CSP Technology

June 2016

2

Company overview

Airlight Energy is a Swiss private company that supplies proprietary solar technologies

for large-scale production of electricity and thermal energy

R&D Facility in Biasca, Switzerland

3

A new paradigm in concentrating solar technologies

‘’Our 5’’ major innovations State of the Art

Air-based receiver

Operate up to 570°Non-polluting fluid

Oil/ molten salts receiver

Potentially polluting and expensive thermal fluid

Fiber-reinforced concrete structure

Durable, inexpensive, locally available material

Metallic structure

Expensive construction material

Film mirrors

Simple manufacturingLow cost per aperture area

Glass mirrors

ExpensiveFragile

ETFE pneumatic enclosure

No dust and low humidity insideTotal water recovery

No cover

Wasting of waterExposure to

environmental conditions

Packed-bed thermal energy storage

Inexpensive, locally available materialLow thermal losses

Oil/ molten salts storage

Potentially pollutingChemical instability

3

4

• Durable: 60 years lifetime

• Cheap construction material

• Locally available

• Increased stiffness, better focusing, greater concentration

• Extensive use of local workforce and resources due to in situ manufacturing

• Anti-seismic mechanism able to withstand extreme seismic events

• Few big pieces allow a simple modular construction

Pre-cast fiber-reinforced concrete structure: optimized beam with accurate shape design

5

TLC

TLE

TTT

ST

PT

FS

TTD+TTS

TTC

ComponentLxWxH Concrete volume Weight

[m] [m3] [t]TLC 17.54 x 1.35 x 2.36 7.87 19.7TLE 17.54 x 1.75 x 1.82 6.55 15.4TTT 12.13 x 1.10 x 5.34 21.13 53.0ST 3.48 x 2.31 x 0.73 1.93 5.0PT 1.50 x 0.97 x 1.25 0.61 1.5FS 5.50 x 4.38 x 0.3 8.47 20.7TTD / TTS 2.30 x 1.73 x 1.82 2.86 7.1TTC 2.30 x 1.35 x 2.36 2.86 7.8

Concrete elements

6

Concrete components manufacturing

7

Concrete components assembly

8

Dampers

Hanging rod

Hanging rod spherical joint

Hanged collector base

Collector tracking mechanismHanging rod sustain structure

Foundation

Collector wheels

Anti-seismic mechanism

9

The mirrors and receiver are protected inside a pneumatic enclosure with a controlled atmosphere, the external film is made of highly transparent ETFE

• ETFE is a widely available industrial product, no production bottlenecks

• Greater resistance than glass against scratching

• No dust and low humidity inside the enclosure

• Easy to wash and total recovery of washing and rain water

• Film assembled by ALE in Biasca and shipped in reels

Did you know that…

…ETFE (Ethylene tetrafluoroethylene) is a fluorine based plastic. After their useful life as pneumatic enclosure for CSP plants the ETFE foils can be recycled in the agricultural industry as greenhouse coverings

Pneumatic enclosure

Ait Baha plant, Morocco

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• Large aperture (9.7 m with 2 mirrors)

• High optical efficiency

• High concentration (60 suns average)

• Simple manufacturing

• Low cost per aperture area

• No production bottlenecks

Did you know that…

…the mirror foils are made from stretched polyethylene terephthalate (PET) a material commonly used in the packaging industry

Mirror foils are kept in shape by differential pressures, linear parabolic configuration

11

Technical developments – Pneumatic sleeves for membrane length adjustment

p1p2p3p4

psleeve,1

psleeve,2

psleeve,4

psleeve,3

mirror membranes

pneumatic sleeves

2 sleeves per beam for compensation of:• manufacturing tolerances among concrete beams• deflection within the beam 2*2*12*4 = 48*4 sleeve pressures to adjust on 212 m long collector

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Technical developments – Concentrator shape measurement system

px camarctan( / )n d fθ = ⋅

Receiver position in camera image (n in pixel) is a measure for angular deviation of on-axis ray from the focus:

Acceptance anglechanges withtransversal coordinateon concentrator:

i macc

cos( )arctan ar

θΦ −Φ =

-150

-100

-50

0

50

100

150

-150 450 1050 1650 2250 2850 3450 4050

targ

et in

ters

ectio

n [p

ixel

]

transversal coordinate [mm]

Nominal arcspline

arcspline composed of 4 circular arcs

parabola

upper receiver limit

lower receiver limit

solar band

2θacc

2aiΦm

Φr

camera

receiver

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Technical developments – Mechanical-optical model of arcsplineconcentrator

Objective: determine arcspline shape for given p and psleeve

Solution: force balances for• N arcs of mirror membrane:

• N – 1 arcs of support membranes:

• N arcs of pneumatic sleeves:

