Changes in the characteristics of silicon photovoltaic cells of solar arrays after current overloads

2020

J. Adv. Dielect.

Self Cite

The ability of a structure in the form of a photovoltaic element with a built-in posistor layer based on a polymer nanocomposite with carbon filler being in direct thermal contact to protect against overvoltages was studied experimentally and by simulation. It was shown that the current and voltage on the reverse-biased [Formula: see text] junction of the photovoltaic layer are limited and decrease from the moment when the temperature of this structure reaches values close to the tripping temperature of the posistor nanocomposite to the low-conductivity state. The temperature of the photovoltaic layer has a value close to the tripping temperature of the posistor layer, which is equal to [Formula: see text]125[Formula: see text]C. The possibility of realizing protection against reverse electrical overvoltages and thermal breakdown of photovoltaic systems based on photovoltaic elements with built-in layers of posistor polymer nanocomposites with carbon fillers was established.

Section: Kinetics Of Reverse Voltage Limitingmentioning

confidence: 99%

Application of a polymer nanocomposite with carbon filler to limit overvoltages in a photovoltaic element

2020

J. Adv. Dielect.

Self Cite

Electrical properties of photogalvanic element with built-in posistor layer based on polymer nanocomposite with carbon filler

2020

ТКЭА

The study considers the problem of preventing overheat and thermal breakdown of a photovoltaic cell when a high reverse voltage is applied to its p—n junction. The overvoltage protection ability of a structure made up of a photovoltaic cell in direct thermal contact with a built-in posistor layer has been experimentally studied. Fragments of solar cells based on single-crystal silicon were used as a photovoltaic cells. The posistor layer was a polymer nanocomposite with carbon filler used in the resettable fuses of the “PolySwitch” technology. The authors study kinetics of changes in the electrical characteristics of such a structure under constant electric overvoltage on a shaded photovoltaic cell, when its p—n junction is turned on in the reverse direction. It is shown that the current and reverse voltage on the shaded photovoltaic cell are limited and reduced from the moment when the temperature of this structure reaches the values close to the temperature of the phase transition of the posistor nanocomposite to the low-conductive state, which is ≈ 125°С. With an increase in the overvoltage value, a decrease in the response time of the considered protection and an increase in the maximum current value through the structure under study are observed. A decrease in the current value required to reach the tripping temperature by the posistor layer can be achieved by reducing the thermal resistance of the contact between the photovoltaic and posistor elements of the structure. The results obtained indicate the possibility of implementing protection against reverse electrical overvoltage and thermal breakdown of photovoltaic systems based on photovoltaic cells with built-in fuse layers of a specified type.

Using a layer based on materials with a metal to semiconductor phase transition for electrothermal protection of solar cells

2021

ТКЭА

One of the main problems in ensuring the reliability of solar electrical power sources is local overheating, when hot spots form in photovoltaic cells of solar arrays. It is currently considered that these negative phenomena are caused, among other things, by overvoltage in the electrical circuits of solar arrays. This leads to the appearance of defective elements and a significant decrease in the functionality of the entire power generation system up to its complete failure. This study considers the possible ways to increase the reliability of solar arrays by using thermistor thermocontacting layers for preventing overvoltage events and overheating. The authors use simulation to study electrical characteristics of a photovoltaic cell in thermal contact with an additional layer based on thermistor materials with a metal to semiconductor phase transition. Vanadium dioxide with a phase transition temperature of ~340 K is considered to be a promising material for this purpose. During the phase transition, electrical resistance sharply decreases from the values characteristic of dielectrics to the values associated with metal conductors. It is shown that such thermistor layers can be used for protecting solar cells from electrical overheating under the following basic conditions: — the layer’s resistance in the «cold» state significantly exceeds that of the lightened forward-biased solar cell; — the layer’s resistance in the «heated» state is sufficiently low compared to those of the reverse-biased photovoltaic cell and of the power source. The current and temperature of the reverse-biased photovoltaic cell are limited and stabilized, and the voltage drop sharply decreases from the moment when the temperature of the thermistor layer reaches the values close to the temperature of its transition to the low-conductivity state. The obtained results substantiate the potntial of the described approach to protect photovoltaic cells of solar modules against electric thermal overloads.