The efficiency of a solar cell is quite low, the research is being conducted on the development of different and advanced materials and technology to build more efficient solar cells.

This is an era of creativity, an era of technology that motivates and improves the lives of millions. In this technology-driven lifestyle, the factor on which countries are compared is their energy consumption.

** More developed the country means more energy consumption per citizen. With the increasing threat of climate change, countries are moving towards non-conventional energy sources to satisfy their energy needs. In many countries, the government is taking the initiative and investing a significant amount in developing technology through which non-conventional energy sources can be efficiently utilized.**

**Solar energy is a prominent source of non-conventional energy, and the solar cell is one of the most popular ways to convert solar energy into a usable form of energy. The efficiency of a solar cell is quite low, the research is being conducted on the development of different and advanced materials and technology to build more efficient solar cells.**

Solar cell basically converts energy received from the sun into electricity. As solar panels need a large area for collection, efficiency plays a vital role. In simple words, efficiency is how much energy output you get for the incident energy or energy spent.

Solar Cell I-V Characteristic Curves are graphs of output voltage versus current for different levels of insolation and temperature and can tell you a lot about a PV (Photovoltaic-which converts light energy into electricity) cell or panel’s ability to convert sunlight into electricity. The most important values for calculating a particular panel power rating are the voltage and current at maximum power.

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**VOC = Open-Circuit Voltage **

- This is the maximum voltage that the array provides when the terminals are not connected to any load (an open circuit

condition). This value is much higher than Vmp which relates to the operation of the PV array which is fixed by the load. This value depends upon the number of PV panels connected together in series.

**ISC = Short-Circuit Current**

- The maximum current provided by the PV array when the output connectors are shorted together (a short circuit condition). This value is much higher than Imp which relates to the normal operating circuit current.

**MPP= Maximum PowerPoint **

- This relates to the point where the power supplied by the array that is connected to the load (batteries, inverters) is at its maximum value, where MPP = Imp x Vmp.

**MPP = Imp x Vmp**

- The maximum power point of a photovoltaic array is measured in Watts (W) or peak Watts (Wp).

**FF = Fill Factor **

- The fill factor is the relationship between the maximum power that the array can actually provide under normal operating conditions and the product of the open-circuit voltage times the short-circuit current, ( Voc x Isc ) This fill factor value gives an idea of the quality of the array.

There are other factors too for measuring the performance of the solar cell such as *Quantum efficiency*, *thermodynamic efficiency*.

These all factors take many things into account, some parameters can be measured directly while it’s challenging to measure others. But the primary motive to calculate these factors is to enhance the performance, know the limitations, and to get close to maximum theoretical efficiency.

Fig: Current and voltage (I-V) characteristics for a particular PV(Photovoltaic) cell.

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Then, up to what percentage of the maximum power (Imp x Vmp) can we expect a solar panel to produce under normal operating conditions?

Then, it is quite usual to calculate to the total energy radiated on a solar panel per day, by multiplying the daily irradiation value by the area of the panel. Then the output power of the panel can be calculated as the product of the received power by the efficiency. Are there ranges of efficiencies for a given panel so that the designer could have an idea of the value to consider?

Thanks, very much for the explanations.

It seems like the slope of the I-V curve, whose reciprocal gives the characteristic resistance of the panel will depend on which scales are used to represent the curent and the voltage on the two axes. If this is so, does it impact the value of the characteristic resistance? If this is not the case, then there will be no reason to worry.

Also, it will be interesting to know how the concavity of the power curve is made so that the MPP be located exactly as the intersection point between the power curve and the bisector line.