01

( )j

k j jk

T p p R=

= −∑

sleeve sleeve sleevesleeve2cos

TT p Rϕ

= =

1 sup,( )j j j jT p p R−= −

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Technical developments – Arcspline pressure regulation

p = 0.95pnominal p = 1.05pnominal

p2

psleeve,2

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Operation – Experimentally measured arcspline shapes after pressure adjustment

intercept factor: 87% 95%

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Operation – intercept factors within single beam (left) and overview of full collector (right)

LEFT TLC RIGHTB 12 B

0.81 A A 0.740.69 B 11 B 0.640.85 A A 0.670.84 B 10 B 0.750.84 A A 0.670.55 B 9 B 0.610.82 A A 0.710.72 B 8 B 0.780.80 A A 0.540.87 B 7 B 0.780.90 A A 0.790.85 B 6 B 0.780.78 A A 0.730.65 B 5 B 0.810.87 A A 0.950.77 B 4 B 0.850.89 A A 0.780.83 B 3 B 0.660.87 A A 0.740.87 B 2 B 0.750.81 A A 0.830.82 B 1 B 0.78

A A

80% avg 74%0.0 0.2 0.4 0.6 0.8 1.0

123456789

101112131415161718

intercept factor [-]

axia

l pos

ition

[m]

Intercept factors on TLC 4 RIGHT

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• Use of conventional materials and no need for high-tech coatings or vacuum insulation

• Easy to manufacture

• Inexpensive and non-polluting thermal fluid, easy to integrate in existing processes

• High performance receiver with low emissivity

• Minimization of piping thanks to inlet and outlet on the same side

• Secondary trumpet mirror for spillage minimization and optical re-concentration

Air is used in a specifically developed receiver with shields insulations

Multi-shield radiative insulation

Linear secondary

concentrator (water-cooled) Glass

Cold air duct

Spiraltube coil cavity(chrysalis)

Microporousinsulation

Hot air duct

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Challenges

• Low volumetric heat capacity large volume flows leading to significant pressure drop

• Low thermal conductivity large active surface area needed for convection heat transfer

Advantages

• No costs and environmental issues• No operating temperature limit and phase

change in the considered temperature range• Near-ambient operating pressure• Allows for the use of inexpensive TES solutions

(pebble stone packed bed)• Straightforward to integrate in thermal

processes where heating is attained conventionally by combustion

- High primary concentration (Cgeom = 70xgeometric)- High optical efficiency (hopt= 0.87)- Split-trough design allowing for greater re-concentration

High-efficiency secondary (lineartrumpet)Cgeom = 100x hopt, sec = 0.98

High operation temperaturespossible

However, current HTFi) have temperature limitations (400 °C with thermal oil)ii) have a complex implementation (molten salts)iii) are difficult to be used in a trough configuration (direct steam)

Air as HTF

High-temperature air as HTF

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Straight pipe:

𝐿𝐿

𝐷𝐷

Array of straight tubes:

𝐿𝐿𝑁𝑁

𝐷𝐷

Array of cross-flow pipes in parallel flow arrangement:

𝑙𝑙

𝐿𝐿

𝐷𝐷

𝐷𝐷 𝑑𝑑

𝑁𝑁

Fundamental limitation of linear tubular receivers:

𝐷𝐷 ↑⇒ Δ𝑝𝑝 ↓,𝑁𝑁𝑁𝑁 ↓⇒ Δ𝑇𝑇 ↑

It would be ideal to control pressure drop and temperature difference independently

• Branching flow up in multiple parallel tubes yields 1 additional parameter

• Arranging them in cross-flow configuration yields 2 additional design parameters

Cross-flow design

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�̇�𝑞𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠,𝑠𝑠𝑎𝑎𝑠𝑠

�̇�𝑞𝑠𝑠𝑟𝑟𝑠𝑠𝑠𝑠𝑟𝑟,𝑐𝑐𝑠𝑠𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐

�̇�𝑞𝑐𝑐𝑠𝑠𝑐𝑐𝑐𝑐�̇�𝑞𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠,𝑠𝑠𝑟𝑟𝑟𝑟𝑠𝑠

�̇�𝑞𝑐𝑐𝑠𝑠𝑐𝑐𝑟𝑟,𝑤𝑤𝑐𝑐𝑐𝑐

�̇�𝑞𝑐𝑐𝑠𝑠𝑐𝑐𝑟𝑟,𝑤𝑤𝑠𝑠𝑠𝑠𝑠𝑠

�̇�𝑞𝑠𝑠𝑟𝑟𝑠𝑠𝑠𝑠𝑟𝑟,𝑐𝑐𝑡𝑡𝑎𝑎𝑟𝑟

�̇�𝑞𝐻𝐻𝐻𝐻𝐻𝐻𝑇𝑇

�̇�𝑚𝐻𝐻𝐻𝐻𝐻𝐻

Spiral tube coil cavity (“chrysalis”)

