The effects of temperature on the production of photovoltaic installations

instalaciones fotovoltaicas

The effects of temperature on the production of photovoltaic installations

Over the past few weeks, information has been given that spoke of a Decreased photovoltaic output due to high heat wave temperatures. With temperatures up to almost 45 º c, the production of photovoltaic installations in Spain has fallen by 4% or 5% over the usual production that they would have had with a temperature of 10 º C LESS.

Obviously the production of a photovoltaic system depends on the number of hours of sun, since the radiation is Direct consequence of what the photovoltaic installations produce, But it is true that at the same time of sun, a higher temperature of the cells and modules that compose a photovoltaic installation reduce their production.

All these concepts are well known by technicians who are dedicated to photovoltaic issues, but are not known to the rest of the public who believe that photovoltaic installations produce more when it is hotter.

the photovoltaic cell behaves like a generator of electric current, whose characteristic is function of three fundamental variables: intensity of the solar radiation, temperature and area of the Cell.

Solar cells are composed of semiconductor materials, mainly silicon, and are elements that directly transform part of the solar energy they receive in electrical energy (production to which we are referring).

The temperature of the cell has an important effect on the value of the voltage in open circuit (Voc, which is the maximum voltage value at the ends of the cell and is given when it is not connected to any load), and we can see it on the curve I-V , as shown in the figure below. thus, when the temperature increases, the open circuit voltage decreases in the order of a few millivolts for each degree Celsius that the temperature rises (2.3 mv/º C for the silicon and between 2 and 2.2 mv/º C in the case of arsenide of gallium).

In addition, as a result of this variation of Voc, as the temperature increases, it causes in turn that the efficiency of the cell do the same: decrease by increasing the temperature (it is reduced between 0.4 and 0.5% by º C in the silicon cells and about 0.3% by º C in those of arsenide of gallium). The following figure illustrates the variations of the main electrical characteristics of a solar cell depending on the Temperature.

Electrical characteristics of a solar cell depending on the temperature

The open circuit voltage of a cell depends exclusively on its temperature, Tc, and The working temperature of the cells depends exclusively on irradiance and ambient temperature.