Component of Solar Central Receiver

8/6/2019 Component of Solar Central Receiver

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Component of solar central receiver Component of solar central receiver 11-- HeliostatHeliostat--The energy collection in a largeThe energy collection in a large- -scale solar scale solar-- thermal power thermal power plant is based on the plant is based on theconcentration of the Suns rays onto a commonconcentration of the Suns rays onto a common

focal point to produce highfocal point to produce high- -temperature heat totemperature heat to runruna steam turbine generator.a steam turbine generator.--The radiation concentration is achieved by usingThe radiation concentration is achieved by usinghundreds of large sunhundreds of large sun- -tracking mirrors calledtracking mirrors called

heliostats.heliostats.-- Each heliostat directs the solar radiation towardEach heliostat directs the solar radiation toward the thehighest point in a tower where the receiver ishighest point in a tower where the receiver is locatedlocatedto absorb the heat.to absorb the heat.


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22-- Receiver Receiver- -Tower Tower

The receiver, placed at the top of a tower, is located atThe receiver, placed at the top of a tower, is located ata point where reflected energy from the heliostats cana point where reflected energy from the heliostats can

be intercepted most efficiently. be intercepted most efficiently.The receiver absorbs the energy being reflected fromThe receiver absorbs the energy being reflected from

the heliostat field and transfers it into a heat transfer the heliostat field and transfers it into a heat transfer

fluid.fluid.There are two basic types of receivers: external andThere are two basic types of receivers: external andcavity.cavity.


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Typ es of receiverTyp es of receiver

Ext ernal Receivers Ext ernal Receivers ::

These normally consist of panels of manyThese normally consist of panels of manysmall vertical tubes welded side by side tosmall vertical tubes welded side by side toapproximate a cylinder.approximate a cylinder.The bottoms and tops of the vertical tubes areThe bottoms and tops of the vertical tubes areconnected to headers that supply heat transfer connected to headers that supply heat transfer

fluid to the bottom of each tube and collect thefluid to the bottom of each tube and collect theheated fluid from the top of the tubes.heated fluid from the top of the tubes.


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C avi ty ReceiversC avi ty Receivers ..

I n an attempt to reduce heat loss from theI n an attempt to reduce heat loss from thereceiver, some designs propose to place thereceiver, some designs propose to place theflux absorbing surface inside of an insulatedflux absorbing surface inside of an insulatedcavity, therecavity, there by reducing the convective heat by reducing the convective heatlosses from the absorber.losses from the absorber.The flux from the heliostat field is reflectedThe flux from the heliostat field is reflected

through an aperture onto absorbing surfacesthrough an aperture onto absorbing surfaces


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C avit y ReceiverC avit y Receiver


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33 --Heat transfer fluidHeat transfer fluid

The choice of the heat transfer fluid to be pumpedThe choice of the heat transfer fluid to be pumpedthrough the receiver is determined by the application.through the receiver is determined by the application.The primary choice criterion is the maximumThe primary choice criterion is the maximum

operating temperature of the system followed closelyoperating temperature of the system followed closely by the cost by the cost--effectiveness of the system and safetyeffectiveness of the system and safetyconsiderations.considerations.

Five heat transfer fluids have been studied in detailFive heat transfer fluids have been studied in detailfor application to central receiver systems.for application to central receiver systems.


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Typ es of heat transfer fluidTyp es of heat transfer fluid

11 -- heat transfer oils :heat transfer oils :their their maximum temperature is around 425maximum temperature is around 425 CC

(797(797 F).F). However, their vapor pressure is low atHowever, their vapor pressure is low at

these temperatures Heat transfer oils cost aboutthese temperatures Heat transfer oils cost about$0.77/kg$0.77/kg22--Steam :Steam :.. Maximum temperature applications are around 540Maximum temperature applications are around 540 CC

(1 000(1 000

F) where the pressure must be about 1 0 MPaF) where the pressure must be about 1 0 MPa(1 450 psi) to produce a high boiling temperature.(1 450 psi) to produce a high boiling temperature. , its, itscost is lower than that of other heat transfer fluids.cost is lower than that of other heat transfer fluids.


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33 -- Nitrate saltNitrate salt--Nitrate salt mixtures can be used as both a heat transfer Nitrate salt mixtures can be used as both a heat transfer

fluid and a storage mediumfluid and a storage medium at temperatures of up toat temperatures of up to565565 C (1 050C (1 050 F).F). However, most mixtures currentlyHowever, most mixtures currently

being considered being considered freeze at temperatures around 1 40 tofreeze at temperatures around 1 40 to220220 C (285 to 430C (285 to 430 F)F) and thus must be heated whenand thus must be heated whenthe system is shutdown.the system is shutdown.

-- The cost of nitrate salt mixtures is aroundThe cost of nitrate salt mixtures is around $0.33/kg$0.33/kg


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44 -- Liquid sodiumLiquid sodium--Liquid sodium can also be used as both a heat transfer Liquid sodium can also be used as both a heat transfer

fluid and storage medium,fluid and storage medium, with a maximum operatingwith a maximum operatingtemperature of 600temperature of 600 C (111 2C (111 2 F).F). Because sodium isBecause sodium isliquid at this temperature, its vapor pressure is low.liquid at this temperature, its vapor pressure is low.

--The cost of sodiumThe cost of sodium- -based systems is higher than the based systems is higher than thenitrate salt systems since sodium costs aboutnitrate salt systems since sodium costs about $0.88/$0.88/kgkg


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55 -- Air or heliumAir or helium--For highFor high--temperature applications such as Braytontemperature applications such as Brayton

cycles, it is proposed to use air or helium as the heatcycles, it is proposed to use air or helium as the heattransfer fluid.transfer fluid.

-- Operating temperatures of aroundOperating temperatures of around 850850 C (C (1 5601 560 F) atF) at1 21 2 atm pressureatm pressure are being proposed.are being proposed.

-- Although the cost of these gases would be low, theyAlthough the cost of these gases would be low, theycannot be used for storage and require very largecannot be used for storage and require very largediameter piping to transport them through the system.diameter piping to transport them through the system.

Component of Solar Central Receiver

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