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How long is the life of a solar battery?
- Mar 22, 2018 -

Solar Battery】How long is the life of a solar battery?

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How long is the life of a solar battery?

There is no specific time for the life of solar batteries. A good single crystal silicon battery can generally be used for more than 30 years.

The degree of bonding of the PN junction within the battery, as well as the purity of the silicon wafer, will affect the life of the battery. These two factors determine the strength of the solar cell generated by the same light [radiation energy], the power of the battery, a long battery life The PN junction will certainly continue to burst, so that the efficiency of power storage will continue to decline. Until the end of life can not meet the needs of users.

Compared with other batteries, the monocrystalline silicon battery has a stronger PN junction and its crystal surface is unidirectional, so the reflectance is relatively small, the energy absorbed is relatively high, and the efficiency is naturally higher and more durable.

The ambient temperature has a great influence on the life of the solar battery. When the ambient temperature rises by 10°C, the lifespan of the solar battery is reduced by approximately 50%. Therefore, in order to prolong battery life, the battery room should be equipped with air conditioning to keep the room temperature at 15~25°C.

Solar panel prices

The 30-square-meter battery board is about 180W. The board needs 20 or 240W boards. It needs 15 blocks (total about 4000W). The battery needs about 35-40 blocks (12V100A). The inverter is one, and the battery board accounts for 60% of the cost. Currently, the market price is about 2.6 U.S. dollars or so, and the storage battery accounts for about 30% of the cost (about 100 U.S. dollars or so). The inverter costs about 5% (about 515-690 U.S. dollars), and the other costs about 5%. The total cost is about 17,000 US dollars. The daylight is calculated as 6H, and the electricity generated in one day is between 20-30 degrees.

Solar battery principle

Solar cell structure and working principle

The structure and working principle of solar cells The shape and basic structure of solar cells are shown in Figure 1. The basic material is P-type monocrystalline silicon, with a thickness of about 0.3-0.5 mm. The upper surface is an N+ type region that forms a PN+ junction. The top surface has a grid-like metal electrode, and the back of the silicon wafer is a metal bottom electrode. The upper and lower electrodes form ohmic contact with the N+ region and the P region, respectively, and the entire upper surface is evenly covered with the antireflection film. When the incoming light shines on the surface of the cell, photons enter the silicon through the anti-reflection film. Photons with energy greater than the silicon forbidden band width excite photo-generated electron-hole pairs in the N+ region, the PN+ junction space charge region, and the P region. The photocarriers in each zone can contribute to the luminescence voltage if they can cross the depletion zone before recombination. Photogenerated electrons remain in the N+ region, and photovoids remain in the P region. Positive and negative charges are accumulated on both sides of the PN+ junction to generate a photo-generated voltage, which is a photovoltaic effect. When a photovoltaic cell is connected at both ends with a load, the photovoltaic cell flows from the P zone to the N+ zone via the load, and the power output is provided in the load. The sensitivity of different regions of the solar cell to different wavelengths is different. The sunlight current near the top of the wet zone is sensitive to short-wavelength violet (or ultraviolet) light, which accounts for 5-10% of the total light source current (which varies with the thickness of the N+ region). The photocurrent of the PN+ junction space charge is sensitive to visible light. About 5%. The photocurrent generated by the cell substrate region is sensitive to infrared light, accounting for 80-90%, and is the main component of the photocurrent.

Convert Photons to Electronics

The solar cells used on calculators and satellites are all photovoltaic cells or modules (a module is a group of cells connected by a circuit and enclosed in a frame). Photovoltaic cells (Photovoltaics), as the name suggests, refer to batteries that convert sunlight into electricity. Photovoltaic cells were only used in space before, but now they are becoming more and more popular and their usage is becoming more and more common. They can even power your home. How do these devices work? Photovoltaic (PV) cells are made of semiconductor materials, such as silicon, which is currently the most commonly used semiconductor. When light shines on the battery, a portion of the light is absorbed by the semiconductor material. This means that the absorbed light energy will be transmitted to the semiconductor. Energy can cause electrons to escape and allow them to flow freely. Photovoltaic cells also have one or more electric fields that can force electrons that are absorbed and released by light to flow in a certain direction. The flow of electrons forms a current. By placing metal contacts on the top and bottom of the photovoltaic cell, we can draw current out for use. For example, current can power the calculator. This current and the battery voltage (generated by the internal electric field) determine the solar cell's power (or wattage).

When the N-type silicon and P-type silicon were put together, an interesting situation occurred. Remember that each photovoltaic cell has at least one electric field. Without an electric field, the battery does not work, and this electric field is formed when the N-type silicon is in contact with the P-type silicon. Suddenly, the free electrons on the N side (they always look for holes to settle) see all the holes on the P side, and then run wildly toward the holes, filling the holes. In the past, from the perspective of electricity, the silicon we used was neutral. Excess electrons are neutralized by excess protons in the phosphorus. The missing electrons (holes) are neutralized by the missing protons in the boron. When holes and electrons are mixed at the interface of N-type silicon and P-type silicon, neutrality is destroyed. Will all free electrons fill all holes? will not. If so, then the whole preparation will be meaningless. However, at the junction, they do mix to form a barrier, making it more and more difficult for the N-side electrons to reach the P side. Eventually equilibrium will be reached so that we have an electric field that separates the two sides. This electric field is equivalent to a diode, allowing (even pushing) electrons to flow from the P side to the N side, not the other way around. It is like a mountain - electrons can easily slide down the hill (to the N side), but cannot climb up (to the P side). In this way, we get an electric field that acts like a diode, in which electrons can only move in one direction. Let's look at what happens when the sun shines on the battery. When light hits a solar cell in the form of photons, its energy releases the electron-hole pair.

Each photon carrying enough energy will normally release exactly one electron, creating a free cavity. If this happens close enough to the electric field, or if free electrons and free holes are within its range of influence, the electric field will send electrons to the N side and holes to the P side. This leads to further destruction of the electrical neutrality. If we provide an external current path, electrons will pass through this path and flow to their original side (P side), where they merge with the holes sent by the electric field and flow during the process. Doing work. The electrons flow to provide current, and the battery's electric field generates voltage. With current and voltage, we have power, which is the product of the two.