Concentrated Solar Power (CSP)

A World Energy Solution

NATIONAL BOARD

MEMBERS TECHNICAL PROGRAM

October 7, 2009

Steve Torkildson, P.E.Principal Engineer

Concentrated Solar Power (CSP)Clean, sustainable energy

Sierra 5 MweLancaster, CA

PS-10 11MWeSpain

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Concentrated Solar Power (CSP)

• The concept:

– Concentrating solar radiation creates the temperatures needed to drive a thermodynamic cycle

– Concentrating solar energy provides a endlessly renewable, low-cost and non-polluting means of generating electricity for the entire cost and non-polluting means of generating electricity for the entire world.

– Solar electricity production can meet the world’s demand for energy far into the future

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Concentrated Solar Power (CSP)

• The Need:

– Increasing electric power demand

• Worldwide electrical consumption will double by 2040

– Dwindling fossil reserves– Dwindling fossil reserves

– Reduction of carbon emissions

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Current world energy consumption is 15 terawatts

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By 2050, world energy consumption is estimated to

be 50 terawatts

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• The Resource: “Our Sun”

– FACT

• The amount of solar energy striking the earth’s surface in a single hour exceeds the amount of energy consumed worldwide in a calendar year

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Solar provides more than 1000 times the energy

required by current demands

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• The Resource: “Our Sun”

– FACT

• the amount of solar energy reaching earth yearly

represents ~ 2 times the energy that can, or will be

developed by all of the earth’s non-renewable

resources including coal, oil, gas and uranium

reserves.reserves.

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Total Non-Solar Energy Reserves

Annual Solar Energy

To generate all of the current US energy demand

requires a tract of land 243 miles square

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• Solar insolation is the direct measure of solar radiation received on a surface in a defined amount of time

– expressed as average irradiance in W/m2

– often expressed as ‘suns’ with 1 sun = 1,000 W/m2

• The average direct normal solar radiation in the

Solar Insolation

• The average direct normal solar radiation in the earth’s upper atmosphere is ~ 1,366 W/m2 which is attenuated in the atmosphere to ~ 1,000 W/m2

– Factors influencing DNI (Direct Normal Incidence) are:

» solar elevation angle (cosine effect)

» cloud cover

» dust & moisture11

Daily Solar Energy Delivery

8000

10000

12000

delivere

d,

kW

/m2

Winter

Summer

0

2000

4000

6000

6 8 10 12 14 16 18 20

Q-d

elivere

d,

kW

/m

Time of day

Winter

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Thin Film PV/CPVPhotovoltaics

Solar Energy

Direct Conversion - Current Approaches

Solar Energy

30¢ kWh30¢ kWh30¢ kWh30¢ kWh

21¢ kWh

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Note: Cost figures given may not reflect current market. Producers continue to innovate and reduce costs.

Power TowerSolar Thermal Troughs

Solar Energy

Concentration Methods

A variety of approaches demonstrated to date use arrays of hundreds or thousands of heliostats (mirrors) to concentrate the sun’s rays to heat a transfer medium between 500oF and 1,800oF

Power TowerSolar Thermal Troughs

16¢ kWh16¢ kWh 13¢ kWh13¢ kWh16¢ kWh16¢ kWh 13¢ kWh13¢ kWh

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– long runs of parabolic Fresnel* single curvature mirrors

– single axis rotation focus energy on a collector tube

– oil is typical heat transfer medium

– ~ 400oC (750°F) oil produces steam in heat exchanger

– conventional steam turbine

– solar/energy conversion efficiency ~ 15%

CSP Solar Troughs

– solar/energy conversion efficiency ~ 15%

– most notable plants are SEGS installations

» Kramer Junction, CA

» 350 MWe are currently installed.

– The 1st of 9 plants went into operation in 1985

* pronounced: pronounced fre’ nɛl (Wikipedia.org)

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– currently has a 5 MWe plant (Kimberlina) operating in Bakersfield CA

– Linear Fresnel reflectors with linear flat mirrors in lieu of the parabolic mirrors (to reduce cost) and forgoing the Therminol in lieu of directly converting

CSP Solar Troughs

to high temperature steam.

» Direct steam conversion offers a simpler solar integration for existing fossil facilities

– Plans are being formalized to develop & build a 177 MWe plant for PG&E in Carrizo Plains, CA

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Power Tower Overview

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� …have been demonstrated successfully at Solar One,

Solar Two, and PS10

� Key development barriers persist…

– Expensive heliostats

– Cost reduction efforts

– Scale-up risk on key components

– Access to transmission / permitting delays

CSP Power Towers ….

