Session 5: CSP Overview - 1Agenda

• Discussion of Homework• Overview• Heat Engines • Storage• Trough Systems• Homework Assignment

Learning Objectives

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Students should be able to

• Compare CSP vs. PV in meeting customer needs • Describe the three basic CSP approaches and their status• Explain how steam, gas turbine and Stirling engines work• Draw a schematic of a power tower system with thermal storage• Modify the above schematic to incorporate a hybrid gas turbine• Calculate the cost-of-electricity for a CSP system• Compare typical CSP and PV plant supply chains• Give examples of current CSP Projects and describe them• Predict how CSP technologies will develop in the future• Conceptually define a CSP system based on given requirements

Example CSP Plants

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So What’s New?

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Dish/Steam Irrigation System circa 1900 at Broadway and the railroad tracks in Tempe, Arizona

Desirable Grid Power• High Quality

• Harmonics• Power Factor

• Available

• Dispatchable

• Continuous

• Low Cost

• Renewable (Gov. Reqt.)

5

Solar Plant Design Considerations

Solar PlantDesign

Fossil Fuel (?)

Solar Input (Variability)

Ambient Conditions

Water

Electrical Power

Design Requirements Risk

6

Basic CSP Concept

Receiver/Heat Engine

Low-level Solar Energy

CONCENTRATOR

Generator

HighTemperatureEnergy

Low TemperatureHeat Sink

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Heat Engine Efficiency• Engines operate on the 2T Principle

• Carnot efficiency

• Engines are limited by the Carnot efficiency

• Goal is to maximize efficiency to reduce collector field size

• At some point, the cost of higher efficiency increases overall cost

Engine W,UsefulWork

Qout at Tcold

Qin at Thot

η = Thot – Tcold = 1 – Tcold Thot Thot

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Power Cycle Efficiencies

Source: Summary Report for Concentrating Solar Power Thermal Storage Workshop, NREL/TP-5500-52134 August 2011

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United States Solar Market

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Source: SES Presentation toAZ/NV SAE, 2005

International Solar Market

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Source: SES Presentation toAZ/NV SAE, 2005

Basic CSP Concept

Receiver/Heat Engine

Low-level Solar Energy

CONCENTRATOR

Generator

HighTemperatureEnergy

Low TemperatureHeat Sink

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CSP System Elements

Concentrator Receiver Heat Engine Generator

BalanceOf

Plant

GRID13

CSP System Elements

Concentrator Receiver Heat Engine Generator

BalanceOf

PlantGRID

• Trough• Heliostats

(Power Tower)• Dish

• Linear• Cavity

• Tubular• Volumetric

• Rankine• Steam• Organic

• Gas Turbine• Stirling• Combined• Hybrid (fossil fuel)

• Synchronous• Induction

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Types of Concentrating Solar Power Systems

Source: Powerpoint Presentation, Muller-Steinhagen et al., Concentrating Solar Power: A Vision for Sustainable Electricity Generation, Institute for Technical Thermodynamics, German Aerospace Center, Stuttgart (DLR)

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Types of Concentrating Solar Power Systems

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Types of CSP Systems

• Single-axis tracking• Parabolic troughs• Moderate temperature• Central engine• Moderate efficiency

• Dual-axis tracking• Heliostats• Flat facets• High temperature• Central engine• Higher efficiency

• Dual-axis tracking• Parabolic facets• High temperature• Distributed engines• Highest efficiency

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Types of Receivers

• Parabolic trough• Moderate temperature

• Power Tower• Dish• Gas and liquid fluid• High temperature• Convection losses

• Power Tower• Dish• Quartz window• Gas working fluid• High temperature• Low convection

losses

Linear Receiver Cavity ReceiverVolumetricTubular

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Cavity Receiver

Source: SES Presentation toAZ/NV SAE, 2005

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Volumetric Receiver

Source: Powerpoint Presentation, Muller-Steinhagen et al., Concentrating Solar Power: A Vision for Sustainable Electricity Generation, Institute for Technical Thermodynamics, German Aerospace Center, Stuttgart (DLR)

