Why wouldn't Silicon cells last forever?

Solar Guppy wrote: »

In theory, yes, cells will last forever. There will be some degrading overtime but its measured in decades and frankly, cells haven't been around long enough to measure greater than 50 years.

I think its more likely the glass will have a great reduction in panel output due to abrasion and other environmental effects

From one of the google link wrote:

Modeling solar cell degradation in space: A comparison of the NRL displacement damage dose and the JPL equivalent fluence approaches.

Abstract
The method for predicting solar cell degradation in space radiation environments developed recently at the US Naval Research Laboratory (NRL) is compared in detail with the earlier method developed at the US Jet Propulsion Laboratory (JPL). Although both methods are similar, the key difference is that in the NRL approach, the energy dependence of the damage coefficients is determined from a calculation of the nonionizing energy loss (NIEL) and requires relatively few experimental measurements, whereas in the JPL method the damage coefficients have to be determined using an extensive set of experimental measurements. The end result of the NRL approach is a determination of a single characteristic degradation curve for a cell technology, which is measured against displacement damage dose rather than fluence. The end-of-life (EOL) cell performance for a particular mission can be read from the characteristic curve once the displacement damage dose for the mission has been determined. In the JPL method, the end result is a determination of the equivalent 1 MeV electron fluence, which would cause the same level of degradation as the actual space environment. The two approaches give similar results for GaAs/Ge solar cells, for which a large database exists. Because the NRL method requires far less experimental data than the JPL method, it is more readily applied to emerging cell technologies for which extensive radiation measurements are not available. The NRL approach is being incorporated into a code named SAVANT by researchers at NASA Glenn Research Center. The predictions of SAVANT are shown to agree closely with actual space data for GaAs/Ge and CuInSe2 cells flown on the Equator-S mission. Published in 2001 by John Wiley & Sons, Ltd.

IEEE Transactions on Electron Devices wrote:

Publication Date: Aug 1971
Volume: 18, Issue: 8
On page(s): 507- 511
ISSN: 0018-9383
Current Version Published: 2005-08-09
Abstract
The Lincoln Laboratory satellites LES-4 and LES-5 each carry solar cell experiments consisting of the following. VocMeasurement of 10 Ω . cm silicon cell with 30-mil cover slide. IscMeasurement of 10 Ω . cm silicon cell with 30-mil cover slide. IscMeasurement of 10 Ω . cm silicon cell with 6-mil cover slide. IscMeasurement of two CdTe thin-film cells (LES-4 only). IscMeasurement of two CdS thin-film cells (LES-5 only). LES-4 was orbited in December 1965 in a highly elliptical orbit with an 18 000-mi apogee and a 100-mi perigee; LES-5 was injected into a quasi-synchronous orbit in July 1967. In the LES-5 experiment, the Si cells exhibit an Iscdegradation of eight percent per year plus an initial short term degradation of four percent; Vocis relatively unaffected. The CdS cells have an Iscdegradation of 20 percent per year plus an initial degradation of five percent. In the LES-4 experiment, the Si cell with the 6-mil cover slide shows two rates of degradation, with the break point occurring at about 100 days; the cell with the 30-mil cover slide shows substantially less degradation. After 700 days, the short-circuit currents of these two cells are 60 percent and 78 percent of their initial AMO values. One CdTe cell has decayed to 38 percent of its initial AMO value after 700 days; the second sample gives anomalous results. In each experiment AM0 to AM1 short-circuit current ratios of approximately 1.09 were noted.

RCinFLA wrote: »

Space rated solar cells and arrays are in a whole different class then typical PV panels used by us mere financial mortals.