ECEN 5007 - Lecture 9

7/31/2019 ECEN 5007 - Lecture 9

1/40

ECEN 5007 SOLAR THERMAL POWER PLANTS

Lecture 9: Thermal Energy Storage and Hybridization

July 26, 2012

Manuel A. Silva, Dr.Ing. - Manuel J. Blanco, Ph.D., Dr.Ing.

TWTH 17:00-19:30 - Class Room: ECCR 1B55

Office Hours: TWTH 15:30-16:30

7/31/2019 ECEN 5007 - Lecture 9

2/40

Dispatchability

The ability to dispatch power. Dispatchable

generation refers to sources of electricity that can be

dispatched at the request of power grid operators;

that is, it can be turned on or off upon demand

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

3/40

Thermal storage and Hybrization

} STP unique features within the RE technologies:} Thermal energy storage. Thermal energy produced by

the solar fieldcan be stored, decoupling power

generation from solar resource.

} Hybridization. Ability to hybridizewith an alternativeenergy source fossil or renewable fuel.

} Thermal energy storage and/or hybridizationprovide the basis for CSP to be:

} Dispatchable} Stable} Reliable

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

4/40

Thermal Energy Storage

27/07/12

} Andasol} Gemasolar

7/31/2019 ECEN 5007 - Lecture 9

5/40

Why Energy Storage?

} Increase operational stability} Reduce intermittence.} Increase plant utilization and capacity factor} Permits time-shifted operation (decouples electricity

generation from solar energy collection)} Reduce generation cost (as long as storage + solar field

oversizing results cheaper than increasing rated power!)

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

6/40

Profile of the electricity demand

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

7/40

Solar-only electricity generation

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

8/40

Solar + Thermal Storage

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

9/40

Thermal energy storage

} A fraction of the thermal energy produced at the solar field isstored, increasing the internal energy of the storage medium.

} Sensible heat} Latent heat} (Thermochemical)

} The solar field has to be oversized} Solar Multiple = (thermal power delivered by the field at design

conditions) / (thermal power required to generate rated electric

power)

}SM > 1

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

10/40

Types of thermal storage

} By utilization} Short term

} Provide operational stability} Medium term

} Increase capacity factor} Shift electrical generation hours

} By type} Direct (same substance as working fluid, does not require HX)} Indirect (different substance, requires HX)

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

11/40

Technical Requirements for TES materials

} High energy density (per-unit mass or per-unit volume)} Good heat diffusivity and conductivity} Good heat transfer between heat transfer fluid (HTF) and the

storage medium

} Mechanical and chemical stability at operating conditions} Chemical compatibility between HTF, heat exchanger and/or

storage medium

} Reversibility for a large number of charging/discharging cycles} Low thermal losses}

Easy to control

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

12/40

Thermal storage options

27/07/12

Solid materials

Liquid materials

Source: Gil, A. et al. State of the art on high temperature thermal energy storage for power generation.

Part 1Concepts, materials and modellization. Renewable and Sustainable Energy Reviews. January 2010

7/31/2019 ECEN 5007 - Lecture 9

13/40

Thermal storage options - PCM

27/07/12Source: Gil, A. et al. State of the art on high temperature thermal energy storage for power generation.

Part 1Concepts, materials and modellization. Renewable and Sustainable Energy Reviews. January 2010

7/31/2019 ECEN 5007 - Lecture 9

14/40

Thermal storage past experiences

Source: Survey of thermal storage for parabolic trough power plants, Pilkington Solar Int. (2000)27/07/12

7/31/2019 ECEN 5007 - Lecture 9

15/40

TES STP commercial installations

} Short term: pressurized water} PS10 and PS20

} Mid term: Molten salt, 2 tank}

Direct (CRS) Gema Solar (Solar Tres)} Indirect (PT) Andasol I

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

16/40

Short term TES

} Pressurized water} Sliding pressure during discharge} Pressure vessel

PS10 / PS20

Max. pressure: 40 bar Thermal capacity: 20 MWh

(50 min at 50% load)

Total Volume: 600 m3 4 tanks, sequentially

operated

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

17/40

Molten salt storage, 2 tank, direct

} Thermal capacity proportionalto T

} Hot cold tank design} Commercial (salt widely used

in process industry)

High operation T limited(salt decomposition)

Need for heat tracing(risk of freezing)

Costly equipment(pumps, valves)

Solar Two (Barstow, CA)

