White bifacial modules

Transcription

1 White bifacial modules improved STC performance and bifacial energy yield Bas Van Aken Miyazaki, 30 th of September

2 Monofacial or bifacial: Pmax under STC power rating monofacial glass bifacial glass white back sheet transparent panel Bifacial module: lower Pmax under STC 2

3 Monofacial or bifacial: rear side irradiance and albedo monofacial glass glass bifacial white back sheet transparent panel Bifacial module: lower Pmax under STC power rating Monofacial module: no energy yield due to rear side irradiance and albedo 3

4 White bifacial modules from module lay-up to outdoor data What is a bifacial white module? IV-measurements Ray tracing Annual energy yield simulations Outdoor measurements 4

5 Introducing the white bifacial module White scattering layer placed between the cells and between cells and module edge Fully non-transparent module Front and rear side appear very similar as can be seen in the mirror white bifacial glass transparent panel 5

6 What to expect? Improved STC measurement Bifacial character remains white bifacial glass transparent panel 6

7 Current [A] STC IV-measurements Measurement according to IEC Black, non-reflecting floor and walls No contribution included from irradiance on the rear monofacial module white bifacial module Isc [A] Pmax [W] bifacial module white bifacial bifacial monofacial Voltage [V] Bifacial module: lower Pmax under STC power rating White bifacial module: similar Pmax and Isc as monofacial module 7

8 Ray tracing simulations On cell and intercell area Spectrum for intercell area of white bifacial module shown All absorbed light contributes to Isc Qualitative match cell area intercell area total Isc obs. Isc monofacial bifacial white bifacial

9 ECN s bifacial PV system model generic set-up Irradiance model based on view-factors for full system, including position effects, direct and self-shading, inhomogeneous irradiance for m x n pixels per module # sheds consisting of # rows & # columns Bypassing of cell strings (if necesarry) P plant (t) 9

10 Applying ECN s system model variations over the shed self shading direct shade + self shading Simulated central shed with 4 rows of 19 modules direct shade top row white bifacial bottom row top row bifacial bottom row top row monofacial bottom row Self-shading lowers the energy yield for bifacial modules lower in the shed and lowers the energy yield for bifacial modules in the middle of the rows 10

11 Applying ECN s system model monthly energy yield (gain) in kwh Simulation for Amsterdam, albedo 0.2 Simulated central shed with 4 rows of 19 modules The simulated energy yield (gain) is 11% higher for bifacial and another 2% higher for white bifacial 11

12 Energy yield [kwh] Energy yield gain [kwh] Applying ECN s system model hourly energy yield (gain) in kwh Simulation for Amsterdam, albedo 0.2 white bifacial bifacial monofacial Hour of the day Simulated central shed with 4 rows of 19 modules Energy production data per clock hour for full year 7 6 white bifacial 5 bifacial Hour of the day The absolute energy yield when the day is longer than 12 hours is relatively small, but the absolute gain is much more pronounced 12

13 Conclusions White interlayer placed around the bifacial solar cells Wp rating very similar to monofacial module Ray tracing explains how the white interlayer bridges the gap between the lower Isc (Pmax) bifacial module and the higher Isc (Pmax) of monofacial modules ECN s PV system model has irradiance, thermal and electrical model based on view-factor for full system, direct and self-shading, for m x n pixels per module and # bypass diodes AEY simulation predict a bifacial gain of 10% and an additional 2% gain in kwh-production for Amsterdam, assuming a low albedo