6-3_McIntosh-PVPMC-2023-1

1 Keith McIntosh, Malcolm Abot and Ben Sudbury Differences betwen advanced and conventional models in bifacial yield simulations PVPMC Workshop 10-May-2023 2 Objective •Quantify the diference betwen models for 8 physical mechanisms −Mostly tested with SunSolve-Yield −And PVSystfor its VF model •Thre system configurations −SATs −Fixed-tilt −Waves •Just one location −Southwest Utah 3 Results preview •MBE 0: yield higher for conventional model than advanced model •Models are convoluted −MBEs of individual models do not sum to BE of al models combined. •MBE = 0 does not imply two models are equivalent. Maybe −morning discrepancy compensated by noon discrepancy, −summer compensated by winter, −one poor sub-model compensated by another poor sub-model. Results for typical 1P SAT located at Cove Mountain, UT. 4 Results preview Average P mod 315 W Results for typical 1P SAT located at Cove Mountain, UT. 5 Three early coments •This is not an investigation into the accuracy of the models. •Results specific to chosen examples. −Model comparisons wil difer for other location, weather, system configurations. −Consider these results as a general guide, with more emphasis on CRMSE than MBE. •By themselves, these results don’t promote any model over another. The value of a model depends on many things: −Acuracy, precision, uncertainty −Ease of implementation & determining inputs −Aceptance by industry −Modeling objective: e.g., annual yield, morning power, structural shading, etc. 6 Simulation details 7 Simulation details —site location Image htps:/ww.kimley-horn.com/project/cove-mountain-solar/ Coordinates for Phase I of Cove Mountain from https:/ww.gem.wiki/Cove_Mountain_Solar Site of Cove Mountain Solar Plant, Utah 37.62 N 113.62 W 1570 m Image: Google Maps 8 Simulation details —weather I = 1.96 MWh/m 2 f D = 26.5% T av = 14.7 o C w av = 3.5 m/s •Good solar resource •Low cloud •Cold winter, warm sumer •Mostly light winds 9 Simulation details —atmosphere 0 0.5 1 1.5 2 2.5 3 3.5 P r ec i p w a t er v a p o u r ( c m ) Giovani 20-yr av Solcast TMY Default for AM1.5g 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 A e r o so l o p ti c a l d e p th a t 5 0 0 n m Giovani 18-yr av Default for AM1.5g 0 50 100 150 200 250 300 350 400 O zo n e ( D o b so n s) Default for AM1.5g Giovani 18-yr av 800 850 900 950 1000 A tm o sp h e r i c p r e ssu r e ( m b ) Default for AM1.5g Giovani 12-yr av Solcast TMY •Relatively dry •Dusty •Moderate ozone •Low presure due to altitude (1570 m) •We use −Solcastfor PWV & P −Giovani for O 3 and turbidity Blue data is long-term daily average from NASA’s satelites and analysis of 1 o bounding box. htps:/giovanni.gsfc.nasa.gov/giovanni. Gren data is daily average of Solcast, recently acquired by DNV. https:/solcast.com/ PWV Turbidty Presure Ozone 10 Simulation details —SAT •1P (one in portrait) •Six modules per bay •Posts betwen bays •Circular torque tube •Smal clamps (rails) •Max tilt ±55 o , backtracking •Example results of ray tracing for 9 am, 10-May, light cloud. Front Rear 11 Simulation details —fixed-tilt •2P (two in portrait). •Six modules per bay •Posts betwen bays •Rafters •Purlins •Tilt 25 o •Example results of ray tracing for 10 am, 10-May, light cloud. Front Rear 12 Simulation details —waves •1P (one in portrait). •Ten modules per wave. •Concrete slabs below modules. •Rafters •Purlins •Tilt 10 o . •Example results of ray tracing for 9 am, 10-May, light cloud Front Rear 13 Simulation details —module 37.62 N 113.62 W P MP 550 W Bifi 70% V OC 49.80 V I SC 13.99 A V MP 41.95 V I MP 13.12 A FF:0.790 Eff: 21.31% LONGI LR5-72HBD 550M 144 half-cut cels 14 Simulation details —general •Infinitely large system —no edge efects from system perimeter. •DC module output —average of al modules in a bay. •1 hourly time steps. 15 Models examined 16 1. Spectral albedo Conventional Advanced •Constant •33.7% •Wavelength-dependent •Yellow-brown soil (NASA) 17 2. Electrical mismatch Conventional Advanced •Constant −Here, we use the anual weighted average mismatch los f M as determined by SunSolve (front & rear combined) •Calculated at al time steps 1. Solve J L in each cell 2. Solve equivalent-circuit of module f M SAT 0.5% Fixed 0.5% Waves 0.7% Fixed f M omits row-to-row shading of direct light since that is acounted for in PVSyst. 