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In August 2022, the Ministry of Industry and Information Technology, the National Development and Reform Commission, and the Ministry of Ecology and Environment jointly issued the Implementation Plan for Carbon Peak in the Industrial Sector, which states that "the vision of carbon peak and carbon neutralization will run through all aspects and the whole process of industrial production", "efficiency first, and source control. We will promote the synergy of pollution reduction and carbon reduction, continue to reduce the consumption of energy resources per unit of output, and reduce carbon dioxide emissions from the source".
Controlling carbon emissions from the source is an important policy guidance, and it is also the only way and process for industrial enterprises to achieve carbon peak and carbon neutralization of their products. Taking transformers as an example, this paper discusses how to promote the dual carbon strategy in the transformer industry, including source control, material selection and green product practice from the perspective of low carbon, so as to promote the wide application of green transformers and make contributions to society.
1、 Source control, low carbon design of transformer
In order to achieve low carbon in transformer manufacturing, it is necessary to understand the carbon factor parameters of various transformer materials, so as to design and manufacture low carbon transformer products.
See the following table for the carbon factor of transformer materials. Data source: China Quality Certification Center (CQC) Low Carbon Assessment Project (2015). The difference of carbon emission factors of raw materials consumed in the production process of each transformer can be seen from the table.
According to the above table, the transformer with higher carbon emission factor is compared with the transformer with lower carbon emission factor. The results are as follows:
1) Silicon steel sheet 3.8+bare aluminum wire 9.49+epoxy resin 8.25+cold-rolled steel sheet 2.2=carbon factor 23.74
2) Amorphous alloy 3.07+enamelled copper wire 0.79+mineral oil 1.74+hot-rolled steel plate 2.02=7.62
It can be seen from the comparison that the difference in the number of carbon emission factors selected for different materials is very large, which is just the difference in the carbon factor and emissions of a transformer. If the weight of materials is considered and the output of transformers in the country is summarized, the difference in carbon emissions is very large.
Therefore, it is very important to design and select low-carbon products in terms of design and material selection.
2、 Practice of Carbon Reduction of Green Transformer
At present, green transformers developed by Chinese enterprises and sold in the market include silicone rubber dry-type transformers, natural ester (vegetable insulating oil) transformers, three-dimensional wound core transformers, open dry-type transformers, amorphous three-dimensional wound core open type transformers, etc. They have made great progress compared with traditional transformers in terms of safety, reliability, energy saving, material saving, noise reduction, etc., especially in terms of low carbon, they have made remarkable achievements, providing a real and reliable practice case for the development of low carbon industry in China.
1. Silicon rubber dry-type transformer
Silicone rubber dry-type transformer uses silicon rubber insulation instead of epoxy resin insulation. The main components of silicone rubber insulation materials are dimethylsiloxane and thermal conductive filler, which are non-toxic. They are harmless to human health and safety during the production and operation of transformer windings, and have no waste gas or liquid discharge. The materials at the end of their life can be recycled, and even if they are buried, they will not pollute the soil. The power consumption in the production process of silicone rubber transformer is only 15% of that in the traditional transformer production. The most valuable thing is that silicone rubber is not sticky to metal materials. It can be separated from metal wires by simple methods and recycled by classification.
In comparison, epoxy resin not only has a high carbon emission, but also is difficult to separate from the metal it encloses. If the copper inside needs to be recycled, the burning will generate toxic gas, which will consume huge energy for mechanical classification, causing difficulties in the recovery of copper windings, which does not meet the requirements of circular economy. For transformers with epoxy resin as insulating material, from the perspective of the whole life cycle, the recovery and treatment in the later period will bring huge environmental problems. Therefore, the appearance of silicone rubber dry-type transformer is a significant progress in transformer insulation materials, especially with low carbon environmental significance.
2. Three dimensional wound core open dry-type transformer
The insulation system consisting of aramid insulating paper, environment-friendly insulating paint and polyimide film is adopted for the open type dry-type transformer with three-dimensional winding core. Among them, aramid insulating paper is a globally recognized high-quality environment-friendly material. The main product during combustion is carbohydrate, which is flame retardant, self extinguishing and non-toxic. The combustible content is about 85% lower than that of epoxy resin dry-type transformer.
The insulation system adopts the cake coil structure of "paper insulation air paper insulation", which is different from the envelope insulation structure of traditional resin dry transformation "paper insulation epoxy resin paper insulation". On the one hand, the combustible content in the coil is greatly reduced; On the other hand, in case of serious product failure, there will be no explosion phenomenon such as epoxy resin encapsulated coil, which will not endanger the safety of surrounding personnel and equipment.
