Parabolic Trough, Linear Fresnel, Power Tower
A Technology Comparison
Robert Pitz-Paal
Thermal Storage vs. Electric Storage
η >95 %
+2000 h
"$
2000 h
200 h
η.*)-
CSP with storage and fossil hybridisation can provide all 3 components of value
Thermal storage economically favorable
no storage
Euro/kWh
0.15
Cost of electricity for CSP system with and without storage
* " #"
"$&
&=7/
$ $
=14//(
8
10' %+
0.1
storage 12 h rated power
solar multiple (sm)
Electricity generation cost as function of solar multiple and storage size
4
How does CSP react under desert conditions?
Water consumption
Mirror washing
2.0%
Recycling
Steam cycle
6.1%
Potable water
0.1%
Dry cooling
Cooling tower
91.8%
Washing (no recycling yet)
75 l / MWh (low soil.)
30 l /m² year (mirror surface)
0,5 l/m² per wasching cycle
Rainfall Cairo = 25 l/m²year
Reflector Soiling
Reflector Degradation?
•  Cleaning of CSP collectors on
Glass mirrors have
a weekly basis,
proven high robustness
over >25 years in operation •  Soiling depends strongly on
site (and seasonal)
DLR has established
conditions.
accelerated aging methods Variations can be in the order
of a factor 2-3
for specific reflector types
•  5% average soiling leads to
revenue losses of 3-6 $/
m²year (depending on
electricity price)
•  Cleaning need 20 – 40 l/m²
year
www.DLR.de • Chart 5
!
!
!
%%
!
!
#
$!
&($'
Land use
(m²/MWh/a)
04)05<
2)3(/'1
6-8
12)16<
!
07)11<
7)0/<
2)3(/'1
4-6
&
!'
1/)16<
04)06<
2)3(/'1
8-12
www.DLR.de • Chart 6
Efficiency Potential of CSP Systems
ηmax= ηth,Carnot* ηabsorber
Parabolic Dish
ηmax
Solar Tower
Parabolic Trough
Flat Plate Collector
(Tabsorber =Tprocess) [K]
www.DLR.de • Chart 7
Market Situation
Ground Requirements
www.DLR.de • Chart 8
Parabolic Trough Plant Scheme
www.solarpaces.org
Solar Field
parabolic trough
collector field
200’000 - 2’200’000 m2
Heat Transfer
& Buffer
2-10 hours
capacity
Power Block
steam cycle
turbine, condenser
30-280 MW
www.DLR.de • Chart 9
Line Concentrators –how do they work?
,
,
www.DLR.de • Chart 10
Line Concentrating Collectors
1-dimensional curvature of reflector
short focal distance
mirror bending required
receiver length equals collector length
absorber typically a tube
heat flux rates 0.01 – 0.1 MW/m²
absorber temperature limited to 400-600°C
absorber insulation required (glass)
parallel rows, only horizontal installation economical
heat transfer fluids: synthetic oil, water/steam, molten
salt, (CO2)
hydraulic and thermodynamic design to operating
conditions
heat storage possible
net solar-to-electric peak efficiency 20-28%
process heat applications
performance modeling is state of the art
www.DLR.de • Chart 11
Linear Fresnel Collector – Working Scheme
secondary concentrator
insulation
receiver
glass window
absorber tube
mirror rows
www.DLR.de • Chart 12
Linear Fresnel Collector - Properties
off-axis, astigmatism
gaps to reduce shading/blocking
flat glass, light weight
less standardized than troughs
max theoretical concentration and optical
efficiency lower than troughs
collector width up to 20 m
focal length up to 30 m
fix receiver
distance between rows 30-40%
capture 55-65% of DNI
two-axis incidence angle impact
low performance on sun rise/set, high at noon
low wind forces (low height)
first commercial plants (Novatec, Areva, )
www.DLR.de • Chart 13
What is the difference between Parabolic Trough and
Linear Fresnel?
70%
Verluste LFK
Verluste Eurotrough
56%
50%
43%
40%
30%
20%
26%
15%
12%
9% 9%
10%
4% 3%
2% 2%
5%
Ei
ge
nb
ed
ar
f
Po
w
er
bl
oc
k
op
t.
Ve
rlu
st
e
W
är
m
ev
er
lu
st
e
An
fa
hr
ve
rlu
st
e
un
te
re
s
D
um
pi
ng
ob
er
es
D
um
pi
ng
0%
#! "' " " !&4'1
60%
64% 64%
www.DLR.de • Chart 14
Why higher optical losses?
www.DLR.de • Chart 15
Why more dumping losses?
Parabolic Trough Collector
15. Jun
max. power dumping
180000
900
used power
800
140000
DNI
700
120000
600
100000
500
80000
400
15. Jun
max. power dumping
300 dumping
min. power
used power
DNI 200
180000
40000
160000
20000
140000
0
0
1
2
3
4
5
6
7
8
Linear Fresnel Collector
900
800
700
100
120000
600
0
100000
9 10 11 12 13 14 15 16 17 18 19
20 21 22 23
local time
500
80000
400
60000
300
40000
200
20000
100
0
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
local time
DNI in W/m²
60000
DNI in W/m²
160000
energy in kWh
energy in kWh
min. power dumping
www.DLR.de • Chart 16
www.DLR.de • Chart 17
www.DLR.de • Chart 18
LCOE of Parabolic Trough (Algeria 2400kWh/m²a)
www.DLR.de • Chart 19
Concept of Tower Technology
Storage
www.DLR.de • Chart 20
Solar Tower
www.DLR.de • Chart 21
Solar Tower – Steam, Molten Salt
Ivanpah-CA 3x123 MW Brightsource
Tonopah-NV 110 MW SolarReserve
Lancaster-CA 5 / 46 MW eSolar
www.DLR.de • Chart 22
Heliostats
www.DLR.de • Chart 23
Receiver Concepts
www.DLR.de • Chart 24
Solar Tower, molten salt – Gemasolar 20 MW Torresol Spain
565 o C
Hot Salt
Storage Tank
Cold Salt
Storage Tank
Steam Generator
Conventional
EPGS
290 o C
25
Ivenpah Solarturm Projekt
www.DLR.de • Chart 26
Example Reference Plant Molten-Salt Tower 100 MW
Algeria
www.DLR.de • Chart 27
Atmospheric Extinction between Heliostat and
Receiver
Receiver
Scattermeter
Transmitter
LIDAR
www.DLR.de • Chart 28
Aerosol Concentration close to ground surface
Slide 29 / Solar Tower
Modularity &
Scalability
www.DLR.de • Chart 30
Conclusions
Trough Tower and Fresnel Systems have very different characteristics
and require complex design tools for their layout
All three technologies have a realistic market potential and can further
reduce costs
www.DLR.de • Chart 31
GIZ Renewable Energy Week > CSP Overview > Dr. Eckhard Luepfert, DLR Institute of Solar Research, Berlin 09/2012
DLR - Institute of Solar Research
www.dlr.de/sf www.dlr.de/tt
www.DLR.de • Chart 32
Solar Tower Jülich – Solair/HitRec – Air as Heat Transfer Fluid
1.5 MW DLR / KA München
Receiver
Hot Air 730º
Steam Generator
Storage
~
Super
Heliostats
Cold Air 110º
heated
Steam