Technology Roadmap Concentrating Solar Power 2050
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2050
2045
2035 2040
Technology Roadmap
Concentrating Solar Power
INTERNATIONAL ENERGY AGENCY
The International Energy Agency (IEA), an autonomous agency, was established in
November 1974. Its mandate is two-fold: to promote energy security amongst its member
countries through collective response to physical disruptions in oil supply and to advise member
countries on sound energy policy.
The IEA carries out a comprehensive programme of energy co-operation among 28 advanced
economies, each of which is obliged to hold oil stocks equivalent to 90 days of its net imports.
The Agency aims to:
n Secure member countries’ access to reliable and ample supplies of all forms of energy; in particular,
through maintaining effective emergency response capabilities in case of oil supply disruptions.
n Promote sustainable energy policies that spur economic growth and environmental protection
in a global context – particularly in terms of reducing greenhouse-gas emissions that contribute
to climate change.
n Improve transparency of international markets through collection and analysis of
energy data.
n Support global collaboration on energy technology to secure future energy supplies
and mitigate their environmental impact, including through improved energy
efficiency and development and deployment of low-carbon technologies.
n Find solutions to global energy challenges through engagement
and dialogue with non-member countries, industry,
international organisations and other stakeholders. IEA member countries:
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online at www.iea.org/about/copyright.asp the work of the IEA.
Foreword
Current trends in energy supply and use The emerging technology known as concentrating
are patently unsustainable – economically, solar power, or CSP, holds much promise for
environmentally and socially. Without decisive countries with plenty of sunshine and clear skies.
action, energy-related emissions of CO2 will more Its electrical output matches well the shifting
than double by 2050 and increased oil demand will daily demand for electricity in places where air-
heighten concerns over the security of supplies. conditioning systems are spreading. When backed
up by thermal storage facilities and combustible
We must – and can – change our current path; we fuel, it offers utilities electricity that can be
must initiate an energy revolution in which low- dispatched when required, enabling it to be used
carbon energy technologies play a lead role. If we for base, shoulder and peak loads. Within about one
are to reach our greenhouse-gas emission goals, to two decades, it will be able to compete with coal
we must promote broad deployment of energy plants that emit high levels of CO2. The sunniest
efficiency, many types of renewable energy, regions, such as North Africa, may be able to export
carbon capture and storage, nuclear power and surplus solar electricity to neighbouring regions,
new transport technologies. Every major country such as Europe, where demand for electricity from
and sector of the economy must be involved. renewable sources is strong. In the medium-to-
Moreover, we must ensure that investment longer term, concentrating solar facilities can also
decisions taken now do not saddle us with sub- produce hydrogen, which can be blended with
optimal technologies in the long term. natural gas, and provide low-carbon liquid fuels for
transport and other end-use sectors.
There is a growing awareness of the urgent need
to turn political statements and analytical work For CSP to claim its share of the coming energy
into concrete action. To spark this movement, at revolution, concerted action is required over the
the request of the G8, the International Energy next ten years by scientists, industry, governments,
Agency (IEA) is developing a series of roadmaps financing institutions and the public. This roadmap
for key energy technologies. These roadmaps is intended to help drive these indispensable
provide solid analytical footing that enables developments.
the international community to move forward,
following a well-defined growth path – from today
to 2050 – that identifies the technology, financing,
policy and public engagement milestones needed
to realise the technology’s full potential. The IEA
roadmaps include special focus on technology
development and deployment to emerging
economies, and highlight the importance of
Nobuo Tanaka
international collaboration.
Executive Director, IEA
Foreword 1
Table of contents
Foreword 1
Table of contents 3
Acknowledgements 4
Key findings 5
Key actions by government in the next ten years 5
Introduction 7
Rationale for CSP 7
The purpose of the roadmap 8
Roadmap process, content and structure 8
CSP status today 9
The importance of the solar resource 9
Current technologies for power production 11
Enhancing the value of CSP capacities 13
Grid integration of CSP plants 16
Plant cooling and water requirements 17
CSP for niche markets 17
Vision of future deployment 19
Existing scenarios and proposals 19
CSP deployment 19
The vital role of transmission 20
Deployment till 2020: intermediate and peak loads 21
Deployment till 2030: base loads and CO2 reductions 22
Deployment beyond 2030: power and fuels 23
Economic perspectives 27
Operation and maintenance costs 28
Costs of providing finance for CSP plants 28
Generating costs 28
Towards competitiveness 28
Milestones for technology improvements 31
Troughs and LFR 31
Towers and dishes 32
Improvements in storage technologies 33
Emerging solar fuel technologies 33
Policy framework: roadmap actions and milestones 35
Overcoming economic barriers 35
Financing innovation 35
Incentives for deployment 36
Addressing non-economic barriers 36
Research, development and demonstration support 36
Collaboration in R&D and deployment 37
Deployment in developing economies 38
Conclusion and role of stakeholders 41
Units, acronyms, abbreviations and references 43
Table of contents 3
Acknowledgements
This publication was prepared by the International Goldman (BrightSource); Bill Gould (SolarReserve);
Energy Agency’s Renewable Energy Division, with Bill Gross (eSolar); Marianne Haug (Hohenheim
Cédric Philibert serving as lead author, under the University); Gregory Kolb (Sandia Lab); Natalia
supervision and with contributions of Paolo Frankl, Kulinchenko (World Bank); Keith Lovegrove
Head of the Renewable Energy Division. Zuzana (ANU); Thomas Mancini (Sandia Lab/SolarPACES);
Dobrotkova helped considerably in researching Mark Mehos (NREL); Pietro Menna (European
the potential growth of concentrating solar Commission); Anton Meier (PSI); Richard Meyer
power (CSP). Several IEA staff members provided (Suntrace); David Mills (Ausra); Jean-Charles
thoughtful comments and support including Brian Mulet (Bertin); Jim Pacheco (eSolar); Jay Paidipati
Ricketts, Tom Kerr, Steven Lee, Joana Chiavari, (Navigant); Charlie Reid (TesseraSolar); Christoph
Driss Berraho and Hugh Ho. Madeleine Barry, Richter (SolarPACES); Gus Schellekens (PwC);
Andrew Johnston, Marilyn Smith and Delphine Frédéric Siros (EDF R&D); Wes Stein (CSIRO);
Grandrieux edited the publication. Bertrand Sadin Yutaka Tamaura (Tokyo Technology Institute);
and Corinne Hayworth designed the graphs and Rainer Tamme (DLR); Andy Taylor (BrightSource);
made the layout. Craig Tyner (eSolar); Jonathan Walters (World
Bank); Zhifeng Wang (Chinese Academy of
This work was guided by the IEA Committee on Sciences); Tex Wilkins (US Department of Energy);
Energy Research and Technology. Its members Albert Young (Alsthom Power); and Eduardo Zarza
provided important review and comments that (CIEMAT/PSA).
