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ECEN 5007 SOLAR THERMAL POWER PLANTS

Lecture 10: Design and Optimization of CSTP PlantsJuly 31, 2012

Manuel A. Silva, Dr.Ing. - Manuel J. Blanco, Ph.D., Dr.Ing.

TWTH 17:00-19:30 - Class Room: ECCR 1B55

Office Hours: TWTH 15:30-16:30

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5 Optimization of plant configuration

THE DESIGN PROCESS

Optimization ofCSTP plant

The Need ofSimulations

The Design Process

Advanced DesignMethods

Classic DesignCriteria

Advanced DesignCriteria

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High number of parameters

q Optical, thermal, hydraulic properties of each component,q Efficiency curves, parasitic consumptions, etcq Size and cost of each componentComplex physical models

q Probabilistic (Monte-Carlo) or convolute optic models,q Thermo-hydraulic models,q High variability of input parameters (meteorological data).Operational strategies

q Defocusing strategy in the solar field,q Backup boiler usage,q Thermal storage system usage,q Start-Up and Cool-down strategies,q Production optimization with respect to economic criteria

Optimization of CSTP plants

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Benefits / Uses of simulation:

q Estimating the final cost of energy from technological data.q Comparing amongst different technologies without the need to build everything.q Setting the next steps in R&D in order to reach a competitive technology.

Where shall we put the effort?q Translating a technological improvement into the final impact in the energy price.q Finding technological niches.Drawbacks / Dangers of simulation:

q Self-fulfilling prophecies.q Shape reality according to the model restrictions.q

Ignoring the accuracy of the model (hypothesis).


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Key decisions:

q Solar technologyq Nominal electric powerq Thermal storageq HybridizationDesign parameters :

q Design Point: Instant of time and conditions for which the plant is designed to produceits nominal electric power.

q Solar multiple: Ratio of actual solar field size to the minimum size required to run aturbine at full capacity at design point.

q Capacity factor: Ratio of the actual output of a power plant over a period of time andits output if it had operated at full nameplate capacity the entire time


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Classic design criteria


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Design point

q Definition Instant of time (day of the year, and time of the

day) and external conditions for which the CSTP

plant is assumed to operate at nominal conditions.

q Information Needed DNI (850 950 W/m2) Date and time - Sun position - Optical efficiency

(cosine factor, shadowing, and blocking)

Ambient temperature (25 30 C) Relative humidity


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Solar multiple

Available Solar Power

Solar Field Thermal Power

Gross Electric Power

Defocused Power

SM< 1

SM= 1

SM> 1

~ 1.2

SM> 1

~ 1.5

SM> 1

~ 2

PowerBlock

SolarField

Q

Q

Nominalthermal,

Nominalthermal,

SM =

q Definition Ratio of actual solar field size to the minimum size required to run a turbine at

full capacity at design point.


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q Definition Ratio of the actual output of a power plant over a period of time and its output

if it had operated at full nameplate capacity the entire time.

Capacity factor

h8760ctorCapacityFa

Nominal

=

werElectricPo

ergyElectricEnYear

Online: 37%

Offline: 63%


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LEC (Levelized Electricity Cost)

q Definition 1 Ratio of the total cost associated with

building and operating a CSTP plant and

the energy produced by that plant overits lifetime.

q Definition 2 Present price at which the electricity

produced by a CSTP plant must be sell sothat the Net Present Value associated to theCSTP investment project is zero.

UsefulLifeAnnualElectric

UsefulLifeAnnual

YearsE

YearsOPEXCAPEXLEC

+

= 0%

10%

20%

30%

40%

50%60%

70%

80%

90%

100%

2 01 0 2 01 1 2 01 2 2 01 3 2 01 4 2 01 5 2 01 6 2 01 7 2 01 8 2 01 9 2 02 0

LCOE

Year

EvolutionoftheLCOEforthedifferentCSTPtechnologies

ParabolicTrough(Max.) ParabolicTrough(Min.) Fresnel(Max.)

Fr esne l(Min.) Po we rTowe r( Max .) Po we rTowe r( Min .)

Dish-Engine(Max.) Dish-Engine(Min.)


