Concentrating Solar Power: Current Cost and …

1 Concentrating Solar power : Current cost and future DirectionsCraig Turchi Systems Analysis Task LeaderThermal Systems R&D GroupMay 30, 2017 NATIONAL RENEWABLE ENERGY LABORATORY2 NREL s System Advisor Model (SAM) CSP costs CSP research directions oMolten salts and other heat storage mediaoAdvanced power cyclesoPlant configuration and value optimizationTopicsNATIONAL RENEWABLE ENERGY LABORATORY3 System Advisor Model (SAM) is a performance and financial model designed to facilitate decision making for people involved in the renewable energy RENEWABLE ENERGY LABORATORY4 Questioned CSP developers and stakeholders regarding the Current cost of CSP Values used to keep SAM s cost inputs up-to-date Separate sections for power tower, parabolic trough, and linear Fresnel systemsNREL 2016 CSP cost SurveySurveyNumber of respondentsTotal questionsQuestions with 3 responsesPowerTower20*3232 (100%)ParabolicTrough20*2615 (58%)

2 LinearFresnel0290* The 20 respondents were not all the same for each technologyNATIONAL RENEWABLE ENERGY LABORATORY5 SAM Changes: power TowersPower Tower (Molten Salt and DSG)SAM2016 SAM 2017 ResponsesComments/JustificationSite Improvements$/m216no change11 Heliostat Field$/m217014517 Wide variability in responsesTower cost formulano change11 Receiver cost formula10 Reduce DSG by about 10%, MS by lesser amountReceiver reference cost (MS)$110,000,000 103,000,000 Receiver cost scaling changeReceiver reference cost (DSG)$55,402,80048,800,000 Receiver cost scaling changeThermal energy storage$/kWh-t262411 power cycle$/kWe1190110012 Balance of plant$/kWe340no change11 Contingency%7no change15 EPC & Owners cost %111313 Sales Tax%5no change135% applied to 80% of direct costsO&M Fixed cost by capacity (MS)$/kW-yr66no change7O&M Fixed cost by capacity (DSG)$/kW-yr50556 Variable cost O&M (both)$ Tax %0no change7reviewers recommend , but left at 0% to match other SAM modelsInsurance % change7 Min.

3 Turbine operation%252010 Max. turbine over design %105no change12 NATIONAL RENEWABLE ENERGY LABORATORY601234567 Way too High(>25%)A little tooHigh (>10%)About Right ( 10%)A little tooLow (<10%)Way too Low(<25%)No Opinion(includesBlank)Number of peopleQuestion: Current installed cost for heliostat field = 170/m2?Heliostat Field cost New SAM value = $145/m2 NATIONAL RENEWABLE ENERGY LABORATORY7 CSP Costs: SAM 2016 vs. SAM 2017 SAM Model with default valuesTotal Overnight Installed cost ($/kW)SAM changePhysical Trough (6 h thermalstorage)6,7056, Salt Tower (10 h thermal storage)7,3656, (no thermal storage)4,7104, Costs assume construction in the southwest region of the United States Applying SunShot financial assumptions (see On the Path to SunShot, NREL/TP-5500-65688, 2016), the lowest levelized cost of energy corresponds to the molten salt power tower with a value of approximately 110 RENEWABLE ENERGY LABORATORY8 SunShot CSP Gen3 Technology RoadmapNATIONAL RENEWABLE ENERGY LABORATORY9 SaltMelting Point (C)

4 MaximumTemp (C)Heat Capacity (J/g-K)Density (kg/L)Viscosity (cP)Relative *Cp(-) Solar Salt (NaNO3/KNO3)220~ ~650? > > > /K2CO3 /Li2CO3 398~ Salt Options for Higher Temperature OperationData sources: Solar salt: SQM Solar thermal salts factsheet Mg chlorides: ORNL/TM-2006/69; Serrano-Lopez et al. (2013); Gowtham Mohan et al. (2017 submitted) Zn chlorides: University of Arizona (private correspondence) Carbonates: An et al. (2016)Physical properties estimated/measured near 600 C for comparisonNATIONAL RENEWABLE ENERGY LABORATORY10 SaltPrimary Benefitvs Solar SaltPrimaryChallengesKNO3 Slightly better thermal stability (600-650 C) Slightly higher Tmp Slightly higher costKCl/MgCl2 Lower salt cost Better thermal stability HigherTmp Lower *Cp( , larger tanks)

