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Solar Power: FAQs
By Peter Hemberger, REPP Staff
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| 4 Times Square, a 48-story skyscraper at the corner of Broadway and 42nd St., has a photovoltaic "skin." |
What
is solar power?
Even though most of the energy of the earth would not be present without the sun, only a few forms of power are considered to be solar power. In the context of renewable energy, solar power is associated with the harnessing of the sun's present emissions of heat or light.
Solar power, besides providing heat and light, also causes the wind that we feel here on Earth. Winds are created when various layers of the atmosphere absorb different amounts of heat and therefore expand differently. This creates regions of lower and higher pressure, resulting in masses of air that circulate both at ground level and at higher altitudes. [1]
Solar power is also responsible for fossil fuels such as petroleum and coal. These substances are the result of large masses of decayed plant matter, which during their lifetime, absorbed solar energy. Fossil fuels are merely concentrated stores of the solar energy that these plants had while alive. [2]
Power from the sun comes to the Earth as heat and light. This heat and light are the effect of the Sun's constant nuclear fusion of hydrogen nuclei. The process of fusion produces helium nuclei along with large amounts of energy. This energy is expressed as electromagnetic radiation (light is a specific frequency range of this radiation) as well as radiated temperatures of more than 6,100 degrees C. This is actually fairly cool compared with the corona and core of the sun that burn at several million degrees C. A small fraction of these extreme levels of energy that are released by the Sun come into contact with the Earth. The average amount of energy that contacts the Earth's surface in a day is 200 W/m2. [3] This means that the average home has more than enough roof space to produce enough electricity to supply all of its power needs. In fact, each day, more energy reaches the Earth from the sun than would be consumed by the global population in 27 years. [4]
Why is solar power renewable?
Solar power is renewable as long as the sun keeps burning the massive amount of hydrogen it has in its core. Even with the sun expending 700 billion tons of hydrogen every second, it is expected to keep burning for another 4.5 billion years. [5] Therefore, technically, solar power is not a completely renewable power source because it will be depleted in 4.5 billion years.
Are there different types of technologies associated with solar power?
There are a variety of types of technologies associated with solar power. These technologies can be divided into two groups. The first group are those that use the sun to generate heat, called solar thermal technologies. Solar thermal technologies include solar concentrator power systems, flat plate solar collectors, and passive solar heating. [6] The other group of solar power technologies directly convert solar radiation into electricity through the photoelectric effect by using photovoltaics (also known as PV).
Solar thermal technologies
- Concentrating solar power systems generate electricity with heat. Concentrating solar collectors use mirrors and lenses to concentrate and focus sunlight onto a receiver mounted at the system's focal point. The receiver absorbs and converts the sunlight into heat. This heat is then transported by means of a heated fluid (either water or molten salt) through pipes to a steam generator or engine where it is converted into electricity. [7]
- Flat plate solar collectors are usually large flat boxes with one or more glass covers. Inside the boxes are dark colored metal plates that absorb heat. Air or liquid, such as water, flows through the tubes and is warmed by heat stored in the plates. [8] These systems are particularly useful for providing hot water to households--and 83% of households in Israel were using solar collectors by 1994. [9] As of 1992, over 4.5 million buildings in Japan were using solar hot water systems. [10]
- Passive solar heating design methods use features such as large south-facing windows and building materials that absorb the sun's thermal energy. Passive solar methods can be used to greatly lower heating bills and can even be used to cool a building using natural ventilation. [11] The simplest and perhaps most common of the passive solar technologies is referred to as direct solar gain. A direct gain system includes south-facing windows and a large mass, usually of composed of stone, brick, or concrete, placed within the space to receive the most direct sunlight in cold weather and the least direct sunlight in hot weather. The result is that in cold weather the large thermal mass in the room absorbs solar energy and radiates heat throughout the room. During warmer times, due to its strategic placement away from the windows most concentrated light, the thermal mass absorbs only the warm air already in the room. This leaves the air cooled in warmer seasons and heated in cooler seasons. [12]
Solar thermal technologies come in various sizes. There are small portable solar cookers that utilize a parabolic concentrating disk to cook food and boil water. There are also large centralized solar power plants, known as "power towers", that use many acres of mirrors to collect and focus the sun's power. This focused heat turns water into steam that is used to power a generator. The "Solar One" and "Solar Two" power plants, both with 10 MW capacities, are examples of these large scale solar thermal power plants. The "Solar Two" produces enough power for 10,000 households. Engineers hope to build larger versions in the future with capacities of 30-200 MW. [13]
