Parabolic trough technology vs tower technology.

Copyright © Abengoa Solar, S.A. 2015. All rights reserved
Innovative Technology Solutions for
Sustainability
ABENGOA
SOLAR
Innovative Technology Solutions for
Sustainability
Solar Thermal Energy:
I. Parabolic Trough Technology
II. Tower Technology

Introduction
Solar Thermal Technology: Dispatchability as a Stand-out Element
Parabolic Trough Technology
Tower Technology

Introduction to Solar Irradiance
 Irradiation coming from the sun goes through the atmosphere generating:
 Direct Normal Irradiance (DNI), which comes to the earth directly. It has a well defined
trajectory, and because of its quality as a vector, can be concentrated.
 Diffuse Horizontal Irradiance (DHI), which has a modified irradiance direction. DHI
doesn’t have a defined trajectory, therefore it can’t be concentrated.
 Global Horizontal Irradiance (GHI), which is the total amount of irradiation that the
horizontal surface of the earth receives.
Direct
Diffuse
Global = Diffuse + Direct
Direct Direct
on horizontal plane
on normal plane
Direct
Diffuse
Global = Diffuse + Direct
Direct Direct
on horizontal plane
on normal plane

Distribution of Direct Normal Irradiance (DNI)

Prediction of production
Medium
predictability
Medium
predictability
Low predictability High predictability
Manageability
High level of
storage and
hybridization
None None High
Certainty of supply High High High
It depends on the
biomass price and
the supply chain
Integration with
conventional technology
Integration with
combined cycles
(ISCC)
Supplement for
gas and coal
None None
Integration with
combined cycles
(ISCC)
Supplement for
gas and coal
STE Photovoltaics Eolian Biomass
For electric companies, biomass and STE are the only
sources of manageable renewable energy
=
+
+
+
=
-
+
-
-
-
+
-
+
+
-
+
+
Differences in Dispatchability:
Solar Thermal Technology vs. Other Renewables

• Parabolic trough and tower are the commercial technologies that generate electricity on a large scale
• Fresnel and disco Stirling technologies provide potential for others uses
+
Parabolic trough Tower Fresnel Disco Stirling
 Parabolic trough collectors
concentrate solar
irradiation in a receiver
tube which contains a
Heat Transfer Fluid (HTF).
Matureness
 Heliostats follow the sun
and reflect the irradiation
at the top of the tower,
where the heat is
transferred to a Heat
Transfer Fluid (HTF).
 Fresnel mirrors
concentrate the
irradiation onto a
receiver tube, which
contains a Heat
Transfer Fluid (HTF).
 A group of Disco parabolic
mirrors reflects the
irradiation on an engine,
located in the focal point.
-
Description
Track record
Application
Main quality
 30 years
 Electricity production
on a large scale
 Modular
 8 years
 Electricity production
on a large scale
 High temperatures
 3 years
 Heat (mainly)
 Low cost
Commercially
tested to
generate
electricity on a
commercial scale
 Validation
 Distributed energy
 High capacity of conversion

8
Introduction
Solar Thermal Technology: Dispatchability as a Stand-out Element
Parabolic Trough Technology
Tower Technology

A Parabolic Trough Plant
Power
Block
Solar Field
Solana, la mayor planta cilindroparabólica con almacenamiento del mundo (Arizona, EE. UU.)

Scheme of a Conventional Parabolic Trough Plant
Evaporator

Copyright © Abengoa Solar, S.A. 2015. All rights reservedCopyright © Abengoa Solar, S.A. 2012. All rights reserved
Solar Field Collector
Storage system Power block

Solar Field
A group of parabolic trough collectors capture the solar
energy and carries it to the power block, where the heat
energy is used to produce steam.

Parabolic Trough Collector
The main elements of a parabolic trough
collector are:
 Foundation and support frame
 Reflective surface
 Absorbent tubes
 Track system
 Hydraulic system
 Instrumentation and control
Parabolic trough collectors concentrate solar
irradiation onto a point or line where the
receiver is situated. It transfers the heat to the
Heat Transfer Fluid (HTF).
The parabolic trough collectors are organized
in lines and oriented towards north and south,
so they follow the sun on one axis.

