Optimal design technology for crystalline silicon photovoltaic modules

Preface

Crystalline silicon is the core device for photovoltaic power conversion, but because the voltage, current and power of a single cell are limited, the cells must be connected in series and parallel to meet the voltage, current and power requirements of electrical equipment and industrial electricity. However, due to the physical brittleness of crystalline silicon photovoltaic cells, they are easy to break, so the cells need to be encapsulated and made into photovoltaic modules for protection.

Crystalline silicon photovoltaic modules are mainly divided into:

Conventional photovoltaic modules (composition: glass, EVA, crystalline silicon cells, backplane, aluminum frame, junction box, etc.);

Transparent photovoltaic modules (composition: glass, EVA, crystalline silicon cells, transparent backplane, aluminum frame, junction box, etc.);

Double-glass photovoltaic modules (composition: glass, PVB, crystalline silicon cells, glass backplane, junction box, etc.);

Frameless photovoltaic modules (conventional modules and transparent modules without aluminum frames);

The design of photovoltaic modules mainly considers three points:

Physical and electrical properties

The power, size, load, installation and other requirements of photovoltaic modules. The physical and electrical performance must meet IEC61215 and IEC61730 or UL1703.

Use Environment

Special designs are required for different environments where photovoltaic modules are used, such as:

If the modules are used in coastal or island areas, they need to be resistant to salt spray and corrosion. In this case, the modules need to meet the standard requirements of IEC61701.

For agricultural areas, the components need to be resistant to ammonia corrosion and meet the IEC62716 standard.

Optimization of cost performance

The design of photovoltaic modules needs to take into account both the performance and cost of the modules so as to optimize the cost performance of the modules.

Transparent components

Purpose of transparent components

Transparent photovoltaic modules can achieve different light transmittances depending on the design, so transparent modules are widely used in roofs and building integrated photovoltaics (BIPV).

Experimental design

2.1 Design Introduction

First of all, the raw materials of transparent components must meet the standards for material import of component factories, and the material tests must meet the performance quality requirements. The reference standards can be based on the raw material specifications, certification information, and the raw material tests evolved by the factory based on IEC61215 or UL1703.

Secondly, since transparent photovoltaic modules involve many variables (such as size, transmittance, cell power, number of cells, material price cost, labor cost, manufacturing cost, etc.), they are simplified here to consider transmittance, cost (yuan/W), and the maximum slope of the straight line passing through the origin in the curve graph = transmittance/(yuan/W).

Transmittance = {1-(cell area*number of cells)/module area} × glass transmittance × transparent backplane transmittance.

Cost (yuan/W) = (battery cell + other material costs)/module wattage.

Maximum slope = transmittance/(yuan/W)--------the maximum slope of the straight line passing through the curve and the origin.

The material composition of the transparent component is shown in Table 1.

Table 1 Material composition of transparent components

2.2 The number of cell power is fixed, and the others are uncertain, to determine the best cost performance

For any component, when the number of cells and power are constant, as the size of the component increases, the transmittance will increase, and the cost will increase accordingly. The best cost-effective point can be obtained by plotting transmittance and cost (yuan/W) as the coordinate axis. The following analysis leads to a relationship diagram between transmittance and cost (yuan/W).

The analysis is as follows:

The relationship between the transmittance Z of photovoltaic modules and the area change rate X of the modules

Z={1-(cell area*number of cells)/module area (1+X)}×glass transmittance×transparent backplane transmittance.

Let: (cell area * number of cells) / module area = a

Glass transmittance × transparent back panel transmittance = b

Therefore, Z={1-a/(1+X)}b, where a, b>0 and are constants, Z>0, X≥0.

A trend graph of the photovoltaic module transmittance Z and the module area change rate X is drawn, as shown in Figure 1:

Figure 1 Trend of component transmittance Z and component area change rate X

Relationship between PV module cost C (yuan/W) and area change rate X

C = {(battery cell + junction box + barcode + label + other material cost (1 + X)}/module wattage

= (cell + junction box + barcode + label) / module wattage + {other material cost (1 + X)} / module wattage

Order: A = battery cell + junction box + barcode + label) / module wattage

B = Other material cost / Component wattage

So, C=A+B(1+X), where X>0, A>0, B>0, and AB are constants.