5 CorrosionKCl/NaCl/MgCl2 Lower salt cost Better thermal stability HigherTmp Lower *Cp CorrosionZnCl2/KCl/NaCl Slightlylower Tmp Betterthermal stability Lower *Cp Corrosion Measureable vapor pressure Slightly higher salt costNa2CO3 /K2CO3 /Li2CO3 Higher *Cp(smaller tanks) Betterthermal stability HigherTmp Corrosion High salt cost (Li2CO3)New Molten Salt Benefits/Challenges Laboratory testing indicates Cl corrosion can be controlled if high purity is maintained in the salt meltNATIONAL RENEWABLE ENERGY LABORATORY11 Challenges Less established within CSP industry Particle durability, attrition (dust emission)

6 Receiver efficiency via convective/radiative and particle losses Increase particle/wall heat transfer Particle-to-sCO2heat exchanger at 700 C, 20 MPaAdvantages No freezing concerns No trace heating Thermally stable particles Direct heating of particles allows for high flux/concentration ratios Direct storage of inexpensive particles Particle handling, heat exchange, and storage techniques well establishedFalling Particle power Tower SystemsNATIONAL RENEWABLE ENERGY LABORATORY12 CSP power Cycle Development The supercritical-CO2 Brayton cycle promises higher efficiency and lower installed cost versus to existing superheated steam cycle $100 million cost -shared project is to build and demonstrate a 10 MWesystem in Texas Cycle performance gains are more pronounced at higher temperatures.

7 DOE program is targeting 700 C turbine inlet temperatureNATIONAL RENEWABLE ENERGY LABORATORY13 Simple OptimizedSystem Operation/Dispatch Optimization MetricSimpleOptimizedAnnual energy (year 1)301,600 MWh289,300 MWhLevelized cost of Energy (real) /kWhPower Purchase Agreement price (year 1) /kWhPrice signalPower to Grid Despite lesser generation, optimized dispatch produces greater value as indicated by a lower acceptable PPA price Matching CSP system design and dispatch to grid demand is essential is a national laboratory of the Department of Energy, Office of Energy Efficiency and Renewable Energy, operated bythe Alliance for Sustainable Energy, you!

8 NATIONAL RENEWABLE ENERGY LABORATORY15sCO2 Cycle Development under STEPI mage: Southwest Research InstituteDOE s STEP project will demonstrate a 10 MWesCO2recompression cycleSupercriticalTransformational Electric PowerNATIONAL RENEWABLE ENERGY LABORATORY16 10 MWesCO2recompression Brayton cycle Turbine inlet temperature of 700 C Demonstrate pathway towards an overall power cycle efficiency of 50% or greater Reconfigurable and can monitor and characterize primary components or subsystems (turbomachinery, heat exchangers, recuperators, bearings, seals, etc.) Demonstrate steady state, transient load following, and limited endurance operation.

9 Capable of test campaigns to assess critical component degradation mechanisms to assess component life and cost STEP Test Facility Attributes and ObjectivesNATIONAL RENEWABLE ENERGY LABORATORY17sCO2 Recompression Cycle715 C249 bar518 C253 bar574 C85bar35 C81 bar95 C82 bar86 C256 bar217 C249 bar267 C84 bar> 720 C~540 CDesign-point values from DOE-funded CSP Gen3 analysis report by Black & VeatchTamb= CNote: SunShot CSP plants are assumed to be dry cooled, so a higher design-point ambient temperature is MW33 MW19 MW