helped to improve the document. Richard Jones
– IEA Deputy Executive Director, Didier Houssin Other individuals who participated in the IEA CSP
– Director of Energy Markets and Security, expert workshop (Berlin, 14 September 2009) also
Bo Diczfalusy – Director of Sustainable Energy provided useful insights: Nikolaus Benz (Schott);
Policy and Technology, and Peter Taylor – Head Ralph Christman (German Environment Ministry);
of Energy Technology Policy Division provided Karina Haüslmeier (German Foreign Office);
additional guidance and input. Klaus Hennecke (DLR); Katerina Hoefer (German
Cooperation Ministry); Rainer Kistner (MAN
Numerous experts provided the author with Ferrostaal); Avi Kribus (Tel Aviv University); Dermot
information and/or comments on working drafts: Liddy (Tessera Solar/SES); Wolf Muth (KfW); Jose
Rainer Aringhoff (Solar Millennium); Pierre Audinet Nebrera (ACS Cobra); Rolf Ostrom (European
(World Bank); Denis Bonnelle (ENS); Hélène Bru Commission); Mariàngels Perez Latorre (ESTELA);
(Total); Terry Carrington (UK DECC); Joe Cashion Robert Pitz-Paal (DLR); Nathan Siegel (Sandia Lab);
(Tessera Solar); Jenny Chase (NEF); Euro Cogliani and Gerd-Uwe Weller (EIB).
(ENEA); Gilbert Cohen (Eliasol/Acciona Solar); Luis
Crespo (Protermosolar); Goncalo Dumiense (A.T. This publication was made possible thanks to the
Kearney); Michael Epstein (Weizmann Institute); support of the Government of France, through the
Alain Ferrière (CNRS); Antonio García-Conde Agency for the Environment and Energy Efficiency
(INTA); Henner Gladen (Solar Millennium); Arnold (ADEME), and the Government of Japan.
4 Technology Roadmaps Concentrating Solar Power
Key findings
Concentrating solar power (CSP) can provide low- CSP facilities could begin providing competitive
carbon, renewable energy resources in countries or solar-only or solar-enhanced gaseous or liquid
regions with strong direct normal irradiance (DNI), fuels by 2030. By 2050, CSP could produce
i.e. strong sunshine and clear skies. This roadmap enough solar hydrogen to displace 3% of global
envisages development and deployment of CSP natural gas consumption, and nearly 3% of the
along the following paths: global consumption of liquid fuels.
By 2050, with appropriate support, CSP could
provide 11.3% of global electricity, with 9.6%
from solar power and 1.7% from backup fuels
Key actions by government
(fossil fuels or biomass). in the next ten years
In the sunniest countries, CSP can be expected Concerted action by all stakeholders is critical to
to become a competitive source of bulk power realising the vision laid out in this roadmap. In
in peak and intermediate loads by 2020, and of order to stimulate investment on the scale required
base-load power by 2025 to 2030. to support research, development, demonstration
and deployment (RDD&D), governments must take
The possibility of integrated thermal storage the lead role in creating a favourable climate for
is an important feature of CSP plants, and industry and utilities. Specifically, governments
virtually all of them have fuel-power backup should undertake the following:
capacity. Thus, CSP offers firm, flexible
electrical production capacity to utilities and Ensure long-term funding for additional RD&D
grid operators while also enabling effective in: all main CSP technologies; all component
management of a greater share of variable parts (mirrors/heliostats, receivers, heat
energy from other renewable sources (e.g. transfer and/or working fluids, storage, power
photovoltaic and wind power). blocks, cooling, control and integration);
all applications (power, heat and fuels); and
This roadmap envisions North America as the at all scales (bulk power and decentralised
largest producing and consuming region for applications).
CSP electricity, followed by Africa, India and the
Middle East. Northern Africa has the potential Facilitate the development of ground and
to be a large exporter (mainly to Europe) as its satellite measurement/modelling of global solar
high solar resource largely compensates for the resources.
additional cost of long transmission lines.
Support CSP development through long-term
CSP can also produce significant amounts oriented, predictable solar-specific incentives.
of high-temperature heat for industrial These could include any combination of feed-in
processes, and in particular can help meet tariffs or premiums, binding renewable energy
growing demand for water desalination in arid portfolio standards with solar targets, capacity
countries. payments and fiscal incentives.
Given the arid/semi-arid nature of Where appropriate, require state-controlled
environments that are well-suited for CSP, a utilities to bid for CSP capacities.
key challenge is accessing the cooling water
needed for CSP plants. Dry or hybrid dry/wet Avoid establishing arbitrary limitations on
cooling can be used in areas with limited water plant size and hybridisation ratios (but develop
resources. procedures to reward only the electricity
deriving from the solar energy captured by the
The main limitation to expansion of CSP plants plant, not the portion produced by burning
is not the availability of areas suitable for power backup fuels).
production, but the distance between these
areas and many large consumption centres. Streamline procedures for obtaining permits for
This roadmap examines technologies that CSP plants and access lines.
address this challenge through efficient, long-
Other action items for governments, and actions
distance electricity transportation.
recommended to other stakeholders, are outlined
in the Conclusion.