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Heat Engines

Steam (Rankine) Cycle(30-35% efficient)

Gas Turbine Cycle(30-40% efficient)

Stirling Cycle(40-45% efficient)

Trough PowerTower

DishPowerTower

Dish

WetCooling

DryCooling

NoCooling

DryCooling

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Steam (Rankine) Cycle

Heater

Turbine

Condenser

Cooler

Ambient Air

P

Pump GenGen

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Gas Turbine (Brayton) Cycle

Combustor

Turbine

Ambient Air

Compressor GenGen

Ambient Air

Qin from fuel

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Semi-Closed Brayton Cycle

Heater

Turbine

Ambient Air

Compressor GenGen

Ambient Air

Qin

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Recuperated Semi-Closed Brayton

Ambient Air

Recuperator

Turbine

Ambient Air

Compressor GenGen

Qin

Heater

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Stirling Engine is Closer to Carnot

• In Rankine system, Thot varies, butTcold is relatively constant

• In Brayton system, Thot varies and Tcold

varies

• In Stirling system, Thot and Tcold approach constant values

For expansion and compression processes:

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Source: SES Presentationto AZ/NV SAE, 2005

CSP System Elements

Concentrator Receiver Heat Engine Generator

BalanceOf

Plant

GRID28

CSP System Elements

Concentrator Receiver Heat Engine Generator

BalanceOf

Plant

GRID

Losses Losses Losses

Losses

Losses

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CSP System Elements

Concentrator Receiver Heat Engine Generator

BalanceOf

Plant

GRID

Losses Losses Losses

Losses

Losses

ηsys = ηconc ηrec ηeng ηgen ηBOP Sunlight-to-Busbar Efficiency

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CSP Advantage: Storage

Concentrator Receiver Heat Engine Generator

BalanceOf

Plant

GRID

Storage

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Storage Advantages

• Extends operation during peak demand hours• Maintains output during transient clouds• Provides power on-demand (dispatchable)

Source: NREL website

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Trough Plant Components

C

A

B

Source: NREL

Source: NREL

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Power Tower Plant Components

A

B

C

Source: NREL

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Dish/Engine Plant Components

A

B

C

Source: SES Presentationto AZ/NV SAE, 2005

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Levelized Cost of Electricity Comparison

Source: PowerPoint presentation, Brett Prior, November 2011, GTM Research, www.greentechmedia.com/article/read/can-solar-thermal-be-cheaper-than-pv/

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Trough CSP

SEGS Units

• Solar Electric Generating Systems

• Mohave Desert, Built 1984-1990

• Trough/Steam/Evap. Cooling

• Up to 25% Output from Natural Gas

• 9 Plants: 14, 30, 80 MWe• 354 MWe Total Output

Aerial view of five (SEGS III – VII), 30-MW SEGS solar plants

Source: NREL

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SEGS VI: 30 MWe• Kramer Junction• Start-up: 1988• Field Supply Temp: 390

degrees Celsius

• Field Size: 188,000 m2

• Luz International• KJC Operating Company

Figure 1.1. Parabolic troughs at a 30 MWe (net) SEGS plant in Kramer Junction, CAJanuary 2006 • Angela M. Patnode • “Simulation and Performance Evaluation of Parabolic Trough Solar Power Plants”

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Solar Field Design• Single-axis tracking collector troughs• Float-formed, parabolic-curved mirrors• Heat collection element

(HCE) runs through focal line

• Thermal energy into heat transfer fluid (HTF)

• Trough axes north-south• Track east to west

SOURCE: January 2006 • Angela M. Patnode • “Simulation and Performance Evaluation of Parabolic Trough Solar Power Plants”

Solar Collector Assembly (SCA)

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Figure 2.1. Layout of the SEGS VI solar trough field. The superimposed arrows indicate the direction of heat transfer fluid flow. (Photo source: KJC Operating Company, 2005)

January 2006 • Angela M. Patnode • “Simulation and Performance Evaluation of Parabolic Trough Solar Power Plants”

