Energy and Power Engineering, 2013, 5, 455-458
http://dx.doi.org/10.4236/epe.2013.57049 Published Online September 2013 (http://www.scirp.org/journal/epe)
High Voltage Stress Impact on P Type Crystalline Silicon
PV Module
Han-Chang Liu*, Chung-Teng Huang, Wen-Kuei Lee, Mei-Hsiu Lin
Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan
Email: *itri960529@itri.org.tw
Received July 18, 2013; revised August 18, 2013; accepted August 25, 2013
Copyright © 2013 Han-Chang Liu et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
The effects of the high voltage stress and other environmental conditions on crystalline silicon photovoltaic module
performance have not been included in the IEC 61215 or other qualification standards. In this work, we are to evaluate
the potential induced degradation on p type crystalline silicon PV modules by three cases, one case is in room tempera-
ture, 100% relative humidity water bath, another is in room temperature, the front sheet coverage with aluminum foil
and the other is in the 85˚C, 85% relative humidity climate chamber. All the samples are applied with the −1000 V bias
to active layers, respectively. Our current-voltage measurements and electroluminescence results showed in these mod-
ules power loss of 37.74%, 11.29% and 49.62%, respectively. These test results have shown that among high voltage
effects the climate chamber is the harshest and fastest test. In this article we also showed that the ethylene vinyl acetate
volume resistivity and soda-lime glass ingredients are important factors to PID failure. The high volume resistivity
which is more than 1014 Ω·cm and Na less contents glass will mitigate the PID effect to ensure PID free.
Keywords: Potential Induced Degradation; High Voltage; Volume Resistivity
1. Introduction
In photovoltaic (PV) solar modules, reliability is the very
important issue for solar power performance, as light
induced degradation is a well-known phenomenon. It has
long been included in the performance guarantees offered
by producers in the industry or the calculations of project
developers and system operators. Light induced degrada-
tion can cause an approximate 2% decrease in system
performance in the first few hours of operation of any
new PV installation. In 2005, a new form of performance
degradation began to be noticed and now called potential
induced degradation (PID) [1] which is high voltage
stress effect in negative potential field relative to ground.
With the more and more growing PV system and in-
creasing system voltages the PID effects are more seri-
ously and the leakage currents are the characterizations.
Possible pathways for the leakage currents from the en-
capsulated cell to the frame are described by J. A. del
Cueto [2]. The domain pathway to cause PID is via the
front sheet as glass to the frame. Higher leakage currents
can be caused by water entering the solar module causing
the encapsulation material to become more conductive.
So far the potential degradation mechanism is not
monitored by the typical PV tests listed in IEC 61215 [3].
Some researchers were trying to find out it. It is known
that metal ions such as Na+ formed from the oxides of the
module glass can drift toward the cell if the cell is biased
negatively [4]. Recently P. Hacke et al. found the in-
creased Na concentrations in the surface and sub-surface
area of PID affected samples were shown by secondary
ion mass spectroscopy (SIMS) [5] and Na precipitates
were found on the surface of such samples [6]. M.
Schütze et al. show that PID can also be caused by other
ions usually not present in photovoltaic modules indicat-
ing that the chemical nature of the ions is not relevant for
PID [7]. The Dr. Liu et al. in their study directly verified
that the PID caused by Na+ from their saline water bath
experiment [8]. Until now, there is no agreement with
evidence that observed metal concentration increasing in
the vicinity or inside the cell is responsible for shunting
of PID affected modules. The effect of the high voltage
and other environmental conditions on module perform-
ance has not been included in the IEC61215 or other
qualification standards. In this work we discussed the
PID effects in different environmental conditions. The
case one is 100% relative humidity (RH) water bath, an-
other is covered with conductive aluminum foil and the
other is tested in the 85˚C/85% RH chamber to provide
*Corresponding autho
.
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