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CONCEPTDESIGN

TECHNOLOGY HTF

TESHYBRIDIZATION

POWERBLOCK

BOUNDARYCONDITIONS

DESIGN POINT

q Location and MDYq CSTP Technology

PT/ Tower / Working fluid

q Thermal Storage System (TES)q Hybridizationq Nominal Powerq Solar Multiple

Main characteristics


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OPTIMIZATION

DESIGN POINT

RECEIVERSOLAR FIELD

SIZE & LAYOUTCONCENTRATING

TECHNOLOGY

OPTIMIZED DESIGN

PERFORMANCEEFFICIENCY

MATRIX

CRITERIA:CAPACITY FACTOR

LEC

q Central Receiver Heliostats Type Number Layout Receiver Type Tilt angle Tower

q Parabolic Trough PT Type Loop Number of Loops Layout (sub-fields) Heat Collection Element

Solar field


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IS ITOK?

EFFICIENCY MATRIXEFF= F (AZ,EL)

DETAILEDMETEOROLOGICAL

DATA (TMY)

THERMAL STORAGE

TURBINE

DETAILED ANNUALEFFICIENCIES

LEC CALCULATION

FINAL DESIGNCONCEPT

RE-CONSIDERATION

YES NO

qAnnual Simulation Very Simple Models

(Efficiency Matrix)

Not a design parameter Checking the adecuation of the

design

Example: Luzergy, Solergy :


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Advanced Criteria

q Four main subsystems: Solar radiation collection and concentration Thermal conversion of the solar energy Electric conversion of the thermal energy Thermal storage

q Desirable technical goals: Minimize optical losses Minimize thermal losses Maximize power block efficiency Minimize TES thermal losses Optimize plant operation

q Main goal: optimize economic performance Trade-off between efficiency and cost


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mxCET CET,mx

q The design of the different sub-systems Is made separately for each one. Is optimized just for a unique design point. Is checked or adapted slightly for a few off-design points.

q The CSTP plant actually Works as a whole (the different systems are interrelated). Works very often in off-design conditions.

q The maximum efficiency at design point of each of the sub-systems does not guarantee the maximum efficiency of thewhole plant.

Holistic Approach


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q Which is the actual goal of a commercial CSTP plant? Producing the maximum possible energy (Capacity Factor). Producing the energy at the lowest price (LCOE). Earn the maximum money...

qActual Goal: Maximum economic efficiency/profitability (cost effective). Usually working in off-design conditions.

q The optimum energy efficiency of the CSTP plant does notguarantee the optimum economic efficiency of the project.

The main goal is the maximum economic efficiency.Depends not only on plant cost and performance, but alsoon external factors..

Holistic Approach


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q The profitability of a CSTP plant strongly depends on itsenvironment:

Legal Framework Market system (premium, PPAs) Financing (Bankability)

q Design should be adapted to the feasible and availablebusiness models in each situation.

New design criteria


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California, 2000

Dispatchability:

q Thermal Energy Storageq Hybridization


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INDICATORS USED FOR TECHNOLOGY ASSESSMENTCriteria Indicator Comments

Production costs LCOE ($kWhe) Levelized cost of electricity.

Capital costs CAPEX ($MWe) Investment costs of the project.

O&M costs OPEX ($MWhe) Operation and maintenance cost.

Financial return Modified IRR (%), Specific NPVModified Internal Rate of Return,Specific Net Present Value.

Financial risk MIRR

Standard deviation of the Modified IRR.

Cost reductionpotential LCOE potential reduction (%) Expected LCOE reduction

Plant efficiency Solar-to-electric net efficiency (%) Mean annual net efficiency of the plant.

MaturityInstalled capacity worldwide (GW), No. ofequivalent operating hours

Commercial plants in operationworldwide.

Developmentperspectives Project pipeline worldwide (GW) Commercial plants projects worldwide.

Local marketcompetitiveness

Share of local manufacturing in totalinvestment costs (%) From local suppliers information

Land use Land needed per energy produced (km2/MWh) Land occupied by the whole installation

Water demandWater consumption per energy produced(m3/MWh)

Consumption for cycle cooling andmirror cleaning.


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q The way a CSTP plant is operated.q Routine operation definition:

Start-up and cool-down procedures DNI, Temperatures, mass flows(solar field, TES, PB) Recirculation while Start-Up / Cool-Down

Control Systems Maintenance/cleaning planning, etc

q This allow to: Reach a stable production on varying conditions. Produce energy at optimum conditions (highest possible efficiency).

