first summer school
TRANSCRIPT
Lecturer: Eduardo Zarza MoyaPlataforma Solar de Almería – CIEMAT(e-mail: [email protected])
First Summer SchoolPart A: Line-focus Solar Thermal Technologies
September 20-24, 2021
Lecture 5:Linear Fresnel Collectors
Slide 22 / 25“Linear Fresnel Collectors”
Contents
IntroductionWorking principleEfficiency of Fresnel collectorsComponentsSummary
Linear Fresnel Collectors
Slide 33 / 25“Linear Fresnel Collectors”
• It has a fixed receiver pipe while mirrors track the Sun
• The concentrator is divided into multiple linear reflectors
• It presents lower optical performance than PTCs
• Cheaper than PTC technology due to simplicity of some of the components.
Linear reflectors
Rotation axes
Absorber tube
Source: CIEMAT
IntroductionLinear Fresnel Collectors
Slide 44 / 25“Linear Fresnel Collectors”
IntroductionWorking principleEfficiency of Fresnel collectorsComponentsSummary
Contents
Linear Fresnel Collectors
Slide 55 / 25“Linear Fresnel Collectors”
• Compared to parabolic-trough collectors, mirrors are located in the same plane.
• Linear reflectors are segments of parabolas with different focal lines.
Sun rays
Focal Point
Focal length of parabola “n”
Y
X
Reflector “n”
Working Principle
Linear Fresnel Collectors
Slide 66 / 25“Linear Fresnel Collectors”
• Sun-tracking principle
Working Principle
Linear Fresnel Collectors
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• Sun-tracking principle:– Individual actuators (1) or one single actuator for the whole (2)
system
Working Principle
Linear Fresnel Collectors
(2) Common actuator for the whole system(1) Individual actuator for each reflector
Slide 88 / 25“Linear Fresnel Collectors”
IntroductionWorking principleEfficiency of Fresnel collectorsComponentsSummary
Contents
Linear Fresnel Collectors
Slide 99 / 25“Linear Fresnel Collectors”
• Incidence angles, which reduce the efective area of reflection• Shading effects• Blocking effects
Optical and Geometrical losses
The optical and geometrical performance of a LFR is governed by:
Slide 1010 / 25“Linear Fresnel Collectors”
1. Longitudinal incidence angle, θL: angle between Sun vector and its projection into de transversal plane
2. Transversal incidence angle, θT: angle between zenith and projection of straight line to the sun into the transversal plane
3. Receiver tube
4. Incidence plane
5. Transversal plane
6. Solar reflectors
Incidence angles in LFR
θT
θL
6
5
4
312
Slide 1111 / 25“Linear Fresnel Collectors”
• K(θL) • K(θT)
K(θ)
• Transversal and longitudinal angles have a significant impact on the optical performance of LFR
• Optical efficiency:
𝜂𝜂𝑜𝑜𝑜𝑜𝑜𝑜 = 𝜂𝜂𝑜𝑜𝑜𝑜𝑜𝑜,0°� 𝐾𝐾(𝜃𝜃)K(θ) = 𝐾𝐾(𝜃𝜃𝐿𝐿) · 𝐾𝐾(𝜃𝜃𝑇𝑇)PTC: 𝐾𝐾 𝜃𝜃𝑇𝑇 = 1LFR: 0≤ 𝐾𝐾 𝜃𝜃𝑇𝑇 ≤1PTC & LFC: 𝐾𝐾 𝜃𝜃𝐿𝐿 is quite similar
The Optical Efficiency of a LFR is much lower than in a PTC
K(θT) in a PTC
𝑲𝑲(θ𝑻𝑻) in a LFR
LFR versus PTC: Optical performance
Slide 1212 / 25“Linear Fresnel Collectors”
Daily performance in a clear Summer day Daily performance in a clear Winter day
Influence of the axis orientation on the seasonal performance(Simulation of a LF-11 Fresnel collector
Linear Fresnel CollectorsTh
erm
alPo
wer
(MW
)
Solar Time Solar Time
Ther
mal
Pow
er(M
W)
Slide 1313 / 25“Linear Fresnel Collectors”
Daily thermal power output in Summer time
0 2 4 6 8 10 12 14 16 18 20 22 240
50
100
150
200
250
300
350
Orientación Norte-Sur Orientación Este-Oeste
P colec
tor->
fluido
(kW
)
Hora Solar
0 2 4 6 8 10 12 14 16 18 20 22 24
0
50
100
150
200
250
300
350
Solar Time
P col
lect
or→
fluid
(kW
)
Parabolic trough collector Linear Fresnel concentrator
LFR versus PTC: Daily Power output
Slide 1414 / 25“Linear Fresnel Collectors”
IntroductionWorking principleEfficiency of Fresnel collectorsComponentsSummary
Contents
Linear Fresnel Collectors
Slide 1515 / 25“Linear Fresnel Collectors”
Components
Linear Fresnel Collectors
Slide 1616 / 25“Linear Fresnel Collectors”
Receiver pipe
Rectangular reflectors
Source: Lidell power station
Linear Fresnel Collectors
Slide 1717 / 25“Linear Fresnel Collectors”
• Reflectors:– Flat or slightly curved mirrors (in support structure)
Linear Fresnel Collectors
Slide 1818 / 25“Linear Fresnel Collectors”
• Reflectors:– Flat or slightly curved mirrors
• Receiver:a) Cavity with parallel pipes b) Non-evacuated pipe +
secondary concentratorc) Evacuated pipe + secondary
concentrator
Source: Pye et al. ANZSES, 2003
Source: DLR
Linear Fresnel Collectors
Slide 1919 / 25“Linear Fresnel Collectors”
• Reflectors:– Flat or slightly curved mirrors
• Receiver:a) Cavity with parallel pipes b) Non-evacuated pipe +
secondary concentratorc) Evacuated pipe + secondary
concentrator• Heat transfer fluid:
– Water/steam • Fluid temperature ≤ 450°C
Parallel pipes receiver
Single pipe receiver
Linear Fresnel Collectors
Slide 2020 / 25“Linear Fresnel Collectors”
• Foundation are lighter and cheaper than in PTC
• There are three different support structures for the receiver:
Linear Fresnel Collectors
Slide 2121 / 25“Linear Fresnel Collectors”
• Foundation are lighter and cheaper than in PTC
• There are three different support structures for the receiver:
Linear Fresnel Collectors
Slide 2222 / 25“Linear Fresnel Collectors”
• Foundation are lighter and cheaper than in PTC
• There are three different support structures for the receiver:
Slide 2323 / 25“Linear Fresnel Collectors”
IntroductionWorking principleEfficiency of Fresnel collectorsComponentsSummary
Contents
Linear Fresnel Collectors
Slide 2424 / 25“Linear Fresnel Collectors”
Mirrors and support structure are lighter and cheaper
Receiver tubes do not need flexible connections (they do not move)
Solar fields with more compact lay-out of rows
Optical efficiency is lower due to the existence of 2 incidence angles
Aerial view of two parallel LFR rows
LFR versus PTC
Summary
Lecturer: Eduardo Zarza MoyaPlataforma Solar de Almería – CIEMAT(e-mail: [email protected])
- Thank you very much for your attention- Questions?
First Summer SchoolPart A: Line-focus Solar Thermal Technologies
September 20-24, 2021
Lecture 5:Linear Fresnel Collectors