solar tower project physics

8/8/2019 Solar Tower Project Physics

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PROJECT ON

SOLAR TOWER


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INTRODUCTION The solar updraft tower is a proposed type ofrenewable-

energy power plant. It combines three old and proventech

nologies: the chimney effect, the greenhouse effect, andthe wind turbine. A

ir is heated by sunshine and contained in avery large greenhouse-like structure around the base of a tallchimney, and

the resulting convection causes air to rise up theupdraft tower. This airflow drivesturbines, which produceelectricity. A research prototype operated in Spain in the 1980s,and

many modelling studies have been published as tooptimization, scale, and economic feasibility. A technologicalreview is available this year


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DESCRIPTION The generating ability of a solar updraft power plant depends

primarily on two factors: the size of the collector area andchimney height. With a larger collector area, a greater volumeof air is warmed to flow up the chimney; collector areas as largeas 7 kilometres (4.3 mi)in diameter have been considered. Witha larger chimney height, the pressure difference increases thestack effect; chimneys as tall as 1,000 metres (3,281 ft) havebeen considered.

Heat can be stored inside the collector area greenhouse to beused to warm the air later on. Water, with its relatively high

specific heat capacity, can be filled in tubes placed under thecollector increasing the energy storage as needed.


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DESCRIPTION Turbines can be installed in a ring around the base of

the tower, with a horizontal axis, as planned for theAustralian project and seen in the diagram above;

orasin the prototype in Spaina single verticalaxis turbine can be installed inside the chimney. Carbon dioxide is emitted only negligibly[citation

needed] while operating, butis emitted moresignificantly during manufacture ofits constructionmaterials, particularly cement. Net energy paybackisestimated to be 23 years.


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DESCRIPTION A solar updraft tower power station would consume a significant

area of land ifit were designed to generate as much electricityasis produced by modern power stations using conventionaltechnology. Construction would be most likely in hot areas withlarge amounts of very low-value land, such as deserts, orotherwise degraded land. A small-scale solar updraft tower maybe an attract

ive option for remote regionsin developingcountries.The relatively low-tech approach could allow localresources and labour to be used for its construction andmaintenance. This structure is expected to keep 830,000 tons

of greenhouse gases out of the atmosphere every year. It isthe tallest manmade structure ever created having a height of1000 mts The tower itselfis hollow, chimneylike, and around itsbase a large, circular solar collector is placed in a 25,000 acrebowl-like shape around the facility.


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DESCRIPTION During the day, thissolar collector absorbs a massive

dose of heat from the sun, and the air under thecolletor is rapidly heated. As this hot air rises atabout 30mph, it will find its way up the centralhollow tower, where the hot air will turn several largewind turbines to generate 200 MW of electricity. Theenergy output will represent an annual saving ofmore than 900,000 tonnes of greenhouse CO2 gases

from entering the environment, with an outstandingLife Cycle Analysis of 2.5 years


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WORKING Melbourne-based EnviroMission Limited recently invested in a

25,000-acre sheep farm in the Australian outbackin order tomake a power plant. But the alternative energy projectisn'tdriven by manure. Instead itll use a kilometer-high thermal

power station called the Solar Tower. Though the project wasannounced several years ago, the details are just being ironedout--construction of the 3,280-foot tower won't begin until 2006at the earliest.

The Solar Tower, according to wired, is one of the mostambitious alternative energy projects on the planet: a

renewable energy plant that pumps out the same power as asmall reactor butis totally safe.


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WORKING Hollow in the middle, the tower has a base with a solar collector, a

25,000-acre skirt. As air under the collector is heated by the sun, itsfunneled up the chimney by convection, asit accelerates to 35 m.p.h.,it begins driving 32 wind turbines thatin turn generate electricity much

like wind farms do. But unlike traditional wind farms and solargenerators, the Solar Tower can operate round the clock, even whentheres no wind, because it has banks ofsolar cells which can storeheat energy.

Though the tower could generate up to 200 megawatts--enoughelectricity to power 200,000 homes and will keep 830,000 tons ofgreenhouse gases out of the atmosphere annuallyit comes at highcost; with production costssomewhere between $500 million to $750million these things dont come cheap.


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NIGHT AND DAY The Solar Towerssupply curve is approximately

bell shaped, peaking with that of the sunsintensity. During summer, itissimilar to thedemand for air-conditioning, and the hotter theday, the more efficient the power plant. If a

more even supply of electricity is required, energycan be stored under the collector during the dayusing black plastic tubing filled with water. Waterhas a heatstorage capacity about 6 times that ofsoil. Further enhancementssuch as doors thatslow/stop the turbines can be installed. Totalfire-up time is 24 hours, however turbines canbe independently slowed/shut down in groups of4. This flexibility allows output to be adjusted forshifting demand patterns. Storage could reducethe peak capacity from 200 MW to a constant 80MW, although the intention is to operate as apeaking station. Annual production from theproposed power plantis just over 700 GWh.


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LOCATION The preferred site is Neds Corner Station near

Mildura. EnviroMission has an option over the property, whichis 70 km west of Mildura. Keeping with the big theme, thestation is the largest parcel of privately titled land in Victoria,

being some 30 km long and 15 km wide. The land, comprisingmainly flatsaltbush, includes water access rights from theMurray River of 110 Mlpa. The A$2.6m option expires on 31March 2002, and the decision to buy will depend on the resultsof extensive testing, including soil and sub-soil analysis toevaluate suitability for the foundation structure of the powerplants tower, as well assite specific solar measurements, andconstruction material sample testing and evaluation. Thecurrent round of geotechnical testing will confirm or refute thesitessuitability.


