Hydrolysis Kinetics and Lifetime Prediction for Polycarbonate and Polyesters in Solar Energy Applications
The hydrolysis kinetics of polyesters and BPA polycarbonate appear to be second order in water, that is, second order in relative humidity (RH). This finding, combined with activation energies for hydrolysis, was used in a service life prediction model for a photovoltaic (PV) module front sheet application. The modeling process involves: (1) finding finely time-parsed climatic data for a benchmark location, (2) calculating module temperature and RH from the climatic data, and (3) applying the kinetics to determine the amount of degradation that occurs in 1 year relative to accelerated laboratory conditions, 85 °C and 85 % RH in this case. Acceleration factors under laboratory conditions are very high, especially for poly(ethylene terephthalate) (PET), leading to predicted lifetimes of several centuries if hydrolysis is the only degradation mode. The model was tested for sensitivity to assumptions and experimental uncertainties, and hydrolysis can be considered unimportant in this solar energy application. Concerns about PET suitability on the basis of its relatively short embrittlement times in the 85 °C/85 % RH damp heat test are unfounded.
KeywordsService life prediction Activation energy Hydrolysis Kinetics PET Polycarbonate Solar
The author thanks Ken Gillen, now retired from Sandia National Laboratories, for inspiring the kinetic analysis, Dennis Coyle at GE Global Research for collaboration at critical points in the kinetic analysis, and Mike Kempe at NREL, Golden, CO, for sharing the Miami climatic data set and for several stimulating and helpful discussions.
- 1.Pickett JE, Sybert PD, Carter RL, Gibson DA, Rice ST (2007) Weathering characteristics of resorcinol arylate copolymers. Polym Prepr 48(1):643–644Google Scholar
- 2.Zhou J, Pickett JE, Chakravarti S US Patent application US 20120248497Google Scholar
- 3.Kempe MD, Wohlgemuth JH (2013) Evaluation of temperature and humidity on PV module component degradation. In: 39th IEEE photovoltaic specialists conference, Tampa, FL, 16–21 June 2013 (also NREL PV module reliability workshop, Golden CO, 26–27 Feb 2013)Google Scholar
- 6.Wilcox S, Marion W (2008) Users manual for TMY3 data sets. Technical report NREL/TP-581-43156, Revised May 2008. http://www.nrel.gov/docs/fy08osti/43156.pdf
- 7.King DL, Boyson WE, Kratochvil JA Photovoltaic array performance model. SAND2004-3535, Sandia National Laboratories. http://prod.sandia.gov/techlib/access-control.cgi/2004/043535.pdf
- 8.TamizhMani G, Ji L, Tang Y, Petacci L, Osterwald C Photovoltaic module thermal/wind performance: long-term monitoring and model development for energy rating. NREL/CD-520-33586, p 936. http://www.nrel.gov/docs/fy03osti/35645.pdf
- 10.Davis MW, Fanney AH, Dougherty BP (2001) Prediction of building integrated photovoltaic cell temperatures. Trans ASME 123:200–210Google Scholar