The development of science and technology has led to the advancement of solar power generation, and solar power generation systems have also entered our lives. Looking at the foreign solar photovoltaic power generation industry, it has gradually matured, and the domestic market is also in hot condition. How far can solar power go? Sungzu made a simple analysis of the development prospects of solar power generation.

First, Solar power generation prospects – bright future

Looking at this issue from the perspective of a bystander, from a few years ago: solar power is likely to largely replace the current dominant coal-fired power station, and the current view: solar power has replaced coal. For one reason, the cause of global warming is the increase in carbon dioxide, and the characteristics of solar power generation are low-carbon and environmentally friendly, and the two are suitable combinations. Another reason is that the application of distributed solar power generation effectively improves the quality of life of people in remote areas and solves the problem that the national grid is difficult to transport electricity due to cost and technology. In remote areas, people use solar power to solve electricity problems.

Second, the prospect of solar power generation – home solar energy development has bottlenecks

There are two major points in the development of solar power:

1. The direct current generated by solar power can only be directly used for pure electric resistance appliances such as lighting and heating; if used in refrigerators, washing machines, color TVs, air conditioners, etc., household appliances need to be converted into alternating current through inverters, which can increase the investment and Operation and maintenance costs.

2. Household solar power is usually installed on the roof and the sun wall, requiring a unified design plan. Some places with poor lighting are constrained, combining the first two points, limiting the use of solar power in rural cities.

Third, the prospect of solar power generation – the problem that needs to be solved now

All technologies that can be widely used are constantly changing and innovating. Solar power generation must be widely accepted and used, and the following technical problems must be solved:

1. The first is whether it can greatly improve the conversion efficiency of solar panels. For example, the conversion efficiency of solar panels used on a large scale is increased from about 18% to about 30% under the condition of ensuring cost reduction.

2. Solve the safety problem of the power grid that the large power grid is subjected to the impact and vibration of photovoltaic power generation. Otherwise, the large grid cannot withstand the high proportion of solar photovoltaic power generation impact.

3. Significantly reduce the cost of solar power generation equipment, so that the cost per kilowatt is quite or even lower than the cost of conventional thermal power generation. At present, the cost of conventional thermal power is about 5,000 yuan per kilowatt, while the cost per kilowatt of solar photovoltaic power generation system is about 10,000 yuan. At the same time, the annual effective power generation time of conventional thermal power plants is more than 6,000 hours, and the effective power generation time of solar photovoltaic power generation systems is only 2,000 hours.

From the above analysis, it can be seen that in the long run, the future prospects of solar power generation are bright. If the photovoltaic technology problem fails to improve and adapt, it will become one of the constraints that restrict the development of solar power.

1. Preparation before purchase, that is, preliminary determination of capacity and brand

Before purchasing a mobile power supply, we must first consider a few issues and combine our own needs: specific use, location, whether a short-term emergency or long-term outing is required. If it is used for emergency charging, it is necessary to select a relatively small product, such a product is easy to carry, and can also make a call while charging, but relatively speaking, the capacity of the battery is small. If it is used for long-term outdoor use, some products with large battery capacity are needed. This product is relatively large in size and inconvenient to carry. Of course, there are some medium-sized, stylish products that may be a good choice for use on the subway or train. As for the choice of outdoor mobile power brands, I think I want to choose a brand with good quality and good image. You can go to the professional rankings to understand.

2. Try to choose brand products

The establishment of a brand requires advertising, and it needs to be passed on from word to mouth. Choosing a well-known mobile power brand, product quality may be better, and future after-sales service is in place.

3. Selection of energy storage media

The main batteries used in mobile power are nickel-metal hydride batteries, lithium iron phosphate batteries, liquid lithium-ion batteries and lithium polymer batteries. The latter two types of batteries are mainly sold in the market. You cannot choose to use the first two types of batteries. Both types of batteries have low output efficiency and do not have any advantages. Don’t buy them. Liquid lithium-ion batteries and lithium polymer batteries have relatively stable output efficiencies, especially lithium polymer batteries are lighter, safer and more efficient than liquid lithium-ion batteries.

4. Product appearance and weight

Depending on the application, it is necessary to choose different types of mobile power. Simple emergency use should choose a small mobile power supply, and the backup power supply should select a mobile power with a large capacity. For products with the same function, you should try to choose a light weight product that is easy to carry.