A trend chart is drawn for the relationship between the photovoltaic module cost C (yuan/W) and the module area change rate X, as shown in Figure 2:

Figure 2 Trend of component cost C (yuan/W) and component area change rate X

As can be seen from Figure 2, as X increases, C also increases linearly.

Plot a graph with transmittance and cost (yuan/W) as the coordinate axes.

Based on Figure 1 and Figure 2, make Figure 3 showing the relationship between the transmittance and cost of photovoltaic modules.

Figure 3 Relationship between module transmittance and module cost (yuan/W)

As can be seen from FIG3 , at point Q, the slope of the straight line passing through the origin is the largest, that is, the value of transmittance/cost is the largest, and the cost performance is the best.

The relationship graph between photovoltaic module transmittance and module cost (yuan/W) should be universal for all transparent modules.

2.3 Given a certain module transmittance and model, but uncertain cell power, how to determine the best cost-performance ratio

When the transmittance of the photovoltaic module is determined (the number of cells and the size of the module are also determined), the power of the cell is changed, the cost (yuan/W) and the change trend of the transmittance are studied, and the best cost-effectiveness is determined.

C cost (yuan/W) = (cell + other material cost) / module wattage

= Cell/Module Wattage + Other Material Cost/Module Wattage

Let: a = battery cell/module wattage --- fixed value

b = other material cost / module wattage. Since other material costs remain unchanged, as module wattage increases, b value decreases, that is, C decreases, while transmittance remains unchanged.

As shown in Figure 4,

Figure 4 Relationship between light transmittance and cost

As can be seen from Figure 4, when the power of the cell increases, the power of the module increases, C (yuan/W) decreases, the transmittance remains unchanged, and the cost performance increases.

Therefore, increasing the power of the battery cell is beneficial to improving the cost performance.

2.4 Comparison of cost performance when the transmittance and cell type are fixed and the module size is uncertain

When the cell power model is constant, the transmittance is constant, and the number of solar cells is different, the changing trend of the cost performance (transmittance/cost (yuan/W)) between large modules and small modules is compared.

Cost C = (cell + junction box + barcode + label + other material costs) / module wattage

= (junction box + barcode + label) / module wattage + (cell + other material costs) / module wattage

Let: a = (junction box + barcode + label) / module wattage

b = (cell + other material cost) / module wattage

That is, cost C = a + b

Among them, a decreases as the power of the component increases.

b basically unchanged.

Therefore, when the cell power model is constant, the transmittance is constant, and the number of cells is different, the cost performance of large components (transmittance/cost (yuan/W)) is higher than that of small components.

2.5 Comparison of the cost performance of monocrystalline and polycrystalline modules with the same transmittance, size and power

When the size, transmittance and power of single crystal and polycrystalline modules are the same, the price of polycrystalline modules is lower than that of single crystal modules. Therefore, the cost performance of polycrystalline modules is higher than that of single crystal modules.

Conclusion

For any transparent photovoltaic module, when the number of cell specifications is constant, as the size of the module increases, the transmittance will increase, and the cost will increase accordingly. Plotting the transmittance and cost (yuan/W) as the coordinate axis can get the point with the best cost performance.

When the module transmittance, number of cells and module size are constant, the greater the cell power, the higher the cost performance of the module (transmittance change trend/cost (yuan/W)).

When the cell power model is constant, the transmittance is constant, and the number of cells is different, the cost performance of large components (transmittance/cost (yuan/W)) is higher than that of small components.

When the size, transmittance and power of single crystal modules and polycrystalline modules are the same, the cost performance of polycrystalline modules is higher than that of single crystal modules (transmittance/cost (yuan/W)).

General components

The raw materials of conventional photovoltaic modules must meet the material standards for the material import of the module factory, and the material tests must meet the performance quality requirements. The reference standards can be based on the raw material specifications, certification information, and the raw material tests of the factory evolved from IEC61215 or UL1703. Or for special requirements, such as for coastal areas or islands, the modules must meet the standard requirements of IEC61701 for salt spray protection. For agricultural areas, the modules need to meet the standard of IEC62716 for ammonia corrosion resistance.