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[Photovoltaic Technology] Photovoltaic Solar Panel Power Generation Principles and Analysis of Rooftop Photovoltaic
- Apr 09, 2018 -

Solar panel roof power generation principle

Sun light shines on the p-n junction of the semiconductor to form a new hole-electron pair. Under the action of the p-n junction electric field, holes flow from the n region to the p region, and electrons flow from the p region to the n region. After the circuit is turned on, a current is formed. This is the working principle of the photoelectric effect solar cell. Photovoltaic distribution box

 

Solar power generation There are two methods for solar power generation. One is the light-heat-electric conversion method, and the other is the light-electricity direct conversion method.

 

(1) Light-heat-moving-electricity conversion methods generate electricity by utilizing the heat energy generated by solar radiation. Generally, a solar collector converts the absorbed thermal energy into working fluid vapor, and then drives the turbine to generate electricity. The former process is the light-heat conversion process; the latter process is the thermal-dynamic conversion to the electrical final conversion process, just like ordinary thermal power generation. The disadvantage of solar thermal power generation is its low efficiency and high cost. It is estimated that its investment is at least 5 to 10 times more expensive than an ordinary thermal power plant.

 

(2) Light-electricity direct conversion method This method utilizes the photoelectric effect to directly convert solar radiation energy into electric energy. The basic device for light-electricity conversion is a solar cell. A solar cell is a device that directly converts solar energy into electrical energy due to the photovoltaic effect. It is a semiconductor photodiode. When the sun shines on a photodiode, the photodiode turns the light energy of the sun into electricity. Current. When many batteries are connected in series or in parallel, they can become a solar cell array with relatively large output power. Solar cells are a promising new power source with three advantages of permanent, cleanliness and flexibility. Solar cells have a long life. As long as the sun is present, solar cells can be used for long-term investment. Compared with thermal power generation, solar cells do not cause environmental pollution.

 

Solar panel composition and function of each part

 

(1) Tempered glass: Its role is to protect the main body of power generation (such as a battery cell). The selection of light transmission is required:

 

1. The light transmittance must be high (generally more than 91%);

 

2. Ultra-white tempering.

 

(2) EVA: used to bond fixed glass and power generation body (cell), the advantages and disadvantages of transparent EVA material directly affect the life of the component, EVA exposed to the air is easy to aging and yellow, thus affecting the light transmission of the component Rate, which affects the power generation quality of the components In addition to the quality of the EVA itself, the laminating process of the component manufacturers is also very large. If the EVA adhesiveness is not up to standard, the adhesive strength between the EVA and the tempered glass and the backplane is not enough, which can cause EVA. Premature aging affects component life.

 

(3) Cell: The main function is to generate electricity. The mainstream of the main power generation market is crystalline silicon solar cells and thin-film solar cells. Both have advantages and disadvantages.

 

Crystalline silicon solar cells, equipment costs are relatively low, but the consumption and the cost of the battery is high, but the photoelectric conversion efficiency is also high, it is more appropriate to generate electricity in the outdoor sunlight.

 

Thin-film solar cells are relatively high in equipment cost, but their consumption and battery cost are low, but the photoelectric conversion efficiency is half that of crystalline silicon cells, but the low-light effect is very good, and they can also generate electricity under ordinary lighting, such as calculators. On the solar battery.

 

(4) back plate: role, sealing, insulation, waterproof. Generally used TPT, TPE and other materials must be resistant to aging, most component manufacturers are 25 years warranty, tempered glass, aluminum alloy generally no problem, the key is to meet the requirements with the backplane and silicone.

 

(5) Aluminum alloy: The protective laminate has certain sealing and supporting functions.

 

(6) Junction box: protects the entire power generation system and functions as a current relay station. If the short-circuit junction box of the module automatically disconnects the short-circuit battery string, the most critical factor in preventing the entire system junction box from being burnt is the selection of the diode. Different types of cells, the corresponding diode is not the same.

 

(7) Silicone: sealing function, used to seal the junction of components and aluminum alloy frame, component and junction box Some companies use double-sided tape, foam to replace silicone, the domestic use of silica gel, the process is simple, convenient, easy to operate, And the cost is low. Photovoltaic distribution box

 

 

The advantages of installing solar panels on the roof

 

1. It is usually easy to receive solar energy resources

 

2. Roof installation Photovoltaic array allows you to use the space that would otherwise be useless, saving space in the yard.

 

3. It is close to the existing power system, which helps to reduce the overall cost.

 

4. Roof-mounted devices have minimal impact on the site

 

 

The disadvantages of roof-mounted solar panels

 

1. The direction of the array is dominated by buildings

 

2. Because of the proximity to the roof, photovoltaic modules operate at higher temperatures (and therefore are less efficient)

 

3. The matrix capacity is limited by the available area

 

4. When the roof needs to be refurbished, the phalanx also needs to be removed (at the beginning the roof is in good condition, so this situation will not occur until 15 years later)

 

5. The phalanx may not be easily accessible. In this case, the ice and snow above the phalanx cannot be removed.

 

6. Penetration of roofs (where holes are fixed in a matrix of squares) may lead to roof leakage.