5. Product compatibility

There are many types of mobile phones and other electronic products. The circuit design and interface are different. The same mobile power supply is not suitable for all electronic products. Therefore, you must first understand the interface, voltage and other information required for electronic products before purchasing. If you can try to bring the counter to the test machine. Usually, the charging voltage and current of the mobile phone is 5V1A. If your phone is special, you should confirm the interface with the merchant.

6. Determine the conversion rate

The conversion rate of mobile power is very important. If the conversion rate is too low, it means that the line loss of the mobile power supply will be very large, which may cause heat or even explosion. The conversion rate can take into account the evaluation of each mobile power model. If an ad claims a conversion rate of more than 90%, it may be reported incorrectly. Typically, products with a conversion rate of about 85% are already very good.

7. Product accessories and additional features

While the main function of mobile power is charging, some additional features will bring us more benefits. For example, there are multiple charging adapters that can extend the range of use, and dual interfaces can simultaneously charge two electronic products, and LED lighting can be used in emergency situations. In addition, some mobile power supplies have a solar charging function. This is actually a chicken rib. Because many users find that solar charging is basically not enough, the time is too slow.

Is a lithium battery really more dangerous than a lead acid battery? But in fact, it’s not! Which of the lithium batteries and lead-acid batteries is safer because of the understanding of the battery and the explosion in some cases?

In terms of battery structure, the current lithium battery pack is basically packaged in 18650 batteries, and the lead-acid battery is basically a maintenance-free lead-acid battery with good sealing performance. If the internal pressure is too large and the safety valve is abnormal, the risk factors for both are basically the same.

If the battery is overcharged and internally hydrogenated, the electrolyte content of the 18650 battery is very limited and the amount of hydrogen evolved is very limited. However, for a lead-acid battery using dilute sulfuric acid as an electrolyte, if overcharge occurs, internal hydrogen evolution of the battery occurs. This phenomenon is very serious and the possibility of deflagration is greatly increased.

From a battery safety point of view, the 18650 battery is designed with a safety valve that not only relieves excessive internal pressure, but also physically disconnects the battery from external circuitry, which is equivalent to physically blocking the battery to ensure battery pair Other batteries are safe.

In addition, the lithium battery pack is usually equipped with a BMS protection board, which can accurately control the state of each battery in the battery pack and directly solve the problem of root overcharge and discharge.

In contrast, lead-acid batteries appear to lack safety protection in addition to safety valves. BMS protection is almost non-existent, and many inferior chargers cannot even fully charge and power down. Safety guarantees are far from lithium batteries.

Of course, if you use a lithium battery that is similar in price to a lead-acid battery, no one can save you in this situation.

Last but not least, if the battery structure is damaged by an accidental collision, the lead-acid battery seems to be safer than the lithium battery. However, in this type of accident, the battery material is exposed to an open environment for a long time and the explosion is not discussed.

The battery is not a bomb. The explosion is caused more by inferior products. From the perspective of battery safety redundancy design, qualified lithium batteries and lead-acid batteries can fully guarantee the safety of users without obvious safety differences. However, due to the large number of low-end small electric vehicles and scooters on the market, and most of them are poor quality lithium batteries, they are relatively more prone to accidents, which makes consumers have the illusion that lithium batteries are unsafe.

AC/DC conversion is the conversion of analog V (eg V = 5V) to digital D (eg D = 255). There are many types of analog/digital (AC/DC) conversions, such as count comparison types, successive approximation types, double integral types, and the like. The successive approximation type is often used in integrated circuit devices, and the basic working principle of AC conversion DC is briefly introduced.

The figure shows the structure of the successive approximation. The AC/DC converter is based on a DC/AC converter, plus a comparator, successive approximation register, set logic and clock. The conversion principle is as follows.

Under the control of the enable signal, the first selection logic is set to give the highest position of the successive approximation register “1”. After converting the DC/AC to an analog quantity, it is compared with the input analog quantity, and the voltage comparator gives the comparison result. If the input quantity is greater than or equal to the output of the D / A conversion, the comparator is 1, otherwise 0, the setting logic is modified according to the result of the comparator output to modify the contents of the successive approximation register, so it passes the analog quantity after D The /A transform continuously approximates the input analog quantity. The number of digital changes after several modifications is the amount of AC/DC conversion results.

