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Lighting conditions, the better is not necessarily higher power output

Release date: 2016-3-31 14:38:48 Visits: 459

Day conditions is an important factor affecting the system generating capacity, however, the best sunlight conditions, when power generation is not necessarily the highest!

In the northern hemisphere, for example, the day of the summer solstice, the sun direct the Tropic of Cancer, Tropic of Cancer and north of the day sunlight conditions reached the highest value of the year, however, the day is not the peak generating capacity throughout the year. Except sunshine conditions, the temperature of the photovoltaic power generation system is critical influence.

The core of the PV modules for solar cells, the current large-scale commercial application is mainly silicon solar cells: monocrystalline silicon solar cells, polycrystalline silicon solar cells and amorphous silicon solar cells. Effect of temperature on silicon-based solar cells, mainly reflected in the open-circuit voltage of the battery slice, the short-circuit current, peak power and other parameters with temperature changes, and then the components will also be affected.

[Note] the better the lighting conditions are not necessarily higher power output

Peak power of solar cells decreases with increasing temperature, Yingli 60cell series of components, for example, as shown above, at NOCT (irradiance 800W / m2, ambient temperature of 20 ℃, wind speed 1m / s assembly in open condition operating temperature state) under test conditions, cells operating temperature is increased by 1 degree, the peak power will decline 0.42%.

It is estimated that in the summer, when the best light conditions, cells operating temperature can reach 80 ℃, at which time the component peak power rating (at 25 degrees) will decrease compared to about

(80-25) × 0.42% = 23.1%

In theory, light intensity, the higher the cell temperature, from the viewpoint of a single factor, increasing the light intensity increases PV power output, temperature rise will reduce the power output of photovoltaic. Therefore, the maximum light intensity when light and temperature affected by two factors, the PV power output is not necessarily the largest.

principle

The main structure is the pn solar cell power generation section, cells will produce a large number of carriers in the vicinity of pn junction in the light conditions, the built-in electric field pn junction carrier separation, so that the positive and negative poles of the charge accumulation in the battery, the positive and negative after the formation of the current output electrode charge is collected. The higher the collection efficiency of the electrode to the positive and negative charges, the higher the output efficiency of solar cells.

In strong light conditions, an increase in the formation of the carrier, the poles can gather more carriers in the battery. But at the same time, strong light causes cells to absorb more solar energy, most of which light energy into heat energy absorbed by cells, the battery chip temperature rises, the carrier movement speed becomes faster, the carrier recombination rate increased. In addition, the environmental conditions in summer low wind, low humidity also make the cells of higher operating temperatures. So, the next Xia Tianqiang light conditions, although the cells internally generated more carriers, but a large number of carriers are collected before the electrode composite out, the power output of solar cells will not necessarily increase.