Key findings 5
Introduction
This concentrating solar power roadmap is part of accelerate the overall RDD&D process in order
a series being developed by the IEA in response to to enable earlier commercial adoption of the
the pressing need to accelerate the development technology in question.
of advanced energy technologies to address
the global challenges of clean energy, climate
change and sustainable development. Ministers Rationale for CSP
from the G8 countries, China, India and South
Korea, acknowledged this need in their June 2008 CSP uses renewable solar resource to generate
meeting (Aomori, Japan) and expressed their desire electricity while producing very low levels of
to have the IEA prepare roadmaps to chart clear greenhouse-gas emissions. Thus, it has strong
paths for the development and deployment of potential to be a key technology for mitigating
innovative energy technologies. climate change. In addition, the flexibility of
CSP plants enhances energy security. Unlike
We will establish an international initiative solar photovoltaic (PV) technologies, CSP has an
with the support of the IEA to develop inherent capacity to store heat energy for short
roadmaps for innovative technologies and periods of time for later conversion to electricity.
cooperate upon existing and new partnerships, When combined with thermal storage capacity,
including carbon capture and storage (CCS) and CSP plants can continue to produce electricity
advanced energy technologies. Reaffirming our even when clouds block the sun or after sundown.
Heiligendamm commitment to urgently develop, CSP plants can also be equipped with backup
deploy and foster clean energy technologies, we power from combustible fuels.
recognize and encourage a wide range of policy
instruments such as transparent regulatory These factors give CSP the ability to provide
frameworks, economic and fiscal incentives, reliable electricity that can be dispatched to
and public/private partnerships to foster private the grid when needed, including after sunset
sector investments in new technologies… to match late evening peak demand or even
around the clock to meet base-load demand.
To achieve this ambitious goal, the IEA has Collectively, these characteristics make CSP a
undertaken, under international guidance and in promising technology for all regions with a need
close consultation with industry, to develop a series for clean, flexible, reliable power. Further, due to
of global roadmaps covering 19 technologies. these characteristics, CSP can also be seen as an
These are evenly divided among demand-side enabling technology to help integrate on grids
and supply-side technologies. larger amounts of variable renewable resources
such as solar PV or wind power.
The overall aim of these roadmaps is to
demonstrate the critical role of energy While the bulk of CSP electricity will come from
technologies in achieving the stated goal of large, on-grid power plants, these technologies
halving energy-related carbon dioxide (CO2) also show significant potential for supplying
emissions by 2050. The roadmaps will enable specialised demands such as process heat for
governments, industry and financial partners industry, co-generation of heating, cooling and
to identify the practical steps they can take to power, and water desalination. CSP also holds
participate fully in the collective effort required. potential for applications such as household
cooking and small-scale manufacturing that are
This process began with establishing a clear important for the developing world.
definition and the elements needed for each
roadmap. Accordingly, the IEA has defined its The possibility of using CSP technologies to
global technology roadmaps as: produce concentrating solar fuels (CSF, such
as hydrogen and other energy carriers), is
… a dynamic set of technical, policy, legal, an important area for further research and
financial, market and organizational requirements development. Solar-generated hydrogen can
identified by the stakeholders involved in its help decarbonise the transport and other end-
development. The effort shall lead to improved use sectors by mixing hydrogen with natural
and enhanced sharing and collaboration of all gas in pipelines and distribution grids, and by
related technology-specific research, development, producing cleaner liquid fuels.
demonstration and deployment (RDD&D)
information among participants. The goal is to
Introduction 7
The purpose of the roadmap Roadmap process,
Concentrating solar power can contribute content and structure
significantly to the world’s energy supply. As
shown in this roadmap, this decade is a critical The IEA convened a CSP Roadmap Expert Meeting
window of opportunity during which CSP could to coincide with the SolarPACES 2009 Conference
become a competitive source of electrical power to (Berlin, 14 September 2009). The workshop
meet peak and intermediate loads in the sunniest was attended by 35 experts from ten countries,
parts of the world. representing academic, industry, financial and
policy-making circles. Sessions focused on five
This roadmap identifies technology, economy topics: CSP technologies; systems integration;
and policy goals and milestones needed to solar fuels; economics and financing; and aspects
support the development and deployment of of policy. The roadmap also takes account of other
CSP, as well as ongoing advanced research in regional and national efforts to investigate the
CSF. It also sets out the need for governments to potential of CSP, including:
implement strong, balanced policies that favour
The European Union’s Strategic Energy
rapid technological progress, cost reductions
and expanded industrial manufacturing of Technology (SET) Plan and the Solar Thermal
CSP equipment to enable mass deployment. Electricity European Industrial Initiative (STEII)
Importantly, this roadmap also establishes a
The Solar America Initiative (SAI)
foundation for greater international collaboration.
China’s solar energy development plans
The overall aim of this roadmap is to identify
actions required – on the part of all stakeholders India’s Solar Mission
– to accelerate CSP deployment globally. Many
countries, particularly in emerging regions, are Australia’s Solar Flagship Initiative
only just beginning to develop CSP. Accordingly,
TheSolar Technology Action Plan of the Major
milestone dates should be considered as indicative
Economies Forum on Energy and Climate
of urgency, rather than as absolutes.
Change.
This roadmap is a work in progress. As global
This roadmap is organised into five major sections.
CSP efforts advance and an increasing number
It starts with the status of CSP today, including
of CSP applications are developed, new data will
considerations relative to the solar resource,
provide the basis for updated analysis. The IEA will
current technologies and equipping CSP for grid
continue to track the evolution of CSP technology
integration. The roadmap then sketches a vision of
and its impacts on markets, the power sector
future large-scale use of CSP, includes an overview
and regulatory environments, and will update its
of the economic perspectives for CSP. Milestones
analysis and set additional tasks and milestones as
for technology improvements are then described.
new learning comes to light.
The roadmap concludes with the policy framework
required to support the necessary RDD&D.
