Solar Facilities for the European Research Area Overview of solar receiver design Alain Ferriere SFERA II 2014-2017, Summer School, June 25, 2014, Odeillo (France)
Solar receiver: a key component Storage fluid / Material Back-up resource Solar radiation Heat transfer fluid Working fluid Storage / Back-up (combustion) Concentrating system Conversion of solar Solar radiation receiver into sensible heat Thermodynamic conversion
Solar receiver: a critical component Highest temperature in the plant: 250 C < T < 1000 C (and more) Careful selection of materials suited for this application Manufacturing issues (shaping, assembly, welding) Thermal fatigue Steep variation of temperature under cloud passing High impact on solar-to-electric conversion efficiency of the plant h sys = h sf x h rec x h pb [h sys = h th x h pb ] High reliability and long lifetime requested High content in intellectual property Cost might be critical
Solar receiver design: general approach Constraints Concentrating system Heat transfer fluid HTF temperature Working pressure Pressure drop Design parameters Class of receiver Materials Shape Size Assembly Performance targets Efficiency Lifetime Reliability Cost Performance is governed by heat transfer capabilities and surface optical properties
Impact of optical properties Qsol _ hsf I0 Q h loss rec A Q Q rec HTF sol A T DNI I 0 (W/m 2 ) sf 4 rec sol Q Q loss sol Q HTF hth hsf I0Asf h C h rec rec A A sf rec h sol sf I C Atmospheric absorption 4 T rec 0 Q radiation Solar receiver aperture A rec (m 2 ) Q reflection Q convection Q HTF Solar field aperture A sf (m 2 ) I 0 x A sf (W) Reflection Absorption Cosine Shadowing Blocking
Impact of optical properties h sf h th sol I 4 T rec 0 C h Carnot 1 T T amb rec h sys 4 rec T h 1 sf sol I C 0 T T amb rec K cycle
Impact of optical properties
Impact of optical properties
Impact of optical properties
Impact of optical properties
Mechanical and thermal materials properties Solid materials Young modulus E Poisson coeff. g Tensile strength R E Thermal expansion coeff. Density r Specific heat C p Thermal conductivity k Solar absorption factor sol Emissivity factor as function of temperature! Heat Transfer Fluids (HTF) Melting temperature T melt Evaporation temperature T evap Viscosity µ Density r Specific heat C p Thermal conductivity k
Examples of materials properties Solid @20 C E [Gpa] g R E [Mpa] [µm/m.k] r [kg/m 3 ] C p [J/kg.K] k [W/m.K] Stainless steel 220 0.29 200 15 7850 476 35 Copper 100 0.34 40 16.5 8930 384 393 Inconel 600 214 0.32 500 10 8470 444 15 SiC 410-400 5.2 3100-125 (@100 C) SiSiC 370-240 4.3 3100-100 (@100 C) Glass 6 0.25 50 6 2600 838 0.98 HTF T melt [ C] T max [ C] µ [10-3 Pa.s] r [kg/m 3 ] @300 C C p [J/kg.K] @300 C k [W/m.K] @100 C Thermal oil 73.5% diphenyl oxide 26.5% biphenyl Molten salt 60% NaNO 3 40% KNO 3 12 C 400 C 0.2 815 2319 0.128 220 C 600 C 3.26 1894 1495 0.537
Sizing of receiver aperture w n Parabolic trough mirror Acceptance angle θ Φ (p rim angle) D
Line focus concentrating systems Bundle of tubes Linear Fresnel technology Single tube HTF water/steam thermal oil
Line focus concentrating systems Parabolic trough technology Evacuated tube HTF thermal oil water/steam molten salt Stainless steel absorber tube with selective coating Solar absorption: >90% (typ. 91,5%) Total hemisph. emissivity: <30% (typ. 14%) PVD (T>350 C), or Co, Cr, Ni black (T<350 C)
Point focus concentrating systems Polar field (latitude >35 ) North South φ CESA 1, Almeria (Espagne) Lat. 37 φ Surrounding field (latitude <35 ) North South Solar Two, Barstow (USA) Lat. 35 φ φ