One beneficial and not immediately apparent application of solar thermal technology is the use of sunlight to cool buildings. Solar thermal energy is used to cool buildings in two ways. The first is by using absorption cooling devices that run on a normal refrigerator cycle by condensing and evaporating a refrigerant fluid. The second method uses dessicant cooling systems, which use a drying agent to absorb water vapor, reduce humidity, and cool the air through evaporation. [14]
Photovoltaics
The second main method for capturing the sun's energy is through the use of photovoltaics. Photovoltaics (PV) utilize the sun's photons or light to create electricity. PV technologies rely on the photoelectric effect first described by French physicist Edmund Becquerel in 1839. [15]
The photoelectric effect occurs when a beam of UV light, composed of photons (quantized packets of energy), strike one part of a pair of negatively charged metal plates. This causes electrons to be "liberated" from the negatively charged plate. These free electrons are then attracted to the other plate by electrostatic forces. This flowing of electrons is an electrical current. This electron flow can be gathered in the form of direct current (DC). This DC can then be inverted into alternating current (AC), which is the electrical power that is most commonly used in buildings. [16] [17]
Why aren't there more solar panels or big solar plants being used today?
There are actually more solar panels and big solar plants being used today than ever before. [18] The PV industry is experiencing annual growth rates of around 25% with higher growth rates in countries such as Japan, where it is currently growing at 63%. [19] However, solar power has clearly not met its full potential. There are a few reasons for this under-exploitation of solar panels and big solar plants.
The main reason for the lack of mass exploitation of solar power technologies is economic. In order for widespread generation of electricity using solar panels to be feasible it needs to be economically advantageous. In order for solar panels to be an economically viable choice for the production of electricity, production costs must go down and efficiency of the final product must go up. It is difficult to find funding to fuel the projects that are necessary to increase the amount of electricity that can be produced for a certain price, when the current technology is not already adequately efficient.
The absence of mass consumer demand for solar technologies is a hidden factor behind the lack of wide-spread solar power production. If there is a demand for a product, there will be people that will supply that product at a cost that fulfills that demand. If there is enough consumer demand, economic and efficient solar power technologies will be developed and exploited more quickly.
Despite a lack of truly substantial financial investment from both consumers and the government (compared to the investments made in conventional energy sources), the efficiency of solar panels continues to improve. Solar technologies have come a long way from the emergence in 1954 with efficiencies of 6% and costs of $600 a watt. [20] Some of the most recent single-crystal silicon cells have as much as 24% efficiency in the lab and commercial cells at 15% efficiency. [21] This increasing efficiency coupled with decreasing module prices may lead to more and more usage of solar power. [22]
As prices go down, efficiencies go up, tax incentives and rebates increase in impact, reliability of standard electrical generation fluctuates, and increased awareness of the dangers of fossil fuel combustion become widespread, the use of solar panels may increase greatly. This increase can already be seen in the solar market. For example, the shipment of PV modules and cells reported by US manufacturers in 1999 jumped by 52% from 1998. [23] NREL and the DOE project that growth in the PV industry of 25% annually is sustainable at least until 2020. [24]
Solar is a good energy option in developing countries. Because of the cost of transmission lines and the difficulty of transporting fuel to remote areas, developing countries are increasingly turning to solar energy as a low cost way to supply electricity. [25] With a third of the world's population still without electricity, most of whom live in developing countries, usage of solar panels will be increasing greatly as the demand for electricity spreads throughout the world. [26] BPSolar, previously Solarex, is one of the first large companies to really start catering to this need in developing areas. They recently completed two $30 million projects, one in the Philippines and another in Indonesia. A $48 million project, that will supply 114 villages with electricity, is currently in the works. [27]
Examples of large-scale solar power applications is not limited to developing countries. For example, in Murcia, Spain, AstroSolar is planning to supply a Spanish power plant with 13 MW of solar cells. This Spanish power plant will be four times larger than any other PV plant and will cover an area the size of 57 soccer fields. [28] The Japanese are currently spending 10-20 times more than the U.S. to commercialize PV, hoping to install 4,600 MW of Solar power by 2010. [29] While growth in the U.S. has not matched international growth, there is still a sizable growth in both PV and solar thermal use in the US residential sector. The EIA reported a 11% increase in the shipment of solar thermal collectors between 1998 and 1999, with more than 90% of these shipments going to the residential sector. [30]
Overall, use of solar power is increasing globally. However, the percentage of energy produced using solar resources is still miniscule.