At full load At partial loads

Schedule the production, up to some limits


Operationalstrategies

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q They severely affect the performance of the CSTP plant in the

long term.

q They affect the whole system:Energetic efficiency of each directly related sub-system.Efficiency/performance of the rest of the sub-systems.

E.g. The operating temperature of the solar fielddetermines the efficiency of the power block.

Dispatchability.Economic profitability.

q Main fields:Solar field operation.Thermal Energy Storage usage.Hybridization usage.

Operationalstrategies


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Advanced Methods Probabilistic approach:

q Uncertainties in simulation parametersq Deterministic Vs. Stochastic simulationsq Probabilistic distributions of the results


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q The design of a CSTP plant is a complex exercise.Careful consideration should be given to the solar

resource assessment, investment costs estimates, andtechnology performance estimates.

Software tools are needed to assist in different stagesof the design process, from the definition of the designmeteorological year, to the energy yield estimates of theCSTP plant.

In most cases trade-off are needed between energyefficiency and cost.


Conclusions

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Overview of available computer tools

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SolTrace:

Monte Carlo ray tracer Optical simulation program of a great variety of solar concentrating systems Proprietary, non-flexible, non-expandable

1 Optical analysis: SOLTRACE

OVERVIEW OF AVAILABLE COMPUTER TOOLS

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Tonatiuh:

Monte Carlo ray tracer Optical simulation program of a great variety of solar concentrating systems Open source, easy to use, expand, adapt, and maintain

1 Optical analysis: TONATIUH


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C++ object oriented Monte CarloRay Tracer

Plug-in architecture. Operating system independent State-of-the-art GUI Open source



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Tonatiuh:

Available at: http://code.google.com/p/tonatiuh/ Web infrastructure support for developers and users

Developers blog

Users groupMain web site

Moderator

Video channel



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Power at the target

DifferencefromT

onatiuhs

estimate(%)

Parabolic trough

TonatiuhSolTrace


1 Optical analysis: comparison between SOLTRACE and TONATIUH

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Frequency distribution of photons

TonatiuhSolTrace

Parabolic trough



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10 20 50 100 200 500 1000

0

50

100

Thousand rays

Maximum flux density

DifferencefromT

onatiuh

sestimate(%)

TonatiuhSolTrace


Parabolic trough


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Parabolic Trough Incident Angle Modifier

Sun Elevation: 5

1 Optical analysis: usage example with TONATIUH


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Sun Elevation: 10



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Sun Elevation: 20



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Sun Elevation: 30



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Sun Elevation: 40



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Sun Elevation: 50



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Sun Elevation: 60



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Sun Elevation: 70



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Sun Elevation: 80



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Sun Elevation: 90




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DELSOL / WINDELSOL:

CRS field design Cone-optics and convolution approach, simplified economic optimization

2 Solar field optimization and analysis: DelSol/WinDelSol


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New Solar Plant Optimization Code (NSPOC):

CRS field design and analysis Combination of optimization algorithms Cone-optics and convolution approach, www.nspoc.com

2 Solar field optimization and analysis: NSPOC


Fig. 3. Radiation flux maps for external and cavity receivers

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HOpS: the Heliostat Optical Simulation

Open-source tool just released by Google to analyze the optical behavior of heliostat fields overthe course of a year with ten-minute granularity.

2 Solar field analysis: HOpS


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System Advisor Model:

PT CRS LFR Parabolic dishes PV & others

3 Plant performance: SAM


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Sensitivity analysis of operational strategies User friendly



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Integrated financial analysis Integrated probabilistic modeling Specialized in the USA regulative framework



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EOS (goddess of the dawn):

Developed by GTER Parabolic troughs Thermal oil, DSG, (molten salts) Physical model of the solar field Empirical model of the power cycle Quasi-stationary, 10-min step by default Detailed calculation of mass flows and

temperatures

3 Plant performance: EOS


0

50

100

150

200

250

300

350

400

450

TemperaturadelHTF[C]

TLE(TiempoLocalEstandar)

En tra da la zos Sa lid a lazos Retorn ocamp o Impu lsin ca mpo

-600

-400

-200

0

200

400

600

800

Caudalde

HTF[Kg/s]

TLE(TiempoLocalEst andar)

CampoSolar CalderaGN Sistemadealmacenamiento Generadordevapor

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Optical analysis Helios Mirval

Optimization andanalysis HFLCAL

Plant performance SimulCET Solergy TRNSYS based

codes

3 Other codes


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ecen 5007 - lecture 10

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