SOLAR THERMAL POWER TOWERPresented by RAMESH V USN:4MC06ME084

1. INTRODUCTION2.SYSTEM DESCRIPTION3.RANKINE CYCLE4.HELIOSTAT5.WORKING OF SOLAR TOWER6.SOLAR ONE7.SOLAR TWO8.USE OF MOLTEN SALT9.REQUIREMENTS10. APPLICATION11.CONCLUSION

CONTENTS

INTRODUCTIONThe solar thermal power tower is a type of solar furnace using a tower to receive the focused sunlight. It uses an array of flat, moveable mirrors to focus the sun's rays upon a collector tower. The high energy at this point of concentrated sunlight is transferred to a substance that can store the heat for later use.

SYSTEM DESCRIPTION AND WORKING

RANKINE CYCLEThere are four processes in the Rankine cycle, each changing the state of the working fluid. Process 4-1: First, the working fluid is pumped from low to high pressure by a pump. Pumping requires a power input.

Process 1-2: The high pressure liquid enters a boiler where it is heated at constant pressure by an external heat source to become a superheated vapor.

Process 2-3: The superheated vapor expands through a turbine to generate power output.

Process 3-4: The vapor then enters a condenser where it is cooled to become a saturated liquid. This liquid then re-enters the pump and the cycle repeats.

HELIOSTAT A Heliostat is a device that tracks the movement of the sun. It is typically used to orient a mirror, throughout the day, to reflect sunlight in a consistent direction. When coupled together in sufficient quantities, the reflected sunlight from the heliostats can generate an enormous amount of heat if all are oriented towards the same target. It was originally developed as an instrument for use in surveying, allowing the accurate observation of a known point from a distance.

SOLAR ONESolar One, which operated from 1982 to 1988, was the worlds largest power tower plant. It proved that large-scale power production with power towers was feasible. The project met most of its technical objectives by demonstratingThe feasibility of generating power with a power towerThe ability to generate 10 MW for eight hours a day at summer solstice and four hours a day at winter solstice.

Solar Two has produced 10 MW of electricity with enough thermal storage to continue to operate the turbine at full capacity for three hours after the sun has set.The Solar Two receiver comprises a series of panels (each made of 32 thin-walled, stainless steel tubes) through which the molten salt flows in a separate path.The energy storage system for Solar Two consists of 875,000 liter storage tanks.Thermal capacity of the system is 110MWh

SOLAR TWO

The molten salt is a mixture of 60 percent sodium and 40 percent potassium-nitrate, commonly called saltpeter.

The salt melts at 430F and is kept liquid at 550F in an insulated cold storage tank.USE OF MOLTEN SALT The salt is pumped to the top of the tower where concentrated sunlight heats it in a receiver to 1050F. The heated salt then flows back down to a second insulated 'hot' storage tank. From here, it can be pumped to a generator that creates superheated steam to drive a turbine or it can be stored and its thermal energy used later.

ADVANTAGES OF USING MOLTEN SALTIt is liquid at atmospheric pressure.It provides an efficient , low cost medium in which to store thermal energy,Its operating temperatures are compatible with today's high-pressure and high temperature steam turbines,

Land(Acreage) :Acreage needs for a parabolic trough or compact linear Fresnel reflector development would average about 5 acres/megawatt (MW), while acreage for the other solar technologies would average about 9 acres/MW. Acreage needs increase if the solar field is oversized to take advantage of thermal or electrical storageLAND AND WATER REQUIREMENTSWater:Parabolic trough, compact linear Fresnel reflector, and power tower technologies would require up to 15 acre-feet per year per megawatt for wet cooling or up to 1.5 ac-ft/yr/MW for dry cooling. Water required for mirror washing would be about 0.5 ac-ft/yr/MW.

ENERGY COST OF SOLAR POWER TOWER

Turbine sizeCapacity costInstalled capital costAnnual operation and maintenance costAnnual fuel costLevelized energy cost100 MW

100MW

200MW

200MW

27% Solar9% Fossil40%Solar

40% Solar

63%Solar$256M

$328M

$564M

$800M$4.9M

$4.9M

$6.1M

$7.4M$3M

-

-

-114/KWh

114/KWh

94/KWh

84/KWh

APPLICATIONS1)The solar thermal systems convert the radiant energy of the sun into heat, and then use that heat energy as desired.2)The solar electric systems convert the radiant energy of the sun directly into electrical energy, which can then be used as most electrical energy is used today

CONCLUSIONSolar thermal power towers meet the needs of todays utility grids.The technology for solar thermal power towers is proven.The cost performance and reliability of solar thermal power towers can be confidently predicted.Power towers will produce electricity at a competitive cost.

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