eduardo zarza basic concepts

Almera (Spain), June 27-28 , 20123rd SFERA Summer School 1

Eduardo ZarzaCIEMAT-Plataforma Solar de Almera,

Apartado 22, Tabernas, E-04200 AlmeraPhone: 950387931 E-mail: [email protected]

Basic principles of solar radiation and STE plants

3rd SFERA Summer School


) Solar Concentrating Systems) Solar Thermal Electricity (STE) Plants

) The Sun and the solar radiationndice de la Presentacin

) STE technologies comparison

Basic principles of Solar Radiation and STE Plants


The Sun and the Solar radiation

Sun is a huge nuclear reactor (7x105

km radius)

emitting a great amount of radiant energy (3,8x1023

kW, 5800K), which can be easily converted into thermal energy


Spectral Solar Irradiance

0,0 0,5 1,0 1,5 2,0 2,50

250

500

750

1000

1250

1500

1750

2000

2250

Extraterrestrial solar radiation

Wave length (m)

S

p

e

c

t

r

a

l

s

o

l

a

r

i

r

r

a

d

i

a

n

c

e

(

W

/

m

2

m

)

Solar radiation at ground level(Air Mass = 1.5)

LE

L

L/LE = 1.5



The Earth intercepts only 1,7x1014

kW of solar radiation (10 days

known fossil fuels resources)

The solar irradiance outside the atmosphere is almost constant (its value is called Solar Constant, 1367 W/m2)

Solar radiation at ground level has two components: Direct Radiation and Difuse Radiation.


km radius)




Direct and Difuse Solar RadiationDi

rect

Radia

tion

Dire

ctRa

diatio

n

Dire

ctRa

diatio

n Diffuse Radiation

Diffuse RadiationDiffuse Radiation

b) d /4 c) d > a) d < /10



The Earth intercepts only 1,7x1014

kW of solar radiation (10 days

known fossil fuels resources)

The solar irradiance outside the atmosphere is almost constant (its value is called Solar Constant, 1367 W/m2)

Solar radiation at ground level has two components: Direct Radiation and Difuse Radiation.

Only Direct Solar Radiation can be concentrated.

Solar radiation reaching any point is not composed of a single ray, but of a cone of rays within a solid angle of 32

(approx.).


km radius)





= inicidence angle

= Reflection angle

=

Reflecting surface

32


) Solar Concentrating Systems) Centrales Termosolares y Crecimiento Sostenible

) The Sun and the solar radiation

) Situacin actual ) Conclusiones

ndice de la Presentacin

Introduccin a los SistemasSolaresTrmicos deConcentracin


Solar Radiation and its Concentration Solar Concentration: Why?

Since solar radiation suffers a significant attenuation in its way to the Earth (from 63,2 MW/m2 to 1 kW/m2) we have to concentrate solar radiation in order to compensate for its low flux density at the Earth surface and thus achieve higher temperatures and efficiencies.


Dependence of the Efficiency and the Optimum Working Temperature on the Solar Radiation Concentration Factor

= f(C, T)

Efficiency versus concentration factor

0

0.25

0.5

0.75

1

0 1000 2000 3000 4000

Temperatura (K)

1.000

5.000

10.000

20.000

Carnot

C=250

0

0.25

0.5

0.75

1

0 1000 2000 3000 4000

Temperature (K)

S

y

s

t

e

m

E

f

f

i

c

i

e

n

c

y

1.000

5.000

10.000

20.000

Carnot

C=250


Solar Radiation and its Concentration

Solar Concentration: Why?Since solar radiation suffers a significant attenuation in its way to the Earth (from 63,2 MW/m2 to 1 kW/m2) we have to concentrate solar radiation in order to compensate for its low flux density at the Earth surface and thus achieve higher temperatures and efficiencies.

