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Solution of Half-cell Module

Solution of Half-cell Module


Alongside the line perpendicular to the direction of the bus bar, laser cuts the standard cell into two same pieces, thus Half-cell Module comes into being after packaged.


Characteristics of Half-cell Module

While the photovoltaic module is operating, grid lines, welding belts and bus bars on the cells bear the important function of current transmission. The current generated by the conventional photovoltaic module during operation is 8 to 10A, which is twice as much as that by the half-cell module. Joule effect will take into effect when the current flows through the cell welding belts. According to Joule's law Q=I2Rt, after the current is halved, the heat of the photovoltaic module in operation is only 1/4 of that of the whole piece. Through the analysis of actual power generation data, the power of the half-cell is increased by 3%-4%.

Low Current of Half Cell

Fig. 1: Low Current of Half Cell

For the coherence of the overall output current and voltage of conventional modules and half-cell modules, and to match the common photovoltaic system components in the market, half-cell batteries generally adopt the structure of series before parallel.

Series-parallel Structure of Half-cell Module

Fig. 2: Series-parallel Structure of Half-cell Module

Compared with the conventional modules, the half-cell module has lower operating temperature, excellent shielding resistance, higher packaging efficiency and lower hot spot temperature in addition to the reduction of internal losses mentioned above.


Besides, due to the low current of the half cell, lower current generates less Joule heat and lower working temperature. The absolute value of the power temperature coefficient of the module can be reduced to below 0.4%/℃, which is 1-2℃ lower than that of the traditional module. In general, the current is directly proportional to the light intensity, while the voltage is inversely proportional to the temperature. The higher the temperature, the lower the voltage. Therefore, The decrease of working temperature increases the power generation of photovoltaic modules in a disguised form. Data show that the power generation capacity can increase by about 1%.


As for packaging efficiency, the packaging loss of traditional conventional modules is generally more than 1%. However, half-cell modules, due to its low current, effectively improves the packaging efficiency. According to experimental data, its power generation can be increased by 2%-3%.


Due to the particularity of the series-parallel structure, the half-cell module has excellent anti-shielding capability. As with conventional module, in order to prevent the photovoltaic module from being damaged by the hot spot effect, three bypass diodes are generally connected in parallel beside the positive and negative poles of the photovoltaic module. When the cell cannot generate electricity due to the hot plate effect caused by shielding, the diodes act as bypasses, allowing the current generated by other cell strings to flow out of the diodes, so that the solar power generation system can continue to work.

Parallel Bypass Diodes of Conventional Modules

Fig. 3: Parallel Bypass Diodes of Conventional Modules

When the conventional modules are arranged longitudinally, the shadow will block the three cell strings at the same time. If all the three diodes are positively conductive, the modules will have no power output. If all the three diodes are not positively conductive, the power generated by the modules will be completely consumed by the blocked batteries, and the modules will have no power output. When the modules are arranged horizontally, shadow only blocks one cell string. The bypass diode corresponding to the blocked cell string will be turned on under positive pressure. At this time, all the power generated by the blocked cell string will be consumed by the blocked cell. At the same time, the diode is turned on forward, which can prevent the blocked cell from consuming the power generated by the unblocked cell string, and the other two cell strings can normally output power.


Therefore, when applying conventional modules, photovoltaic modules are often laid horizontally to avoid corresponding shielding areas. Lateral laying will increase the cost of mounting systems and cables, whereas avoiding shielding areas will waste land use area, which is a waste of resources. To a certain extent, the structure of half-cell modules connected in parallel with upside and downside solves this problem. This structure ensures not to affect each other. Even if the photovoltaic modules are laid longitudinally, the normal power generation of the upper half can be guaranteed when the lower half is shielded, thus not only improving the land use rate, but also reducing the influence of shielding on power generation and the hot spot effect.


When a cell or a group of cells in the module is shaded or damaged, the current provided by the cell is reduced. When the working current of the module exceeds the short-circuit current of the shielded cell, the two ends of the shielded cell are subjected to reverse bias to become load power consumption, resulting in the high local temperature. However, the power loss of hot spot happening in half-cell modules is half of that of conventional modules, which means it is safer under high power. On the one hand, the higher the power of the module and the hot spot temperature, the greater the security risks of the power station. Compared with the whole cell, the hot spot temperature of the half cell can be reduced by about 20℃, greatly improving the safety factor of the power station.


Application Scenarios

1. Complicated roof condition with obstacles

2. Limited roof area

3. Pursuit of higher power generation Benefit

4. Areas with high temperature and high radiation


Development Trend

As the photovoltaic market pursues higher power generation efficiency, the demand for LCOE is also increasing. More attention is paid to the safety of photovoltaic power systems. Compared with conventional modules, half-cell modules increase costs mainly in cell slicing, auxiliary materials, labor costs, equipment depreciation costs in the manufacturing process.


However, the power of the half-cell module can be increased by 5W-10W or even higher than that of the full-cell module. As the price of modules continues to decline, the overall system cost of half-cell modules is reduced.


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    If you are interested in our products and want to know more details,please leave a message here,we will reply you as soon as we can.