Types of photovoltaic panels and power calculation

Photovoltaic panels, also known as solar panels, are assemblies of several solar cell modules assembled in a certain way on a board, usually as a unit of a photovoltaic array.

A single solar cell cannot be used directly as a power source. A number of individual cells must be connected in series and parallel and tightly packaged into modules for power supply. The solar module (also called solar panel) is the core part of the solar power system. It is also the most important part of a solar power system. Its role is to convert solar energy into electrical energy, either by sending it to a battery for storage or by pushing the load to work. The quality and cost of the solar panel will directly determine the quality and cost of the entire system.

1. Cell Types

1) Monocrystalline silicon photovoltaic cells

The photovoltaic conversion efficiency of monocrystalline silicon solar cells is about 15%, with the highest reaching 24%. This is currently the highest photoelectric conversion efficiency of all types of solar cells. But the production cost is large. So much so that it is not yet widely and commonly used in large numbers. As monocrystalline silicon is generally encapsulated with tempered glass and waterproof resin. Therefore, it is robust and durable. The service life is generally up to 15 years and up to 25 years.

2) Polycrystalline silicon photovoltaic cells

The production process of polycrystalline silicon solar cells is similar to that of monocrystalline silicon solar cells. However, the photovoltaic conversion efficiency of polycrystalline silicon solar cells is much lower, and its photovoltaic conversion efficiency is about 12%. In terms of production cost, it is cheaper than monocrystalline silicon solar cells, easy to manufacture materials, save electricity consumption, and the total production cost is lower. Therefore, it has been developed in large numbers. In addition, the service life of polycrystalline silicon solar cells is shorter than that of monocrystalline silicon solar cells. In terms of performance-to-price ratio, monocrystalline silicon solar cells are also slightly better.

3) Amorphous Silicon Photovoltaic Cells

Amorphous silicon solar cell is a new type of thin-film solar cell that appeared in 1976. It is completely different from monocrystalline silicon and polycrystalline silicon solar cells in terms of fabrication methods. The process is greatly simplified, silicon material consumption is minimal, and electricity consumption is much lower. Its main advantage is that it can generate electricity even in low-light conditions. However, the main problem of amorphous silicon solar cells is the low photoelectric conversion efficiency. The international advanced level is about 10%, and it is not stable enough, and the conversion efficiency decays with the extension of time.

4) Multi-compound photovoltaic cells

Multi-compound solar cells refer to solar cells that are not made of single-element semiconductor materials. There are many varieties of solar cells researched by various countries, most of which are not yet industrially produced, mainly the following.

a) Cadmium sulfide solar cells

b) Gallium arsenide solar cells

c) Copper indium selenium solar cells (new multi-band gap gradient Cu(In, Ga)Se2 thin film solar cells)

2. Power Calculation

Solar AC power systems consist of solar panels, charge controllers, inverters, and batteries. Solar DC power generation system does not include an inverter. In order to make the solar power system provide enough power for the load, it is necessary to choose each component reasonably according to the power of the appliances. The following is an example of how to calculate 100W output power and 6 hours of use per day.

1) First of all, you should calculate the number of watt-hours consumed per day (including the loss of the inverter).
If the conversion efficiency of the inverter is 90%, then when the output power is 100W, the actual output power required should be 100W/90%=111W.
If it is used for 5 hours per day, the power consumption will be 111W*5 hours=555Wh.

2) Calculate the solar panel.
According to the effective sunshine time of 6 hours per day, and considering the charging efficiency and the loss in the charging process, the output power of the solar panel should be 555Wh/6h/70%=130W. 70% of which is the actual power used by the solar panel in the charging process.