Ways to concentrate the direct solar radiationa) by Reflection

b) by Refraction


Direct radiation

Reflecting surface

Receiver

Direct radiation

a) by Reflection

Direct Solar Radiation can be concentrated by Reflection and by Refraction:

Receiver

Direct radiation

b) by Refraction

Fresnel lens




Limiting factors for solar concentration

Theoretical and practical limits for solar concentration Point focus concentrators: 46200 (theoretical); 5000 y 10000 (practical) Linear focus concentrators: 220, (theoretical); 20

80 (practical)

a) The apparent size of solar sphere is 32as seen from the Earthb) Inaccuracies and optical errors of solar concentrators

Solar Concentration: Why?Since solar radiation suffers a significant attenuation in its way to the Earth (from 63,2 MW/m2 to 1 kW/m2) we have to concentrate solar radiation in order to compensate for its low flux density at the Earth surface and thus achieve higher temperatures and efficiencies.

Ways to concentrate the direct solar radiationa) by Reflection

b) by Refraction


32

Actual shape

Theoretical shape

Concentration limit due to the Sun disk size

Concentration

= L/ddL


) Solar Concentrating Systems) Solar Thermal Electricity Plants

) The Sun and the solar radiation

) Situacin actual ) Conclusiones

ndice de la Presentacin

Introduccin a los SistemasSolaresTrmicos deConcentracin


Solar Thermal Electricity PlantsWhat is a Solar Thermal Electricity (STE) plant ?A STE plant is a system where

solar radiation is concentrated and then converted intothermal energy at medium/high temperature (300C

800C). This thermal energy is then used in a thermodynamic cycle to produce electricity.


Optical Concentrator

RECEIVER

Waste Heat

Heat

Thermallosses

Opticallosses

Simplified Scheme of a typical STE PlantSimplified Scheme of a typical STE PlantDirect Solar Radiation

ConcentratedSolar Radiation

ThermalStorage

Solar System

Mechanical energy

G Electricity generator

ThermodynamicCycle


What is a Solar Thermal Electricity (STE) plant ?

9 There is a huge market worldwide for these solar plants

9 These plants do not increase the emissions of CO2 :

-

Every GWh

of electricity produced by a STP plant saves 800 tons of CO2

9 There are many Countries with good solar radiation level

-

A STP plant saves 2000 Tons of CO2

per year and MWe

installed

Why are Solar Thermal Power plants interesting nowadays ?

9 These plants demand a lot of manpower for construction, as well as for O&M

9 It is already profitable in some Countries due to public subsidies or incentives

9 The technology is mature enough for commercial deployment

A STE plant is a system where

solar radiation is concentrated and then converted intothermal energy at medium/high temperature (300C

800C). This thermal energy is then used in a thermodynamic cycle to produce electricity.

Solar Thermal Electricity Plants


100 mHeliostat field

Receiver

Power Conversion System

Tower

Current Technologies for STE plants (I)Central Receiver Technology


Receiver Tube

Parabolic trough concentratorStructure

Current Technologies for STE plants (II)Parabolic Trough Collectors


Solar field

Power Conversion System

STE Plant with Parabolic Trough Collectors

Current Technologies for STE plants (II)


ConcentratorReceiver

Structure

Stirling DishesCurrent Technologies for STE plants (III)

Solar Stirling engine


Receiver pipe

Rectangular reflectors

Linear Fresnel ConcentratorCurrent Technologies for STE plants (and IV)


Technologies comparison

PTC CentralReceiver

ParabolicDishes

LFC

Unit plant powerWorking temperaturePeak efficiency (solar-electric) Yearly net Efficiency

15-200 MW390 C20 %

11-16 %

15-100 MW575 C23 %

7-20 %

9-25 kW750 C30 %

12-25 %

15-200 MW390C

1813

Current status

Technological riskStorage availabilityHybrid designs

Available

LowSiSi

Available

LowSiSi

Prototypes-Demonstration

LowSiSi

Available

High-MediumSiSi

Solar Thermal Electricity Plants


End of Slide Show

! Thank you for your attention

Basic principles of solar radiation and STE plants

3rd SFERA Summer School

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eduardo zarza basic concepts

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