Advantages of half-cell solar panels: low power loss, low heat spot risk, low packaging loss...
Half piece technology: What is a half-cell solar panel?
The half-slice technique essentially cuts an ordinary whole solar cell in half. Instead of having 60 or 72 cells like typical PV modules, they have 120 or 144 half-cells, but keep the same design and size as regular modules.
Half cell technology generally uses laser cutting method, along the direction perpendicular to the main grid line of the battery standard battery is cut into the same two half batteries, and then welded in series.
As with conventional components, the half-piece battery package is packaged with tempered glass, EVA, and a back plate. A conventional solar panel usually contains 60 0.5-0.6V solar cells in series. The voltage is increased in series so that the 60-piece assembly operates at a voltage of 30-35V. If half the cells are connected together, as in a standard assembly, they will produce half the current and twice the voltage, with no change in resistance.This is an unreasonable approach, as shown below：
In order to ensure that the overall output voltage and current of the conventional components are consistent, the upper half of the battery module in the plate design generally adopts the series-parallel structure design, which is equivalent to two components connected in parallel.
The open-circuit voltage of a half cell is the same as that of a full cell, and the number of half cells is doubled. After being divided into two parts, the number of cells in each part is the same as that of the full cell, and the voltage of the two parts connected in parallel is the same as that of each part alone, so the total output voltage is not changed compared with that of the full cell.
Half -Cell is half the size of a regular Cell,So each cell has only half the current of a conventional cell。The plate is designed to be connected in parallel with the upper and lower parts, and the output current is restored to the current value of the whole battery.
Half a cell has only half the resistance of a full cell, so each part connected in parallel has only half the resistance of a full cell. If the two parts with only half of the resistance are connected in parallel, the total circuit resistance is only 1/4 of the full resistance.
The change of the design makes the junction box connection design also different, generally using a tricad junction box
Advantages of half cell design
1.Shadow tolerance reduces power loss
In a photovoltaic array, a number of modules are usually connected in series and then connected in parallel with other submodules. The current flows in and out of each of the components in series in turn in the same substring.
For the traditional PV module design, once the power loss of a module due to various reasons of shadow, it will affect all the components of the substring.In a half-cell module, the by pass diode limits the power loss in the shaded part rather than the whole module. It creates an alternative path for current flow in the non-shaded part and avoids current flow through the shaded part, reducing the impact of shadows and improving its performance.
2.Lower packaging loss
Because the internal current and line resistance are reduced, the internal loss consumed in the internal circuit is reduced. The power loss is proportional to the current. Half of the current and a quarter of the resistance allow the half-chip component to reduce the power loss by 4 times, and the corresponding power output and generation is increased.
At the same time, due to the reduction of internal loss, the operating temperature of the component and the junction box also drops. Under the outdoor working condition of the component, the temperature of the half-piece component is about 1.6℃ lower than that of the conventional whole-piece component, and the lower temperature enables the component to have higher photoelectric conversion efficiency.
3.Shadow tolerance reduces the risk of hot spots
Instead of having three panel battery strings like standard components, the half-cell solar panel has six battery strings, making it a six-string panel. Although a small shadow on the assembly (leaves, bird droppings, etc.) can disable the entire battery string, THE BYPASS diode design (marked in red below) does not affect other battery strings, reducing the effect of the shadow.
Six separate battery strings with three bypass diodes provide better local shadow tolerance. Even if one half of the component is shaded, the other half still works.
4.Low current reduces hot spot temperature
A half cell distributes internal current through the system and improves its performance, lifetime, and shadow tolerance.When a piece of a battery string in an assembly is obscured, the battery forms a hot spot in the circuit, and the continuous high temperature can damage the assembly. Since the number of half component battery string is twice the original, it means that the heat in the hot spot is only half, and the lower heat will cause less damage to the component, so it can improve the ability to resist the damage of the hot spot and improve the service life of the component.
Half a cell can provide great advantages and improve performance under shadowing conditions, which is of great significance for improving the overall photovoltaic power generation of buildings that are easily affected by other building obstacles.
Half a cell can increase power generation, but its system design is similar to that of a full piece, with no additional installation cost, ensuring a lower LCOE. Improvements in laser cutting technology have made the cutting defects of half a cell almost negligible