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Next-CSP Final Infoday
July 8th, 2021
This project has received funding from the EU Horizon 2020 Framework Programme for
Research and Innovation under grant agreement no 727762
High Temperature Solar Thermal Power Plant with Particle Receiver and Direct Thermal Storage
High efficiency conversion cycles
Manuel Romero / IMDEA Energy
Main contributors
Manuel RomeroDeputy Director of IMDEA Energy and Research Professor
José González-AguilarHead of Unit High Temperature Processes
Francesco RovensePostdoctoral researcherAt present Marie Curie fellow at URJC/IMDEA Energy.
Rui ChenPredoctoralresearcherCSU/IMDEA Energy
Miguel Angel ReyesPostdoctoral Researcher. At present Assistant Professor at URJC
System integration
820ºC
Transport&
Storage
Models
Design Methodology
Target about 50% cycle and 30% global
4
T involves a cascade of effects
Power Cycles Screening: let’s go for 50%
High temperature solar receiver (up to 820 ºC) allows for highly efficient cycles(Carnot’s Theorem)
Parameter UnitSupercritical fluids Combined
cyclesteam CO2
Power plant nameplate capacity MW 150 10 150
Receiver outlet temperature ºC 650 700 – 750 800-820Turbine Inlet Temperature (TIT) ºC 620 680 – 730 780-800Target cycle net efficiency % > 45 50 50Condenser type dry wet/dry Dry
650-820 ºC D6.2 – Report on thethermodynamic cycles that arebest suited to the solar loop(IMDEA-EDF, Month 18)
Unfired
Heat Exchangers network (DPS-HX)
Tem
per
atu
re (
C)
Specific entropy (J/kgK)
4
6
7
9 12
8
Tsteam,live + ΔT
Double reheating (higher pressure ratio)
10 13
1
407 ºC
800 ºC
600 ºC
800 ºC
Mass flow distribution: mair (HP hot DPS-HX) = mair (IP DPS-HX) =
mair (LP DPS-HX) = mair (HP cold DPS-HX)
mDPS (HP hot DPS-HX) ≈ mDPS (IP DPS-HX) ≈mDPS (LP DPS-HX) ≈ 3 · mDPS (HP cold DPS-HX)
Unfired (only solar)
combined cycle
Preferred working conditions: Solar pure mode TIT = 800 ºC Brayton no-intercooled &
double-reheated Rankine reheated with no steam
extractions & 3-pressure levels
Table 1: Power plant main specifications
Parameter Value Units
Net power output 150 MWe
Topping cycle net power 80 MWe
Bottoming cycle net
power70 MWe
Power Block nameplate
efficiency 49.4 %
Gas turbine air inlet
temperature 800 ºC
Inlet heat exchanger DPS
temperature819 ºC
Outlet heat exchanger
DPS temperature606 ºC
Final result 49.4%
efficiency
Close to 50% target
7
Power block unfired CC 800ºC (150 MW)
D6.4 Optimized solution
8
Solar battery dispatch
750 MWh and 950 MWh electrical dispatch (1.5-2.5 GWh thermal)
Not only Gen-3, also needs to be ready for hybrid dispatches with PV
9
Single receiver efficiency >80% at >820ºC
Receiver Model data
Parameter Value Units
Receiver active tube height 7 m
Average flux 400 kW/m2
Peak flux 500 kW/m2
Absorptivity of tubes 0.9 -
Emissivity of tubes 0.85 -
Tubes thickness 2 mm
Tubes spacing 10 mm
Number of tubes 240 -
Maximum surface temperature 1,000 ºC
Thermal power to be absorbed 44 MWth
Particles inlet temperature 606 ºC
Particles outlet temperature 825 ºC
Tubes internal diameter 53 mm
Particles mass flow (calculated) 165 kg/s
Cavity radius 9 m
A cavity of about 9 m radius would be required to avoid peak flux above 500 kW/m2 into panel of 7 m length tubes.