What happens when the sun doesn't shine?
The amount to which a period of little or no sunlight will effect a home using solar power varies greatly depending on the physical location of a particular home and the nature of the solar system being used. For instance, if the home uses PV and solar thermal, and is also connected to the standard electricity grid, a period of no sunlight will simply mean relying on grid power. On the other hand, homes that are not connected to grid power must either be able to rely on other energy producers, such as a fuel cell, a wind turbine, a diesel generator, or on a supply of electricity stored in batteries. For some solar technologies, such as passive solar applications that utilize a large thermal mass, stored power in batteries or power from a standard utility cannot serve as a backup.
For more information on batteries read Renewable Energy World magazine.
How do different solar technologies effect the environment?
During operation, PV and solar thermal technologies produce no air pollution, little or no noise, and require no transportable fuels. One environmental worry with solar technologies is the lead-acid batteries that are used with some systems. This is a concern especially in developing countries where proper disposal and recycling is not always available. The impact of these lead batteries is lessening however as batteries become more recyclable, batteries of improved quality are produced and better quality solar systems that enhance battery lifetimes are created. [31]
A second environmental concern with solar technologies is the difficulty or recycling heavy metals such as cadmium, which are used in PV cells. Just as there is a large worry about the large amount of discarded personal computers that may pile up and leach cadmium, mercury, and lead into the environment, there is a worry that the cadmium used in discarded PV panels may also be an environmental threat. [32] Since the use of cadmium sulfide in the production of PV panels is on the rise (replacing the more expensive silicon)this is an issue that should be considered. [33]
Since the environmental impact of solar technologies is relatively small, it is perhaps more beneficial to take a look at the enormous amount of pollution that is prevented due to the use of solar technologies. The US EPA has developed a solar environmental benefits calculator which computes, based on the amount of electricity produced by a PV system and the geographic location of that system, the amount of nitrogen oxide (NOx), sulfur dioxide (SO2), and carbon dioxide (CO2) that is prevented from being emitted each year. A similar calculator is provided by BP Solar.
The amount of emissions that can be prevented through the use of a small PV system is surprising. For example, if in Iowa, a relatively small 500 watt PV system was installed, emissions of 4 lbs. of NOx, 8 lbs. of SO2, and 6,733 lbs. of CO2 would be avoided annually. [34] At the same location, if a modest 66 gallon solar hot water system was installed, an additional 18 lbs. NOx, 37 lbs. SO2, and 8,546 lbs. of CO2 would be avoided annually. [35]
How much does solar power cost?
Currently solar power is more expensive than other methods of producing electricity. However, utilities using fossil fuels and nuclear are able to provide a lower price, in part, because of government subsidies and incentives as well as the avoided cost of pollution control, and NOx credits in some places. It is also important to remember that as supplies of fossil fuels continue to be depleted their price will increase. Solar technologies on the other hand will become less expensive as they evolve into more efficient forms. With solar power, along with some batteries for backup, one is also paying for the extra reliability with their increased resistance to the simple line failures of standard utility electricity. [36]
There are different parts of the whole system to consider when looking at price. There is the price per watt of the solar cell, price per watt of the module (whole panel), and the price per watt of the entire system. It is important to remember that all systems are unique in their quality and size, making it difficult to make broad generalizations about price. The average PV cell price was $2.01 per peak watt in 1999 and the average per peak watt cost of a module was $3.62 in the same year. [37] The module price however does not include the design costs, land, support structure, batteries, an inverter, wiring, and lights/appliances. With all of these included, to buy a full system it can cost anywhere from $7 per watt to $20 per watt. [38] So, for example, if you wanted to put in a 10 kilowatt-hour per day system in an area with on average 5 hours of sun a day, you will need a 2 kilowatt system. At $7 a watt it would cost about $14,000. [39] With most average homes drawing from 1 kilowatt to 2 kilowatts, a system of this size would offset a significant portion of load during hours of maximum sunlight, maintenance free for 15-20 years.
