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Heat-Based Solar Technologies

Mengpin GeJustin Glier

Fraser Kitchell

Andrew KuoSanchit WarayChenlu Zhang

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Concentrating Solar Collectors

Image courtesy of Solarpower.com

Image courtesy of U.S. Department of Energy Image courtesy of BBC

Image courtesy of Gizmag.com

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Solar Heat Utilization

Solar Heat Collection Stirling Engine

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Concentrating Solar Collectors

Image courtesy of Solarpower.com

Image courtesy of U.S. Department of Energy Image courtesy of BBC

Image courtesy of Gizmag.com

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Parabolic Trough Integrated Solar Combined Cycle System (ISCCS)

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Concentrating Solar Collectors

Image courtesy of Solarpower.com

Image courtesy of U.S. Department of Energy Image courtesy of BBC

Image courtesy of Gizmag.com

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Power Tower

• Several demonstration projects worldwide

• Heat collection through heliostats

• Store heat through molten salt

• Less prone to intermittency• Steam cycle generates

electricity• Can be supplemented by

combined cycle gas turbines

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Concentrating Solar Collectors

Image courtesy of Solarpower.com

Image courtesy of U.S. Department of Energy Image courtesy of BBC

Image courtesy of Gizmag.com

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Life Cycle AssessmentEconomic cost& Environmental impact

Manufacturing of materials and components • Solar field

• Tower • Storage system • Buildings• Power block

Construction activities

• Cranes• Transports

Operation and maintenance

• Electricity • Natural gas • Water

Dismantling activities

• Dismantling cranes

• Transports to landfill

• Land filling

Solar Thermal Power Plant

Energy

Resources

Emissions

Electricity to the grid

System Boundary

Fig. Life cycle of a solar thermal power plantg CO2 equiv./kW h Central Tower Parabolic trough Solar field 5.61 7.88Power block 0.64 0.5Storage system 9.49 14.6Tower 0.04

Buildings 1.03 0.46Construction 0.18 0.34Decommissioning 0.000431 0.0198Subtotal 17 24Operation 186 161Total 203 185

Table. GHG emission in the life cycle of the solar thermal power plants in g CO2 equiv./kW h

Table: Cumulative energy demand in the life cycle of the solar thermal power plants in MJ/kW h

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Life Cycle AssessmentEconomic cost

r: discount rateN: # of years of plant operationICi: investment cost

land& equipment construction labor engineering and other

services grid connection permits, financing, etc.

OMi: Routine Operating & Maintenance CostsFCi: Fuel CostEi: Net Energy Produced and Sold *footnote i means in year i.*This expression assumes that the discount rate is fixed

Fig. Estimate of typical LCOE for CSP plants, for moderate and high levels of DNI, compared to a cost forecast of conventional electricity generation.

Figure ： Total Installed Cost Breakdown of 100 MW Parabolic Trough and Solar Tower*Parabolic trough system has 13.4 hours of thermal energy storage and solar tower system 15 hours

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Materials Technology in CSPReflector materials

Requ

irem

ents

:

High specular reflectivity (>90%);Durability under tough outdoor service conditions (>20 years plant lifetime);Low manufacturing cost in large volume (<10.80/m2 )Easy curving and structural rigidity;

To d

ate

solu

tion:

Bla

ck-s

liver

ed

glas

s re

flect

or

Dra

wba

cks:

High accuracy curving of glass by thermal sagging or elastic defromation is expensiveThin glass(<1mm) easier to curve and lower in cost, but too fragile and difficult to handleSliver supply shortage

Alte

rnati

ve re

flect

or sy

stem

Al or Al/Ag coatingpolished Al substrate; top protective layer of anodization or polymerPolymer substrate with silver coating and poly protectionSubstrate Materials:•polyethylene terephthalate (PET)

•PET laminated to stainless-steel foil

•chrome-plated carbon steel strip.

Top Protective Layer (0.5-4 μm Al2O3)

Reflective Layer (100 nm Ag)Metal Back Layer (50 nm Cu)

Substrate (PET) or Chrome-Plated Steel (203 μm, 8 mils)

Fig. Structure of advanced solar reflective material.

