CSP Storage Insights for South Africa's Future

CSP Storage: SouthAfrica provides insight into the current and future prospects of storage technology,
as well as assessing the dispatchability potential for the South African market. In addition, it contains
exclusive extracts from the CSP Today business intelligence reports.
The guide has been published in conjunction with the exciting launch of CSPToday South Africa 2014,
taking place on 8-9 April in CapeTown.The must attend event for CSP developers and EPC groups who
are looking to identify the opportunities and reduce CSP costs in South Africa.
B U S I N E S S I N T E L L I G E N C E
Researched &
produced by
8-9 April, Cape Town
CSP Storage: South Africa
For more details on CSPToday SouthAfrica 2014 please visit: www.csptoday.com/southafrica
In association with:
CSPToday South Africa 2014

XXX
Overview
XXX
CSP TODAY | CSP Storage: South Africa | www.csptoday.com/southafrica • 2
CONTENTS
CSP with Storage: Beneﬁts and
Challenges in South Africa
Introduction: South Africa’s Energy Mix.......3
A Brief History of CSP in South Africa.....3
Introduction: Thermal Energy Storage........4
Thermal Energy Storage in South Africa ....4
CSP StorageTechnologies
Introduction: Thermal Energy Storage
technologies.................................................7
Molten Salt ...................................................7
Phase Change Materials (PCM)................7
Concrete........................................................7
Solid TES materials cont. ..........................8
Saturated Steam..........................................8
Thermochemical storage...........................9
Graphite.........................................................9
Ammonia and hydrogen .............................9
Compressed air energy storage..............10
With South Africa providing one of the most
exciting CSP markets in the world, industry
focus has now turned towards understanding
the intricacies of the country’s energy mix.
One of the key features of CSP technology is
the potential to utilize storage and provide a
truly dispatchable renewable energy supply.
With energy stability and supply a critical
issue for South Africa, the opportunity exists
for CSP to play a leading role.
This is why CSP Today have created this
guide, that outlines the drivers for storage in
South Africa, as well as the drivers for this
technology in South Africa.

CSP with Thermal Energy Storage (TES): Benefits and Challenges in South Africa
Introduction: South Africa’s Energy Mix
South Africa’s energy supply is currently characterized
by insecurity and extreme uncertainty. There is simply
insufficient power supply to meet demand. In winter
months the national grid gets dangerously close to
the brink of shutdown, a situation which continually
threatens to destabilize commerce and industry, and
compromise foreign investment.
Government, authorities and the media constantly
remind the country’s people about the ever prevailing
and distinct prospect of a recurrence of rolling power
blackouts, with which the country was beset in the
later months of 2007. South Africa’s State-owned utility,
Eskom, is faced with ever increasing challenges, which
could make the threat of blackouts a reality again.
Just as crucial as reliable energy supply is the need
for South Africa to comply with worldwide legislation
to reduce its global carbon footprint, move away from
Eskom’s coal-fired plants and contribute to the global
effort to tackle climate change.
Renewable energy meets a broad array of needs,
not just much needed reliable, consistent electricity
supply, but also a way to possibly bring down the
recent increases in power tariffs in South Africa going
forward. The rising costs of energy are demonstrated
by Eskom’s request for a 16% per annum tariff
increase for five years. This request was rejected
by the National Energy Regulator of South Africa
(NERSA), which granted an 8% average increase per
annum over this period.
Yet renewable energy in its totality has certain
restrictions – the key issue being its intermittency, as
it is guided by the times that the sun is shining and
the wind is blowing. It is right here that Concentrated
Solar Power (CSP) stands out from the crowd. It is CSP
which offers the unique characteristic, Thermal Energy
Storage (TES), which overcomes intermittency. The
ability to store energy enables CSP power stations to
supply electricity even when there is no sun. CSP can
therefore supply electricity during the evening peak
time, when demand is highest. In doing so it avoids the
intermittency problems encountered by PV and wind,
and many renewable energy industry players advocate
CSP as an integral part of the energy mix in South
Africa for years to come.
A Brief History of CSP in South Africa
In March 2011 South Africa’s Department of Energy
(DOE) finalised details of the Integrated Resource Plan
(IRP), a 20-year blueprint that showed the government’s
commitment to energy from renewable sources.
The IRP indicated that renewable energy will make
up a substantial 42% of all new electricity generation
(totalling 17,800MW) from 2010-2030, and gave strong
backing to Wind, Solar Photovoltaic’s (PV) and CSP
within this new energy mix.
Under the IRP the DOE committed to produce
8400MW from solar PV, 8400MW from wind and
1000MW from CSP through the Renewable Energy
Independent Power Producer Programme (REIPPP).
In August 2011 the first request for proposals for
renewable projects was opened by the government

