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 + DirectDirect Direct

on horizontal plane

on normal plane

Direct

Diffuse

Global = Diffuse + DirectDirect Direct

on horizontal plane

on normal plane


Distribution of Direct Normal Irradiance (DNI)


Introduction



Tower Technology


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

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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

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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.

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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

Copyright © Abengoa Solar, S.A. 2015. All rights reserved 8

Introduction



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 reserved Copyright © 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 • Parabolic trough technology • 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 • Parabolic trough technology • Operational since 2015


Introduction



Tower Technology


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 reserved Copyright © Abengoa Solar, S.A. 2012. All rights reserved

Sections and Components of a Tower Plant

Solar Field Receiver

Storage System Power Block


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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


PS10 1

• 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

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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