Concentrated Solar Power Course - Session 4 - Thermal Storage and Hybridization

By Manuel A. Silva Pé[email protected]

April 27, 2010

Concentrated Solar Thermal PowerTechnnology Training

Session 4 – THERMAL STORAGE AND HYBRIDIZATION

http://www.leonardo-energy.org/csp-training-course-5-lessons

THERMAL STORAGE AND HYBRIDIZATION

Manuel A. Silva PérezGroup of Thermodynamics and Renewable EnergyETSI – University of Seville

http://www.leonardo-energy.org/csp-training-course-lesson-4-thermal-storage-and-hybridization



CSP MARKETS

Utility (centralized) Capacity > 10 MW Types of utility generators:

Base load (nuclear, coal) Dispatchable (gas, CSP) Intermittent (wind, PV)

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




CSP MARKETS

Distributed generation Capacity: 3 kW to 10 MW Close to consumer Reduces transmission losses Reduces investment in transmission

infrastructure

Stand-alone applications Modularity, avaliablity, reliability




THERMAL STORAGE AND HYBRIZATION

CSP unique features within the RE technologies: Thermal energy storage. Thermal energy

produced by the solar field can be stored, thus decoupling power generation from solar resource.

Hybridization. Ability to hybridize with an alternative energy source –fossil or renewable fuel.

Thermal energy storage and/or hybridization provide the basis for CSP to be: Dispatchable Stable Reliable




WHY ENERGY STORAGE?

Increase operational stability Reduce intermittence. Increase plant utilization and capacity factor Provides “peak-shaving” ability (time-shifted

operation) Reduce generation cost (as long as storage is

cheaper than increasing rated power!)




PROFILE OF THE ELECTRICITY DEMAND




SOLAR-ONLY ELECTRICITY GENERATION



SOLAR + THERMAL STORAGE



THERMAL ENERGY STORAGE

A fraction of the thermal energy produced at the solar field is stored, increasing the internal energy of the storage medium. Sensible heat Latent heat (Thermochemical)



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)



TECHNICAL REQUIREMENTS FOR TES MATERIALS High energy density (per-unit mass or per-

unit volume) Good heat conductivity Good heat transfer between heat transfer

fluid (HTF) and the storage medium Mechanical and chemical stability 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



THERMAL STORAGE OPTIONSSource: Survey of thermal storage for parabolic trough power plants, Pilkington

Solar Int. (2000)



THERMAL STORAGE PAST EXPERIENCES

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

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



SHORT TERM TES

Pressurized water Sliding pressure during

discharge Pressure vessel

PS10 / PS20

PS10 TES main characteristics• Max. pressure: 40 bar• Thermal capacity: 20 MWh

(50 min at 50% load)• Total Volume: 600 m3

• 4 tanks, sequentially operated



MOLTEN SALT STORAGE, 2 TANK, DIRECT

Thermal capacity proportional to ΔT

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)



MOLTEN SALT STORAGE, 2 TANK, INDIRECT

• Intermediate oil-to-salt HX• Freezing Temp = 220 oC• High temp. limited by HTF• Large volumes• Higher investment costs

• Provides high storage capacity to PT power plants (Thermal oil)

Andasol (Granada, Spain)



ANDASOL STORAGE -TECHNICAL CHARACTERISTICS Type: 2-Tank Molten Salt Storage Fluid: Nitrate salt mixture

(60% NaNO3 and 40% KNO3)

Melting Point: 223°C Storage Capacity: 1,010 MWh

(~7.5 hrs full load operation)

Storage Tank Size: 14 m height 37 m diameter

Salt Mass: 27,500 tons Flow Rate: 953 kg/s Cold Tank Temperature: 292° C Hot Tank Temperature: 386°C



ANDASOL, MOLTEN SALT 2-TANK TES



TES – ADVANCED EXPERIENCES



TES – ADVANCED EXPERIENCES



TES COSTS AND BENEFITS Improves plant controlability and operability,

expanding de range 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



HYBRID SOLAR THERMAL POWER PLANTS

Two energy sources: Solar energy Fossil or renewable fuel

Hybridisation of STP plant Eases plant operation during transients Eases turbine startup Reduces number of turbine stops Increases full-load operation time Can be used to maintain temperature of HTF or

storage medium



HYBRIDIZATION OPTIONS



SEGS 30 MW



ANDASOL-TYPE PLANTS (THERMAL STORAGE AND AUXILIARY BOILER)



ISCCS

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



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



THANKS FOR YOUR ATTENTION!



Concentrated Solar Power Course - Session 4 - Thermal Storage and Hybridization

Technology