View
1
Download
0
Category
Preview:
Citation preview
Assessment of a Falling Solid Particle Receiver
with Numerical Simulation
Birgit Gobereit, Lars Amsbeck, Reiner Buck,
Hans Müller-Steinhagen, Robert Pitz-Paal
Birgit.Gobereit@dlr.de, DLR Stuttgart, Germany
SolarPACES 2012, Marrakech, Morocco
SolarPaces 2012, Morocco, Birgit Gobereit
Contents
- Introduction
- Modeling-Workflow
-Model Parameters
- Results-Reflection Losses
-Variation of Solar Absorptivity of the Walls
-Wind Effects
- Summary and Conclusions
www.DLR.de • Chart 2
SolarPaces 2012, Morocco, Birgit Gobereit
Particle Receiver
- Electricity generation (about 10..50 MWel, resp. 50..350 MWth)
- Solid ceramic particles as absorber, transport and storage material
- Direct absorption
- No freezing
- No decomposition
- High temperatures
- Inherent Storage
- Low Levelized Electricity
Costs (LEC)
www.DLR.de • Chart 3
SolarPaces 2012, Morocco, Birgit Gobereit
Falling Particle Receiver in
Face-Down Cavity
concentrated
solar radiation
www.DLR.de • Chart 4
20°section
Particle-
curtain
particle inlet
particle outlet
particle
curtain
SolarPaces 2012, Morocco, Birgit Gobereit
Modeling
www.DLR.de • Chart 5
SolarPaces 2012, Morocco, Birgit Gobereit
Workflow
CFD calculation
-air: continuous, Euler phase
-particles: discrete Lagrange
phase
Monte Carlo raytracing
-solar radiation
CFD calculation
-Euler-Lagrange
-heat transfer
-diffuse radiation:
discrete ordinate model
-sequentially solving of
equations
www.DLR.de • Chart 6
- Reference case Matlab-model presented by Röger et al.
(Solar PACES, 2010, J. Sol. Energy Eng. 2011):
- particles: sintered bauxite (main constituent Al203)
- averaged particle diameter: 0.7 mm
- absorptivity of particles: 0.93
- solar input power: 394 MW
- aperture: 22.1 m diameter
- cavity height: 21.5 m
- absorptivity of walls: solar 0.25 / thermal 0.7
- temperature increase from 300 °C to 800 °C
- different operation strategies, recirculation
SolarPaces 2012, Morocco, Birgit Gobereit
Reference Case
Model Parameters
www.DLR.de • Chart 7
inT
outT
m&
inT
inTT >
1
1T
1TT
out>
2/m& 2/m&
SolarPaces 2012, Morocco, Birgit Gobereit
Results
www.DLR.de • Chart 8
SolarPaces 2012, Morocco, Birgit Gobereit
Reflection losses
- Both models predict significant decrease of reflection losses (relative to
input power) with increasing mass flow rate per unit inlet slit length.
www.DLR.de • Chart 9
- Good agreement at high
particle mass flow rates, but
difference at low mass flow
rates, due to different
calculation of air
entrainment.
- Receiver walls with low solar
absorptivity cause reflection
losses in excess of 20 %
during part load operation
with low particle mass flows.
- Recirculation can reduce
reflection losses to 2 % !
SolarPaces 2012, Morocco, Birgit Gobereit
Solar Absorptivity of The Walls
- Variation of solar absorptivity of the wall, test case 100 % load, 2 drops
- Realistic values: ceramic insulation 0.25, high temperature paint 0.95
- Decrease of reflection losses
from 5 % (solar absorptivity of
0.25) to less than 1 % (solar
absorptivity of 0.95).
www.DLR.de • Chart 10
- Convection, thermal radiation,
and conduction losses
increase due to slight higher
temperatures, but all together
less than 1.5 %-point.
- Black walls recommended.
SolarPaces 2012, Morocco, Birgit Gobereit
Wind Effects
Quantitative Results
- Horizontal side wind, different wind speeds
- Efficiency decreases with wind speed from 89 % to 84 %
- Major effect is the increase of convection losses (5.4%-points)
- The thermal radiation and conduction losses decrease slightly due to
convective cooling (0.3%-points)
www.DLR.de • Chart 11
SolarPaces 2012, Morocco, Birgit Gobereit
Wind Effects
Qualitative Results
velocity and temperature field in mid plane
www.DLR.de • Chart 12
SolarPaces 2012, Morocco, Birgit Gobereit
Wind Effects
Qualitative Results
velocity and temperature field in mid plane
www.DLR.de • Chart 13
SolarPaces 2012, Morocco, Birgit Gobereit
Wind Effects
Qualitative Results
- increasing vortex
with increasing
wind speed
velocity and temperature field in mid plane
www.DLR.de • Chart 14
SolarPaces 2012, Morocco, Birgit Gobereit
Wind Effects
Qualitative Results
- further work:
design optimization
to reduce losses,
wind shielding
- increasing vortex
with increasing
wind speed
velocity and temperature field in mid plane
www.DLR.de • Chart 15
SolarPaces 2012, Morocco, Birgit Gobereit
Summary and Conclusions
- Particle receiver power plant has advantages for large scale electricity generation (direct absorption, inherent storage and high temperatures).
- Promising receiver concept: falling particle in face-down cavity.
- Receiver model was developed which includes movement of air and particles, solar radiation, convective and radiative heat transfer.
- For receiver with high solar absorptivity of the walls an increasing particle mass flow decreases reflection losses from 22 % to 2 % → recirculation.
- The use of black walls is an other possibility to lower the reflection losses.
- Wind increases convection losses 5 %-points → design optimization.
Main issues for further work:- Assessment of different parameters for layout and optimization. - Further experiments for validation of partial models.- Build a prototype receiver for demonstration and model validation.
www.DLR.de • Chart 16
SolarPaces 2012, Morocco, Birgit Gobereitwww.DLR.de • Chart 17
Thank you for your attention! Birgit.Gobereit@dlr.de
Recommended