Search

By the end of 2020, most countries in the world have successively proposed carbon-neutral targets. Among them, the major economies in the world, such as the United States (USA), the European Union, Japan, and Canada, have proposed to achieve carbon-neutral targets by 2050. As the world’s largest carbon emitter, China has a total carbon emissions of more than 11.3 billion tons, accounting for about 30% of global carbon emissions. Therefore, the carbon emission reduction required for China is much higher than that of other economies, and its carbon-neutral tasks are obviously more complex and diversified. On 22 September 2020, the Chinese government announced in the 75th Session of the UN (United Nations) General Assembly (New York, USA) that China aims to achieve carbon neutrality before 2060. The announcement of the carbon-neutral target clearly indicated that China needs to carry out a self-revolution to achieve zero CO2 emissions before 2060. The concept of carbon neutrality is essentially a balance between carbon sources and carbon sinks. The carbon source is the process of releasing CO2 into the atmosphere, and the carbon sink is the process of absorbing CO2 from the atmosphere. Investigating the atmospheric system within a certain period, when the amount of CO2 emitted by all carbon sources into the system is equal to the amount of CO2 absorbed by all carbon sinks from the system, carbon neutrality can be achieved. There are various carbon sources and sinks in nature with complicated relationships. Among them, the most important carbon source related to human activities is energy production. In 2020, China’s power sector emitted about 4 billion tons of CO2 per year, which is close to 40% of the total emissions. Thus, the power sector is one of the key areas in emission reduction to achieve the carbon-neutral goal. Building a carbon-neutral power system is the only way to achieve decarbonization in the energy sector. Based on the carbon balance principle, this paper proposed the critical equation of carbon neutrality for power systems. And the further strategies in establishing a carbon-neutral power system were explored according to the carbon neutrality equation: (1) Improve energy efficiency thus reducing the consumption of carbonaceous energy; (2) adjust the energy structure and reduce the proportion of carbonaceous energy; (3) rebuild the balance of sources and sinks by adopting CO2 capture, utilization and storage (CCUS) technology to achieve low-carbon utilization of carbonaceous energy. Results indicate that, although improving energy efficiency of carbonaceous energy is effective in CO2 mitigation, it is limited by the declining energy saving potential of thermal power plants to be the main technical way in carbon emission reduction. Besides, increasing the proportion of renewable energy can quickly reduce the carbon emission intensity of the power system, which is currently the main technical way to reduce the CO2 emission of the power system. However, although energy conservation and the development of renewable energy can reduce the carbon emission intensity of the power system, the CCUS technology and the negative emission technology will be indispensable to achieve the goal of carbon neutrality. And the large-scale promotion of the CCUS technology must overcome technical obstacles of the rather high energy consumption of CO2 capture. Thus, building a carbon-neutral power system in the future requires a combination of energy efficiency, renewable energy and CCUS technology.

A LiBr-[EMIM]Cl/H2O ternary system has been suggested as an alternative absorption working pair in this work. The crystallization temperature, vapor pressure, specific heat capacity, specific enthalpy, specific entropy, density, and viscosity of this ternary system at a mass ratio of 2.5:1 (LiBr/[EMIM]Cl) were measured systematically. The results showed that the vapor pressure of the LiBr-[EMIM]Cl/H2O was nearly identical to that of LiBr/H2O at an 8.5% lower mass fraction. Under the same absorption ability, LiBr-[EMIM]Cl/H2O had a crystallization temperature much lower than LiBr/H2O, as well as much lower viscosity than ionic liquids. LiBr-[EMIM]Cl/H2O shows a certain potential as an alternative working pair in the absorption heat pump system.