight using hundreds or thousands of flat tracking mirrors on a tower-mounted receiver. Water is converted to steam in the receiver and used to directly power a steam turbine.
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HeatStorageforSolarHeating - Ch 9 Objectives Heat Storage...

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