Advantages

• Cylindrical cavity → high apparent absorptivity• Lowest temperature at cavity opening → lower apparent

emissivity• Secondary flow in coil → high h and low ΔT • Low cost

The air "chrysalis"

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System modeled simultaneously from different perspectives:

• Optical design (PREC-ETHZ)• Cavity model

• Semi-analytical model of cavity coupled with ray-tracing (PREC-ETHZ)

• CFD model (ICIMSI-SUPSI)• Receiver insulation (ICIMSI-SUPSI)• Entire receiver airflow modeling (ICIMSI-SUPSI)

System models

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0

100

200

300

400

500

600

700

800

900

1000

10:19:12 11:31:12 12:43:12 13:55:12 15:07:12

DNI [W/m2] T Chrysalis 1 [°C] T Chrysalis 2 [°C] T Chrysalis 3 [°C]

T Chrysalis 4 [°C] T Chrysalis 5 [°C] T Runback 1 [°C] T Runback 2 [°C]

On-sun recevier prototipe test

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Assembled receivers

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0

50

100

150

200

250

300

350

400

0%

10%

20%

30%

40%

50%

60%

70%

80%

-17.5 -12.5 -7.5 -2.5 2.5 7.5 12.5 17.5 22.5 27.5 32.5 37.5 42.5 47.5 52.5

Year

ly D

NI [

kWh/

m2]

Colle

ctor

effi

cien

cy

Skew angle [deg]

Yearly DNI

Collcetor eff.

Collector efficiency 𝜂𝜂𝑐𝑐𝑠𝑠𝑠𝑠 = 𝜂𝜂𝑠𝑠𝑜𝑜𝑐𝑐 � 𝜂𝜂𝑐𝑐𝑡 as a function of incoming radiation skew angle. Yearly DNI as a function of the skew range for Ait-Baha, Morocco is also shown (N-S orientation of collector axis.)

Receiver performance

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• Continuous production, compensating intermittency of sun availability

• Low thermal losses in the range of 1% every 24h

• Highly competitive production costs

• Robust, fail-safe technology

• Locally available construction materials

• Non-polluting, non-corrosive requirements

• Simple manufacturing

• No maintenance required

Did you know that…

…this is a simple, proven and effective technology first patented in 1929

Detail of Ait-Baha pilot plant, Morocco

Simple storage using a closed concrete container filled with stone gravel

11

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Packed-bed thermal energy storage

R&D Facility in Biasca, Switzerland

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Packed-bed thermal energy storage

Ait Baha Plant, Morocco

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First CSP booster: the solar field feeds 3MWth to an existing 12MWel ORC turbine

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Schematic example for CSP plant, Ait-Baha, Morocco

CSP Booster plant layout and integration with existing process

13

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More than 50% of the value of the project is generated locally thanks to the use of locally available materials and local manufacturing.

Local content generation

For the construction phase of the Ait-Baha project approx. 25 local workmen were employed.

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Technology characterized by lower tecnical barriers and higher local content

Level of barriers for local manufacturing of CSP components (in MENA area)

State-of-the-art

CSP technologyAirlight Energy CSP technology

Civil works Low Low

EPC Medium Medium

Assembly Low Very low: precast assembly

ReceiverHigh

Low: locally available materials,

on-site assembly

Flat glass for mirrors High Not used: plastic foil mirrors (no glass)

Mirror (flat) High Not used: plastic foil mirrors (no glass)

Mirror (parabolic) High Not used: plastic foil mirrors (no glass)

Mounting structure Low Low

HTF High Not used: air as thermal vector

Connecting piping Medium Medium

Storage system Medium Low

Electronic equipment Low Low

Source: ESMAP, World Bank; Airlight Energy estimates

Airlight Energy has lowered level of barriers

preventing local manufacturing of CSP

components and could generate up to 60% of

value locally

For the purpose of this comparison the total investment cost does NOT include: EPC costs, power block, balance of plant (assumed to be the same for both technologies and therefore not considered for local content assessment

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CSP as standalone application or to boost energy intensive industrial processes

*Direct Normal Irradiance

DNI*

Standalone

>250 MW th, 50-100 MW el

Electricity generation Heat-dependent processes

Combined cycle booster

20-300 MW th

Coal plant integrated

20-300 MW th

Waste heat recovery

10-100 MW th, 3-30 MW el

Industrial process heat

3-100 MW th

Water desalination

50-300 MW th

Biofuel production / biomass gasification

10-100 MW th

>2’

000

kWh/

m2

1’60

0-2

’000

kWh/

m2

1’20

0-1

’600

kWh/

m2

High

Low

Thank Youandrea.pedretti@airlightenergy.com