Lecturer: Eduardo Zarza Moya
Plataforma Solar de Almería – CIEMAT(e-mail: [email protected])
First Summer SchoolPart A: Line-focus Solar Thermal Technologies
September 20-24, 2021
Lecture 1:An Introduction to Concentrating Solar Thermal (CST)
Technologies and Applications
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An Introduction to CST Technologies and Applications
• Introduction
Content
• Summary
• Concentrating Solar Thermal Technologies
• Concentrating Solar Thermal Systems
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The Earth intercepts only 1,7x1014 kW of solar radiation (10 days ≅known fossil fuels resources)
The Sun and the Solar Radiation
Sun is a huge nuclear reactor (7x105 km radius) emitting a great amountof radiant energy (3,8x1023 kW, 5800ºK), which can be easily convertedinto thermal energy
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View of a typical PV panel
Commercial Use of Solar Energy
Photovoltaic solar Plants:- Static PV panels
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Vistas plantas fotovoltaicas de paneles estáticos
Commercial Use of Solar Energy
Photovoltaic solar Plants:- Static PV panels
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Vistas de seguidor solar y planta fotovoltaicas con seguimiento solar
SHSolar
- PV panels with solar tracking
Commercial Use of Solar Energy
Photovoltaic solar Plants:- Static PV panels
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- PV panels with solar concentration
PV panels using flat mirrors for solar concentration
Commercial Use of Solar Energy
- PV panels with solar tracking Photovoltaic solar Plants:- Static PV panels
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PV panels with curved mirrors for solar concentration
Commercial Use of Solar Energy
- PV panels with solar concentration- PV panels with solar tracking Photovoltaic solar Plants:- Static PV panels
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Solar Thermal Plants:
- Solar systems for low temperature (125ºC)
Commercial Use of Solar Energy
- PV panels with solar concentration- PV panels with solar tracking Photovoltaic solar Plants:- Static PV panels
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Domestic solar system for hot water
Commercial Use of Solar Energy
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- Solar systems for médium temperature (125ºC<T<500ºC)
- Solar systems for high temperature (>500ºC)
Concentrating Solar Thermal Systems
Commercial Use of Solar Energy
Solar Thermal Plants:
- Solar systems for low temperature (125ºC)
- PV panels with solar concentration- PV panels with solar tracking Photovoltaic solar Plants:- Static PV panels
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The Solar Radiation and its concentrationSolar radiation at ground level has two components: Direct Radiation
and Diffuse Radiation. The sum of direct and diffuse radiations onto aplane is called Global Radiation
b) d ≈ λ/4 c) d > λa) d < λ/10
Only Direct Solar Radiation can be concentrated !!!, because solarconcentrators are optical devices making use of the Specular ReflectionLaw
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Ө = incidence angle β = Reflection angle
Ө = β
Reflecting surface
Law of Specular Reflection
The Solar Radiation and its concentration
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An Introduction to CST Technologies and Applications
• Introduction
Content
• Summary
• Concentrating Solar Thermal Technologies
• Concentrating Solar Thermal Systems
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What is a Concentrating Solar Thermal System ?System concentrating the direct solar radiation to increase its flux density(kW/m2) and thus achieve higher temperatures when converting the solarradiation into heat (thermal energy).
Solar Concentration: Why ?Solar radiation suffers a significant attenuation in its way to the Earth (from63,2 MW/m2 to 1 kW/m2) and it has to be concentrated to increase its lowflux density at the Earth surface to achieve higher temperatures andefficiencies.
Concentrating Solar Thermal Systems
η = f(C, T)
0
0.25
0.5
0.75
1
0 1000 2000 3000 4000
1.0005.000
10.000
20.000
Carnot
C=2500
0.25
0.5
0.75
1
0 1000 2000 3000 4000Temperature(K)
Syst
em E
ffici
ency
1.0005.000
10.000
20.000
Carnot
C=250
Dependence of the Efficiency andthe Optimum Working Temperatureon the Solar Radiation ConcentrationFactor, C
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What is a Concentrating Solar Thermal System ?System concentrating the direct solar radiation to increase its flux density(kW/m2) and thus achieve higher temperatures when converting the solarradiation into heat (thermal energy).
Solar Concentration: Why ?Solar radiation suffers a significant attenuation in its way to the Earth (from63,2 MW/m2 to 1 kW/m2) and it has to be concentrated to increase its lowflux density at the Earth surface to achieve higher temperatures andefficiencies.