allocating 200MW to CSP in this initial stage, leaving
800MW available for future rounds.
By December 2011 the Department of Energy had
received 53 bids across all the different technologies,
awarding 28 projects to independent power producers
made up of 632MW of PV, 150MW of CSP and
634MW of Wind.
The two CSP tenders were awarded to Abengoa,
a leading Spanish multinational renewable energy
developer, that included the 50MW Khi Solar One plant
and the 100 MW KaXu Solar One plant.
The bidding for window II of the REIPPP closed on
5 March 2012 with a total of 79 bids received. The
total capacity of bids amounted to 3,255MW, far
exceeding the cap that was set at 1,275MW across
all technologies. The CSP allocation for window II was
a maximum of 50MW (the capacity remaining from
the 200MW assigned to CSP in the initial request for
proposals).
On 21 May 2012 this 50MW was allocated to a
consortium led by ACWA Power International, the Saudi
Water and Power giant, and the South African energy
company Solafrica to develop the Bokpoort CSP Power
Plant.
In September 2012 the DOE announced delays
to Round III of the REIPPP due to the difficulty in
advancing Round I and II projects to financial close. The
deadline for window I projects was initially scheduled
for 20 June 2012, but was pushed back to October
that year. Window II also faced delays, achieving the
financial close milestone on 9 May 2013, over 5 months
later than the initial 13 December deadline.
200 MW was allocated to CSP for the third window
of the REIPPPP. Originally scheduled to take place on
7 May 2013, Round III of the REIPPPP closed on 19
August, and the industry will learn who the preferred
bidders are on 29 October.
Introduction: Thermal Energy Storage (TES)
The incorporation of energy storage into CSP plants
gives solar thermal technologies a unique advantage
over other renewable energy technologies and in
particular over solar PV at a time when the latter is able
to deliver highly-attractive LCOE values. Thermal energy
storage is nowadays essential to CSP plants to produce
price-competitive energy through dispatchability.
Although, the initial investment costs are increased
when implementing a TES system, the overall LCOE
of the plant is reduced, making the CSP plant more
economically and technically attractive.
The integration of TES is not only driven by the
reduction of LCOE and technology improvements,
but also by emerging solar policies: Governments
around the world have realized the relevance of CSP
with TES as a potential ingredient to their future
electrical energy portfolio. With fluctuating capacity,
inherent to most renewable energy technologies,
addressing grid stability will become capital. In addition
to the allocation of capacity for the development of
CSP plants, many governments have also included
mandatory use of TES for this reason.
Thermal Energy Storage in South Africa
To encourage CSP with storage to generate energy
during peak time, the South African Department of
Energy (DoE) recently introduced an incentive in the
form of a Time of Day (TOD) tariff.
A base tariff applies during the day and a higher tariff
will be applied for supplying energy during peak time.
According to the initial proposal, a bidder supplying
energy during the peak time between 17h00 and
21h00 would get 240% of the base tariff, while there is
no payment for supplying energy at night. Recently the
peak period was extended from 16h30 to 21h30 and
the tariff increased to 270% of the base tariff.
What has the reaction been from industry players to
the new TOD tariff?
California-based global solar power developer,
SolarReserve, provider of utility scale CSP with
thermal energy storage (TES), sees the TOD tariff in
a very positive light. In a recent interview with CSP