Point focus concentrating systems External receiver Suited for all fields Suited for aiming point strategy Easy design and assembly Moderated cost Cavity receiver Suited for polar solar field Suited for very high temperature applications Decreased thermal loss Complex design and assembly Elevated cost Elevated heat transfer coefficient high flux density & small size receiver better efficiency Example: HT pressurized air solar receiver at CSIRO (Newcastle, Australia) 900 C achieved
Point focus concentrating systems Surface absorber Volumetric absorber Fluid flow in channel Conduction in wall & turbulent convection High pressure drop Correlations Nu=f(Re, Pr) Analytical models Suited for gas HTF Fluid flow in porous medium Reduced radiation loss Coupled heat transfer radiation/convection/conduction Numerical simulations
Point focus concentrating systems Examples External plate receiver Suited to surrounding field (cylindrical receiver) Easy construction Low cost Elevated convection loss Ex : esolar superheated steam receiver 55 bar, 420 C Ex: Solar Two Molten salt receiver 80 MW th, 560 C H ~ 8 m & D ~ 4,5 m
Point focus concentrating systems Examples Cavity receiver Suited to polar field Reduced heat loss (convection and radiant through aperture) Ex: molten salt receiver, Themis, 8 MW th, 450 C Stainless steel tubes painted with Pyromark A = 4 m x 4 m L = 3 m Ex: direct saturated steam generation receiver PS10 (260 m², 50 MW th ) & PS20 (90 MW th )
Point focus concentrating systems Examples Open volumetric absorber Air ambiant Atmospheric pressure Heat transfer fluid = gas (HT) Outlet Temperature ~ 700 C Porous ceramic material (HT) SOLAIR receiver (3MW th ) tested at PSA Almeria and operated at Jülich
Point focus concentrating systems Examples Pressurized volumetric absorber Stream of pressurized air in the absorber Pressurized air receiver HTF = air (HT, HP) Quartz window Closed receiver: quartz window Absorber material: porous metallic foam/mesh (800 C) or ceramic foam (1000 C) Ex : REFOS receiver (1 MW th ) tested at PSA Almeria
Point focus concentrating systems Examples Pressurized surface absorber Heat transfer fluid = air (HT, HP) No window Absorber material: metal (900 C) or ceramic (1200 C) Performances are driven by the heat transfer coefficient / pressure drop Schematic of the «Pegase» receiver Tube receiver «Solhyco»
Point focus concentrating systems Examples Solid particles solar receivers HTF = solid particles Suited for HT chemical reactions (solar thermochemical reactors) Complex construction Difficult operation (instabilities, sensitivity to wind) Current research works: Designs by DLR, Sandia, CNRS Experimental testings Target T = 1000 C
Point focus concentrating systems Other concept: beam down Small tower Receiver at the bottom of tower Increased optical loss 33 heliostats (3x3 m 2 ) tower 18 m Participants : Tokyo Institute of Technology, Cosmo Oil Co and MASDAR Ex : SOLZINC experiment in Israël MASDAR/Tokyo Tech Beam-down (100 kw, Abu Dhabi)
CPC concentrators (secondary optics) Geometric concentration ratio: CR sin 1 accept / 2
Volumetric solar receivers
Pressurized air solar receivers Receiver Absorber technology Thermal power [kw th ] Maximum air temperature [ C] Heat transfer coefficient [W/m².K] Peak flux density [kw/m²] Absorber material Sirocco surface 500 845 120 180 Metal alloy REFOS DIAPR Pressurized volumetric Pressurized volumetric 650 960-770 Metal (LT) and SiC (HT) 1200 1200 130 5000 SiC Solhyco tube 182 800 400 - Inconel / Copper Pegase Surface 4000 750-800 1500 2000 600 Inconel / Copper
Solar Facilities for the European Research Area Thank you alain.ferriere@promes.cnrs.fr www.promes.cnrs.fr SFERA II 2014-2017, Summer School, June 25, 2014, Odeillo (France)