18 3. Solar position Conventional Advanced •PVSyst[1] −Simple equations. −Omits refraction. •Reda–Andreas 204 [2] −Mases of tables and equations. −Accounts for refraction. −Zenith and azimuth to within ±0.0003 o betwen 200 BCE and 600 CE. [1] https:/ww.pvsyst.com/help/solar_geometry.htm [2] Reda and Andreas, “Solar position algorithm for solar radiation aplications,” Solar Energy76(5), 57–589, 2004. 19 3. Solar position Conventional Advanced •PVSyst[1] −Simple equations. −Omits refraction. •Reda–Andreas 204 [2] −Mases of tables and equations. −Accounts for refraction. −Zenith and azimuth to within ±0.0003 o betwen 200 BCE and 600 CE. –0.3 o q s +0.3 o –0.6 o f s +0.5 o 20 4. Difuse sky distribution Conventional Alternative implementation •PVSystPerez (190) [7] •PVL Perez (190) [7] Perez et al., “Modelingdaylight availability and iradiance components from direct and global iradiance,” Solar energy44 (5),.271-289, 1990. [8] Hay and Davies, “Calculation of solar radiation incident on an included surface,“ 1stCanadian Solar Radiation Data Workshop, Ontario, 16, 1980. NB: Change in yield when using Hay–Davies [8] rather than Perez in our example: Conventional (PVSyst) Alternative (SunSolve-Yield) SAT -1.35%+0.15% Fixed -1.50%+0.17% Waves -0.65%+0.80% 21 Models, like simple Perez (190), approximate the difuse light with thre sources: •isotropic •circumsolar •horizon 4. Difuse sky distribution isotropic horizon circumsolar 22 4. Difuse sky distribution •Adaption for infinite field acounts for shading from odules. •PVSyst’simplementation of Perez 190: •isotropic −partial shading •circumsolar −posible shading •horizon −same shading as isotropic isotropic & horizon mod u l e circumsolar 23 4. Difuse sky distribution •Adaption for infinite field acounts for shading from odules. •PVL’s implementation of Perez 190: •isotropic −partial shading •circumsolar −posible shading •horizon −completely shaded circumsolar isotropic horizon mod u l e 24 5. Module optics Conventional Advanced Highly absorbing material 100% Transmision calculated from IAM 0% Si Glas Glas EVA SiN x Ag Al Al 2 O 3 SiN x ARC 100% 96% 95% 22% 3.5% 3.8% 3.3% 3.0% Ex am p l e r a y Ex am p l e r a y 95% 25 5. Module optics Conventional Advanced •‘Simple’ (like PV Syst, SAM, etc.) −No reflection −IAM from lok-up table −l-independent −No cel spacing −No frames −Spatialy uniform −J L responds linearly to absorption •Ray tracing into the module −Reflection −Calcs with Fresnel & thin-film optics −l-dependent −Cel layout −Frames −Fingers, ribons, backsheet, pyramids, etc. −J L responds linearly to absorption 26 5. Module optics Conventional –IAM •PAN files sometimes contain an unrealistic IAM. •Sometimes it’s even “certified”. •PVSystallows a calculated IAM instead of PAN IAM •For conventional, we use calculated IAM, “Fresnel, AR coating” •“Certified” gives 1.45% more yield for SATs! 27 6. Thermal model Conventional Advanced •Faiman[3] •PVL (PVSC 202) [4] distinguishes −Radiative losses −Transient efects −Tilt dependence •Inputs fit to experiment [3] D. Faiman, “Asesing the outdor operating temperature of photovoltaic modules,” Progres in Photovoltaics, 16 (4), 307-315, 2008. [4] K.R. McIntosh et al., “The influence of wind and module tilt on the operating temperature of single-axis trackers,” 49th IEE PVSC, 103-1036, 2022. MBE: 0 °C RMSE: 1.4 °C MBE: +3.2 °C RMSE: 4.5 °C FTC SAT FTC SAT U C U V SAT 251.2 Fixed251.2 Waves 270 28 7. Solar spectra Conventional Advanced •AM1.5g •Calculated at al time steps −SPECTRL2 for clear skies [5] −Ernst modification for cloudy skies [6] •Affected by −Air mass (i.e., solar location) −Precipitable water vapour −Turbidity −Ozone −Air presure −Far-field albedo [5] Bird and Riordon, “Simple solar spectral model for direct and diffuse iradiance…,” Journal of Climate and Aplied Metrology, 25, 87–97, 1986. [6] M. Ernst, et al. “SUNCALCULATOR: A program to calculate the angular and spectral…” Solar Energy Materials and Solar Cels, 157913–922, 2016. 29 7. Solar spectra Air mas PWV Turbidity 30 8. System optics Conventional Advanced •View-factors & bifacial los factors −Structural shading, f S −Transmision, f T •Ray tracing