First, does solar photovoltaic power generation have radiation to the human body
Photovoltaic systems have electromagnetic radiation, but less, the use of qualified equipment, will not cause harm to the human body and cause interference to household appliances. The photovoltaic module is direct current and does not produce radiation, and the radiation of the inverter is strictly controlled within the safe range.
Photovoltaic power generation is the direct conversion of light energy into direct current energy through the characteristics of semiconductors, and then the direct current is converted into alternating current that can be used by us through the inverter. Photovoltaic system is composed of photovoltaic modules, supports, DC cables, inverters, AC cables, distribution cabinets, transformers, etc., of which the support is not charged, naturally will not produce electromagnetic interference. Photovoltaic modules and DC cables, inside is DC current, the direction does not change, can only produce electric fields, can not produce magnetic fields. Although the output transformer is AC, the frequency is very low, only 50Hz, and the magnetic field generated is very low. Inverter is the direct current into alternating current equipment, which has a power electronic conversion, the frequency is generally 5-20KHz, so it will produce alternating electric field, so it will also produce electromagnetic radiation. However, the state has strict standards for the electromagnetic compatibility of photovoltaic inverters. The electromagnetic radiation of photovoltaic inverters, compared with household appliances, is about the same as that of laptops, lower than induction stoves, hair dryers, refrigerators.
Therefore, solar photovoltaic power generation will not only cause harm to human health, but also provide the earth with green and clean high-quality energy, which is the future direction of human energy development.
Second, the advantages and disadvantages of solar photovoltaic power generation
(1) Advantages
1. Solar energy resources are inexhaustible, and the solar energy irradiated to the earth is 6,000 times larger than the energy currently consumed by mankind. Moreover, solar energy is widely distributed on the earth, and photovoltaic power generation systems can be used as long as there is light, regardless of regional, altitude and other factors.
2, solar energy resources are available everywhere, can be nearby power supply, do not have to long-distance transmission, to avoid the loss of electricity caused by long-distance transmission lines.
3, the energy conversion process of photovoltaic power generation is simple, is directly from light energy to electrical energy conversion, there is no intermediate process (such as thermal energy conversion to mechanical energy, mechanical energy conversion to electromagnetic energy, etc.) and mechanical movement, there is no mechanical wear. According to thermodynamic analysis, photovoltaic power generation has a high theoretical power generation efficiency, up to more than 80%, and the technical development potential is huge.
4, photovoltaic power generation itself does not use fuel, does not emit any substances including greenhouse gases and other exhaust gases, does not pollute the air, does not produce noise, is environmentally friendly, will not suffer from the impact of energy crisis or fuel market instability, is a truly green and environmentally friendly new renewable energy.
5, photovoltaic power generation process does not require cooling water, can be installed in the desert without water on the Gobi. Photovoltaic power generation can also be easily combined with buildings to form an integrated photovoltaic building power generation system, which does not need to occupy a separate area and can save valuable land resources.
6, photovoltaic power generation without mechanical transmission parts, simple operation, maintenance, stable and reliable operation. A set of photovoltaic power generation system can generate electricity as long as there are solar modules, coupled with the widespread use of automatic control technology, basically can achieve unattended, low maintenance costs.
7, photovoltaic power generation system stable and reliable performance, long service life (more than 30 years). Crystalline silicon solar cells can last up to 20 to 35 years. In the photovoltaic power generation system, as long as the design is reasonable and the selection is appropriate, the life of the battery can also be as long as 10 to 15 years.
8, the solar cell module is simple in structure, small in size, light in weight, easy to transport and install. Photovoltaic power generation system construction period is short, and according to the power load capacity can be large or small, convenient and flexible, easy to combine and expand.
(2) Disadvantages
Of course, solar photovoltaic power generation also has its shortcomings and shortcomings, summed up in the following points.
1. Low energy density
Although the total amount of energy that the sun casts on the earth is extremely large, because the earth's surface area is also very large, and most of the Earth's surface is covered by the ocean, the solar energy that can really reach the land surface is only about 10% of the solar radiation energy that reaches the Earth, resulting in less solar energy that can be directly obtained on the unit area of the land. Usually expressed in solar irradiance, the maximum irradiance of the Earth's surface is about 1.2kw / ㎡, and the vast majority of areas and most sunshine hours are below 1kw / ㎡. The utilization of solar energy is actually the collection and utilization of low-density energy.
2, covers a large area
Due to the low energy density of solar energy, this makes the area of photovoltaic power generation system will be large, every 10kw photovoltaic power covers about 100 square meters, and the average power generation power per square meter area is 100w. With the maturity and development of photovoltaic building integrated power generation technology, more and more photovoltaic power generation systems can use the roofs and facades of buildings and structures, which will gradually overcome the shortage of photovoltaic power generation.
3. Low conversion efficiency
The most basic unit of photovoltaic power generation is the solar cell module. The conversion efficiency of photovoltaic power generation refers to the ratio of light energy to electricity. At present, the conversion efficiency of crystalline silicon photovoltaic cells is 13% to 17%, and amorphous silicon photovoltaic cells are only 5% to 8%. Because the photoelectric conversion efficiency is too low, the power density of photovoltaic power generation is low, and it is difficult to form a high-power power generation system. Therefore, the low conversion efficiency of solar cells is the bottleneck that hinders the large-scale promotion of photovoltaic power generation.
4, intermittent work
On the surface of the earth, the photovoltaic power generation system can only generate electricity during the day, and can not generate electricity at night, unless there is no day and night in space, solar cells can continuously generate electricity, which is inconsistent with people's electricity needs.
5, greatly affected by climate and environmental factors
The energy of solar photovoltaic power generation directly comes from the irradiation of sunlight, and the solar irradiation on the earth's surface is greatly affected by the climate, long-term rain and snow, cloudy, foggy and even cloud changes will seriously affect the power generation state of the system. In addition, the impact of environmental factors is also very large, the more prominent point is that the particles in the air (such as dust) settle on the surface of the solar cell module, blocking some of the light, which will reduce the conversion efficiency of the battery module, resulting in reduced power generation and even damage to the panel.
6. Strong regional dependence
Geographical location is different, the climate is different, so that the sunshine resources in each region are very different. Photovoltaic power generation system is only applied in areas rich in solar energy resources, its effect will be good.
7, the system cost is high
Due to the low efficiency of solar photovoltaic power generation, so far, the cost of photovoltaic power generation is still several times that of other conventional power generation methods (such as thermal power and hydropower), which is the most important factor restricting its wide application. However, it should also be noted that with the continuous expansion of solar cell production capacity and the continuous improvement of battery photoelectric conversion efficiency, the cost of photovoltaic power generation system has also fallen very fast. The price of solar modules has fallen from more than $70 per watt in the past few decades to around $2 per watt today.
8, the manufacturing process of crystalline silicon cells is high pollution and high energy consumption
The main raw material of crystalline silicon battery is pure silicon. Silicon is the most abundant element on Earth after oxygen, mainly in the form of sand (sio2). From silica sand to crystalline silicon with a purity of more than 99.9999% step by step, it must go through multiple chemical and physical processes, which not only consumes a lot of energy, but also causes certain environmental pollution.