8 Technology Roadmaps Concentrating Solar PowerCSP status today
The basic concept of concentrating solar power is The importance
relatively simple: CSP devices concentrate energy
from the sun’s rays to heat a receiver to high of the solar resource
temperatures.1 This heat is transformed first into
mechanical energy (by turbines or other engines) The sunlight hits the Earth’s surface both directly
and then into electricity. CSP also holds potential and indirectly, through numerous reflections and
for producing other energy carriers (solar fuels). deviations in the atmosphere. On clear days, direct
irradiance represents 80% to 90% of the solar
CSP is a proven technology. The first commercial energy reaching the Earth’s surface. On a cloudy
plants began operating in California in the period or foggy day, the direct component is essentially
1984 to 1991, spurred by federal and state tax zero. The direct component of solar irradiance
incentives and mandatory long-term power is of the greatest interest to designers of high-
purchase contracts. A drop in fossil fuel prices then temperature solar energy systems because it can
led the federal and state governments to dismantle be concentrated on small areas using mirrors or
the policy framework that had supported the lenses, whereas the diffuse component cannot.
advancement of CSP. In 2006, the market re- Concentrating the sun’s rays thus requires reliably
emerged in Spain and the United States, again in clear skies, which are usually found in semi-arid,
response to government measures such as feed- hot regions.
in tariffs (Spain) and policies obliging utilities
to obtain some share of power from renewables The solar energy that CSP plants use is measured as
– and from large solar in particular. direct normal irradiance (DNI), which is the energy
received on a surface tracked perpendicular to the
As of early 2010, the global stock of CSP plants sun's rays. It can be measured with a pyrheliometer.
neared 1 GW capacity. Projects now in development
or under construction in more than a dozen DNI measures provide only a first approximation
countries (including China, India, Morocco, Spain of a CSP plant’s electrical output potential. In
and the United States) are expected to total 15 GW. practice, what matters most is the variation in
sunlight over the course of a day: below a certain
Parabolic troughs account for the largest share threshold of daily direct sunlight, CSP plants have
of the current CSP market, but competing no net production (Figure 1), due to constant heat
technologies are emerging. Some plants now losses in the solar field.
incorporate thermal storage.
CSP developers typically set a bottom threshold
1 By contrast, photovoltaics (PV) and concentrating for DNI of 1900 kWh/m2/year to 2100 kWh/m2/
photovoltaics (CPV) produce electricity from the sun's rays year. Below that, other solar electric technologies
using direct conversion with semi-conductor materials.
Figure 1: O
utput of a SEGS plant in kWh/m2/day
as a function of the DNI in kWh/m2/day
1.8
Electric production (kWh per m2 per day)
January
1.6 February
1.4 March
1.2 April
May
1.0
0.8
0.6
0.4
0.2
0.0
0 1 2 3 4 5 6 7 8 9 10 11
2
Direct sunlight (kWh per m per day)
Source: Pharabod and Philibert, 1991. 2
2 Unless otherwise indicated, data for tables and figures reflect IEA analysis.
CSP status today 9that take advantage of both direct and diffuse measurements can only be achieved through
irradiance, such as photovoltaics, are assumed to ground-based monitoring; satellite results must
have a competitive advantage. thus be scaled with ground measurements for
sufficient accuracy.
Distribution of the solar
Several studies have assessed in detail the
resource for CSP potential of key regions (notably the United States
and North Africa), giving special consideration
The main differences in the direct sunlight available
to land availability: without storage, CSP plants
from place to place arise from the composition
require around 2 hectares per MWe, depending on
of the atmosphere and the weather. Good DNI
the DNI and the technology.
is usually found in arid and semi-arid areas with
reliably clear skies, which typically lay at latitudes Even though the Earth’s “sunbelts” are relatively
from 15° to 40° North or South. Closer to the narrow, the technical potential for CSP is huge. If
equator the atmosphere is usually too cloudy and fully developed for CSP applications, the potential
wet in summer, and at higher latitudes the weather in the southwestern US states would meet the
is usually too cloudy. DNI is also significantly better electricity requirements of the entire United States
at higher altitudes, where absorption and scattering several times over. Potential in the Middle East
of sunlight are much lower. and North Africa would cover about 100 times the
current consumption of the Middle East, North
Thus, the most favourable areas for CSP resource
Africa and the European Union combined. In
are in North Africa, southern Africa, the Middle
short, CSP would be largely capable of producing
East, northwestern India, the southwestern United
enough no-carbon or low-carbon electricity and
States, Mexico, Peru, Chile, the western part of
fuels to satisfy global demand. A key challenge,
China and Australia. Other areas that may be
however, is that electricity demand is not always
suitable include the extreme south of Europe and
situated close to the best CSP resources.
Turkey, other southern US locations, central Asian
countries, places in Brazil and Argentina, and other
parts of China. Transporting and exporting
electricity from CSP
Recent attempts to map the DNI resource
worldwide are based on satellite data (Figure 2). As demonstrated over decades by hydropower
While existing solar resource maps agree on dams in remote regions, electricity can be
the most favourable DNI values, their level transported over long distances to demand
of agreement vanishes when it comes to less centres. When distance is greater than a few
favourable ones. Important differences exist, hundred kilometres, economics favour high-
notably with respect to the suitability of voltage direct-current (HVDC) technology over
northeastern China, where the most important alternative-current technology. HVDC lines of
consumption centres are found. However, precise gigawatt capacity can exceed 1 000 km and can
Figure 2: Solar resource for CSP technologies (DNI in kWh/m2/y)
2
3 000 kWh per m per yr
2
2 500 kWh per m per yr
2 000 kWh per m2 per yr
1 500 kWh per m2 per yr
1 000 kWh per m2 per yr
500 kWh per m2 per yr
0 kWh per m2 per yr
Source: Breyer & Knies, 2009 based on DNI data from DLR-ISIS (Lohmann, et al. 2006).
10 Technology Roadmaps Concentrating Solar Powerbe installed across the seabed; they also have emitting very little infra-red radiation. The pipes
a smaller environmental footprint. Electricity are insulated in an evacuated glass envelope. The
losses are 3% per 1 000 km, plus 0.6% for each reflectors and the absorber tubes move in tandem
conversion station (as HVDC lines usually link two with the sun as it crosses the sky.
alternative-current areas).
Parabolic trough All parabolic trough
This creates opportunities for CSP plant operators plants currently
to supply a larger range of consumers. However, in commercial
the cost of constructing major transmission and operation rely on
distribution lines must be taken into account. synthetic oil as the
Reflector fluid that transfers
Absorber tube heat (the heat
Current technologies for Solar field piping transfer fluid) from
collector pipes to
power production heat exchangers,
where water is preheated, evaporated and then
At present, there are four main CSP technology
superheated. The superheated steam runs a
families, which can be categorised by the way they
turbine, which drives a generator to produce
focus the sun’s rays and the technology used to
electricity. After being cooled and condensed, the
receive the sun’s energy (Table 1).
water returns to the heat exchangers.