Today, Stephen Mullennix, Solar Reserve’s Senior Vice
President of Asset Management, emphasized that
“Utility scale energy storage is critical for South Africa
in order to maintain stability in the grid, and to match
energy supply with energy demand”.
Mullennix went on to explain that “the TOD tariff
recognizes the intrinsic value of storage for shifting
generation in order to meet demand. SolarReserve
believes that South Africa will capture more significant
value by offering a TOD tariff, than by procuring
intermittent energy”.
“The tariff enables a CSP plant with utility scale storage
to be built instead of both an intermittent renewable
supply, as well as a backup fossil supply. This derives
greater value for all parties from the significant capital
investment needed to bring the plant online. In addition
it brings economic stability to the operating period for
all parties compared to the volatile fuel pricing markets
such as coal.”
Marc Immerman, a Director of Solafrica, who recently
commenced construction at its 50MW Bokpoort
project in the Northern Cape, says: “The TOD
tariff structure should result in a more sustainable
procurement for CSP in South Africa given the morning
and evening peak electrical demand in South Africa.
As CSP is the only renewable technology able to
store energy, this inherent value is now effectively
recognized by the South African Department of
Energy.”
Professor Wikus van Niekerk, Director of the Centre
for Renewable and Sustainable Energy Studies at
Stellenbosch University, comments. “I think this
incentive is exactly what the CSP projects in South
Africa need in order to demonstrate the real value of
the electricity that CSP can generate.
“The TOD tariff for CSP is a significant breakthrough
that acknowledges the contribution of thermal energy
storage. This will now allow CSP to not only compete
with the existing open cycle gas turbine (OCGT)
peaking plants but will also augment the PV plants in
the evening hours.”
Interestingly, as a result of the new tariff, some
prospective bidders without storage who were
planning to submit for Window 3 of the REIPPP
program were forced to withdraw their bids.
“The new TOD tariff does not make financial sense
for a CSP project without storage, and will force all
future CSP plants to have storage,” says Riaan Meyer,
CEO of GeoSUN Africa, a spin-off of the Centre for
Renewable and Sustainable Energy Studies (CRSES) at
Stellenbosch University.
“I support the new TOD tariff since it will promote
CSP with storage, but it was released only in early
May this year, three and a half months before the bid
submission of 19 August. This meant that CSP projects
without storage planning to submit withdrew their bids.
The developers I spoke to will resubmit in a next bid
window projects with storage,” Meyer continues.