Most currents approximate AC/DC use a binary search method, which first compares the 1/2 value of the maximum allowable voltage range with the input voltage value, ie up to “1”, and the remaining bits are “0”. If the search value is within this range, a value of 1/2 of the range is taken, that is, the second highest position is “1”. If the search value is not within this range, another 1/2 range of the maximum allowable input voltage value of the search value is sequentially executed, that is, the highest bit is “0”, and the search range is narrowed down. The range is 1/2 each time. An n-bit AC/DC conversion can be obtained by n comparisons. The successive approximation method has a faster conversion speed, so the integrated AC/DC chip mostly adopts the above method.

As can be seen from the figure, the AC/DC conversion needs to perform external start control signals and is divided into two types: pulse start and level start. Chips that use pulse-on-chip include ADC0804, ADC0809, and ADC1210. The chips that use level-on are ADC570, ADC571, ADC572, and so on. This start signal is provided by the CPU. When the AC/DC converter is activated, after n comparisons by the binary search method, the contents of the successive approximation register are the converted digital quantities. Therefore, after the AC/DC conversion is completed, the digital quantity must be taken from the successive approximation register.

To this end, the DC/AC chip specifically sets the conversion end signal pin, sends a conversion end signal to the CPU, notifies the CPU to read the converted digital quantity, and the CPU can detect the AC/DC conversion end signal or the inquiry mode by interrupt, and from A. The digital register is taken from the data register of the /D chip (ie, the successive approximation register in Figure 10-9).

Component attenuation, including LID (photoinduced attenuation, including LeTID), PID, attenuation due to aging of the package material and battery connections, is an important factor affecting module power generation. Recently, due to the heated discussion of the LeTID issue, the attenuation of PV modules has attracted more and more attention.

LeTID (light decay under high temperature conditions, typically 50-80 ° C) was found and is typically present in the polycrystalline PERC component. With the improvement of laboratory research, under certain conditions, single crystal P-type Cz, FZ and N-type A can be seen similarly on the silicon wafer. The LeTID mechanism is relatively complex. The root cause of LeTID may be: metal impurities such as Cu and Ni in silicon wafers, hydrogen entering silicon wafers from SiNx and AlOx, or a combination of hydrogen and impurities. Related mechanism debate,

Therefore, the outdoor demonstration of the State Key Laboratory of China Electric Apparatus Research Institute in Sanya, Hainan, and Turpan, Xinjiang (2016.10~2017.9) can provide an important reference for the industry (as shown in the above figure, the highest temperature is the monthly maximum temperature. Component backplane, temperature is the component. The average temperature of the component backsheet between 10 and 14 o’clock during the day answers the question of the first year of decay of the single crystal PERC component. Although the previously published results were primarily used to study power generation data, in practice, the component electrical performance parameters were accurately tested before and after sampling the components. The components purchased were from the first-line manufacturer and the initial power supply consistency was very good.

In the Sanya test site, the module’s average operating temperature is 40-50 ° C, the maximum operating temperature is about 70 ° C, the module experienced 14.5 months of high temperature, high humidity and outdoor exposure, and the single-chip PERC module relative to the initial power The average attenuation is 1.99. %, (relative nominal power attenuation is 0.93%), the open circuit voltage and short circuit current attenuation is small, mainly the attenuation fill factor FF. The initial power attenuation of the two polycrystalline components was 3.77% and 2.77% (3.26% and 0.53% relative to the nominal power attenuation), and the main attenuation was the attenuation of the short circuit current.

In the Turpan test site, the average daily temperature (10~14 hours) of the components in June to August can reach 50C or more, and the highest working temperature in August reaches 70C or more. After 14 months of high temperature, high radiation, dust and The higher the day and night, the seasonal temperature difference, the average single-chip PERC component is attenuated by 1.59% relative to the initial power, (the average attenuation is 0.58% relative to the nominal power). Compared with the Sanya empirical project, the attenuation of FF is reduced from 1.25% to 0.86%. The single crystal PERC component has a small attenuation dispersion. The attenuation of the two polycrystalline components relative to the initial power is 3.22% and 2.65%, and the main attenuation is still the attenuation of the short circuit current.

From the empirical results of the two bases, for this harsh outdoor environment, the aging attenuation of the components is much more significant than in the general mild environment, and the single-crystal PERC assembly (from LONGi) has better attenuation, indicating single crystal. PERC technology combined with low light attenuation technology can effectively cope with outdoor high temperature working conditions.