solar energy conversion: solar thermal
TRANSCRIPT
Solar energy conversion:
Solar thermal
Davide Del Col
Department of Industrial Engineering
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Solar thermal collectors and applications
40°C – 80°C
Flat plate collectors
80°C – 120°C
Evacuated tube
collectors (with CPC)
120°C – 250°C
Small linear
concentrating
collectors
250°C – 450°C
Large troughs and
Fresnel
Solar tower in
heliostats field
Temperature
Size<10 kW 100 kW 10 MW 500 MW
Low temperature processes
Single effect absorption cooling
Space heating
Domestic hot water
Utility scale
solar power generation
MATURE
MATURE
Power generation with ORC
Industrial process heat
Double effect absorption
cooling
Water desalination
LOW
FAMILIARITY
AND LEVEL OF
ADOPTION
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Applications for solar process heat
Source: Soltigua
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Main topics and issues for research
Architectural integration of solar collectors (for low and medium
temperature applications)
Enhancement of performance, durability and cost effectiveness of the
collector (for all the applications)
> Improvement of collector component
Optimization of other components and configuration in plants using
common fluids (water, steam, thermal oil)
Design of new plant configurations for innovative applications with
uncommon working fluids (i.e. CO2)
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
The building integration challengeFor low temperature applications
Source: Report IEA
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
The building integration challengeInstallation on industrial rooftop for
medium temperature production
Source: Chromasun
Source: NEP Solar
Source: UNIPD
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Optimizing collectors: flux mapping
Characterize the optical performance
Assess tracking system, mechanical
structure, durability
Design receivers with optimized and
advanced geometry
Develop of reliable models of the
system
Improve the aiming strategy (for
central receiver of heliostat fields)
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Receivers with enhanced heat transferIn concentrating collectors, the solar flux distribution on the receiver surface is
strongly non uniform. This leads to:
thermal stresses and strains which may provoke mechanical instability
peak temperatures that damage the selective coating
instability and out-of-control of direct steam generation process
New solutions are required, especially for medium temperature applications
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
The concept of volumetric absorptionVolumetric
(direct)
absorption
collectors
Typical
surface
absorption
collectors
Today nanotechnologies allow
the production of nanofluids
-with excellent optical properties
-stable
-safe and non toxic
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Research activity overviewAim of the project
Analysis of the thermal performance of a volumetric receiver for heat
generation in the medium temperature range. The working nanofluid is an
aqueous suspension of single wall carbon nanohorns.
Comparison between the volumetric receiver and an advanced surface
absorption receiver in terms of performance, environmental and economical
aspects.
Performed activities
Measurement of concentrated flux distribution on the focal region of the
concentrator at CO.EN.SO lab
Experimental analysis of the performance of the advanced surface receiver
Design of the volumetric receiver
Preparation of the nanofluid, thermophysical and optical characterization
(collaboration with CNR)
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Solar energy conversion lab
ASYMMETRICAL
PARABOLIC
TROUGH
2-axes tracking
aperture width: 2.9 m
trough length: 2.4 m
focal length: 1.81 m
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Solar flux mapping apparatus
z
x
Parabolic
mirrors
z
x,z optimal concentration plane
semi automatic linear hangling system
+
water cooled heat flux microsensor (HFM)
x
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Solar flux mapClear sky day DNI 890 W m-2
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Study on a surface absorption receiverReceiver length: 1.2 m
width: 68 mm
Geometrical concentration ratio: 42
Internal turbulator for heat transfer
enhancement and efficient direct
steam generation
Test runs have been performed in two
modes
- liquid heating
- direct steam generation up to 140°C
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Study on a surface absorption receiver
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 0,02 0,04 0,06 0,08 0,1 0,12 0,14 0,16 0,18
Ov
era
ll t
he
rma
l e
ffic
ien
cy
[ /
]
Reduced temperature difference [ K m2 W-1 ]
single phase tests
two phase tests
efficiency curve (single phase tests only)
efficiency curve (all data)
Thermal efficiency of
66% when producing
steam at 140°C
It can be improved by
working on the
selective coating and
glass covering
Levi Cases Retreat DayMonday, January 18th, 2016
Aula Magna – Pentagono – Agripolis, Legnaro (PD)
Design of a volumetric absorption
receiver and nanofluid preparation
Source: UNIPD
Source: CNR