Protective Layer of anodization or polymer)

Aluminum or aluminum/silver coating

Polished aluminum substrate

Poly protection(methyl methacrylate)

Silver coating

Polymer substrate

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Hig

h-effi

cien

cy R

anki

ne

stea

m p

lant

s

Requisite• High-

temperature components-Receiver

• >600°C, 200–300 bar pressure

Tube materials for high-temperature receivers •Inconel•similar high-quality stainless steel

•Nickel alloys, which tend to be very expensive.

Spec

tral

ly s

elec

tive

abso

rber

coa

ting

Challenge• From today’s

400-500°C, vacuum protected operation

• Future direct steam systems at >600°C tower-top receiver and no vacuum envelope.

• Stable under an oxidizing and humid atmosphere at high operating temperature.

Materials• multilayer and

cermet composites

Air (

gas

turb

ine)

pla

nts

Requisite• 800-1,400°C;

maintain 30 bar pressure

• High cost tubular •Expensive high-tem metals(e.g., Nickel-based)

•operates at lower end of range;• High thermal

conductivity of tube wall

•ceramic tubes; SiC• Mechanical strength

and robustness• under thermal

shock and various mechanical loads (wind forces, thermal expansion, etc.).

• joining and sealing the ceramic elements

Volu

met

ric re

ceiv

er

Requisite•Transparent window•sustain high internal pressure and temperature

Challenge•devitrification (loss of transparency),

•Polluted by contact with traces of alkali metals or other chemicals

Materials• fused quartz•only when shaped in an appropriate convex form

•select-ive coating that rejects IR radiation);

•alternative glassy materials

Materials Technology in CSPAbsorber/receiver materials

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Mat

eria

ls re

quire

men

t for

Hea

t-tr

ansf

er &

ther

mal

sto

rage

in a

sol

id

med

ium

:

Broader range of liquid phaseHigh specific heat and thermal conductivityLow viscosity across temperature rangeStability under thermal cycling and high temperatureChemical compatibility with pipe and tank materials such as stainless steel.Low cost

HTF

Synthetic oil•Trough plants • Limits steam temperature to

about 390°C, reduce operating temperature and cycle efficiency.

Direct steam generation(two-phase flow system)•Power tower and linear Fresnel

System but not in parabolic-trough plants

Molten nitrate saltTower systems•Up tp 560°C steam temperature

& Easy heat storage without separate heat transfer to other medium

•Difficulties in site management and protection against freezing at 240°C,

Alternative HTFs (pressurized CO2, some ionic liquids) •Early research phase

Stor

age

Mat

eria

ls

Molten nitrate salt(mixture of NaNO3 and KNO3) •Sensible heat with restricted 280–560°C range

Concrete and crushed rock:• low cost but low thermal conductivity

Graphite•excellent thermal conductivity at higher cost

Cons

umpti

on a

nd C

ost

If CSP reaches 8000 TWh/year in 2050:Consume up to 50-120% of today’s nitrate salt production

Materials Technology in CSPHeat-transfer fluids & Storage materials

Original

•wet-cooled•mined nitrates

salts• two-tank,

thermal energy storage (TES) system

•26g CO2eq per kWh&

•0.40 Mjeq/kWh of energy

•4.7L/kWh water

•1 year EPBT

Alternative

•Dry-cooling• Synthetically

derived nitrate salt

•Thermocline TES

• Increase CO2& CED by 8%

•Reduce LC water consumption by 77%

Source: HITTITE

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References

• Resource: Fundamentals of materials for energy and environmental sustainability Edited by: Ginley, David S.; Cahen, David © 2012 Cambridge University Press

• Burkhardt, J., G. Heath, and C. Turchi. 2011. Life Cycle Assessment of a Parabolic Trough Concentrating Solar Power Plant and the Impacts of Key Design Alternatives. Environmental Science & Technology. 45: 2457–2464. http://dx.doi.org/10.1021/es1033266

• Yolanda Lechon, Cristina de la Rua, and Rosa Saez, “Life Cycle Environmental Impacts of Electricity Production by Solarthermal Power Plants in Spain,” Journal of Solar Energy Engineering 130, no. 2 (May 0, 2008): 021012-7. http://lca.jrc.ec.europa.eu/lcainfohub/study.vm?sid=207

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Characteristics of studied solar thermal power plants for life-cycle-analysis