This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
This study focuses on the implications of a high reverse bias breakdown in silicon heterojunction cells (SHJ). In relevant literature, there is a lack of explicit investigation which
compares high breakdown voltage cells (commonly SHJ) to low breakdown voltage cells
(commonly silicon homojunctions) in an installation setting. In addition, their…
This study focuses on the implications of a high reverse bias breakdown in silicon heterojunction cells (SHJ). In relevant literature, there is a lack of explicit investigation which
compares high breakdown voltage cells (commonly SHJ) to low breakdown voltage cells
(commonly silicon homojunctions) in an installation setting. In addition, their relationship with
shading and how they react with bypass diodes are also not very prevalent. Therefore, my project
dives into how shading impacts a string of high breakdown voltage cells and a string of low
breakdown voltage cells, as well as how those cells interact with a bypass diode.
In order to conduct this investigation, I used the simulation software LTSpice XVII to
create an accurate simulation model of a SHJ cell with a 21 V reverse breakdown voltage. With
this cell model, I strung 10 cells together, and varied the shading on a single cell while measuring
the string’s output current, voltage, and power. Next, I attached a bypass diode to the shaded
cell, and continued to increase the number of cells attached to the bypass diode while continuing
to examine the string’s output. Once I gathered this data, I modified the original cell model to
have a lower reverse breakdown voltage of 5 V. From here, I strung 10 cells together again, and
repeated the same measurements from the 21 V string.
Upon completing these measurements, I found that the SHJ cells were in fact harder to
force into reverse bias than the cells with the lower reverse breakdown voltage, suggesting that
solar installation owners should consider transitioning to SHJ-based modules. When bypass
diodes are being considered, my results demonstrated that heavy shading (about 65% and
higher) was required for the bypass diodes to have an observable impact on the string’s power
output. Therefore, owners should consider how severe the shading their installation may receive
before investing in bypass diodes. If owners do find the need for the bypass diodes, my findings
also show that the diodes should be used sparingly and in a compromise with output power and
cost.