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Solar radiation at minimum 2,000 MWh per

square metre per year

yes

Low humidity yes

Access to power grid above 220 kVSouth Australia/Redcliffs main line.

Proximity to local electricity market Mildura/Murray Basin

Flat open landyes

Land use restrictions native title,

environmental, building/height restrictions

?

Environmental issues to be identified and

addressed through the Environmental

Impact Statement

Access to concrete, aggregate and sandyes

Tourism potentialMilduras image as a sun/solar city*.

Telecommunication/defence opportunities yes


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IDEA EnviroMission had a smaller

prototype builtin Spain in the1980s, which was 200 Metershigh, with a skirt that covered 8

acres. They were able to gather agreat deal of data during theseven years thatit wasinoperation.

One thing those testsshowed isthat even on cloudy days, there isenough solar penetration to run

the system, with only a slight dropin power. The primary driver isthe heat differential, which isstillmaintained on cloudy days.


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IDEA


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RECENT MODIFICATIONS EnviroMissionsscientists have come up with a few modifications

that will increase the overall efficiency of the tower. The firstmodification involves using the phenomena of the vortexmechanism of tropical cyclones. The second modification

includes more usage of water vapor in the air underneath theskirt. The greater the amount of water vapor, the greater the aircan be saturated to make it lighter and create the much neededdraftinside the tower. Moreover, water is a great collector andstorage medium for heat, which allows the air to heat up quicklyand easily.

The plan of the first tower has been designed to be of 1000meters. However, a 50 Kw model has already been constructedand issuccessfully working in Manzaneres, Spain.


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PROJECT BENEFITS 100% Clean Green Energy Generation Zero Water Use * Zero Emissions Zero Pollution Reliable & Sustainable Energy Generation Green Jobs - Shovel ready High Capacity Factor Low Operating Costs Cost Competitive Tailored to meet demand profile (peak or base load) Efficient use ofInfrastructure Site Flexibility Heatstorage availability Exceptional Carbon Credits Clean air equal to taking 220,000 typical motor vehicles from the roads annually.


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The optimum configuration is an 800- to 1,000-meter tower (twice theheight of the Empire State Building) surrounded by a greenhouse canopy1.5 miles (2.5 kilometers) in radius on the ground.

"It is a sizeable footprint [on the land], but with the rising cost of carbonfuels, it's becoming more commercial," Fort said.

On a sunny day, the air at the top of the tower would be 70 degreesFahrenheit (20 degrees Celsius), whereas the air in the greenhouse couldreach 160 degrees Fahrenheit (70 degrees Celsius). As this hot airescapes up the tower at 34 mph (15 meters per second), it spins 32turbines that generate up to 200 megawatts of electricity.

Even with all this power, the solar tower is less than one tenth as efficientas solar cells in converting the sun's energy into electricity.

The advantage for a solar tower is that its materials are much lessexpensive.

A 200-megawatt solar tower would cost upwards of a billion dollars tobuild. According to a 2005 industry report, this would imply about 10 cents

per kilowatt-hour, which is roughly a third of the cost of electricity fromcurrent solar cells.

However, a solar tower must be fairly big to be effective.


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FREQUENT ASKED

QUESTIONS 1. Whatis Solar Tower renewable energy technology?

Solar power technology is a renewable energy power stationtechnology that generates clean green sustainaible energy from theheat ofsun. Passive and non-polluting, the technology doesnt needwater at any stage of the electricity generation process.

Research and engg. Modelling indicates a solar power tower stationwill operate efficiently for more than 50 yrs with a life cycle analysis(LCA)* of approximately 2.5 yrs

*LCA:-Itis the amount of time of cleaning operation needed to equalizethe pollution assosiated with the manufacture and constructionprocess. For eg:- The carbon pollution resulting from the manufactureand transport of concrete.


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QUESTION-22. How does Solar Tower technology work?1. The tower:-

The tower is the thermal engine of the solar tower technology. In itheatis transformed in to mecanical energy. The updraftinside thetower, produced by the rising lighter, hot air, is essential for this.The greater the velocity of the tower, the higher the column of airis and the stronger the updraft. Thererefore, a high capacity powerplantshold have the highest tower possible.

2. The canopy:-The canopy converts a large percentage of the insulation in to heat,

which in turn, heats the air trapped under the canopy roof or isstored in the ground soil thermal storage system. One of the main

objectives of the canopy is to lose as little heat as possible in to theambient.


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3. The turbines:-

The turbines transforms the energy from

the heat and pressure of the air in tomecanical energy and the generatorsconvertsin to electricity. They work lie thewell known keplan turbines used in hydro

electric power stations.


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QUESTION-33. Can a solar tower operate on a cloudy day?Solar tower technology is designed to operate 365 days

a year in all weather including cloudy or wet days a

solar tower does operate in diffused sunlight.Radiant heat from the sun is the critical energy source

for solar tower technology, radiant heat will heat theair under a solar tower canopy in the same way theair inside a green house or hothouse is always higher

than the anbient external temeperature due to theuse of radiant heat.Air under the solar tower canopy will always have a

higher temeperature than the

solar tower project physics

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