Research and application prospect analysis of the

Research and application prospects of solar refrigerators

as a large refrigerator consumer, China has tens of millions of refrigerators entering the market every year. Refrigerators not only bring convenience to people's lives, but also consume a lot of power resources. According to statistics, at present, China has 130million refrigerators. The urban penetration rate of household refrigerators has exceeded 90%, and the rural penetration rate has also exceeded 16%. Its annual power consumption has reached 600billion kwh, accounting for 25% - 45% of the total household power consumption. At the same time, China still uses coal as its main resource for power production, which will emit a large amount of carbon dioxide and other harmful gases. Under the attack of the two crises of the depletion of conventional energy and the deterioration of the ecological environment, the promotion of solar refrigerators can greatly reduce the emissions of harmful gases, help reduce the pollution of the atmosphere, and promote the sustainable use of domestic energy

current situation of solar refrigeration technology

solar refrigeration is an important aspect of solar energy utilization, and people have carried out a lot of research in this field. At present, there are two main forms of solar refrigeration: one is photoelectric conversion refrigeration, which is actually an application of solar power generation. First, realize photoelectric conversion, and then use solar cells to drive the compression refrigeration system of the refrigerator; The other is solar thermal conversion refrigeration, which mainly includes solar absorption refrigeration, solar adsorption refrigeration and solar ejector refrigeration

1. Absorption refrigeration system. The low-pressure steam from the evaporator enters the absorber and is strongly absorbed by the absorbent. The heat released in the absorption process is taken away by the cooling water. The formed concentrated solution is pumped into the generator, heated by the heat source and evaporated, producing high-pressure steam, which enters the condenser for cooling, while the dilute solution is decompressed and returned to the absorber to complete a cycle

2. Adsorption refrigeration system. The working process consists of thermal desorption and cooling adsorption. The basic cycle process is to use solar energy or other heat sources to desorb the mixture (or complex) formed by adsorbent and adsorbate in the adsorber, release high-temperature and high-pressure refrigerant gas into the condenser, and the condensed refrigerant liquid enters the evaporator through the throttle valve. When the refrigerant evaporates, it absorbs heat to produce refrigeration effect. The evaporated refrigerant gas enters the adsorption generator and forms a new mixture (or complex) after being adsorbed, so as to complete an adsorption refrigeration cycle

3. Ejector refrigeration system. After absorbing heat in the heat exchanger, the refrigerant vaporizes and pressurizes to produce saturated steam. The steam enters the ejector, which is sprayed and expanded at a high speed through the nozzle, creating a vacuum near the nozzle, sucking the low-pressure steam in the evaporator into the ejector, and the mixture from the ejector points out to enter the condenser to release heat and condense, Then condensation introduces in detail the company's technological innovation and product utilization in the field of automotive materials. Part of the liquid enters the evaporator through the throttle valve to absorb heat and vaporize. The cycle completed by this part of the working medium is the refrigeration cycle

photoelectric conversion refrigeration principle is simple and easy to realize, but its solar cell cost is high; Although the technical requirements of light heat conversion refrigeration are high, the cost is low. Absorption refrigeration technology appeared first, and the technology is relatively mature. At present, solar lithium bromide absorption refrigerator has been widely used in the field of large-scale air conditioning, but the absorption refrigeration system is huge, the operation is complex, and the refrigerant has shortcomings such as easy crystallization, strong corrosion, evaporation temperature can only be above 0 ℃. At the same time, its working pressure is high, which is dangerous. In the jet refrigeration technology, the circulating pump is the only operating component. The system is relatively simple, stable and reliable, but the effect of jet refrigeration is low. In view of this, at present, the realization ways of solar energy used in refrigerator technology are mainly solar photovoltaic conversion refrigeration technology and solar adsorption refrigeration technology

solar photovoltaic refrigeration refrigerator technology

solar photovoltaic refrigeration refrigerators mainly include solar photovoltaic refrigerators and solar semiconductor refrigerators. Solar photovoltaic refrigerator is developed on the basis of ordinary traditional compression refrigerator, which is composed of solar cells, controllers, batteries, refrigerators and other components. Because the internal structure of the solar photovoltaic refrigerator is the same as that of the traditional refrigerator, but the power supply device is changed to solar cells, so it is relatively simple to realize

foreign literature reports show that many experimental results show that after transforming the traditional AC refrigerator into a DC refrigerator suitable for photovoltaic solar system, all components can operate normally and the refrigerator can work normally. In China, there are many researches on solar photovoltaic refrigerators, and some progress has been made. In 2007, the Journal of solar energy reported the research results of Liu Qunsheng and others on the operating performance of a photovoltaic DC refrigerator system. The only power source of the system is solar energy, which uses a DC compressor and is equipped with a battery. The experimental results show that the minimum temperature of the refrigerator freezer can reach -16 ℃, and the freezer can reach 0~10 ℃. When working at an ambient temperature of 25 ℃, the operation rate is 48%. As early as 1997, Huang Fulin applied the new full digital SPWM modulation method to the frequency conversion circuit of the solar photoelectric refrigerator, and realized the automatic control of the refrigerator temperature

in the research of solar semi-conductor refrigerator, zoujinping and Luo Bin of Gansu Institute of natural energy have written articles to introduce the basic structure of the solar cell driven semi-conductor refrigerator system, establish a theoretical model of the solar cell driven semi-conductor refrigerator, and conduct numerical simulation of the system performance, and analyze the impact of solar radiation intensity and environmental wind speed changes on the performance of the solar semi-conductor refrigerator system