CSP Storage: South Africa was created by CSP Today using its latest business intelligence reports: the
ParabolicTrough Report 2014: Cost, Performance andThermal Storage and the SolarTower Report
2014: Cost, Performance andThermal Storage. This first section contains extracts from these technology
reports to explain the potential for CSP integration with storage.
CSP StorageTechnologies
The thermal storage capability of a CSP plant is one of
the main features facilitating the integration of CSP into
the grid. The objective of TES is as follows:
 Provide dispatchable energy, extending the
operating hours beyond sunset when no solar
radiation is available
 Avoid fluctuations associated with the intermittent
solar resource
 Reduce dumped energy making the plant more
efficient
The current TES technology employed in commercial
operating plants consists of one or more pairs of tanks
where molten salts are stored at two temperature
levels, providing a temperature differential that is used
to generate steam. The molten salts have a melting
point in the range of 230-240°C, and TES in a parabolic
trough plant consists of the following components:
 Cold tank(s) where molten salts are stored at a
temperature range of 290-300°C
 Hot tank(s) where molten salts are stored at a
temperature range of 380-390°C
 Heat exchangers where the molten salts exchange
thermal energy with the HeatTransfer Fluid (HTF).This
feature is not required if the HTF is also molten salt
 Pumps to move the molten salt between the cold
and hot tank(s)
During the charge mode of theTES, some hot HTF mass
flow leaving the solar field is sent to theTES where it
heats up the circulating molten salts from the cold tank(s)
to the hot tank(s). As a consequence, the cold molten salt
is heated up to 380-390°C and is stored in the hot tank(s)
for later use. During the discharge mode of theTES, the
operating principle is reversed and the molten salts stored
in the hot tank(s) are sent to the cold tank(s), passing
through the heat exchangers where they release thermal
energy to heat up the HTF. (See Figure 1 for an overview
of an oil HTF parabolic trough plant withTES).
Commonly in modern solar power tower plants molten
salt is used as the heat transfer medium (HTF), and it is
also used forTES. In this system molten salt, at 290°C,
is pumped out of a “cold” storage tank to the external
receiver on top of a tower where it is heated to 565°C
and delivered to a “hot” storage tank.The hot salt is then
Figure 1: Oil HTF ParabolicTrough Schematic
-390°C -375°C
380°C
290°C
Heat
exchanger
Thermal
energy
storage
Steam
generator
Steam
turbine
Condenser
Solar field
Source: ParabolicTrough Report 2014: Cost, Performance andThermal Storage

extracted for the generation of 552°C/ 126bar steam in
the steam generator.This principle of using the molten
salt as both the HTF andTES is also being demonstrated
in new parabolic trough plants, such as Enel’s Archimede
plant in Sicily.These higher operating temperatures are
favourable for increased thermal conversion efficiency,
and ultimately mean that more watt-hours are stored per
unit of fluid. (See Figure 2 for an overview of a molten salt
HTF parabolic trough plant withTES).
An Overview: Thermal Energy Storage
technologies
Although a wide range of energy storage solutions
have been proposed, only molten salts and synthetic
oils are seeing serious commercial use. However,
current R&D efforts have led to a number of
developments in energy storage, mainly spurred
on by the possibilities of plants operating at higher
temperatures. (See Figure 3 on the next page for an
overview of Thermal Energy Storage technologies).
Molten Salt
As of today, molten salt has been the only technology
implemented for extended utility-scale parabolic trough
and solar tower TES using a eutectic mixture of 60%
sodium nitrate and 40% potassium nitrate.
Very few single-component salts exist which have
melting point within the 300 to 500°C range, such
as sodium and potassium nitrates. While single-
component salts are more practical from an industrial
perspective, the scarcity of such salts limits their
application, and therefore, multi-component systems
are considered more practical for industrial applications.
To decrease the cost of molten salt TES systems, the
energy storage density of the fluid must either be
increased, or the storage temperature must be raised.
For the former to be achieved, new multi-component
formulations can be devised, or additives used.
Additives can also prevent solid freeze from occurring,
and ensure the solid-state salt remains as slush.
Phase Change Materials (PCM)
PCM, where a material stores and releases energy
when changing between its solid, liquid or gaseous
states, holds much promise. Current efforts to utilize
phase change materials are geared to using tried-and-
tested sodium and potassium nitrate eutectics and
leveraging the latent heat required to melt the solid salt
combination.
The world’s largest PCM pilot is in Carboneras, in the
Almeria region of Spain and is intended to show whether
PCM could become a viable alternative to molten
salt as a thermal storage medium for CSP, although
commercialization is likely to be several years away.
One challenge to address in PCM was the insulating
properties of the solid salt in the heat exchanger
pipes. Researchers say they were able to get around
this problem by adding fins to the exchange tube,
increasing the heat transfer surface area.
Concrete
The German Aerospace Center (DLR) is exploring the
performance, durability and cost of using solid, thermal
Figure 2: Molten Salt HTF ParabolicTrough Schematic
-550°C 535°C
550°C
290°C
Auxiliary
Heater
Thermal
energy
storage
Steam
generator
Steam
turbine
Condenser
Solar field

