This document discusses bifacial photovoltaic modules and the challenges in modelling their performance and economics. It provides a brief history of bifacial modules and lists current suppliers of different bifacial module technologies. It identifies several key factors that impact the gross margin from bifacial systems, including module yield and capital expenditures, as well as the module design, installation environment, and electrical system architecture. Specific modelling challenges discussed include variables in bifacial flash testing, the impact of albedo from different ground covers, mechanical mounting designs, and electrical considerations like optimal inverter sizing and requirements for multi-input microinverters.

1. Introduction to Bifacial Modules
and Modelling
Teresa W. Zhang, PhD

2. P. 2 | SunEdison Confidential
Brief History of Bifacial Modules
 1966: U.S. Patent on a p+np+
solar cell
 1977: Multiple presentations at
1st European Photovoltaic Solar
Energy Conference (PVSEC)
 2000: Russia deploys 10 kW on
the International Space Station
 2009: Sanyo (now Panasonic)
released first commercial bifacial
product
 2015: >100 patents granted and
10’s of MWs deployed

3. P. 3 | SunEdison Confidential
(Soon to be) Active Bifiacial Suppliers

4. P. 4 | SunEdison Confidential
HIT Suppliers
HIT – Heterojunction with Intrinsic Thin Layer
a.k.a. HJT – Heterojunction Technology
a.k.a. HCT – Hybrid Cell Technology (Sunpreme)

5. P. 5 | SunEdison Confidential
PERT Suppliers
PERT – Passivated Emitter Rear Contact, Rear Totally Diffused
a.k.a. BiSoN – Bifacial Solar Cell on N-type (MegaCell)
Related to PERC – Passivated Emitter Rear Contact
Related to PERL – Passivated Emitter Rear Contact, Rear Locally Diffused

6. P. 6 | SunEdison Confidential
Modelling Challenges
𝐺𝑟𝑜𝑠𝑠 𝑀𝑎𝑟𝑔𝑖𝑛 = 𝑓
𝑌𝑖𝑒𝑙𝑑
𝐶𝑎𝑝𝐸𝑥
= 𝑓
𝑀𝑜𝑑𝑢𝑙𝑒
𝐸𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡
𝑆𝑦𝑠𝑡𝑒𝑚 𝐴𝑟𝑐ℎ𝑖𝑡𝑒𝑐𝑡𝑢𝑟𝑒

7. P. 7 | SunEdison Confidential
Modelling Challenges
𝐺𝑟𝑜𝑠𝑠 𝑀𝑎𝑟𝑔𝑖𝑛 = 𝑓
𝑌𝑖𝑒𝑙𝑑
𝐶𝑎𝑝𝐸𝑥
= 𝑓
𝑴𝒐𝒅𝒖𝒍𝒆
𝐸𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡
𝑆𝑦𝑠𝑡𝑒𝑚 𝐴𝑟𝑐ℎ𝑖𝑡𝑒𝑐𝑡𝑢𝑟𝑒
 Variables in Bifacial Flash Testing:
Front
Only
BackFront
vs. x
White
Black
vs.
vs.
None
1. Sides Flashed 2. Shield on the
opposite side
3. Distance to the
back of the flasher
+

8. P. 8 | SunEdison Confidential
Modelling Challenges
𝐺𝑟𝑜𝑠𝑠 𝑀𝑎𝑟𝑔𝑖𝑛 = 𝑓
𝑌𝑖𝑒𝑙𝑑
𝐶𝑎𝑝𝐸𝑥
= 𝑓
𝑀𝑜𝑑𝑢𝑙𝑒
𝑬𝒏𝒗𝒊𝒓𝒐𝒏𝒎𝒆𝒏𝒕
𝑆𝑦𝑠𝑡𝑒𝑚 𝐴𝑟𝑐ℎ𝑖𝑡𝑒𝑐𝑡𝑢𝑟𝑒
 Albedo:
Image courtesy of Colorado State University

9. P. 9 | SunEdison Confidential
Modelling Challenges
𝐺𝑟𝑜𝑠𝑠 𝑀𝑎𝑟𝑔𝑖𝑛 = 𝑓
𝑌𝑖𝑒𝑙𝑑
𝐶𝑎𝑝𝐸𝑥
= 𝑓
𝑀𝑜𝑑𝑢𝑙𝑒
𝑬𝒏𝒗𝒊𝒓𝒐𝒏𝒎𝒆𝒏𝒕
𝑆𝑦𝑠𝑡𝑒𝑚 𝐴𝑟𝑐ℎ𝑖𝑡𝑒𝑐𝑡𝑢𝑟𝑒
 Albedo:
Composite
Shingle
White
EPDM
Unpainted
Metal Roof
White
Gravel
0 1005025 75

10. P. 10 | SunEdison Confidential
Modelling Challenges
𝐺𝑟𝑜𝑠𝑠 𝑀𝑎𝑟𝑔𝑖𝑛 = 𝑓
𝑌𝑖𝑒𝑙𝑑
𝐶𝑎𝑝𝐸𝑥
= 𝑓
𝑀𝑜𝑑𝑢𝑙𝑒
𝐸𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡
𝑺𝒚𝒔𝒕𝒆𝒎 𝑨𝒓𝒄𝒉𝒊𝒕𝒆𝒄𝒕𝒖𝒓𝒆
 Mechanical Design:

11. P. 11 | SunEdison Confidential
Modelling Challenges
𝐺𝑟𝑜𝑠𝑠 𝑀𝑎𝑟𝑔𝑖𝑛 = 𝑓
𝑌𝑖𝑒𝑙𝑑
𝐶𝑎𝑝𝐸𝑥
= 𝑓
𝑀𝑜𝑑𝑢𝑙𝑒
𝐸𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡
𝑺𝒚𝒔𝒕𝒆𝒎 𝑨𝒓𝒄𝒉𝒊𝒕𝒆𝒄𝒕𝒖𝒓𝒆
 Mechanical Design:
Image courtesy of gammasolar, via NREL

12. P. 12 | SunEdison Confidential
Modelling Challenges
𝐺𝑟𝑜𝑠𝑠 𝑀𝑎𝑟𝑔𝑖𝑛 = 𝑓
𝑌𝑖𝑒𝑙𝑑
𝐶𝑎𝑝𝐸𝑥
= 𝑓
𝑀𝑜𝑑𝑢𝑙𝑒
𝐸𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡
𝑺𝒚𝒔𝒕𝒆𝒎 𝑨𝒓𝒄𝒉𝒊𝒕𝒆𝒄𝒕𝒖𝒓𝒆
 Electrical Design:
 Optimal inverter capacity
 Does the DC:AC ratio metric make
sense for bifacial modules?
 Requirements for multiple MPPT
windows or string-/micro-inverters;
can they handle the additional
current?
 Implications for DC wiring
 Interpretation of electrical codes
Image courtesy of Sungrow

13. P. 13 | SunEdison Confidential
Modelling Challenges
𝐺𝑟𝑜𝑠𝑠 𝑀𝑎𝑟𝑔𝑖𝑛 = 𝑓
𝑌𝑖𝑒𝑙𝑑
𝐶𝑎𝑝𝐸𝑥
= 𝑓
𝑀𝑜𝑑𝑢𝑙𝑒
𝐸𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡
𝑆𝑦𝑠𝑡𝑒𝑚 𝐴𝑟𝑐ℎ𝑖𝑡𝑒𝑐𝑡𝑢𝑟𝑒