Introduction of Half Cell technology
For Half Cell Size technology, they actually cut ordinary solar cells in half. Unlike the common photovoltaic modules with 60 or 72 cells, they become 120 or 144 half cells, but maintain the same design and size as conventional modules.
Half cell technology generally adopts laser cutting method, which cuts the standard battery into two half cells in the same direction perpendicular to the main grid line of the battery, and then weld them in series.
Like conventional components, the half cell package is also packaged with tempered glass, EVA and backplane. Conventional solar panels usually contain 60 0.5-0.6V solar cells in series. The voltage is increased in series, so the working voltage of 60 pieces of components is 30-35v. If half of the batteries are connected together as in the standard components, they will produce half the current and twice the voltage, while the resistance remains unchanged (as shown in the figure below).
In order to ensure the consistency of the overall output voltage and current with the conventional components, the half battery module will generally adopt the series parallel structure design in the plate type design, which is equivalent to two small components in parallel.
As shown in the above figure, the open circuit voltage of a half cell is the same as that of a whole cell, and the number of half cells has doubled. After being divided into two parts, the number of cells in each part is the same as that of the whole cell, while the voltage of the two parts in parallel is the same as that of each part alone, so the total output voltage has not changed relative to the whole cell.
Because half of the battery is only 520w half cells size of the conventional battery, the current of each battery is only half of that of the conventional battery. And in The plate type is designed to have the upper and lower parts in parallel, and the output current returns to the current value of the whole battery.
The resistance of half battery is only half of that of the whole one, so the resistance of each part in parallel is only half of that of the whole component. Connect the two parts with only half of the resistance in 520w half cells size, and the total loop resistance is only 1/4 of the whole resistance.
The connection design of junction box is also different due to the change of plate type design. Generally, a three part junction box is used.
Advantages of Half Cell design
-Lower package loss
As mentioned above, due to the reduction of internal current and line resistance, the internal loss consumed in the internal circuit is reduced, and the power loss is proportional to the current. 520w half cells size of the current and one quarter of the resistance enable the half module to reduce the power loss by four times, and the corresponding output power and power generation are also increased.
At the same time, due to the reduction of internal loss, the working temperature of the module and junction box also decreases. Under the outdoor working state of the module, the temperature of the half module itself is about 1.6 ℃ lower than that of the conventional whole module. The lower temperature makes the module have higher photoelectric conversion efficiency.
Even if the two parts of 520w half cells size are not connected in parallel, but all half of the cells are connected to work like a standard solar panel, the current is only half, but the resistance is the same, and the power consumption is only 1/4.
-Shadow tolerance reduces the risk of hot spots
The half panel resists the influence of shadow better than the standard solar module.
Unlike the standard module, which has three panel battery strings, the 520w half cells size‘s half mode has six battery strings, making it a six string battery board. Although a small part of the shadow (leaves, bird droppings, etc.) on the component will invalidate the whole battery string, because of the design of the bypass diode (marked in red in the figure below), the string will not affect other battery strings, reducing the impact of the shadow.
Six independent battery strings have three bypass diodes, providing better local shadow tolerance. Even if half of the component is shaded, the other half can still work.
-Low current reduces hot spot temperature
Half cell can distribute internal current in the system and improve its performance, life and shadow tolerance.
When a battery of a battery string in the module is shielded, the battery will form a hot spot in the circuit, and the continuous high temperature may damage the module. Since the number of 520w half cells size battery strings is twice that of the original, which means that the heat at the hot spot is only half, and the lower heat causes less damage to the module, it can improve the ability to resist hot spot damage and improve the service life of the module.
-Shadow tolerance reduces power loss
In a photovoltaic array, many modules are usually connected in series, and then connected in series and parallel with other sub modules. Current flows into and out of each component in series in the same substring.
For the traditional component board design, once a component has power loss due to various reasons of shadow, it will affect all components of the substring. In the 520w half cells size module in the figure above, the bypass diode limits the power loss of the shaded part rather than the whole module. It creates an alternative path for the current to flow in the non shaded part, and avoids the current from passing through the shaded part, reducing the influence of the shadow and improving its performance.
The future of half Cell technology
The use of 520w half cells size can provide great advantages and improve performance under shadow conditions, which is of great significance for the overall power generation of building photovoltaic, which is vulnerable to other building obstacles.
Half battery can increase the power generation, but its system design is similar to that of the whole module, without increasing the installation cost, ensuring a lower lcoe. The improvement of laser cutting technology makes the cutting defects of half battery almost negligible.
With the popularity of large components and large silicon wafers, the trend of half or even three pieces is becoming more and more obvious. According to the estimates of relevant industry institutions, the market share of 520w half cells size components is expected to exceed 50% in the next three years.
