At present, the challenge and cognition of carbon neutralization in the industry are limited, and there are six misunderstandings and five practical paths. On July 15, at the opening of the national carbon market, Liu Ke, a foreign academician of the Australian National Academy of engineering and Dean of the school of innovation and Entrepreneurship of the Southern University of science and technology, made a speech on the theme of "carbon neutralization misunderstanding and its practical path" in the academician's lecture hall of scientific and technological innovation jointly sponsored by Shenzhen Institute of innovation and development and other units.

According to Liu Ke, China emits about 10.3 billion tons of carbon dioxide per year, with a per capita emission of 7.4 tons. A family of three emits an average of 22 tons of carbon dioxide per year. Although wind energy, solar energy, carbon dioxide conversion into chemicals, CCS (carbon capture and storage technology), CCUs (carbon capture, utilization and storage technology) and energy efficiency improvement will all contribute to carbon reduction more or less, which is worth encouraging, exploring and implementing; However, the reduction rate of carbon dioxide emissions per day is quite limited.

Six misconceptions about carbon neutralization the first misconception is that wind energy and solar energy are cheaper than thermal power, so solar energy and wind energy can completely replace thermal power to achieve carbon neutralization. The fact is that 8760 hours a year, while the annual number of solar power generation hours varies from place to place, with an average of about 1700 hours; That is to say, solar energy is cheaper than thermal power in the period of 1/5 - 1/6; In other 5/6 time periods, the cost of power storage will be much higher than that of thermal power. Despite the huge increment of wind and solar energy in China, the total power generation is still a drop in the bucket compared with coal-fired power. Moreover, the concept of "battery based power storage" of the power grid is very dangerous. It is estimated that the world's five-year battery capacity can only meet the three-day power outage in Tokyo. Solar energy and wind energy need to be vigorously developed, but at present, when the cost of power storage is still very high, it will not be able to completely replace fossil energy power generation in the foreseeable future.

The second misunderstanding is that people think that there is a magic large-scale power storage technology, but in fact, the energy industry does not have Moore's law in the computer industry. "People have spent more than 100 years of research and development, and the energy density of the battery has not been revolutionized and fundamentally changed". So far, the cheapest large-scale GW and power storage technology is the pumped storage technology invented more than 100 years ago.

The third misunderstanding is that carbon dioxide is used to make chemicals, but in terms of scale, carbon dioxide does not have carbon reduction value. About 87% of the world's oil is burned, and about 13% of the oil produces all our petrochemical products. The contribution of carbon dioxide conversion to other chemicals to carbon reduction is quite limited.

The fourth misunderstanding is that CCUs technology can be carbon neutral. Capturing and purifying the carbon dioxide emitted from the production process and putting it into the new production process for recycling or storage can theoretically achieve large-scale capture of carbon dioxide. However, "carbon neutralization is not only a technical problem, but also a comprehensive problem of balancing economic and social development". Academician Liu Ke stressed that under the current technology, the cost is very high, and complete carbon sequestration cannot be achieved, Moreover, it is very difficult to collect carbon dioxide in nature. So far, the carbon dioxide emissions reduced by CCS or CCUs are very limited.

The fifth myth is that carbon neutrality can be achieved by improving energy efficiency. Increasing energy efficiency can significantly reduce carbon emissions in industrial processes and products. In the first 20 years, China's energy efficiency has indeed improved significantly, but in the same period, the total carbon emissions have not decreased, but increased a lot. Therefore, improving energy efficiency is an important means of carbon reduction. However, as long as fossil energy is used, the contribution of improving energy efficiency to carbon neutralization is very limited. Improving energy efficiency is indeed the lowest cost of reducing carbon emissions and should be the most priority.

The sixth misunderstanding is that we hope to reduce carbon emissions by replacing fuel vehicles with electric vehicles. In fact, the dispute between electric vehicles and fuel vehicles began a hundred years ago. Academician Liu Ke said, "if the energy structure does not change, if 67% of the power grid is still coal-fired, then electric vehicles are increasing carbon emissions, not reducing carbon emissions. Only when the energy structure and the power grid are mostly composed of renewable energy, can electric vehicles be considered as clean energy".

Methanol may be the best hydrogen storage carrier

Why did electric vehicles fail to beat fuel vehicles in the first 100 years? Academician Liu Ke pointed out that, on the one hand, it is the problem of energy density and infrastructure. For example, the energy density of liquid fuel is much higher than that of gas. At the same time, "liquid energy has a very good feature, which can be transmitted by pipeline on land and cheaply across the sea at sea". In addition, humans have built liquid fuel filling facilities all over the world. On the other hand, it is the problem of mass production cost and pollution. The main reason is that the heavy metals (nickel, cobalt, lead, cadmium, etc.) used in batteries are easy to cause ecological pollution, and the battery recycling technology needs to be further developed.

Academician Liu Ke believes that hydrogen energy has obvious advantages. "It has high power generation efficiency, can reduce the dependence on oil, and can be discharged as steam, and the cost can be reduced after large-scale mass production of fuel cells.". However, hydrogen energy also has some problems, such as high cost of hydrogen storage and transportation, great potential safety hazards, and high investment in infrastructure.

Why hasn't the hydrogen car been industrialized? Academician Liu Ke pointed out that the most fundamental reason is that hydrogen is not suitable for being the energy carrier shared by the public. "Hydrogen production is easy, but hydrogen storage and transportation are difficult".

Academician Liu Ke believes that methanol is a very good carrier for liquid hydrogen storage and transportation. Why is the methanol line proposed? He said that methanol can be made from coal and natural gas. In the future, methanol can be made from carbon dioxide and water catalyzed by solar energy, which will become green methanol. China now has the highest methanol production capacity in the world, about 80 million tons, which is close to 1/4 of gasoline in terms of tonnage. In addition, the shale gas revolution has enabled the world to discover more than 100 years of inexhaustible natural gas. "There is natural gas that cannot be used up for more than 100 years, and there is methanol that cannot be used up for more than 100 years." He pointed out that in the future, we can also use solar energy to make methanol, so the methanol produced will be completely green.

The biggest problems of electric vehicles and fuel cells lie in the land cost of infrastructure and the endurance in winter. The supply of hydrogen energy by liquid fuels such as methanol can solve the pain points of electric vehicle charging and fuel cell hydrogenation station construction. At present, methanol filling stations have been successfully demonstrated in many provinces and cities across the country. The existing gas stations can also be completed through simple transformation, and the storage and transportation are basically mature; The storage and transportation of alcohol aqueous solution is equivalent to the storage and transportation of 64wt% alcohol, and the related technology is more mature; At the same time, the underground parking lot can also set up its own methanol hydrogen power generation system without power grid.

Reprinted from China Science and technology network