Dear Vangelis

This is a very good question. My suggestion is that it be best for you to start with the NREL stiudies:

http://www.nrel.gov/pv/performance_reliability/real_time.html

From a financial analysis angle on component failures, you can download 

http://www1.eere.energy.gov/solar/sunshot/financial_opps_detail.html?sol_id=575

Trust this helps

Gerro

IEA-PVPS Task 13 Annual Report is also a good reference.

(T13-01 2014 Review of Failures of PV Modules)

http://www.iea-pvps.org/index.php?id=275

Please find a complete Review of Failures of Photovoltaic Modules  in 

http://engineering.case.edu/centers/sdle/sites/engineering.case.edu.centers.sdle/files/iea-pvps_t13-01_2014_review_of_failures_of_photovoltaic_modules_final.pdf