energy storage media (high-temperature concrete or)
in parabolic trough power plants using standard heat
transfer media that passes through pipes located within
the solid storage material. As previously stated, solid
media provide considerable saving potential, but also
have issues which include maintaining good contact
between the concrete and piping, and lower to the
heat transfer rates into and out of the solid medium.
At the Almeria Solar Platform in Southern Spain,
Ciemat and DLR performed initial testing to
demonstrate that both castable ceramics and high-
temperature concrete are suitable as solid media for
sensible heat storage systems. That said, the high-
temperature concrete would be preferable for its lower
costs, higher material strength, and easier handling as
well as longevity.
The modularity of concrete also constitutes a strong
incentive towards this material, also allowing for
perhaps better integration with the solar field and
power cycle
SolidTES materials
Other solid materials have been proposed and utilized
for TES, including rocks, pebbles, slag, sand and
manufactured ceramic spheres. However, different
minerals have varying thermal properties, so care must
be taken in their selection.
Benefits:
 Locally available
 Reduce transport and purchase costs.
 Cheap
 Applicable to Trough and Tower
 Heat up to 650°C
 Scalable
One challenge is that the casing containing the solid
TES is relatively sophisticated as stones, for example,
undergo thermal expansion, so very rigid walls are
required. This means the walls themselves will be
good thermal conductors, which could not only mean
leakage of heat outside the system but would corrupt
the heat stratification of the thermal storage unit. To
counter this, a thin layer of high-resistance concrete
on the inside of the casing, surrounded by a more
porous concrete for insulation of the system, then a
microporous insulator layer, a foam glass layer and
finally a concrete outer structure are required.
Saturated Steam
For storage, Direct Steam Generation (DSG) poses a
limitation, as opposed to molten salts and oil HTFs,
since a combination of sensible heat storage for
preheating and superheating, as well as latent heat
storage for evaporation, has to be used. This could,
however, be achieved using PCMs, or two independent
storage media. For sensible heat, the same storage
media can be used as for other HTFs, but for latent
heat, for example, sodium nitrate could be used, as
proposed by DLR.
There is also another type of heat storage, called
Ruths storage, which works as a steam accumulator
using pressurized liquid water. Hot steam enters the
Thermal Energy
Storage
Latent
Salts
Metal alloys
Sensible
Molten salt two tank
Packed bed thermocline
Concrete thermocline
Sand-shifting two tank
Thermochemical
Metal oxide
Sulfur cycles
Ammonia decomposition
Figure 3: Possible CSPThermal Energy StorageTechnologies

system and is then compressed, converting the steam
into superheated liquid water. However, research has
shown that this has a limited application for CSP as it is
expensive.
Thermochemical storage
Thermochemical TES is a promising new type of TES,
which permits more compact storage through greater
energy storage densities.
Thermochemical storage is based on a reversible
chemical reaction, which is energy demanding in one
direction and energy yielding in the reverse direction.
Benefits:
 Very high energy densities achievable
 Mitigates losses
 Extend dispatchability towards base-load power
generation
Unlike sensible and latent approaches to energy
storage, thermochemical systems can retain their
stored energy for almost unlimited time periods. If
thermochemical energy storage can be proven at
a reasonable scale within the few next years then
commercial deployment might be possible sometime
after 2020.
Graphite
Graphite can be heated to thousands of degrees, which
could greatly increase the efficiency of CSP compared
to the 560-570ºC of molten salts. Furthermore, only
a few suppliers can offer molten salt of the quality
required by the industry, which has increased costs to
the point where the storage material is a significant
expense for operators. Graphite, on the other hand, is
comparatively plentiful and cheap.
Benefits:
 High energy density
 High level of thermal inertia
 Good relationship between heat input and output
 Ease of working and shaping
 Relatively low cost and high availability
Weaknesses:
 It glows and oxidizes above 450°C. This can be
overcome by encasing the material in an oxygen-
free environment
 It’s too heavy, limiting scalability, particularly with
power towers
 Large amounts of piping needed
Ammonia and hydrogen
These alternative fuels are carbon-free and can be
produced from any energy source. CSP can produce
hydrogen and ammonia and then use the final product
as a fuel either to generate electricity, or act as a
replacement for gasoline or diesel to power vehicles.
For hydrogen, the heat generated by CSP could be
used with a solid oxide electrolyzer cell to split water at
temperatures up to 900°C with a higher efficiency than
conventional steam (alkaline) electrolysis at near-room
temperature.
Ammonia, meanwhile, has been used periodically
as a fuel for the last 60 years and it can be used in