Parabolic troughs Parabolic troughs are the most mature of the
(line focus, mobile receiver) CSP technologies and form the bulk of current
commercial plants. Most existing plants, however,
Parabolic trough systems consist of parallel rows have little or no thermal storage and rely on
of mirrors (reflectors) curved in one dimension combustible fuel as a backup to firm capacity. For
to focus the sun’s rays. The mirror arrays can be example, all CSP plants in Spain derive 12% to 15%
more than 100 m long with the curved surface of their annual electricity generation from burning
5 m to 6 m across. Stainless steel pipes (absorber natural gas. Some newer plants have significant
tubes) with a selective coating serve as the heat thermal storage capacities.
collectors. The coating is designed to allow pipes
to absorb high levels of solar radiation while
Table 1: The four CSP technology families
Focus type Line focus Point focus
Collectors track the Collectors track the sun along
sun along a single axis two axes and focus irradiance
and focus irradiance at a single point receiver. This
on a linear receiver. allows for higher temperatures.
This makes tracking
Receiver type the sun simpler.
Fixed receivers are stationary devices
that remain independent of the
Linear Fresnel
Fixed
plant’s focusing device. This eases Towers (CRS)
Reflectors
the transport of collected heat to the
power block.
Mobile receivers move together with
Mobile
the focusing device. In both line
Parabolic Troughs Parabolic Dishes
focus and point focus designs, mobile
receivers collect more energy.
CSP status today 11Linear Fresnel reflectors (line designers can choose from a wide variety of
focus, fixed receiver) heliostats, receivers, transfer fluids and power
blocks. Some plants have several towers that feed
Linear Fresnel one power block.
reflectors (LFRs)
approximate the Parabolic dishes (point focus,
parabolic shape of mobile receiver)
trough systems but
by using long rows of Parabolic dishes concentrate
flat or slightly curved the sun’s rays at a focal point
mirrors to reflect propped above the centre of
the sun’s rays onto the dish. The entire apparatus
a downward-facing tracks the sun, with the
linear, fixed receiver. dish and receiver moving in
A more recent design, tandem. Most dishes have an
known as compact linear Fresnel reflectors (CLFRs), independent engine/generator
uses two parallel receivers for each row of mirrors (such as a Stirling machine or
and thus needs less land than parabolic troughs to a micro-turbine) at the focal
R
produce a given output. point. This design eliminates
the need for a heat transfer fluid
The main advantage of LFR systems is that their and for cooling water.
simple design of flexibly bent mirrors and fixed
receivers requires lower investment costs and Dishes offer the highest solar-to-electric conversion
facilitates direct steam generation (DSG), thereby performance of any CSP system. Several features
eliminating the need for – and cost of – heat – the compact size, absence of cooling water,
transfer fluids and heat exchangers. LFR plants are, and low compatibility with thermal storage and
however, less efficient than troughs in converting hybridisation – put parabolic dishes in competition
solar energy to electricity and it is more difficult to with PV modules, especially concentrating
incorporate storage capacity into their design. photovoltaics (CPV), as much as with other CSP
technologies. Very large dishes, which have been
Solar towers (point focus, proven compatible to thermal storage and fuel
fixed receiver) backup, are the exception. Promoters claim that
mass production will allow dishes to compete with
Central receiver Solar towers, larger solar thermal systems.
also known as
central receiver Parabolic dishes are limited in size (typically tens
Solar Tower
systems (CRS), of kW or smaller) and each produces electricity
use hundreds independently, which means that hundreds or
or thousands of thousands of them would need to be co-located
small reflectors to create a large-scale plant. By contrast, other
(called heliostats) CSP designs can have capacities covering a very
to concentrate wide range, starting as low as 1 MW. The optimal
the sun’s rays on size of troughs, LFR and towers, typically from
Heliostats
a central receiver 100 MW to 250 MW, depends on the efficiency of
placed atop a the power block.
fixed tower. Some commercial tower plants now
in operation use DSG in the receiver; others use Other systems
molten salts as both the heat transfer fluid and
Some smaller CSP devices combine fixed receivers
storage medium.
with parabolic troughs or, more often, dishes
The concentrating power of the tower concept (called “Scheffler dishes”). They are notably used
achieves very high temperatures, thereby in India for steam cooking devices in facilities that
increasing the efficiency at which heat is converted serve thousands meals per day. Dishes have also
into electricity and reducing the cost of thermal been used for process heat by gathering the heat
storage. In addition, the concept is highly flexible; collected by each dish; feeding a single power
12 Technology Roadmaps Concentrating Solar Powerblock to produce electricity this way is possible, places. Furthermore, human activity and thermal
but this option does not seem to be pursued inertia of buildings often maintain high demand
at present. for electricity several hours after sunset. To provide
a larger share of clean electricity and maximise
Solar thermal electricity without concentration is
CO2 emission reductions, CSP plants will need to
also possible. Highly efficient non-concentrating
provide base load power. Thermal storage and
solar collectors could evaporate enough steam to
backup or hybridisation with fuels help address
run specific power blocks (e.g. based on organic
these issues.
Rankine cycles). The efficiency would be relatively
low in comparison to CSP technologies discussed
above, but non-concentrating solar power could Thermal storage
capture both direct and diffuse sunlight (like PV
All CSP plants have some ability to store heat
modules) and thus expand the geographic areas
energy for short periods of time and thus have a
suitable for solar thermal electricity. Low-cost
“buffering” capacity that allows them to smooth
thermal storage and fuel backup could give this
electricity production considerably and eliminate
technology interesting features when and if it
becomes commercial. the short-term variations other solar technologies
exhibit during cloudy days.
Recently, operators have begun to build thermal
Enhancing the value storage systems into CSP plants. The concept of
of CSP capacities thermal storage is simple: throughout the day,
excess heat is diverted to a storage material (e.g.