Whole solar system packages can be purchased from suppliers, such as Jade Mountain, at a range of sizes and costs.
What percentage of solar power currently is part of the electricity mix in the US?
The amount of solar power that is currently part of the electricity mix in the U.S. is quite small. According to the Annual Energy Review of 1999 provided by the EIA, 0.076 quadrillion BTU's of energy were produced by solar power. This is about 0.1% of the overall 72.523 quadrillion BTU's produced in the U.S. This percentage is dwarfed by the 57.673 quadrillion BTU's, or 80% of the total, produced using fossil fuels. Coal alone produced 52% of the electricity produced in the US in 1999. [40] From an environmental perspective, this is troubling, since coal is the most potent emitter of lead and mercury as well as a leading emitter of CO2, NOx, and SO2. The process of mining the coal is itself harmful in a number of ways. 95% of acidic mine drainage is a product of coal mining along with 18.8 million metric tons of methane (CH4) each year. [41] All of this damage is done even before coal is burned!
Why don't we build a solar plant
on the moon and beam the energy back to Earth?
Transmitting electricity over long distances through air or
space has been discussed by physicists and engineers for some
time. The process could be similar in principal to that used
by communications satellites to send information encoded in
electromagnetic energy to Earth, but with a tighter beam to
allow full capture of the beamed power. While perhaps technically
feasible, the economics of deployment and operations, issues
of national security, and health and environmental impacts,
as well as a number of other issues, must be addressed. The
initial barrier of high cost has so far prohibited commercial
application of space-based power. For more information on the
subject see the following articles:
The Case for Space Based Solar Power Development. August
2003. http://www.spacedaily.com/news/ssp-03b.html
Solar Power Via the Moon. The Industrial Physicist. April/May
2002. http://www.aip.org/tip/0402.html
Laying the Foundation for Space Solar Power: An Assessment
of NASA's Space Solar Power Investment Strategy. 2001. http://www.nap.edu/execsumm/0309075971.html
Congressional Testimony on NASA's Fresh Look Study of the
concept of solar space power. (1997)
http://commdocs.house.gov/committees/science/hsy297160.000/hsy297160_0.HTM
What are some examples of solar power technologies or case studies online?
There are many good examples of solar power technologies and case studies online.
A wonderful place to start is the Global Energy Marketplace section of this website.
Other sites to check out are:
U.S. Department of Energy: find residential applications of solar power and other case studies.
Siemens Solar: A leader in solar technologies giving information on solar applications in telecommunications, transportation, water delivery and treatment, residential, and architectural areas.
Renewable Energy World Online: This magazine is full of current projects and new applications of solar power technologies.
EcoIQ: A quarterly journal dedicated to the building of sustainable communities.
Home Power: An online version of a quality renewable energy magazine. Full of content related to residential solar applications.
National Renewable Energy Laboratory: Case studies of solar projects currently underway.
Minnesota Renewable Energy Society: How to build a model solar car.
These websites give case studies and examples of solar power being used in a variety of ways. They give information on how solar power can be used in telecommunications, traffic and railroad settings, the delivery of water and water treatment, recreational vehicles, boats, architecture, and even how to make a solar electric car.
What are some policies that might promote the proliferation of solar power in the US?
There are policies already in place both at the state and federal level that promote the development and use of solar power. Current policies include:
- The Energy Tax Act of 1978 gave residential solar credits to those using solar technologies. However, this act expired on December 31, 1985. [45]
- The Energy Policy Act of 1992 extends 10% business tax credits for solar equipment indefinitely. [46]
- PURPA (Public Utilities Regulatory Policies Act) is a beneficial policy that requires electric utilities to purchase power produced by qualified renewable power facilities at avoided cost. [47]
- There are also some Residential Tax Credits that affect solar power. These include bills S.207 and S.293, which aim to create a refundable tax credit for up to 50% of increased residential energy costs, and is applicable to a variety of residential equipment including solar water heaters and PV. Bill S.465 establishes a 15% residential tax credit for homeowners who purchase photovoltaics and solar thermal equipment. [48]
The Bush administration has also called for tax credits for rooftop solar equipment starting in 2002. [49]
To find out the policies that are currently in place at the state level, visit the DSIRE website. The Database of State Incentives for Renewable Energy (DSIRE) gives a complete overview by state of the current tax incentives, loans, and rebates that are available to those hoping to install and use solar power.