Concentrating Solar Thermal Systems
Limiting factors for solar concentrationa) The apparent size of solar sphere is 32´as seen from the Earthb) Inaccuracies and optical/geometrical errors of solar concentrators
Theoretical and practical limits for solar concentration• Point focus concentrators: 46200 (theoretical); 5000 y 10000 (practical)• Linear focus concentrators: 220, (theoretical); 20 – 80 (practical)
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32”
Actual shape
Theoretical shape
Concentration limit due to errors and the Sun disk size
Concentration = w/π·dd
w
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Sistemas Solares Térmicos de Concentración
Different ways to concentrate the direct solar radiation
Direct radiation
Reflecting surface
Receiver
Direct radiation
a) by Reflection
f
X
Y
Y = X2 /4.f
The Parabolic concentrator
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Sistemas Solares Térmicos de Concentración
Receiver
Direct radiation
b) by Refraction
Fresnel lens
Direct radiation
Reflecting surface
Receiver
Direct radiation
a) by Reflection
Different ways to concentrate the direct solar radiation
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Main applications for concentrating solar termal systems
Concentrating Solar Thermal Systems
Industrial process heat: Concentrated solar radiation is converted intothermal energy, which is then used to feed industrial processes demandingheat within the range 125ºC - 2000ºC
Electricity Generation: it is the most important commercial application atpresent, with more than 5700 MWe currently in operation. These solarsystems are called Solar Thermal Power Plants, which are systemswhere direct solar radiation is concentrated and then converted intothermal energy at medium/high temperature (300°C - 600°C). This thermalenergy is then used in a thermodynamic cycle to produce electricity.The thermodynamic cycles used are: Rankyne, Brayton and ORC
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ThermalStorage
Fossil backup
Termodinámico
RECEIVER
Direct solar radiation
ÓPTICAL CONCENTRATOR
Concentrated solar radiation
Usefulheat
Process demandingthermal energy
Concentrating Solar Thermal SystemsSimplified Scheme for Industrial Process Heat
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Thermal Storage
Fossil backup
Mechanical energyTermodinámicoWaste heat
RECEIVER
Direct solar radiation
OPTICAL CONCENTRATOR
Concentratedsolar radiation
Usefulheat
ThermodynamicCycle
G
Electricity
Simplified Scheme of a Solar Thermal Power Plant
Concentrating Solar Thermal Systems
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An Introduction to CST Technologies and Applications
• Introduction
Content
• Summary
• Concentrating Solar Thermal Technologies
• Concentrating Solar Thermal Systems
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Campo de Colectores Solares
Sistema de Conversión de Potencia
Concentrating Solar Thermal Technologies
Campo Solar
There are four different concentrating solar thermal technologies:
Parabolic Trough collectors
Central receiver technology
Stirling Parabolic Dishes
Lineal Frenel ConcentratorsLine-focus technologies
Point-focus technologies
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Campo de Colectores Solares
Sistema de Conversión de Potencia
Sistema de Conversiónde Potencia
Solar Field
Power Block
Parabolic Trough collector
Plants with Parabolic-trough Collectors
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100 mHeliostats
Receiver
Power Conversion System
Tower
Central Receiver Plant
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l The reflecting surface is made of back-silvered glass mirrorsl Specific cost nowadays is of about 115 €/m2
l New designs will be soon available with a cost of less than 100€/m2
Heliostats
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Concentrator Receiver
Structure
Stirling Parabolic Dish
Stirling engine
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Lineal Fresnel Concentrator
Receiver
Longitudinal reflectors
Lineal Fresnel Concentrator
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(30 + 1,4 MWe)
Puerto Herrado I&II (Murcia, Spain)
Plants with Lineal Fresnel Concentrators
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An Introduction to CST Technologies and Applications
• Introduction
Content
• Summary
• Concentrating Solar Thermal Technologies
• Concentrating Solar Thermal Systems
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Concentrating solar thermal systems can achieve higher temperatures and efficiencies when converting solar radiation into thermal energy
There are 4 concentrating solar thermal technologies: Central Receiver, Parabolic-trough Collectors, Linear Fresnel Concentrators and Parabolic Dishes.
Summary
The two main applications of concentrating solar thermal systems are: Industrial Process Heat (SHIP) and Solar Thermal Electricity (STE)
Basic Concepts and Commercial Potential of solar Thermal Power Plants
Lecturer: Eduardo Zarza Moya
Plataforma Solar de Almería – CIEMAT(e-mail: [email protected])
First Summer SchoolPart A: Line-focus Solar Thermal Technologies
September 20-21, 2021
Lecture 1:An Introduction to Concentrating Solar Thermal (CST)
Technologies and Applications
• Thank you very much for your attention• Questions?