In arid and semi-arid areas suitable for CSP molten salts). When production is required after
production, sunlight usually exhibits a good match sunset, the stored heat is released into the steam
with electricity demand and its peaks, driven by cycle and the plant continues to produce electricity.
air-conditioning loads. However, the available
sunlight varies somewhat even in the sunniest
Storage system in a trough solar plant
This graph shows how storage works in a CSP plant. Excess heat collected in the solar field is sent to the
heat exchanger and warms the molten salts going from the cold tank to the hot tank. When needed, the
heat from the hot tank can be returned to the heat transfer fluid and sent to the steam generator.
Source: SolarMillennium.
CSP status today 13Studies show that, in locations with good sunlight extending production after sunset. For example,
(high DNI), extending electricity production to some trough plants in Spain store enough heat in
match this demand requires a storage capacity molten salts to produce power at the rated capacity
of two to four hours. In slightly less sunny areas, of the turbine (50 MWe) for more than 7 additional
storage could be larger, as it also helps compensate hours (See box).
for the somewhat less predictable resource. The
solar field is somewhat larger relative to the rated
electrical capacity (i.e. the plant has a greater 3 T he solar multiple is the ratio of the actual size of a CSP
solar multiple3), to ensure sufficient electricity plant’s solar field compared to the field size needed to
production. As a result, at maximum sunlight feed the turbine at design capacity when solar irradiance
is at its maximum (about 1 kW/m2). Plants without
power, solar fields produce more heat than their
storage have an optimal solar multiple of roughly 1.1 to
turbines can absorb. In the absence of storage, on about 1.5 (up to 2.0 for LFR), depending primarily on the
the sunniest hours, plant operators would need to amount of sunlight the plant receives and its variation
“defocus” some unneeded solar collectors. Storage through the day. Plants with large storage capacities
avoids losing this energy while also allowing for may have solar multiples of up to 3 to 5.
Tailoring storage to serve purpose
Varying the storage capacity is a means of tailoring CSP plant to meet different needs. All four
hypothetical plants below have the same solar field size and produce the same amount of
electricity, but at different times and different power rates.
Figure 3: F
our different configurations
of CSP plants of a given solar field size
Intermediate load The intermediate load
configuration is designed
Solar field to produce electricity
when the sunshine
available covers peak
and shoulder loads. It
has a 250 MW turbine
Small storage 250 MW turbine
and requires only a small
amount of storage. It has
Production from 08.00h to 19.00h the smallest investment
costs and the least-
expensive electricity
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 2324h output.
The delayed Delayed intermediate load
intermediate load
Solar field
design collects solar
energy all day but
produces electricity
from noon on and after
sunset, corresponding 250 MW turbine
to peak and shoulder Medium-size storage
loads. It has the same
size turbine as the Production from 12.00h to 23.00h
intermediate load plant
but requires a larger
amount of storage. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 2324h
14 Technology Roadmaps Concentrating Solar PowerBase load The base load
configuration
Solar field
runs 24 hours per day
for most of the year; it
needs a larger amount
120 MW turbine of storage and a smaller
turbine. If the costs
Large storage of storage capacity
are lower than those
24/24h Production of larger turbines,
electricity from the base
load plant is slightly
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 2324h cheaper than that of
delayed intermediate
load plant. This will likely be the case with higher working temperatures, which will allow for less-
expensive storage but require more sophisticated and costly turbines.
The peak load plant is
Peak load
designed to provide
electricity only for a
few hours to meet the
extreme peak load. It
requires a large turbine
(600 MW) and a large
amount of storage. Of all
four designs it produces
the most expensive, but
also the most valuable
electricity.
Source: Julien Octobre and Frank Guihard, Systèmes Solaires, 2009.
CSP plants with large storage capacities may be Backup and hybridisation
able to produce base-load solar electricity day and
night, making it possible for low-carbon CSP plants Virtually all CSP plants, with or without storage,
to compete with coal-fired power plants that emit are equipped with fuel-powered backup systems
high levels of CO2. For example, one 17 MW solar that help to regulate production and guarantee
tower plant under construction in Spain will use capacity – especially in peak and mid-peak
molten salts as both heat transfer fluid and storage periods. The fuel burners (which can use fossil
medium and store enough heat energy to run the fuel, biogas or, eventually, solar fuels) can provide
plant at full load for 16 hours. energy to the heat transfer fluid or the storage
medium, or directly to the power block.
Storage has a cost, however, and cannot be
expanded indefinitely to prevent rare events of solar In areas where DNI is less than ideal, fuel-powered
energy shortages. A current industry focus is to backup makes it possible to almost completely
significantly increase the temperature to improve guarantee the plant’s production capacity at a
overall efficiency of CSP plants and reduce storage lower cost than if the plant depended only on the
costs. Enhanced thermal storage would help to solar field and thermal storage (Figure 4). Providing
guarantee capacity and expand production. Storage 100% firm capacity with only thermal storage
potentially makes base-load solar-only power would require significantly more investment in
plants possible, although fuel-powered backup and reserve solar field and storage capacity, which
hybridisation have their own advantages and are would produce little energy over the year.
likely to remain, as described below.
CSP status today 15Figure 4: Combination of storage and hybridisation in a solar plant
50
40
Firm capacity line To storage
30
MW
20
Fuel backup Solar direct From storage
10
0
0 2 4 6 8 10 12 14 16 18 20 22 24
Time of day
Source: Geyer, 2007, SolarPACES Annual Report.
Fuel burners also boost the conversion efficiency being built adjacent to existing or new fossil fuel
of solar heat to electricity by raising the working power plants in Algeria, Australia, Egypt, Iran, Italy
temperature level; in some plants, they may be and the United States (in the state of Florida).
used continuously in hybrid mode.
CSP can also be used in hybrid by adding a small
solar field to fossil fuel plants such as coal plants Grid integration
or combined-cycle natural gas plants in so-called
integrated solar combined-cycle plants (ISCC). As
of CSP plants
the solar share is limited, such hybridisation really The storage and backup capabilities of CSP plants
serves to conserve fuel. A positive aspect of solar offer significant benefits for electricity grids. Losses
fuel savers is their relatively low cost: with the in thermal storage cycles are much smaller than
steam cycle and turbine already in place, only in other existing electricity storage technologies
components specific to CSP require additional (including pumped hydro and batteries), making
investment. Such fuel savings, with capacities the thermal storage available in CSP plants more
ranging from a few megawatts to 75 MW, are effective and less costly.