Future policy moves that may help the proliferation of solar power technologies:
- Voluntary labeling and development programs such as Energy Star, Building America, and Rebuild America, that raise awareness and consumer knowledge can be expanded. [50]
- Standardization of interconnection codes could be implemented, which will make the installation of solar systems easier and cheaper from state to state. [51]
- Extension of the $0.015 kWh production tax credit for the first ten years of operation for wind and biomass technologies to solar power. [52]
- Implementation of a Renewable Portfolio Standard (RPS) could be helpful. According to the American Wind Energy Association (AWEA):
"an RPS is a flexible, market driven policy that can ensure that the public benefits of wind, solar, biomass, and geothermal energy continue to be recognized as electricity markets become more competitive. The policy ensures that a minimum amount of renewable energy is included in the portfolio of electricity resources serving a state or country and ö by increasing the required amount over time ö the RPS can put the electricity industry on a path toward increasing sustainability. Market implementation will result in competition, efficiency, and innovation that will deliver renewable energy at the lowest possible cost." [53]
- Removal of the "grandfather" clause that has allowed older higher polluting, coal-fired plants to continue to operate as they always have without having to internalize all of the negative externalities which they are imposing on others (humans as well as the rest of life on earth). [54] This will in effect remove a subsidy to fossil fuels and help level the playing field for renewables such as solar energy.
Who are some of the big players commercially in solar power?
Applied Power Corporation of Lacey, Washington: Applied Power was acquired by the Idaho Power Company, a company with $1.1 billion in annual revenue that was the first U.S. utility to offer solar electric service to its customers. Applied Power itself recently acquired Alternative Energy Engineering of California, Ascension Technology of Massachusetts and Colorado, and Solar Electric Specialties of Colorado. Applied Power assembles and sells PV systems for applications such as remote sites in national parks, mountaintop telecommunication systems, solar homes and village water pumping systems in developing countries, etc.
AstroPower, Inc. of Newark, Delaware: Originally a government contractor that has become a publicly-traded commercial manufacturer, AstroPower manufactures PV modules, single crystal cells and silicon thin film. Total annual sales equaled $20 million. In June, 1999, AstroPower agreed to develop products for GPU, Inc., a major New Jersey-based utility company; in return, GPU made a major purchase of AstroPower stock.
BP Solarex of Frederick, Maryland: In 1999, British Petroleum merged with Amoco, which with Enron Corporation was a joint owner of Solarex, a photovoltaic firm with 600 employees in Maryland, Virginia and Australia, and annual revenue of $58 million. Enron subsequently sold its share to BP Amoco, making BP Amoco sole owner of America's largest photovoltaic firm. It remains unclear how BP Amoco will merge the operations of Solarex with BP's solar arm, BP Solar, a firm with 900 employees in India, Australia, Spain and California, and annual revenue of $95 million. BP Solar projects annual revenues of $150 million, representing 20 per cent of the global market, and the firm seeks $1 billion in annual revenue by 2007.
Solarex has manufactured both polycrystalline silicon and potentially cheaper-but so far less efficient-thin film modules. Recently, the firm purchased a Swedish and a South African PV module manufacturer, to assemble American-made PV cells into modules ready for installation in growing European and African markets. Meanwhile, BP Solar has built markets in 160 nations, and particularly in developing nations, for its mono-crystalline and thin film technology. A vertically integrated firm, BP Solar manufactures cells, assembles PV systems, and installs and services grid-connected and stand-alone systems.
Golden Genesis Company of Scottsdale, Arizona: Kyocera Corporation, the world's largest PV cell producer, acquired Golden Genesis (formerly Photocomm, Inc.) in July of 1999. The resulting merger produces a vertically-integrating PV firm with combined annual sales of $185 million, to be named Kyocera Solar. The merged company will assemble, distribute and install products made from Kyocera cells, including PV power systems for lighting, telecommunications, cathodic protection and data acquisition for oil and gas pipelines, water pumping, etc.
