Solar Thermal Power Plant with Thermal Storage - Ignacio Burgaleta (Torresol Energy)

11 June 2013, Madrid © Torresol Energy

SOLAR THERMAL POWER PLANT WITH THERMAL STORAGE

WORKSHOP ON APPLICATIONS OF SOLAR FORECASTING

Juan Ignacio Burgaleta

Director of Technology

© Torresol Energy 2 11 June 2013, Madrid

SOLAR THERMAL POWER PLANT WITH

THERMAL STORAGE

INDEX

1. Torresol Energy

2. Molten Salt Storage System

3. Advantages of Molten Salt Storage Systems

4. Estimation of DNI & Cloud Prediction System

5. Solar Thermal Electricity (STE) Plant, PTC Technology

6. Dispatchability capacity

7. Conclusions



THERMAL STORAGE

1. Torresol Energy

• Engineering, consulting, and systems inte-

gration company. Founded in 1956.

• Very active in Solar Energy since 2000. – Technology developer: SENERtrough collector system, Sensol

software, heliostats, heliostat axis drive mechanisms, molten salt

technology (as storage system and as heat transfer fluid) central

tower receiver… amongst many other innovations.

– PSA Tower Prototype

– Turn Key Projects: Andasol 1 & 2, in Granada; Extresol 1, 2

& 3, in Badajoz; one plant in La Garrovilla (Badajoz); one

plant in Alvarado (Badajoz); and two plants in Navalvillar de

Pela (Badajoz).

60% 40%

• 100% “Mubadala Development

Company” stockholding.

• Mubadala Development Company”

belongs to the Abu Dhabi Emirate.

• Goal: development and commer-

cialization of innovative technologies

in renewable, alternative and sus-

tainable energies.

A STRONG ALLIANCE



THERMAL STORAGE

1. Torresol Energy

GEMASOLAR

(Tower)

VALLE 1

(PTC)

VALLE 2

(PTC)



THERMAL STORAGE


• Solar Thermal Electricity (STE) Plants are the only source of renewable energy that can have a

long-range thermal storage system.

• Thermal storage system allows to store part of the primary energy collected in the solar field to

be used later.

50 MWe STE Plant, 3D design of the molten salt storage system



THERMAL STORAGE


Spring/Summer sunny day

Out of focus



THERMAL STORAGE


• Of the different Thermal Storage Systems, the Molten Salt Storage Systems allows to be

used in commercial solar plants.

• The salts used in these systems are: 60% Na NO3, 40% K NO3.

• The characteristics of these salts are:

– Stable fluid at high temperature in liquid phase.

– Reduced steam pressure.

– Storage to atmospheric pressure.

– Density: 1899 kg/m³.

– Melting point: 222 ºC. Molten Salt Piping



THERMAL STORAGE


• The prediction of electric production is function of the prediction of direct normal radiation (DNI).

• With the models developed to predict the direct normal radiation and the capacity of

thermal storage, the accuracy of the production prediction 24 hours in advance is 95 %.

• The Thermal Storage System is one of the key elements for the future reduction of the

generation costs.

Molten Salt Storage System (Left PTC plant, right Tower Plant)



THERMAL STORAGE

• It improves energy efficiency.

• It reduces the cost per kWh produced.

• The turbine operates most of the time at nominal conditions, reducing significantly the

turbine operation at partial load.

• Due to the storage system, the turbine operation is not immediately affected by a

cloud or a sudden high speed wind.

• It reduces the number of turbine stop and start cycles of the generation system.

• The electricity supply to the grid is dispatchable in a safe, predictable and

programmable way.

• It allows to increase the share of renewable energy compensating the problems

caused to the grid by other renewable energy such as photovoltaic and wind.

3. Advantages of Molten Salt Storage Systems



THERMAL STORAGE

IS IMPORTANT A DNI (Direct NormaWHY l Irradiation) FORECAST

AND CLOUDS PREDICTION?

• Predict the energy that it is going to be generated and wheeled into the

electric grid.

