The document discusses the need for standardization of IV measurements for bifacial solar cells and modules. It proposes two initial standards - one for inline inspection of cells and modules under bifacial STC conditions, and another for offline energy rating of bifacial modules. For the bifacial STC standard, it recommends simultaneous front and back illumination with 1000 W/m2 AM1.5G for the front at 25°C, and 200 W/m2 AM1.5G for the back within 2% non-uniformity. Additional illumination conditions could also be considered.

1. Need for standardization of
IV-measurements of
bifacial cells and modules
Dr. Axel Metz
Managing Director
h.a.l.m. elektronik GmbH, Frankfurt, Germany
bifi PV workshop, 2014
Chambery, France, May 26th & 27th 2014

2. Company profile
 30 years of measurement experience in industrial environment
 Headquarter in Frankfurt, Germany + local office in Suzhou, China
 Expertise in various industrial areas
 Active in PV industry since more than 15 years
 More than 900 systems sold worldwide, equivalent > 30 GWp/a
 References: Yingli, Trina, Solarworld, FhG ISE, PTB, TÜV, VDE, ...
www.halm.de © h.a.l.m. elektronik gmbh

3. Product portfolio
IV measurement and sun simulating systems for:
 Solar cells (production and research)
- High speed inline testers up to 5100 cells/hour
- EL and IR imaging
- Highly flexible lab systems
 PV-Modules (production and research)
- High throughput sun simulators up to 240 modules/hour
- Optional EL integration
- Lab system with high precision temperature control unit
 PV-Systems
- High precision portable outdoor measurement system
www.halm.de © h.a.l.m. elektronik gmbh

4. Why do we need standards?
 To make things comparable world wide
 To ensure quality and reduce risks
 To save money at all levels of the value chain
 As manufacturer
 As equipment or material supplier
 As testing institute
 As system integrator
 As end customer
© h.a.l.m. elektronik gmbh

5. Outline
 Applications for bifacial solar cells and modules
 Important design parameters of bifacial systems
 Requirements for reproducible IV-measurement of bifacial PV devices
 Considerations for different levels of the value chain
 Conclusions
© h.a.l.m. elektronik gmbh

6. Applications for bifacial cells and modules
Bifacial solar cells
 Assembly in modules with opaque back cover
 Monofacial module
 back side performance
almost independent
from mounting conditions
 Assembly in modules with transparent back cover
 Bifacial module
 back side performance
strongly dependent
on mounting conditions
© h.a.l.m. elektronik gmbh

7. Applications for bifacial cells and modules
Bifacial PV modules
 Sound barrier
 Mounted vertically (preferrably east/west orientation)
 Roof mounted
 on a flat roof
 on a tilted roof
 Solar park
 ground mounted at fixed angle
 mounted on tracking system
 Building integrated
 facade integrated
 as shadowing element
 roof integrated
© h.a.l.m. elektronik gmbh

8. Important parameters for bifacial systems
Relevant for system performance
 Module position
 tilt angle
 module direction
 module orientation (portrait or landscape)
 Albedo
 System geometry
 distance from reflector
 geometry of opaque, transparent and open area
© h.a.l.m. elektronik gmbh

9. Requirements for reproducible measurements
Front side
 STC: 1000 W/m2, AM1.5G, 25°C
Back side
 Intensity
 Spectrum
 Non uniformity
 Temporal stability
Timing
 Simultaneous front and back illumination or
 Sequential front and back illumination
© h.a.l.m. elektronik gmbh

10. Considerations for different levels of the value chain
Cell
 classification for optimum matching in module (inline 100%)
 cell power at bifacial STC (inline, 100%)
Module
 module power at bifacial STC (inline, 100%)
 energy rating (offline, per module type)
System
 energy yield modelling for specific applications, mounting
and climate conditions
© h.a.l.m. elektronik gmbh

11. Conclusions
 Short term need for standards for IV-measurement
of bifacial devices
 To reduce complexity, two standards are required:
 bifacial STC for 100% inline inspection
 offline energy rating of bifacial modules
 New standards for bifacial devices should be:
 based on existing standards
 simple and pragmatic
© h.a.l.m. elektronik gmbh

12. Proposal for standardized IV measurement of bifacial devices
Front side
 STC: 1000 W/m2, AM1.5G, 25°C
Back side
 Intensity: 200 W/m2
 Spectrum: AM1.5G
 Non uniformity: 2%
Timing
 Simultaneous front and back illumination
Optional
 additional illumination conditions
 front 1sun / back 0 sun and/or
 front 1 sun / back 1 sun and/or
 front 0 sun / back 1 sun
© h.a.l.m. elektronik gmbh