– Access to transmission / permitting delays

– Large project cost & risk

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– 11MWe

• saturated steam generator (495oF/580psi)

• 624 mirrors >800,000ft2

• north solar field

ABENGOA Solar PS-10

• north solar field

• tower @ 377 ft

• Receiver eff’y @ 92%

• 30 – minute storage

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• saturated steam generator (495oF/580psi)

• large mirrors (1,291 ft2)

• 1255 mirrors >1,615,000 ft2

• north solar field

• tower @ 525ft

• 235 acres required

ABENGOA Solar PS-20

• 235 acres required

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eSolar Concept

• Small heliostats

• Tracking software creates a virtual parabolic mirror

• Automatic software driven calibration of mirror position

• Maximize factory assembly

• Minimize field assembly

• Utilize existing technologies where feasible

– Conventional steam cycle

– Wind turbine towers

• Rapid deployment

• Goal: solar plant cost = coal plant cost

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The Problem with Solar: Economics

• Conventional Combined Cycle Power plant:

– $1.00 - $1.25/watt installed cap cost + fuel costs + volatility costs + uncertain carbon cost

• Solar Thermal Industry benchmark:

– Solar field ~45% of Total Plant Cost

– Installation/construction ~20% “

eSolar

PS-20

– Installation/construction ~20% “

– Receiver ~10% “

– Power Block ~15% “

• Prevailing Installed Solar Thermal Power Plants:

– $3.5/watt to over $4.00 per watt installed

• eSolar addresses all four major cost components to make solar thermal

power cost competitive

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Why smaller mirrors?

• Lighter

• Less wind load

• No concrete foundation – sits on compacted soil

• Assembly without heavy equipment

• Low cost production due to high volume• Low cost production due to high volume

• Rapid deployment

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Populating the heliostat

field

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eSolar Evolution

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First production unit running 16 months after test facility demonstration.

Starting Small eSolar Evolution

1st steam April

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1 steam April 2nd 2008

Test Facility

Unit

Using computational power to create a system that is:

� Modular

� Pre-fabricated

� Dramatically less expensive

Heliostat

Stick Assembly

Module One tower + receiver

Unit16 ModulesOutput: 46 MW

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• Multiple 46 MW Units can scale easily and quickly

to any generation capacity to meet growing demand

Layout flexible to accommodate land resource availability

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eSolar has addressed traditional CSP challenges by……….

Leveraging pre-fabricated, mass manufactured components

� Assembled in a factory, saving high costs of field construction and civil work

� Flat mirrors are less expensive, faster to manufacture, and easier to deploy

Focus mirrors using software, not concrete and steel

� Breakthrough computer calibration and dual-axis sun-tracking control

Reduce costs through a modular and scalable design

� 46 MW standard units, fast deployment to over 1 GW at a single site

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• Tower height @ 153’

• North & South heliostat fields @6,000 mirrors /field

• eSolar

– 5 MWe demonstration plant @ Lancaster CA

– 1st sun on receiver April 18th 2009

– Key Performance criteria achieved June 20th, 2009

• Heliostat @ 12 ft2

• Total mirror surface @ 144,000 ft2

• Land area @ 10 acres/ module

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eSolar’sSteam Receiver Design Specs

• Natural circulation

• Modular (shippable) configuration (minimum field assembly)

• Weight limitation @ 60 tons

• Tube Materials: Carbon steel & T22

• Peak heat flux @ 130,000 Btu/hr-ft2

• Average flux rates: -• Average flux rates: -

– Evaporator surface @ 45,000 Btu/hr-ft2

– Superheater surface @ 35,000 Btu/hr-ft2

• Extreme Cyclic Duty: -

• Daily start-up and cloud transients

• >20,000 lifetime startup cycles

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Receiver prototype designs

Dual Cavity“External”

Dual Cavity currently operating successfully on Tower 1External receiver commissioning currently underway.

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– Dual Cavity Receiver

• Captures 97% of incident energy

• Superheater surface captures ‘reflected’ radiation

• Lower convection/radiation losses

Prototype designs

•External Receiver

•Surfaces mat -black for max. absorption (94%) of direct

incident radiation

•Higher convection/radiation losses

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Cavity Receiver

– Natural circulation

• 42” steam drum, turbo separators

– Membrane evaporator & pre-heater panels

– ‘tangent-tube’ superheater panels

MCR Steam Conditions:30,000 pph900 psig825oF

Feedwater425oF

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5-MW Sierra Commercial Demonstration

All solar-related components being demonstrated at commercial

plant sizes, mitigating scale-up risk

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Pointing / Tracking Progress

June 22ndMay 7th

June 22nd

The World’s largest digital display?

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Solar Receiver Operational Challenges

• Receiver area inaccessible during operation

– Risk of exposure to solar flux

• Time required for daily inspections

– Lock-out procedure must be followed

– Time to move from tower to tower

– Time to ride service lift to top of tower– Time to ride service lift to top of tower

– Approx. ½ hour per receiver. 16 receiver plant = 8 hours

• Inspection Access

– Improvements needed to provide for inspection, maintenance, repairs.

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Proposals for enhanced inspection capability

• Generous use of TV cameras to monitor critical areas and instruments

• Movable access platforms

• Replace daily start-up inspections with more rigorous weekly inspection

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