• Reduce penalty costs due to deviations of energy generation imposed by

the grid operator

• Optimize the production - Avoiding the saturation of the molten salt tank,

producing during the coldest temperature hours or reducing the number

of the steam turbine shut-downs

• Selection of the optimal moment for the daily starting and shutting down

of the system.




THERMAL STORAGE




THERMAL STORAGE


• Prediction of clouds crossing

over the solar field for a time-

horizon of 1-2 hours with a

resolution of 1 minute.

• Hemiespheric camera and

Meteosat Second Generation

satellite (MSG) images.

• To optimize the amount of

working hours during a whole

year.

• Help to draining the molten

salts with the last sun rays for

each cloud cover.



THERMAL STORAGE

• Piping materials, equipments and components.

– Verify corrosion effects

• Molten salt pumps.

– Long vertical axis

– Overhang assembly

• Risk of molten salts solidification

• Heat tracing in piping and electrical heaters inside the tanks

• Thermal losses

– Insulation to reduce heat loss

– Special foundation

– Temperature Lost < 1 °C per day

– High efficiency heat exchangers (99,9%)


MOLTEN SALT STORAGE SYSTEM



THERMAL STORAGE


• 50 MWe STE Plant PTC technology and 7 hour thermal storage

• Molten salt: 60 % NaNO3, 40 % KNO3

• Two Tanks: 14 m height and 38.5 m diameter (cold at 292 C and hot at 386 C

• Thermal HTF/molten salt heat exchanger

• Thermal storage: 131 MWt

• In operation since 2008.



THERMAL STORAGE


SOLAR

FIELD

TURBINE

STORAGE

262 MWt

131 MWt

131 MWt 50 MWe

131 MWt




THERMAL STORAGE


PTC (50 MWe) Flow Diagram



THERMAL STORAGE


PTC (50 MWe). Daytime Operation



THERMAL STORAGE


PTC (50 MWe). Daytime operation during cloudy periods



THERMAL STORAGE


PTC (50 MWe). Nighttime operation



THERMAL STORAGE


• Valle 1 & 2 Plants



THERMAL STORAGE


Power Block Valle 1



THERMAL STORAGE


Molten Salt Storage System Valle 1



THERMAL STORAGE

Heat Exchangers HTF/Molten Salts. Valle 1




THERMAL STORAGE


Thermal energy from

the solar field

Electricity production

Thermal

energy in

the tank

PT plant – Turbine 100 MWe – Without storage

Parabolic trough plant operation without and with storage

PT plant – Turbine 50 MWe – 7.7 hours thermal storage



THERMAL STORAGE


• Single Tank design

• Prototype at Valle-2

• Cost decrease. Simplifies O&M

Storage System Evolution



THERMAL STORAGE


Typical demand

curve

in summer days

Electricity production 25-31 July 2011

“Information supplied by

Protermosolar”

August the 14th 10194 MWh

Solar Thermal electricity generation in Spain



THERMAL STORAGE

COMPARATIVA MODELO-REALIDAD

0

200

400

600

800

1000

1200

Desde 07/ago/2009 06:00 a 08/ago/2009 06:00

DN

I (W

/m2)

En

erg

ía e

n e

l ta

nq

ue (

MW

h)

0

10

20

30

40

50

60

Po

ten

cia

tu

rbin

a (

MW

)

Po

ten

cia

cald

era

GN

(M

W)

DNI TURBINE POWER

STORAGE

LEVEL

PLANT PERFORMANCE




THERMAL STORAGE


• Valle 1 Plant




THERMAL STORAGE

7. Conclusions

• The Thermal Storage System with molten salt currently in

operation allows to the Solar Thermal Electricity Plants (STE) to

supply electricity to the grid in a dispatchable way.

• The Thermal Storage System makes the Solar Thermal Electricity

Plants (STE) more competitive.

Solar Thermal Power Plant with Thermal Storage - Ignacio Burgaleta (Torresol Energy)

Technology

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