In April 2006, the State Energy Leadership Group chaired by Premier Wen Jiabao pointed out [4]: ​​The energy issue concerns China's economic development, social stability, and national security. We must adhere to the principle of developing equal emphasis on conservation and saving energy in the first place, adopt more effective measures to comprehensively promote energy conservation, and vigorously develop renewable energy sources [5]. The contradiction between China's energy supply and demand will persist for a long time. To ensure energy security and build a stable, economic, and clean energy supply system, sustainable development of energy to support sustainable economic and social development is a major long-term strategic task in China's modernization. Drying operations involve a wide range of national economies and are also one of the major energy consumers in China. The energy used accounts for about 12% of the total national energy consumption [6]. Some industries such as wood drying energy consumption, accounting for about 40% -70% of total energy consumption [7]. In addition, the pollution caused by the drying process is often an important source of environmental pollution in China, so the energy saving and environmental protection issues of the drying technology are very important. Solar energy is a clean, cheap and renewable energy source that is inexhaustible. Solar radiant energy reaching the earth's surface every year is about 10,000 times more than the energy consumed by the world at present. China has abundant solar energy resources, and about 2/3 of the country's annual radiation time exceeds 2200 hours. The annual radiation total exceeds 5000MJ/m2. The solar energy that has been irradiated to China's vast area for the whole year is equivalent to more than 2,000 times the energy provided by all conventional energy sources such as coal, oil, natural gas, and all kinds of fireweed. The annual total solar radiation across the country was 3340-8400 MJ/m2, and the median was 5852 MJ/m2. From the distribution of total solar radiation in China, Tibet, Qinghai, Xinjiang, southern Ningxia, Gansu, southern Inner Mongolia, northern Shanxi, northern Shaanxi, Liaoning, southeastern Hebei, southeastern Shandong, southeastern Henan, western Jilin, Yunnan The total amount of solar radiation in the central and southwestern regions, southeastern Guangdong, southeastern Fujian, eastern and western Hainan, and the southwestern part of Taiwan, is particularly large in the Qinghai-Tibet Plateau. The total annual solar radiation in Sichuan and Guizhou Provinces and Chongqing Municipality is the smallest, especially in the Sichuan Basin [8, 9]. Solar drying is more suitable for the drying of agricultural and sideline products. Generally, the temperature is below 60°C, which will not damage the nutritional value of food. The use of solar pre-drying for wood not only saves energy, but also prevents cracking and deformation of wood due to high drying temperature. Application of solar drying technology Foreign application profile The research and application of solar energy drying technology has been carried out in many countries around the world. The research work is mainly in developed countries such as the United States, Britain, France, Germany, Canada, Australia, New Zealand and Japan [7,10]. As early as the 1970s and 1980s, developed countries such as the United States, Germany, the United Kingdom, and France established solar drying test devices of different scales in their own countries and in some developing countries. They initially focused on small-scale and large-scale solar energy. Drying system. In the United States, solar drying equipment has been commercially produced in certain quantities and is welcomed by small-scale dryer users. India, Thailand, Indonesia, and other countries also have small-volume commercial applications, but commercial solar drying rooms in Europe are less [8, 9]. The application of solar drying is mostly in tropical and subtropical countries such as South Africa, Fiji, Uganda, Nigeria, Brazil, Philippines, Thailand, India, Indonesia, Bangladesh and China (including Taiwan) and other countries [11..12]. As early as the 1980s, Thailand promoted the use of a solar dryer to dry grains. During the non-harvesting season, it can also be used to dry peppers, peppers, coffee beans, shrimp, etc., which can be profitable throughout the year. Thailand uses solar energy as an auxiliary energy and conventional energy in combination with dry tobacco leaves. Experiments have proved that it can effectively save 30%-40% of conventional energy. Even in the high-temperature and rainy regions like Malaysia, the use of simple and inexpensive solar drying devices is promoted. They believe that solar drying devices are low in cost and easy to manufacture, and can better solve the problem of drying three crops a year. India has developed a solar dryer with a combination of flue gas and a daily drying capacity of 650-1000 kg/d. There are also solar grain dryers with an hourly drying capacity of 375 kg/h; there is also a solar drying room for drying peppers, which works well; in addition, India promotes solar drying technologies for crops such as tobacco and potatoes [13, 14 ]. Most of Indonesia's solar drying devices are greenhouse-type, and they also use wood chips as a combination drying device for fuel heating water as an auxiliary energy source. Drying objects are mainly crops such as grains. At present, the application scale of solar-powered dry wood in the world is very small. Most of them are simple greenhouse-type solar drying rooms with a volume of less than 10m3. According to incomplete statistics, there are currently more than 300 solar energy-based wood drying in the world. Room, of which there are nearly 20 in China [7,15]. At home and abroad, most of the early solar drying equipment was greenhouse type, semi-greenhouse type, or a smaller collector type. Large-scale solar drying devices are basically collector-type and are combined with conventional energy sources to maintain the continuity of the drying process. According to relevant data, a large number of large-scale solar dryers with a lighting area of ​​more than 500m2 have been built abroad, including four in the United States, two in India, and one in Argentina [16, 17]. This indicates that solar drying has entered the production and application stage in the world. As the global energy and environmental issues have become increasingly prominent, the application of solar drying technology has seen significant development in the past decade. Taking a broad view of the promotion and application of international solar drying technology has the following characteristics: (1) Solar energy drying targets mainly agricultural and sideline products such as grain, tobacco, and fruits, followed by wood drying. (2) The development direction of solar drying is to increase the thermal efficiency and reduce the cost of the solar drying device. (3) Focus on practicality and try to use cheap materials. For example, dry sand is used as a heat absorber and a plastic film is used as a light-transmitting material. (4) Many countries have corresponding encouragement and support policies for the development and application of new energy such as solar energy and wind energy. For example, Sweden has 15% financial support for energy-saving drying technology. Countries such as Germany, the United States, Australia, Japan, and Indonesia implement preferential measures such as tax exemption, tax reduction, subsidies, interest-free or discounted loans for solar drying. Qingdao SUBA CNC Technology Co., Ltd , https://www.cncrouter-china.com
As we all know, energy is an important material basis for economic construction and social development. With the rapid growth of our economy and the continuous improvement of people's living standards, the demand for energy has also increased. At present, China is already the second largest energy consumer in the world, and its consumption is equivalent to 1/3 of that of the United States. However, China has a large population and its per capita resources are less than half of the world average. To achieve the goal of doubling the country’s GDP in 2020 than in 2000, the country’s energy consumption will at least double over that in 2000, and the contradiction between energy supply and demand will further intensify. Moreover, conventional energy sources such as coal, oil, and natural gas are non-renewable and eventually face depleted energy sources. At the same time, with the rapid growth of energy demand, the resulting environmental pollution has become increasingly serious, and our country is facing unprecedented tremendous pressure on energy and the environment. China's energy utilization rate is low and energy consumption per unit of GDP is 3 times the world average. 4-6 times for developed countries, 3.5 times for the United States, and 10 times for Japan. According to relevant experts' estimates, if China's environmental pollution factors are taken into account, GNP GDP will drop by approximately two percentage points, because the removal of pollutants in the air is about 10 times the cost of fuel needed. [1, 2 ]. The increasing intensification of atmospheric pollution has not only caused huge losses to the national economy, but also caused great harm to people’s lives and health. According to the assessment of the World Bank, losses caused by diseases caused by environmental pollution account for 2%-3% of China's GDP. 400,000 people die prematurely due to air pollution each year, and many people in the country drink different levels of pollution. Water [3].