Energy conservation is the foundation for achieving carbon neutrality goals. To realize low-carbon development, we must first do a good job in energy conservation.
" The purpose of energy conservation is to reduce the use of fossil energy, and the purpose of energy low-carbon transformation is to no longer rely on fossil energy. Therefore, energy conservation and low-carbon are closely related. They not only share common goals, but also have a lot of overlap in specific measures." At the recently held 2023 China Energy Conservation and Low-Carbon Development Forum, Jiang Yi, academician of the Chinese Academy of Engineering and director of the Tsinghua University Building Energy Conservation Research Center, shared his thoughts on the relationship between energy conservation and low-carbon development.
Jiang Yi believes that energy conservation is the foundation for achieving carbon neutrality goals. In specific work, it is necessary to establish a zero-carbon power system, adopt zero-carbon heat, and fully develop and utilize various types of waste heat to meet heat demand. We should be driven by innovation to build a new low-carbon energy system, contributing to thoroughly solving energy problems and achieving sustainable development.
Energy Conservation is an Important First Step
Jiang Yi said that looking at the history of human development, the proportion of fossil energy use has grown rapidly in the past 200 years. With the growth of fossil energy consumption, problems such as energy security, air pollution, and climate change have followed, seriously affecting the sustainable development of society and mankind as a whole.
Against this background, the energy revolution targeting low carbon will bring tremendous changes to mankind. Jiang Yi pointed out that the energy revolution is to change the source and mode of energy use, realize sustainable development in the energy field, end the history of human dependence on fossil energy, and establish a new mode of energy production and use, so as to no longer be troubled by energy problems and truly achieve sustainable development in the energy field.
" Energy conservation and low-carbon development have common goals: on the one hand, to improve energy use efficiency; on the other hand, to reduce the use of fossil energy." Jiang Yi pointed out that in this process, we should focus on wind, solar, and hydropower, and develop various types of zero-carbon energy. Although the initial investment cost of zero-carbon energy is high, once it is built, the operating cost is extremely low. In contrast, fossil energy has a lower initial investment, but the operating cost is very high. Considering the environmental cost, its comprehensive cost is even higher.
Jiang Yi believes that energy conservation is the foundation for achieving carbon neutrality. To achieve low-carbon development, we must first do a good job in energy conservation. Even zero-carbon energy requires resources, especially space resources. For example, building hydropower requires suitable geographical conditions, and building nuclear power plants requires sufficient space. Once zero-carbon energy develops excessively, it will lead to a super-linear increase in costs. " Therefore, only by saving energy and reducing the total demand can we realize zero-carbon energy supply at an acceptable cost. Energy conservation is a very important first step, and only on this premise can we better achieve low-cost energy transformation."
Establishing a Zero-Carbon Power System
How to balance energy conservation and low-carbon development? Jiang Yi reminded that while improving efficiency, we should pay more attention to electricity flexibility and demand-side response under the low-carbon model, and focus on reducing fuel demand.
In Jiang Yi's view, one of the main tasks to achieve carbon neutrality is to establish a zero-carbon power system. " The installed capacity of rooftop photovoltaics in China's cities is about 870 million kilowatts, which can generate 1 trillion kWh of electricity a year. In rural areas, except for a few mountain valleys that are not exposed to the sun, the total power generation can reach 2.5 trillion kWh, which is 1/3 of China's total power generation in 2019. Therefore, in the future, China will focus on the development of wind and solar power, combining centralized and distributed forms. More than 60% of wind and solar power will be developed in the central and eastern regions of China, and rooftop photovoltaics and photovoltaics in idle open spaces will be the main directions of the photovoltaic industry."
It should be noted that as wind and solar power gradually develop, problems such as time mismatch between power generation and consumption, and large cost differences have become increasingly prominent. " At present, the power cost at different times differs by more than 10 times. When wind and solar power are abundant, the power cost is particularly low. Take Shandong Province as an example, the midday electricity price in Shandong can be as low as 1.10 yuan/kWh. However, when wind and solar power are insufficient, thermal power + CCS and energy storage facilities are needed to generate electricity to meet the demand, resulting in extremely high costs." Jiang Yi said.
" Therefore, flexible electricity use according to changes in power costs is more important than reducing electricity use by improving efficiency." Jiang Yi believes that it is necessary to develop interruptible electricity consumption methods in industrial production, and direct and indirect energy storage, such as making full use of the energy storage resources of electric vehicle on-board batteries. " It can be said that flexible electricity use and distributed energy storage are important ways to solve the problem of wind and solar power consumption, and are also the key and focus of establishing a stable and reliable zero-carbon power system."
To realize the active participation of electricity terminals in regulation and solve the problem of end-demand response, Jiang Yi suggested that electricity should correspond to carbon emission responsibilities, and the value of carbon emission responsibilities is closely related to factors such as the balance between supply and demand of the power grid and the proportion of wind and solar power. This will fully arouse the enthusiasm of the whole society for carbon emission reduction and enable users to take the initiative to implement regulation at the terminal. " Facing different system structures and regulation modes, it is necessary to redesign policy mechanisms according to the actual situation. The method of using dynamic carbon emission responsibility factors for electricity may become a simple and feasible way to adapt to changes in the power source structure."
Fully Developing and Utilizing Various Types of Waste Heat
Adopting zero-carbon heat and fully developing and utilizing various types of waste heat to meet heat demand is also one of the main tasks to achieve carbon neutrality. China will need 24 billion gigajoules of heat in the future, including heating for urban buildings in northern China, domestic hot water preparation, and industrial heat use. Under the goal of carbon neutrality, how to meet these heat source demands while solving the problem of pollutant emissions? Jiang Yi believes that waste heat will be the most important heat source in China's society in a zero-carbon environment.
According to Jiang Yi's calculation, a variety of low-grade waste heat resources are the best zero-carbon heat sources. If 70% of the waste heat is utilized to form a cross-regional multi-heat source sharing system, the problem of heat use can be solved.
Jiang Yi believes that China has good conditions for developing a zero-carbon waste heat system. At present, many places are building large heat networks, with rich experience in combined heat and power generation. Some power plants have realized in-depth recovery of waste heat from combined heat and power generation, and there are also many successful cases of industrial waste heat recovery. Relevant key equipment and technologies are already available.
It should be noted that although developing waste heat resources is a good path, it still faces three major obstacles. First, the time mismatch problem: although the total amount meets the standard, the output time does not completely match the heat use time. Second, the location mismatch leads to the problem of supply and demand imbalance. Third, the grade problem: that is, the output grades of various heat sources are different, and the thermal temperature ranges required by various users are also different.
In the face of the above problems, Jiang Yi pointed out that it is necessary to achieve breakthroughs in three key technologies: large-scale cross-seasonal heat storage technology, long-distance and low-cost heat transmission technology, and heat conversion technology based on heat pumps. The solution to these problems involves a large number of new products, new equipment, and new infrastructure, which can create huge market demand and help achieve zero-carbon heating and sustainable development.