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

18/40

Molten salt TES

} GEMASOLAR (Torresol Energy)

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

19/40

GEMASOLAR

} Type: 2 tanks, molten salts} Fluid: NO3 mixture

(60% NaNO3 - 40% KNO3)

} Freezing point: 223C} Capacity: 640 MWh

(~15 h full load operation)} Tank size: 14 m high, 23 m diameter} Molten salt mass: 8000 tons approx} T cold tank: 290 C} T hot tank: 565C

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

20/40

Molten salt TES, 2 tanks, indirectANDASOL and other

Needs oil-to-salt HXs Freezing point = 220 oC T max. limited by HTF Large volumes (small T) Increases investment

Provides large storagecapacity to PT plantsusing thermal oil as HTF

Andasol (Granada, Spain)

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

21/40

Andasol TES Technical characterisitics

} Type: 2 tanks, molten salts} Fluid: NO3 mixture

(60% NaNO3 - 40% KNO3)

} Freezing point: 223C} Capacity: 1,010 MWh

(~7.5 h full load operation)} Tank size: 14 m high, 37 m diameter} Molten salt mass: 27,500 tons} T cold tank: 292 C} T hot tank: 386C

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

22/40

ANDASOL

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

23/40

R&D Activities. Concrete storageDual medium

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

24/40

R&D activities.Thermocline, phase change, sand storage

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

25/40

R&D activities. Thermocline} Single tank system, .} Hot and cold fluids separated by stratification;

the zone between the hot and cold fluids iscalled the thermocline.

} Usually a filler material is used to help thethermocline effect.

} Sandia National Laboratories identifiedquartzite rock and silica sands as potentialfiller materials.

} Depending on the cost of the storage fluid,the thermocline can result in a substantiallylow cost storage system.

} This system has an additional advantage: mostof the storage fluid can be replaced with alow cost filler material, for example, quartziterock and sand.

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

26/40

Thermocline tank operation

HTF from Field

HTF Return

Salt-to-Oil

Heat

Exchanger

Thermocline Tank

7/31/2019 ECEN 5007 - Lecture 9

27/40

Latent heat storage (Phase change)

27/07/12

} Isothermal thermal energy storage as the latent heat of phasechangephase change materials (PCM).} Reduced in size compared to single-phase sensible heating

systems.

} Heat transfer design and media selection are more difficult,} Degradation of salts after moderate number of freezemelt

cycles (experience with low-temp salts).

} Phase change materials allow large amounts of energy to bestored in relatively small volumes, resulting in some of the

lowest storage media costs of any storage concepts.

7/31/2019 ECEN 5007 - Lecture 9

28/40

R&D activities. Phase change.Cascaded LHS

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

29/40

R&D activities. Phase change. DISTOR project

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

30/40

R&D activities. Sand (fluidised bed)

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

31/40

TES costs and benefits

} Improves plant controlability and operability, expanding derange of possible operating strategies

} Facilitates Dispatchability} If adequately designed, can improve

} The efficiency of the plant} The profitability of the project

} Extends lifetime of equipment (reduces the number of strat-stop cycles)

} Increases investment} Oversized solar field}

Tanks, HX, molten salt management equipment, heat tracing, safety} Increases O&M costs

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

32/40

Simulating operational strategies with EOS

Clear day, summer

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

33/40

Simulating operational strategies with EOS

Cloudy day, winter

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

34/40

Gemasolar

27/07/12

ntral de

17 MWe & 15 horas de almacenamiento. 24h de produccin en veran

Energa trmica delcampo solar

Energa trmicaen el tanque

Produccin de energa

7/31/2019 ECEN 5007 - Lecture 9

35/40

Hybridization options

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

36/40

SEGS 30 MW

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

37/40

Andasol-type plants(thermal storage and auxiliary boiler)

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

38/40

ISCCS

}3 projects in North Africa (Morocco, Algeria, Egypt)

27/07/12

7/31/2019 ECEN 5007 - Lecture 9

39/40

Unit #1 (100 kW hybrid GT) (Aora Solar, Israel)

14/7/1038 GEEN 4830 ECEN 5007

7/31/2019 ECEN 5007 - Lecture 9

40/40

HybridizationCosts and benefits

Improves controlability and operability Faciltates dispatchability Improves plant overall efficiency Improves capacity factor Improves profitability of the plant Extends equipment lifetime Increases investment and O&M costs CO2 emmissions

27/07/12