SEGS VI Layout

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January 2006 • Angela M. Patnode • “Simulation and Performance Evaluation of

Parabolic Trough Solar Power Plants”

Parabolic Trough Collector End of Row

Flexible Joints

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Figure 2.3. Schematic of a Solar Collector Assembly (SCA) (Source: Stuetzle, 2002)January 2006 • Angela M. Patnode • “Simulation and Performance Evaluation of

Parabolic Trough Solar Power Plants”

Overall Trough Collector Design

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Heat Collection Element (HCE)

• Steel absorber tube 70 mm in diameter• Coated with either black chrome or cermet• Vacuum between absorber and glass envelope

to limit heat loss

Photo source:Solel UVAC, 2004

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Heat Transfer Fluid (HTF) • Synthetic oil -- mixture of biphenyl and diphenyl

oxide (Therminol VP-1) • Receives solar energy and transfers it to steam

cycle in a three-stage boiler (reheater not shown)

Solar Field

Superheater

Steam Generator

Pre-heaterPump

Steam Cycle/Generator

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Simplified Overall Schematic

Source:G. Cohen, Solargenix Energypresentation to IEEE RenewableEnergy, Las Vegas, May 16, 2006

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Transfer of HTF Energy to Steam Plant

Source: January 2006 • Angela M. Patnode • “Simulation and Performance Evaluation of Parabolic Trough Solar Power Plants”

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Figure 2.1. Layout of the SEGS VI solar trough field. The superimposed arrows indicate the direction of heat transfer fluid flow. (Photo source: KJC Operating

Company, 2005)Source: January 2006 • Angela M. Patnode • “Simulation and Performance Evaluation of Parabolic Trough Solar Power Plants”

SEGS VI Layout

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SEGS VI: Solar Field Layout

Adapted from “Simulation and Performance Evaluation of Parabolic Trough Solar Power Plants” Jan 2006,

Angela M. Patnode

Steam Heat

Exchangers

Row of 8 SCAs

Row of 8 SCAs

Row of 8 SCAs

Row of 8 SCAs

East Field(25 Parallel Loops)

Row of 8 SCAs

Row of 8 SCAs

Row of 8 SCAs

Row of 8 SCAs

West Field(25 Parallel Loops)

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SEGS VI Performance

Source: January 2006 • Angela M. Patnode • “Simulation and Performance Evaluation of Parabolic Trough Solar Power Plants”

June 21, 2004 December 21, 2004

Why is Solar Input so low in winter?

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Trough Plants are Single Axis Tracking

Source: January 2006 • Angela M. Patnode • “Simulation and Performance Evaluation of Parabolic Trough Solar Power Plants”

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SEGS VI Performance for 1998

Source: An Overview of the Kramer Junction SEGS Recent Performance Scott Frier, KJC OPERATING COMPANY 1999 Parabolic Trough Workshop August 16, 1999 Ontario, California

• Average Daily Normal Insolation = 7.913 kWh/m2/day

• Percentage measured = 106.3 %

• Solar DNI Input = 577,200 MWht

• Gross Electrical Output from Solar Production = 67,358 MWhe

• Station Use = 11.7% of Gross Energy

• Net Electrical Output from Solar Production = 59,477 MWhe

• Overall Efficiency = Net Electrical Out/Solar DNI In = 10.3%

• Solar Capacity Factor = 22.6%

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Saguaro (near Marana) Also uses parabolic trough collectors to heat up a

“thermal oil heat transfer” fluid, up to 288 °C Instead of steam, the Rankine cycle uses an organic

liquid (pentane) that can boil at a lower temperature 1 MW capacity No storage capability Went online in 2006 Open for tours on the last Wednesday of the month

(http://www.aps.com/_files/renewable/SP017SaguaroSolarTrough.pdf)

Source: Arizona Public Service

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Saguaro Diagram

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Saguaro “Power Block”

Homework for Session 6

• Review slides for Sessions 6 and 7• Select a current CSP Plant and describe it

• Two-pages• Professional quality• Be prepared to discuss in class