Two examples of backup and/or hybridisation
The SEGS CSP plants, built in California between 1984 and 1991, use natural gas to boost
production year-round. In the summer, SEGS operators use backup in the late afternoon and run
the turbine alone after sunset, corresponding to the time period (up to 10:00 p.m.) when mid-peak
pricing applies. During the winter mid-peak pricing time (12:00 noon to 6:00 p.m.), SEGS uses
natural gas to achieve rated capacity by supplementing low solar irradiance. By law, the plant is
limited to using gas to produce only 25% of primary energy.
The Shams-1 trough plant (100 MW), planned in the United Arab Emirates, will combine
hybridisation and backup, using natural gas and two separate burners. The plant will burn natural
gas continuously during sunshine hours to raise the steam temperature (from 380°C to 540°C)
for optimal turbine operation. Despite its continuous use, natural gas will account for only 18% of
overall production of this peak and mid-peak plant. The plant will use a natural gas heater for the
heat transfer fluid. This backup measure was required by the electric utility to guarantee capacity,
but will be used only when power supply is low due to lack of sunshine. Over one year, this second
burner could add 3% to the plant’s overall energy production.
16 Technology Roadmaps Concentrating Solar PowerCSP plants can enhance the capacity of electricity penalty. As water cooling is more effective but
grids to accommodate a larger share of variable more costly, operators of hybrid systems tend to
energy sources, thereby increasing overall grid use only dry cooling in the winter when cooling
flexibility. As demonstrated in Spain, connecting needs are lower, then switch to combined wet and
CSP plants to some grid sub-stations facilitates a dry cooling during the summer. For a parabolic
greater share of wind energy. CSP plant backup trough CSP plant, this approach could reduce water
may also eliminate the need to build fossil-fired consumption by 50% with only a 1% drop in annual
“peaking” plants purely to meet the highest loads electrical energy production.
during a few hours of the day.
Although the optimal size of CSP plant is CSP for niche markets
probably 200 MW or more, many existing grids
use small power lines at the ends of the grid in CSP technologies can be highly effective in various
less-populated areas, which cannot support the niche markets. Mid-sized CSP plant can fuel remote
addition of large amounts of electricity from solar facilities such as mines and cement factories.
plants. Thus, in some cases, the size of a CSP plant Even small CSP devices (typically using organic
could be limited by the available power lines or Rankine cycles or micro-turbines) can be useful on
require additional investment in larger transport buildings to provide electricity, heat and cooling.
lines. Furthermore, it is often easier to obtain
sites, permits, grid connections and financing for CSP plants can produce significant quantities
smaller, scalable CSP plant designs, which can also of industrial process heat. For example, a solar
enter production more quickly. tower will soon produce steam for enhanced oil
recovery in the United States. At a smaller scale,
concentrating sunlight can be used for cooking
Plant cooling and artisanal production such as pottery. The
advantages could be considerable in developing
and water requirements countries, ranging from independence from
As in other thermal power generation plants, fossil resources, protection of ecosystems from
CSP requires water for cooling and condensing deforestation and land degradation, more
processes. CSP water requirements are relatively reliable pottery firing and, in the case of cooking,
high: about 3 000 L/MWh for parabolic trough and reduction of indoor air pollution and its resulting
LFR plants (similar to a nuclear reactor) compared health impacts. The scope of this roadmap
to about 2 000 L/MWh for a coal plant and only precludes a full investigation of these possibilities,
800 L/MWh for combined-cycle natural gas plants. barriers to their dissemination, or policies to
Tower CSP plants need less water per MWh than overcome such barriers.
trough plants, depending on the efficiency of the Large CSP plants may also prove effective for co-
technology. Dishes are cooled by the surrounding generation to support water desalination. CSP
air, and need no cooling water. plants are often located in arid or semi-arid areas
Accessing large quantities of water is an important where water is becoming scarcer while water
challenge to the use of CSP in arid regions, as demand is increasing rapidly as populations and
available water resources are highly valued by economies grow. CSP plants could be designed
many stakeholders. Dry cooling (with air) is one so that low-pressure steam is extracted from the
effective alternative used on the ISCC plants under turbine to run multi-effect distillation (MED)
construction in North Africa. However, it is more stages. Such plants would produce fresh water
costly and reduces efficiencies. Dry cooling installed along with electricity, but at some expense of
on trough plants in hot deserts reduces annual efficiency loss in power production. Economic
electricity production by 7% and increases the studies suggest that it might be preferable,
cost of the produced electricity by about 10%. The however, to separate the two processes, using
“performance penalty” of dry cooling is lower for CSP for electricity production and reverse osmosis
solar towers than for parabolic troughs. for desalination, when the working temperature
is relatively low, as with trough plants. Co-
Installation of hybrid wet/dry cooling systems is a generation of electricity and fresh water would
more attractive option as such systems reduce water probably work best with higher temperature
consumption while minimising the performance levels, such as with towers.
CSP status today 17With respect to concentrating solar fuels, current
R&D efforts have shown promise in a number of
necessary steps, including water splitting, fossil
fuel decarbonisation and conversion of biomass
and organic wastes into gaseous fuels. Success
in these areas affirms the need for larger-scale
experiments to support the further development
of CSF as part of the global energy mix.
18 Technology Roadmaps Concentrating Solar PowerVision of future deployment
Existing scenarios of it, mostly from onshore wind and solar power.
CSP plants would form the backbone of the export
and proposals capacities from North Africa to Europe.
The IEA publication Energy Technology Perspectives
2008 (ETP 2008) includes CSP as one of the
many cost-effective technologies that will lower
CSP deployment
CO2 emissions. In the ETP BLUE Map scenario, This roadmap foresees a rapid expansion of CSP
global energy-related CO2 emissions by 2050 are capacities in countries or regions with excellent
reduced to half their 2005 level, and CSP produces DNI, and computes its electricity production
2 200 TWh annually by 2050 from 630 GW of local as progressively growing percentages of the
capacities (no exports taken in account). CSP is overall consumption forecast in IEA climate-
expected to contribute 5% of the annual global friendly scenarios in these regions (Table 2). In
electricity production in 2050 in this scenario. neighbouring but less sunny regions, a lower
contribution of CSP electricity is expected, which
In the Advanced scenario of CSP Global Outlook
mixes local production and electricity from nearby
2009, the IEA SolarPACES programme, the
sunnier areas.
