Hybrid Solar and Coal-Fired Steam Power Plant with Air Preheating Using a Solid Particle Receiver

Hybrid Solar and Coal-Fired Steam Power Plant with Air Preheating Using a Solid Particle Receiver T. Prosin1, T. Pryor1, C. Creagh1, L. Amsbeck2, R. Buck2 Murdoch University 2 German Aerospace Centre 1

Outline •

Solarisation of boiler fired steam power plants - state of the art

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Solarisation of air into a boilers inlet air stream

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Solid Particle Receiver (SPR)

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Cycle and solar systems modelling

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Results and comparisons

Hybrid Solar-Coal Power Stations •

Enables stable solar energy deployment using existing infrastructure

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Transition to low carbon energy sector with lower upfront costs

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Current method: Fresnel collector based concentrating solar power (CSP) systems producing water/steam

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Solar steam introduced into the cycle after feedwater heaters - Turbine Bleed Steam (TBS) solarisation

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750MWel Kogan Creek power station in QLD - Supercritical steam plant with reheat

Turbine Bleed Steam (TBS) Solarisation •

Low solar share and annual coal saving - due to limitation in mass flow of the TBS insertion point - due to limited operation hours of Fresnel (no energy storage)

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Low solar heat to electric power efficiency - due to operating temperature of solar collector system - and reduction in the cycle performance

KOGAN CREEK POWER STATION HBD

Hybrid Solar-Coal Using Solar Air Heating •

Solar heating of inlet secondary air, after air preheater

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Advantages over turbine bleed steam (TBS): - Higher temperatures can be introduced - Improved performance of boiler and cycle

Hybrid Solar-Coal •

Solar boost vs solar fuel saver - only assessed fuel savings for equal conditions

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Solar air preheating implemented with a CSP solid particle receiver with a heliostat field solar collector system

SPR System Operation •

Particles transported by lift up tower to receiver

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Heated by sun, then delivered to storage

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Particle to air heat exchange on demand

Par$cle receiver (SPR)

Li? (transport in insulated container)

High temp. storage

Par$cle to fluid Heat exchanger Heliostats (mirrors)

Solar tower

Low temp. storage

*Image from DLR

SPR Heliostat Collector Field

Solar Solid Particle Receiver (SPR) •

Avoids necessity of expensive manufacturing techniques with expensive high temperature metals or ceramics

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Particles directly stored inexpensively in insulated vessels

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Particle temperatures only limited by the particle sintering temperature (>1000°C)

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A robust solution with no practical flux limits

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High efficiency obtained even at high temperatures due to high flux concentration density from the collector field

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Low cost construction

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Potential for very low energy costs

Centrifugal Particle Receiver Operation •

Fast rotating inclined cylinder on top of tower

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Centripetal acceleration from rotation forces particles on the wall

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Particles form a thin optically dense layer

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Control of radiation exposure/temperature by variation of rotational velocity (no need for recirculation)

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Continuous flow of particles from buffer tank fed by a lift system

CSP Modelling •

Annual performance of Fresnel system calculated using US-NREL Solar Advisor Model software

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Annual performance of SPR system calculated by detailed models for every component Receiver Solar field

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Storage

SPR model

Transport system

Solar performance simulation results were combined with power cycle modelling results from Ebsilon software and cycle HBD

Figures of Merit (Complete System) •

Solar Share (Xs)– represents the portion of fuel saved due to solarisation during operation X s ,m! =

•

Fuel saved % Fuel consumed without solar

Solar to Power Efficiency - gives the efficiency at which incident solar energy is converted to electricity

Solar to power efficiency =

Power generated due to solar energy % Incident solar energy

Results – Steady State Design Conditions •

Two operating temperatures investigated for solar air preheating - 950C to show the theoretical limit of the SPR technology - however the temperature range 500-600 is easier to implement Result / Case

Unit

Ref. case

Air 950°C

Air 540°C

TBS 335°C

Boiler eff.

%

94.4

96.8

95.3

94.6

Cycle eff.

%

45.2

45.2

45.2

44.5

System efficiency

%

40.4

41.6

40.9

39.9

Solar share

%

0

32.2

11.7

4.4

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Solar by air preheating increases the power plant efficiency due to improvements in boiler efficiency from lower exhaust losses

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TBS solarisation decreases the power plant efficiency due to reduced steam flow through the TBS path

Annual Performance Results •

Figures of merits for energy system comparisons are only useful on an annual basis to evaluate the actual real world performance Annual result / Case Unit

Air 950°C

Air 540°C

TBS 335°C

Solar share

%

20.0

7.6

0.72

Solar to el. eff.

%

22.1

23.2

13.9

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SPR air heating has 66% higher solar to electric conversion efficiency than the currently existing solar hybridisation option

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Both systems can be incorporated into the same power station -SPR system can be retrofitted to an existing plant with TBS solar

Conclusion •

Air hybridisation improves efficiency of power plant while TBS hybridisation decreases performance efficiency

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SPR with storage has superior solar performance and operational hours, resulting in massively reduced annual fuel consumption

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The thermal energy produced from the SPR system can cost 27% more and still produce electricity at an equal cost

Thank you for your attention

This project has been supported by the Australian Government through the Australian Renewable Energy Agency (ARENA)

T.Prosin@Murdoch.edu.au  Â