The open solid core dry transformer has a more compact structure, and its volume and weight are greatly reduced compared with the traditional epoxy resin dry transformer. Compared with the traditional epoxy resin dry-type transformer with the same capacity and shell, the open type solid core dry-type transformer produced by some enterprises in China is about 34% smaller in volume and 41% lighter in weight.
The open dry-type transformer with three-dimensional winding iron core has realized the replacement of high carbon materials with low carbon materials, achieved technological progress in structure, and become a typical low-carbon environmental protection product.
3. Natural ester (vegetable insulating oil) transformer
Traditional mineral oil is refined from petroleum and belongs to non renewable resources. Its carbon emissions in the whole life cycle are large. Natural ester insulated oil transformer can greatly reduce the consumption of non renewable resources and reduce carbon emissions. The carbon emission of natural ester insulating oil in the whole life cycle is only about 1.5% of that of traditional mineral oil. In addition, natural ester insulating oil also has significant environmental advantages such as biodegradability and non-toxic.
The low carbon property of natural ester insulated oil transformers will greatly reduce the total carbon emissions of traditional oil immersed transformers insulated with mineral oil. At present, Chinese enterprises have developed various types of natural ester insulated oil transformers below 500kV, with obvious carbon reduction effect.
3、 Demonstration role of green transformer as a typical low-carbon product
The Implementation Plan for Carbon Peak in the Industrial Sector of the three ministries and commissions proposed that "leading enterprises should be encouraged to cooperate with upstream and downstream enterprises and inter industry enterprises to carry out collaborative carbon reduction actions, build an industrial chain where enterprises are connected end-to-end, supply and demand each other, and connect with each other, and build a number of demonstration projects of" industrial collaboration "and" carbon fixation by chemical means ".
The development of green transformers has strongly supported the development of green low-carbon materials in the upstream, generating huge industrial synergy.
For example, amorphous alloy is the pearl product of steel industry, while automobile industry and transformer industry are the supporting industries of amorphous alloy. High specification silicone rubber was also a product that needed to be imported in the past, and the high specification silicone rubber for silicone rubber is completely a new product independently developed by China. In addition, China has a complete industrial chain of vegetable oil (natural ester insulating oil). Vegetable oil can not only be used in transformers, but also can replace the past high carbon materials in many electrical fields.
In the field of copper recovery, the industrial synergy generated by green transformers is particularly obvious. China needs to import a large number of copper products to support the development of many industries in China. In the past, because of the use of epoxy resin as transformer insulation, it was very difficult to recover copper, which caused environmental problems that were difficult to deal with. The use of green transformers, such as silicone rubber transformers, three-dimensional rolled iron core open type dry-type transformers, natural ester (vegetable insulating oil) transformers, is very easy to recover transformer copper. Since copper can be recycled 100%, such recycling and recycling will be a huge social resource saving. It is estimated that by 2050, China's per capita cumulative copper consumption will reach a historical peak, and the copper produced by recycling will meet all the needs.
While green transformers have low carbon synergy with upstream material industry, they also provide high-quality low carbon products for downstream industries, such as power grid companies, data centers, new energy power generation, high-speed railways, subways, electric vehicle charging stations, high-rise buildings, etc. These industries are all rapidly developing industries in China at present, and their demands for safety, energy conservation, environmental protection, miniaturization and low noise are exactly what green transformers can meet.
The development of green transformers can be regarded as a typical demonstration project of low-carbon "industrial synergy". What is particularly valuable is that during the exploration of industrial low-carbon road in all walks of life, green transformers have tended to mature and have been favored and applied by more and more users.
The innovation of green transformer on the low-carbon road includes innovation in design, material application, manufacturing process, processing equipment and product type. On the basis of these innovations, we can produce transformer products that can meet customer needs, including its progress in energy conservation, environmental protection, safety and reliability, maintenance free, material saving and miniaturization, This provides users with a new choice of low carbon. In addition, most of the green materials of green transformers are produced in China. Green transformers have full proprietary intellectual property rights, which can realize the safety and independent development of the industrial chain.
The Implementation Plan for Carbon Peak in the Industrial Sector points out that the green and low-carbon concept will be applied throughout the whole process of product design, raw material procurement, production, transportation, storage, use and recycling, and the construction of a unified green product certification and identification system will be accelerated to promote the green and low-carbon development of the whole supply chain. Encourage "one chain, one policy" to formulate low-carbon development plans and release carbon emission reduction performance reports of core suppliers. Green transformers have practiced green and low-carbon development throughout the supply chain.
To sum up, the green transformer has achieved green and low-carbon development in the whole process of product design, raw material procurement, production, transportation, storage, use and recycling, providing a practical example for reference to promote industrial low-carbon in China.