Parabolic Trough Collector
 A complete parabolic trough collector is
formed by 10 or 12 modules.
 A collector module is formed by 28
mirrors (4 lines and 7 columns).
 Parabolic trough collectors are coupled
in loops in order to keep a continuous
heating process in each plant. A loop is
formed by 4 collectors.

Parabolic Trough: Reflective Surface
 A group of mirrors of glass-metal technology made with a parabolic shape.
 The reflectivity of these mirrors is higher than the 92% for the wavelengths
that compound most of the solar irradiation spectrum.

Absorbent Tubes
 The absorbent tube is one of the most important elements in every parabolic trough
collector. It is formed by these elements:
 The absorbent tube which is made of stainless steel, with a selective coating where the
Heat Transfer Fluid (HTF) circulates.
 A glass tube with an non-reflexive coating for a better solar transmission. The vacuum
between the absorbent tube and the glass tube eliminates the heat spread.
 Dilatator (bellows) absorbs the thermal expansions.
 A Getter maintains the vacuum.

Power Block
Storage tanks Cooling tower
Water treatment
plant
Turbine

Examples of Parabolic Trough Plants
Solana
• Arizona, U.S.
• 280 MW
• 6 h molten salts storage
• Parabolic trough technology
• Operational since 2013
Solar Extremadura Complex
• Extremadura, Spain
• 4 plants of 50 MW
• Solaben 2 & Solaben 3: operational since 2012
• Solaben 1 & Solaben 6: operational since 2013
KaXu Solar One
• Northern Cape, South Africa
• 100 MW
• 2,5 h molten salts storage
• Operational since 2015

Scheme of Tower Plants
Evaporator
Molten Salt
Tower
Super-heated
Steam Tower

Scheme of a Parabolic Trough Plant
Power
Block
Solar Field
PS10, the world’s first operational commercial tower

Copyright © Abengoa Solar, S.A. 2015. All rights reservedCopyright © Abengoa Solar, S.A. 2012. All rights reserved
Sections and Components of a Tower Plant
Solar Field Receiver
Storage System Power Block

23
Heliostat: a mirror mounted
on a dual-axis structure
rotating clockwise, capable
of redirecting solar
irradiation on one point.
Solar Field - Heliostats
Heliostats Components
 Mirror
 Structure
 Track system
 Control system

Solar Receiver
Receiver System
The solar receiver is located on the
highest part of the tower where the
solar energy is concentrated. In this
point, the steam can be directly
generated or a Heat Transfer Fluid (HTF)
can be heated up to later be used for
steam generation.

Steam storage tanks at Khi Solar One (Northern
Cape, South Africa). This allows this solar
thermal plant to produce 50 MW for two hours.
Thermal energy storage tanks in molten salts in
Solana (Arizona, U.S.). This system allows the
plant to produce 280 MW for 6 hours.
Different kinds of storage systems
There are usually two storage technologies at solar thermal tower plants. These are steam storage
tanks, or, for a plant that needs 3 or more ours of storage, molten salt tanks.

Turbine
Storage tanks
Cooling tower
Water treatment plant
PS20, la segunda planta comercial del mundo, entró en operación en 2009

PS101
• 11 MW
• Storage
• Receiver’s technology: saturated steam
• Operational since June 2007
• 624 heliostats, of120 m2 each
• 6.700 tCO2 avoided per year
PS20
• 20 MW
• Storage
• Receiver’s technology: saturated steam
• Operational since May 2009
• 1.255 heliostats, of 120m2 each
• 12.100 tCO2 avoided per year
2
ABENGOA SOLAR

 Generation of superheated steam at the receiver maximizes the efficiency
of the technology.
 Characteristics:
 50 MW
 Steam storage
 Superheater + 2 systems of evaporation
 Natural draft cooling system
 A 200 m high tower
 A 4120 heliostats solar field
 19 steam storage tanks
Khi Solar One: superheated steam tower

 Located at the Maria Elena commune, in the Atacama desert
 110 MW of installed power
 Thermal storage system with capacity for 17,5 hours of production
 Capable of producing 24 hours a day
 Avoids the emission of 643.000 tons of CO2 per year
 Construction started in 2014
 Operation scheduled for 2017
Atacama 1: Molten Salt Tower

Parabolic trough technology vs tower technology.

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