Average flux onto cavity aperture: about 1,500-2,000kW/m2
10
Solar field efficiency 65-72% at solar noon
(solar elevation angle between 36-83º)
Heliostat field simulated data (SolTRACE)
Parameter Value Units
Simulated heliostat area 83971 m2
Simulated heliostat count 1731 -
Power incident on field 75574 kW
Power onto aperture 54259 kW
Shadowing and Cosine efficiency 92.74 %
Reflection efficiency 87.97 %
Blocking efficiency 99.05 %
Image intercept efficiency 88.84 %
Solar field optical efficiency 71.80 %
Incident flux on cavity aperture 2009.6 kW/m2
Cavity apertura area 27 m2
Heliostat data
Parameter Value Units
Supplier SBP (Stellio)
Area 48.5 m2
Reflectivity 93.5 %
Soiling factor 95.0 %
Slope error (2D) 0.9-1.7 mrad
Pointing error (2D) 0.85-1.7 mrad
Multiple solar-fields & towers feeding single Combined Cycle Power Block
Particles transportation system between multi-solar fields units & common particles
TES & heat exchangers network
Multi-tower solar field with cavity receivers:
Current approach for scale-up
Solar field main specifications (per unitary solar field)
Parameter Value Units
Site Ouarzazate (Morocco) -
Day design point Spring Equinox, solar noon -
DNI design point 900 W/m2
Tower optical height 110 m
Receiver type Cavity -
Power onto receiver @ design
point53.2 MW
Average flux 2 MW/m2
Tilt angle versus horizontal 30 º
11
𝐸𝑅𝑒𝑐 (t) = 𝐷𝑁𝐼(𝑡) ∗ 𝜂𝐻𝐹 𝑓(𝑒, 𝑎)t1−∆𝑡
t0+∆𝑡
𝑁𝑆𝐿 = (1 + 𝛼𝑛)𝐸𝑐𝑎𝑠𝑒,𝑛
)𝐸𝑅𝑒𝑐(𝑡𝐴𝑇𝑜𝑡
Two configurations- Seven solar loops;- Eight solar loops.
12
Energy production [GWh]
Stored Energy [GWh] Case 1 Case 2
7 loops 8 loops 7 loops 8 loops
1.0 115.1 115.1 115.0 115.8
1.5 188.0 194.9 188.5 194.9
2.0 238.0 251.1 241.7 255.9
2.5 239.2 252.4 274.1 295.0
3.0 239.2 252.4 274.1 295.0
Unlimited 259.7 265.3 279.7 325.8
Energy production (GWh/year)
Particle weight corresponding to energy stored
Parameter Value Units
1.0 GWh 14061.89 tons
1.5 GWh 21092.84 tons
2.0 GWh 28123.79 tons
2.5 GWh 35154.74 tons
3.0 GWh 42185.68 tons
13
Case 1 - seven SL – 2.0 GWh TES Case 2 - eight SL – 2.5 GWh TES
Hourly net electricity production along the year
14
Case 1 - seven SL – 2.0 GWh TES Case 2 - eight SL – 2.5 GWh TES
Particles stored for best cases
The maximum number of particles stored is 28,123.79 tons for DS1 and 35,154.74 tons for DS2 that is required for thermal energy storage sizing.
Capacity/Utilization Factors
15
Highest value of the CF is 22.45%, for theCase 2 and 8 solar loops, 2.5 and 3.0 GWh. For7 solar loops the highest CF is of 20.86%.
The highest value of the UF is 33.48%, obtained for Case 1 and eight towers for 2.0 GWh of stored energy
𝐶𝐹 =𝑌𝑒𝑎𝑟𝑙𝑦 𝑒𝑛𝑒𝑟𝑔𝑦 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑
𝑁𝑎𝑚𝑒𝑝𝑙𝑎𝑡𝑒 𝑝𝑜𝑤𝑒𝑟 ∗ 8760𝑈𝐹 =
𝑌𝑒𝑎𝑟𝑙𝑦 𝑒𝑛𝑒𝑟𝑔𝑦 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑
𝐷𝑖𝑠𝑝𝑎𝑡𝑐ℎ𝑎𝑏𝑙𝑒 𝑛𝑜𝑚𝑖𝑛𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 ∗ 365
16
Levelized Cost of Electricity
17
Solar island CAPEX
Seven solar loops
18
Solar island CAPEX
Eight solar loops
19
CAPEX uncertainty HX and conveyors
Case 1 - seven SL – 2.0 GWh TES Case 2 - eight SL – 2.5 GWh TES
Particles transport has important impact on LCoE(CAPEX is 3x HX)
Supercritical CO2 PowerRecompression Cycle
- Large amounts of heat must be recuperated
- Need of compact heat exchangers
- specific heat of the cold side flow is two to three times higher than that of the hot side flow in recuperators.