current vehicle engines and fuel or gas power plants
with only minor modifications. Unlike hydrogen, it can
be distributed using existing gas and oil pipelines. It
also has an energy density two to four times that of
hydrogen.
Compressed air energy storage
Compressed air energy storage (CAES) has many
potential applications for energy storage beyond CSP,
and is not a form of TES. Essentially, power is used to
compress air, which is later released to drive a turbine.
Compression heats the air, while decompression
cools it, so heat exchangers and possibly heaters
may be required to ensure temperatures stay within
an acceptable range, which of course has a negative
impact on the thermal efficiency of the process.
In the only two operating commercially-viable,
largescale CAES facilities, this adiabatic process is
used to hold pressurized air in large underground
caverns. This places geographical constraints on the
method. More flexible approaches include those
proposed by SustainX Energy Storage Solutions and
LightSail Energy, which would store the compressed
air in tanks, making it less location-dependent than
existing geological systems. LightSail uses a fine water
spray to capture the heat of compression, which is
then used in the expansion phase of the process. The
company claims that the roundtrip thermal efficiency
is 90%, scalable up to 100 kW. LightSail has attracted
funding from backers such as Bill Gates and Peter Theil.
The SustainX system, meanwhile, compresses and
expands the gas within hydraulic cylinders, which
allows the controlled transfer of heat with the ambient
surroundings during compression and expansion.
The company has demonstrated thermal efficiencies
greater than 90% for both compression and expansion.
According to the company, a US DoE-funded
demonstration project is currently underway.
We hope that this guide to CSP storage potential for South Africa proved useful. With
the market in South Africa gaining momentum, a pipeline of CSP projects is emerging
- creating opportunities for companies to build a business in the region.
The guide was created in conjunction with the launch of CSPToday South Africa 2014,
taking place next February in Johannesburg. The event will show you how to reduce
CSP costs and risk through international experience and investor insight to prove your
competitiveness.
For more information please visit: www.csptoday.com/southafrica
or contact Brandon Paramo: +44 20 7422 4302
brandon@csptoday.com
+44 20 7422 4302
brandon@csptoday.com
Published in August 2013, CSPToday’s latest business intelligence reports – the Parabolic
Trough Report 2014: Cost, Performance andThermal Storage and the SolarTower
Report 2014: Cost, Performance andThermal Storage – respond to the most critical needs
of CSP stakeholders, representing 5 months of research and culminating in high-quality
data and analysis. At the core of these publications – which follow a mirrored structure
for comparative purposes – is the desire to firstly determine the true cost attributes and
performance outputs associated with each technology across 8 global markets based
upon the latest industry validated and localised cost data, and secondly, use these
techno-economic and inter-market benchmarking results to identify where the greatest
cost reduction and performance optimization gains can both be made and are required.
For more information on these publications and to view our complete Business
Intelligence Portfolio please visit www.csptoday.com/research

CSP Storage Insights for South Africa's Future

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Ähnlich wie CSP Storage Insights for South Africa's Future

Ähnlich wie CSP Storage Insights for South Africa's Future (20)

Mehr von David Williams

Mehr von David Williams (20)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

CSP Storage Insights for South Africa's Future