Powerlight of Berkeley, California: PowerLight is a full-service company offering unique solar electric products and complete energy solutions, from initial consultation to installation, project development, maintenance and financing. According to the company, Power Light’s patented photovoltaic (PV) products provide solar energy at the lowest possible cost in the industry, and are uniquely designed to install seamlessly onto existing building infrastructures, without penetrations.
Siemens Solar Industries of Camarillo, California: Siemens Solar is affiliated with Siemens AG of Germany and Siemens Corporation of the U.S.; the Siemens Solar Group as a whole enjoys annual revenue of $78 million (1997), employs 475 people worldwide, and has American facilities in California and Vancouver, Washington. Siemens produces both crystalline and thin film PV cells, which are sold wholesale to PV system integrators.
Spire Corporation of Bedford, Massachusetts: In addition to its biomedical processing and optoelectronic divisions, Spire is the world's largest producer of PV manufacturing equipment. Spire also supports its production lines with process technology, spare parts, training and equipment warranty. Annual revenue is $14 million.
Trace Engineering Corporation of Arlington, Washington: Trace designs and manufactures battery chargers and inverters, which convert the direct current generated by photovoltaic systems into the alternating current used by most appliances and the national electric grid. Trace also manufactures accessories such as cables, charge controllers and remote controls. Trace employs 125 people, and recently acquired the rights to bankrupt Kenetech Windpower's power conversion technology, which it will manufacture as Trace Technology Corporation.
Who are some major players in the solar water heater (SWH) industry?
The small SWH industry, notwithstanding the technology's favorable economics and large potential market, does not have participation by nationally known firms.
Sun Earth of Ontario, California: Sun Earth manufacturers the solar components of SWHs, including flat-plate collectors, thermosiphons, etc., selling approximately 10,000 systems annually. It is owned by Solarray, a Hawaii-based wholesaler of water heating equipment for the Pacific market. Solarray supplies the water heater components for SWHs sold by Sun Earth. Solarray has annual sales of approximately $14 million.
Sun Earth distributes SWHs in Albuquerque through Semco, Inc. Energy Labs, Inc. of Jacksonville, Florida: Energy Labs develops solar energy technologies for private firms. It also licenses technologies for others to use. It has a cooperative research and development agreement with Sandia National Labs to create a new, low-cost SWH. It has revenues of approximately $500,000 and 9 employees. [55]
Where can I get more information on solar power?
Where do I buy solar powered devices?
Search the Global Energy Marketplace (GEM) on the CREST homepage. Use the GEM database to search for any renewable energy technology, company, policy, as it relates to any specific area of the world.
There is an exhaustive list of companies that sell and/or produce solar powered devices provided by the U.S. Department of Energy Photovoltaics Program.
Jade Mountain is a supplier of renewable energy products with a selection from "60 year light bulbs to complete solar homes." Big Frog Mountain offers alternative energy equipment which supplies power using micro-hydro, solar panels, and wind turbines to people around the world everyday.
The U.S. Department of Energy also provides an extensive list of PV suppliers that provides information on how to contact module manufacturers, system designers and installers, balance-of-systems manufacturers, related product manufacturers and information on suppliers, consultants, standards, testing, and training.
Here's a short list of some larger companies:
BP Solar
Siemens Solar
PV Energy Systems, Inc.
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Photo Credit: PIX number
06456
Title: 4 Times Square, a 48-story skyscraper at the corner of Broadway and 42nd St., was the first major office building to be constructed in New York City in the 1990s
Caption: The building's most advanced feature is the photovoltaic skin, a system that uses thin-film PV panels to replace traditional glass cladding material. The PV curtain wall extends from the 35th to the 48th floor on the south and east walls of the building, making it a highly visible part of the midtown New York skyline. The developer, the Durst Organization, has implemented a wide variety of healthy building and energy efficiency strategies. Kiss + Cathcart Architects designed the building's PV system in collaboration with Fox and Fowle, the base building architects. Energy Photovoltaics of Princeton, NJ, developed the custom PV modules.
Credit: Kiss + Cathcart - Architects
Publications: Photovoltaics and commercial buildings -a natural match: a study highlighting strategic opportunities and locations for using photovoltaics to power businesses (DOE/GO-10098-657 , September 1998)
Date: 7/1/1998
Index Date: 9/10/1998
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