3 Common FAQs About Solar Module Microcracks
By Paul Wormser
What are Microcracks?
Microcracks are tiny cracks in solar cells that are produced from very thin and brittle wafers of silicon. While they start out as too small to be seen, they can grow when subjected to the normal stresses that solar modules go through during their operating life. As tiny cracks in a silicon solar cell, microcracks are often benign. Once they grow, they can compromise module output, longevity and safety.
What Causes Microcracks?
Microcracks can be caused during manufacturing, shipping, installation, and even after installation.
During manufacturing, microcracks can result from mechanical and thermal stress. Wafers are thin slices of (principally) silicon, cut from blocks. If the cut isn’t clean, if the thickness isn’t uniform, if the wafer has a defect, the wafer (and the cell that is made from it) becomes even more fragile. If the soldering machine introduces too much heat too fast, the thermal stress can cause cracks; the solderingstep is the cause of the most insidious cracks. And then there are many steps in a process where handling can cause cracks. Remember – wafers and cells are brittle. Modern cell processes also use cell cutting; if not done “just so,” the cut can weaken a cell. And there are many other ways for microcracks to form. These stresses and process and material defects can also cause large cracks.
During shipment, handling during warehouse deliveries, cargo transfers, and final delivery can cause microcracks to become large cracks, even after modules leave the factory. Vibrations from numerous points between the factory and the jobsite can drive existing microcracks to grow in size. New cracks can also be created.
During installation, dropping, bending, stepping on, and leaning on modules during installation can lead to excessive module stress points that can drive existing microcracks to grow in size.
After installation, hailstorms, high winds, and other weather events can drive existing microcracks to grow in size.
Why is it Important for Developers and Asset Owners to Detect Solar Module Microcracks?
Cells with cracks can limit the power output of a module or a series string of modules. Some cracks can result in cells becoming hot, which can lead to catastrophic failure -- even fire. One source of cracks is microcracks. It’s important to take steps to avoid buying modules with microcracks.
Modules ship from factories every day with some amount of microcracks. Over time, these cracks are likely to grow. Some will become a problem, and some will become a serious problem.
Microcracks, by nature of being small and often hidden beneath solar cell interconnect ribbon, can be elusive to detection in a factory. Solar manufacturers do take steps to prevent and minimize the impact of microcracks.
They look for cracks – large and small, including microcracks— and repair modules when they can, or they remove modules that don’t meet their specification for cracks. These steps are not 100% effective. Good product design, good manufacturing processes, and attention to quality are essential; third-party oversight helps identify and correct gaps.
Want to Learn More?
View Paul Wormser’s 7-part video series on microcracks:
Paul Wormser is Vice President, Technology at Clean Energy Associates. Paul has 40+ years of solar industry experience with management roles in solar technology and business development for the world’s largest solar companies, including SunEdison, First Solar, Sharp, Konarka, Mobil Solar and Exxon Solar.