solar adsorption refrigeration refrigerator technology

in the 1990s, China has begun to study solar adsorption refrigeration refrigerators, but most of them are still limited to laboratories and have not reached the expected degree of practicality, mainly due to the high production temperature and the time limitations of solar energy. At the same time, the pipeline connection between the outdoor adsorption bed and the indoor refrigerator of the solar adsorption refrigeration refrigerator is also the main obstacle that affects the solar adsorption refrigeration refrigerator to enter the mass production stage

in order to solve the above defects, domestic researchers have carried out a detailed analysis and Research on the solar solid adsorption refrigeration technology from many aspects, such as the system cycle mechanism, the selection of adsorption refrigeration working pairs, the performance of solar refrigerators, internal and external characteristics analysis and optimization design. After years of painstaking research, sun Changjiang, the Thermal Environment Research Office of the Refrigeration Institute of Shanghai Jiaotong University, has manufactured two solar adsorption refrigerators according to the process and process required for mass production. The experimental results show that the performance of the refrigerator is relatively stable, which proves that this solar refrigerator has mature production conditions in technology

in solar adsorption refrigerators, the selection of adsorption working pairs is very important. Domestic researchers try to study the adsorption characteristics of different working pairs, including cof2-nh3, SrCl2-NH3, activated carbon methanol, activated carbon ethanol, etc. The experimental results show that the unit adsorption capacity of cof2-nh3 working fluid pair is large, the temperature requirement when reaching the maximum adsorption capacity is low, the adsorption cycle is short, and after repeated adsorption for many times, it is neither caking nor expanding, which provides a new possibility for the miniaturization and practicality of chemical adsorption refrigeration system; SrCl2-NH3 working pair has a large adsorption refrigeration capacity, which is suitable for solar energy or low-grade waste heat drive. It is a working pair with excellent performance; Activated carbon methanol working pair is more suitable for solar solid adsorption ice making machine than activated carbon ethanol working pair

high efficiency solar collectors are the key components of solar refrigerators, including non focusing solar collectors and focusing solar collectors. Among them, non focusing solar collectors are divided into flat plate type, vacuum tube type and CPC type. The collector temperature of these three types of collectors is not high, which is below 250 ℃, belonging to low-temperature or medium temperature solar collectors; Focusing solar collectors are divided into three types: trough type, operation skills of wear resistance testing machine, dish type and tower type. Generally, the collection temperature of these three types of focusing solar collectors can reach more than 300 ℃, belonging to medium and high temperature collectors. For solar refrigerators, non focusing solar collectors are mainly used in solar adsorption refrigeration refrigerator systems, while focusing solar collectors can be used in solar photovoltaic refrigeration refrigerator systems. At present, the research and utilization of solar collectors at home and abroad are mostly limited to the range of medium and low temperature

development and application of solar refrigerators

at present, solar photovoltaic refrigerators are the most studied and more practical at home and abroad, while the research on solar adsorption refrigerators is still based on the basic theory of solar refrigeration and the development of experimental prototypes

solar photovoltaic refrigerators generally use conventional refrigerators with external solar power generation devices, and the research focuses on the charging and discharging characteristics of solar cells. Due to less consideration of the photovoltaic characteristics of refrigerator compressors, the research on the matching of various components of solar photovoltaic refrigerators is not perfect, and the efficiency of solar heat absorption devices is very low, so the efficiency of the whole system cannot be compared with that of traditional refrigerators, The cost is also much higher than traditional refrigerators. In terms of solar adsorption refrigeration refrigerator, the current research focuses on the performance of adsorbent refrigerant working pair. It is necessary to solve the problems of how to further strengthen the heat transfer performance of adsorption bed, how to effectively solve the relationship between daytime heat collection and nighttime heat dissipation of adsorption bed and heat collector, and how to effectively store the nighttime cooling capacity for daytime use

the author believes that the key technologies that need to be further solved in the application and development of solar refrigerators are as follows:

1 High efficiency solar collector technology

solar collector is a device that converts solar energy into heat energy, and plays an important role in the solar refrigerator system. Its efficiency and price will directly affect the efficiency and economy of the whole solar refrigerator. In order to improve the efficiency of solar collectors, the current research is mostly limited to the improvement of the structure of absorbers and condensing devices, and less investment is made in the research on the heat absorption essence of collectors, which is reflected in the optical properties of materials, that is, the absorption capacity of light in a certain band. Therefore, the author believes that the development of the absorber and its surface absorbing coating material will be the key to improve the efficiency of the solar refrigerator collector. There are still many areas worthy of improvement and development in technology, such as coating the surface of the absorber with a very high spectral absorption ratio of solar radiation to maintain the maximum collection of solar radiation energy; Or reasonably select the heat absorbing surface material according to the radiation characteristics of the material to make it within 0.3~3 μ The spectral absorption ratio in the wavelength range of M is close to 1

2. High efficiency solar energy storage technology

in order to overcome the defect that the working conditions of the refrigerator during the day and night are inconsistent due to the timeliness of solar energy, a reasonable energy storage device should be designed in the system design, so that part of the energy generated during the day can be stored for use at night or in rainy days, so as to truly realize all-weather refrigeration, so as to achieve the same effect as the conventional refrigerator. At present, solar photovoltaic energy storage mainly includes the following types, namely, capacitor energy storage, lead-acid battery energy storage, nickel hydrogen battery power storage and potassium ion battery power storage. The application technology of the above energy storage batteries has been relatively mature, but the energy storage capacity