European Solar Thermal Electricity Association and
Greenpeace estimated global CSP capacity by 2050 Plants built before 2020 mostly respond to
at 1 500 GW. The SolarPACES forecast sees large intermediate and peak loads, while a first set of
storage and solar fields that would enable capacity HVDC lines is built to connect some of the CSP
factors of 59% (5 200 hours per year), with a yearly plants in sunny areas to large demand centres.
output of 7 800 TWh. From 2020 to 2030, as costs are reduced and
performance enhanced, the deployment of CSP
In its study of the renewable energy potential
continues with base-load plants, thus maximising
in the Middle East/North Africa region, the
CO2 emission reductions. After 2030, while CSP
German Aerospace Center (DLR) estimates that
continues to develop, solar fuels enter the global
by 2050, CSP plants could provide about half of
energy mix. By 2050, CSP represents about 11% of
the region’s electrical production, from a total
global electricity production.
capacity of 390 GW.
The overall estimated growth of CSP electricity
According to a recent study by PriceWaterHouse
output is represented in Figure 5 in comparison
Cooper, Europe and North Africa together
with three other scenarios: the BLUE Map scenario
could by 2050 produce all their electricity from
of ETP 2008, and the Advanced and Moderate
renewables if their respective grids are sufficiently
scenarios of Global CSP Outlook 2009.
interconnected. While North Africa would consume
one-quarter of the total it would produce 40%
Figure 5: Growth of CSP production under four scenarios (TWh/y)
9 000
8 000 ETP Blue
7 000 This roadmap
6 000 Global outlook adv.
Global outlook mod.
TWh/y
5 000
4 000
3 000
2 000
1 000
0
2007 2020 2030 2040 2050
Vision of future deployment 19Table 2: Electricity from CSP plants as shares of total electricity consumption
Countries 2020 2030 2040 2050
Australia, Central Asia,4 Chile, India
(Gujarat, Rajasthan), Mexico, Middle East,
5% 12% 30% 40%
North Africa, Peru, South Africa, United
States (Southwest)
United States (remainder) 3% 6% 15% 20%
Europe (mostly from imports), Turkey 3% 6% 10% 15%
Africa (remainder), Argentina, Brazil,
1% 5% 8% 15%
India (remainder)
Indonesia (from imports) 0.5% 1.5% 3% 7%
China, Russia (from imports) 0.5% 1.5% 3% 4%
4 Includes Afghanistan, Kazakhstan, Kyrgyzstan, Pakistan, Tajikistan,
Turkmenistan, and Uzbekistan.
Figure 6 shows the growth of CSP electricity feed Indonesia; the Central Asian countries supply
production by region according to this roadmap Russia; Northern African countries and Turkey
as it is further detailed below. This projection deliver power to the European Union; northern
takes into account a significant amount of and southern African countries feed equatorial
electricity transportation. Africa; and Mexico provide CSP electricity to the
United States.
The vital role of transmission The transfer of large amounts of solar energy
from desert areas to population centres has
This roadmap sees long-range transportation of been promoted, in particular, by the DESERTEC
electricity as an important way of increasing the Foundation (Figure 8). This idea has inspired two
achievable potential of CSP. Large countries such
major initiatives in Europe, the Mediterranean
as Brazil, China, India, South Africa and the United
Solar Plan and the DESERTEC Industry Initiative.
States (Figure 7) will have to arrange for large
The first, developed within the framework of the
internal transmission of CSP-generated electricity.
Barcelona Process: Union for the Mediterranean,
In other cases, high-voltage transmission lines aims to bring about 20 GW of renewable
will cross borders, opening export markets for electricity to EU countries by 2020 from the
CSP producing countries and increasing energy various developing economies that adhered to this
security for importing countries. Australia might recently created intergovernmental organisation.
Figure 6: Growth of CSP production by region (TWh/y)
5 000
4 500 EU + Turkey
4 000 Pacific
China
3 500
Central Asia
3 000
TWh/year
South America
2 500 Middle East
2 000 India
1 500 Africa
North America
1 000
500
0
2010 2020 2030 2040 2050
20 Technology Roadmaps Concentrating Solar PowerFigure 7: V
ision of possible HVDC lines linking
the Southwest to the rest of the United States
Source: Hank Price, US DOE, 2007.
Figure 8: The DESERTEC concept applied to EU-MENA Region
Source: the DESERTEC Foundation.
The second initiative, announced in July 2009, electricity losses. Further, the current feed-in tariffs
takes the form of a limited liability company, with in Spain or France for large-scale, ground-based
12 shareholders. 5 The DESERTEC Industry Initiative solar electricity would largely cover the costs of
aims to establish a framework for investments to production of electricity in North Africa, assessed
supply the Middle East, North Africa and Europe at USD 209 (EUR 150)/MWh on best sites, plus
with solar and wind power. The long-term goal is to its transport to the south of Europe, assessed at
satisfy a substantial part of the energy needs of the USD 21 (EUR 15)/MWh to USD 63 (EUR 45)/MWh.
Middle East and North Africa, and meet as much as
15% of Europe’s electricity demand by 2050.
Deployment till 2020:
The abundant sunlight in the Middle East and
North Africa will lead to lower costs, compensating intermediate and peak loads
for the additional expected transmission costs and
From 2010 to 2020, the global rollout of CSP
initiated before 2010 is expected to accelerate,
5 T hese are ABB, Abengoa Solar, Cevital, DESERTEC Foundation, Deutsche
Bank, E.ON, HSH Nordbank, MAN Solar Millennium, Munich Re, M+W
thanks to ongoing industry efforts and the adoption
Zander, RWE, Schott Solar and Siemens. of suitable incentives for CSP in sunny countries.
Vision of future deployment 21You can also read