- CO2 flow is split to compensate for the specific heat difference.
- Recompression improves- Air cooling strong penalty
Ahn, Y. et al. (2015) Nuclear Engineering and Technology, 47(6), 647–661.
Schematic diagram for recompression S-CO2 Brayton cycle integrated with particle receiver. MC, RC, LTR. HTR and DPS refer to main compressor, recompressor, low temperature recuperator, high temperature recuperator and dense particle suspension.
Developing a common methodology
Homogeneously assess the plant performance of six SCO2 Brayton cycles integrated with
particle receiver and a dry cooling system at both design and off-design conditions
Homogeneous model
(MATLAB)
Six layouts• Simple regeneration• Recompression• Precompression• Inter-cooling• Partial cooling• Split expansion
Component-based• Turbomachinery• Compressor • Heat exchanger
Design and Off-design model
22
Fixed parameters Value Note
Net electrical power (MW) 10 Representative system capacity considered by NREL for using in
CSP [37]
Minimum cycle pressure (MPa) 7.8 Near the critical pressure of CO2 [19]
Maximum cycle pressure (MPa) 25 Available and economic piping [19]
Air inlet temperature (℃) 20 Recommended design air temperature for direct dry cooling [43,
44, 45]
CIT (T1) (℃) 40 Possible under dry cooling with 20 ℃ temperature difference
with air inlet temperature [43, 44, 45]
T11= T1 in intercooling cycle; T10=T1 in partial cooling
DPS inlet temperature (℃) 700 Recommended inlet DPS design temperature in Ref. [19]
TIT (℃) 680 20 ℃ difference with DPS inlet temperature [19]
Turbine efficiency (%) 93 Projection of mature, commercial size radial flow turbine
efficiency [29]
Compressor efficiency (%) 89 Lab test result [46]
PCHE recuperator efficiency (%) 95 The common value reported in the literature [6, 19, 22]
Fixed design boundaries and component
efficiencies used for these six cycles.
23
Configuration Cycle efficiency
(%)
Specific work
(kJ/kg)
The temperature difference
of DPS in PHE (℃)
Simple
regeneration43.63 131.04
216.62
Recompression 50.00 116.60 158.71
Precompression48.56 132.91
196.92
Intercooling 52.11 130.67 174.28
Partial Cooling 49.46 141.91 205.26
Split Expansion 49.54 115.26 160.26
Comparison of six cycle performances
under their optimal design conditions
24
Conversion efficiency for
recompression cycle at design point
Results for standard Stellio beam quality and CIT = 40ºC
Effect of air temperature variation on
off-design performance of six cyclesDesign point
Ambient temperature increases from design value (20℃)• The decrease in net work output can be grouped into
two typical categories. The more complex systems (intercooling, partial cooling) show bigger degradation
• Precompression cycle could not operate well when air temperature is higher than 46 ℃
• Simple regeneration and recompression cycle perform better with ambient temperature higher than 30 ℃
Main conclusions
- Two cycles with 50% efficiency (design point) retained for integration with DPS
technology: unfired combined cycle and s-CO2.
- Very regenerative cycles with relevant role of DPS heat exchangers.
- Unfired CC at 800ºC with Brayton no-intercooled & double-reheated and Rankine
reheated with no steam extractions & 2-pressure levels
- Multi-tower solar field with cavity receivers and constrained peak power
dispatch: Current approach for scale-up though limited capacity factors
- s-CO2 needs lower TIT (680ºC) though very sensitive to CIT
- In general, simple regeneration and recompression cycle present better
adaption to sunny areas, where air temperature could be higher than 30℃ for
long periods of time.
