Bifacial gain simulations of modules and systems under desert conditions bifi PV Workshop 2017 25 26 October 2017, Germany, Konstanz David DASSLER 1,2, Stephanie Malik 1, Benjamin W. Figgis 3, Prof. Joerg Bagdahn 2, Dr. Matthias Ebert 1 1 Fraunhofer Center for Silicon Photovoltaics (CSP), Halle, Germany 2 Anhalt University of Applied Sciences, Koethen, Germany 3 Qatar Environment & Energy Research Institute, Doha, Qatar
Application of bifacial modules in desert conditions GHI dose world map ( Solargis) Desert climates makes bifacial modules more interesting Significantly higher irradiance dose than in moderate climate Bright ground with albedo up to 40% ( E-W vertical) More diffuse light due to dust in the atmosphere However, high continuous dust deposition (soiling) makes yield estimation difficult Investigation of module performance and their benefit in desert environment are required Dusted solar modules in desert ( PI Berlin) 2
Approach of outdoor investigation and bifacial gain simulation Environmental influences Irradiance Ambient temperature Wind Valid values (1) Outdoor measurements Observed values (2) Cleaning from disturbing influences Disturbances during measurements Instrument malfunction Shading (3) Energy yield evaluation (4) Bifacial gain simulation based on outdoor measurements 3
(1) Outdoor measurements in Qatar Single and system measurements since 09/2016 in Doha, Qatar Bifacial modules with 270 Wp, installed 2016 Reference: monofacial module 220 Wp, installed 2012 Module data: IV-curve, module temperature Environmental data: irradiance, amb. temp., rel. humidity, wind Outdoor measurements provided by Qatar Environment & Energy Research Institute 4 Installation of bifacial module (front and rear side) at Solar Test Facility at Doha
(2) Cleaning from disturbing influences (1) To get a reliable data-set: Plausibility: data within physical correct limits and only day-values Excluding outliers: (2) data within 3-sigma intervall 1 of quotient I SC /G and P MPP /G, Fig. (1) Simultaneous cleaning state: by linear regression of I sc,bi vs. I sc,mono daily slopes within statistical range, Fig. (2) 5 1 Zhu: Outlier identification in outdoor measurement data effects of different strategies on the performance descriptors of photovoltaic modules, IEEE 2009
Irradiance Class [W/m²] Irradiance [W/m²] Irradiance [W/m²] Monofacial E mono Irradiance Class [W/m²] Bifacial E bi Irradiance Class [W/m²] Irradiance Class [W/m²] (3) Energy yield evaluation 1200 6 1200 1000 800 600 400 200 0 0 10 20 30 40 50 60 70 1200 1000 800 600 400 200 Module Temp. [ C] Module Temperature Class of bifacial module [ C] 20 30 40 50 60 70 perature Class of bifacial module [ C] 0 0 10 20 30 40 50 60 70 Module Temperature Class of bifacial module [ C] Averaged yield 5,5 [Wh] Monofacial Yield (averaged) [Wh] 1000 Monofacial Yield (averaged) [Wh] Module Temp. [ C] 5,5 5,0 4,5 4,0 3,5 3,0 2,5 5,0 4,5 4,0 3,5 3,0 2,5 2,0 1,5 1,0 0,5 0,0 5,5 5,0 4,5 4,0 3,5 3,0 2,5 2,0 Bifacial Yield (averaged) [Wh] 1,5 1,0 0,5 0,0 800 600 400 200 1200 1000 800 600 400 200 Factor 0 0 0 10 20 30 40 50 60 70 0 10 20 30 40 50 60 70 Module Temperature Class of bifacial module [ C] Module Temperature Class of bifacial module [ C] Ratio of average energy yields for irradiance and module temperature classes (width: 50 W/m²; 2 C), first period of measurements 2,0 Bifacial: 1,5 Shift of absolute yield upwards 1,0 0,5 Almost constant energy yield levels with rising 0,0 temperatures until 800 W/m² Bifaciality up to 45% for moderate module temp. Factor Factor 1,50 1,45 1,50 1,40 1,45 1,40 1,35 1,35 1,30 1,30 1,25 1,25 1,20 1,20 1,15 1,10 1,05 1,05 1,00 1,00
Energy yield [Wh] Bifacial module (3) Energy yield evaluation How is the impact of soiling on bifacial modules? Currently, no standard to determine the classical Performance Ratio for bifacial modules Introduction of Yield Ratio : the slope of a linear regression between daily irradiance yield and corresponding module yield Yield Ratio increases by cleaning or decreases by dust deposition, but as well with rising temperature Filtering for module temperature at 48 C ± 5 % Irradiance yield [Wh/m²] Scheme of the determination of daily Yield Ratio 7
Daily Yield Ratio [%] (3) Energy yield evaluation Yield Ratio Uniform behaviour between bifacial and monofacial modules Temporary degradation of Yield Ratio due to soiling events Jumps are as the scheduled cleaning events Time Daily Yield Ratio for bifacial and monofacial module over one year 8
Norm. Yield Ratio [%] (3) Energy yield evaluation Soiling rate Determination of Soiling rate as linear slope over Yield Ratio, normalized to the cleaned state Monofacial Bifacial Soiling rate 0.57 %/day 0.61 %/day In this time period, a soiling rate around 0.6 %/day has occurred Independently of the installed module ( no influence on rear side) No. of days Normalized daily Yield Ratio for bifacial and monofacial module (1 month and 3 weeks) 9
(4) Bifacial gain simulation based on outdoor measurements and yield evaluation Aim: Bifacial gain simulation of modules in desert regions Using Artificial Neural Networks (ANN) Based on observed multidimensional information Pattern learning and generalized knowledge after learning Flexibility to uncertainties Fast processing Input layer GHI DHI DNI POA Tamb Rel. humidity Pressure AOI Wind speed Wind direction Yield Ratio of the last day Hidden layers Architecture of used ANN Day-wise simulation and calculation of YR Output layer Pmpp Tmod 10
Daily Yield Ratio [%] (4) Bifacial gain simulation based on outdoor measurements and yield evaluation Training of network based on the information (every minute) of first quarter of data Training Validation Validation of trained network for remaining shows less averaged errors RMSE 1 Monofacial 0.30 % Bifacial 0.48 % Method of ANN is usable for both technologies Measured and simulated Yield Ratio for both modules; Subdivision of the data in training and validation 11
Irradiance Class [W/m²] Summary and Outlook 1200 1000 800 600 Factor 1,50 1,45 1,40 1,35 1,30 1,25 Application of bifacial modules in desert is still recommended. 400 200 0 0 10 20 30 40 50 60 70 Module Temperature Class of bifacial module [ C] 1,20 1,15 1,10 1,05 1,00 Bifacial gain simulation with a high resolution based on outdoor measurements Promising strategy independently of the technology For optimization of cleaning cycles Further investigations to improve yield prediction Applicable for module and system level Further investigations with comparison to vertical installations and of the reusability of trained data at other sites and climates 12
Contact: Fraunhofer Center for Silicon Photovoltaics Otto-Eissfeldt-Strasse 12 06120 Halle (Saale), Germany David DASSLER Tel. +49 345 5589 5214 David.Dassler@csp.fraunhofer.de www.csp.fraunhofer.de Thank you for your attention!