Xi Zhang

Under the requirements of China's strategic goal of ''carbon peaking and carbon neutrality'', as a renewable, clean and efficient secondary energy source, hydrogen benefits from abundant resources, a wide variety of sources, a high combustion calorific value, clean and non-polluting, various forms of utilization, energy storage mediums and good security, etc. It will become a realistic way to help energy, transportation, petrochemical and other fields to achieve deep decarbonization, and will turn into an important replacement energy source for China to build a modern clean energy system. It is clear that accelerating the development of hydrogen energy has become a global consensus. In order to provide a theoretical support for the accelerated transformation of hydrogen-related industries and energy companies, and provide a basis and reference for the construction of ''Hydrogen Energy China'', this paper describes main key technological progresses in the hydrogen industry chain such as hydrogen production, storage, transportation, and application. The status and development trends of hydrogen industrialization are analyzed, and then the challenges faced by the development of the hydrogen industry are discussed. At last, the development and future of the hydrogen industry are prospected. The following conclusions are achieved. (1) Hydrogen technologies of our country will become mature and enter the road of industrialization. The whole industry chain system of the hydrogen industry is gradually being formed, and will realize the leap-forward development from gray hydrogen, blue hydrogen to green hydrogen. (2) The overall development of the entire hydrogen industry chain such as hydrogen production, storage and transportation, fuel cells, hydrogen refueling stations and other scenarios should be accelerated. Besides, in-depth integration and coordination with the oil and gas industry needs more attention, which will rapidly promote the high-quality development of the hydrogen industry system. (3) The promotion and implementation of major projects such as ''north-east hydrogen transmission'', ''west-east hydrogen transmission'', ''sea hydrogen landing'', and utilization of infrastructures such as gas filling stations, can give full play to the innate advantages of oil and gas companies in industrial chain nodes such as hydrogen production and refueling, etc., which can help to achieve the application of ''oil, gas, hydrogen, and electricity'' four-station joint construction, form a nationwide hydrogen resource guarantee system, and accelerate the planning and promotion of the ''Hydrogen Energy China'' strategy.

In the last decade, a number of severe urban power outages have been caused by extreme natural disasters, e.g., hurricanes, snowstorms and earthquakes, which highlights the need for rethinking current planning principles of urban energy systems and expanding the classical reliability-oriented view. In addition to being reliable to low-impact and high-probability outages, power system should also have high level of resilience to withstand high-impact and low-probability (HILP) events. Compared with power system, multi-energy systems (MESs) have advantages in improving resilience through energy shifting across multiple energy sectors, a variety of generalized energy storage resources and thermal inertia of heat/cooling loads. This paper proposes a resilience-oriented planning method to determine optimal configuration of distribution level MES, e.g., urban energy supply systems, considering comprehensive impacts from supply, network and demand sides in MES. Impacts of energy shifting at supply side, pipe storage at network side and thermal inertia at demand side are described in the same linear modeling framework using energy hub (EH) model. Generalized energy storage resources including centralized and distributed energy storage devices, pipe network storage and building heat capacity are all modeled into centralized energy storage to facilitate an efficient configuration planning of MES.

Multi-energy systems (MESs) make it possible to satisfy consumer's energy demand using multiple coupled energy infrastructures, thus increasing the reliability of the energy supply compared to separate energy systems (SESs). To accurately and efficiently assess and improve the reliability of MESs, this paper proposes a MES reliability and vulnerability assessment method using energy hub (EH) model. The energy conversion, transmission and storage in MESs are compactly and linearly described by EH model, making reliability and vulnerability assessment of MESs tractable. Indices for MES vulnerability assessment are proposed to find the key components for improving MES reliability. Multi-parametric linear programming (MPLP) with a self-adaptive critical region set is proposed to reduce the computational burden caused by iteratively solving LP problems for a large number of samples during the assessment process. The results of a case study show that the proposed reliability and vulnerability assessment method is able to effectively evaluate the energy supply reliability of different energy sectors in MES as well as find the critical component of an MES from reliability perspective to support its planning. The proposed algorithm, i.e., MPLP with a self-adaptive critical region set, can improve the computational efficiency by an order of magnitude compared to the traditional LP method.

The interaction between electricity and heat systems will play an important role in facilitating the cost effective transition to a low carbon energy system with high penetration of renewable generation. This paper presents a novel integrated electricity and heat system model in which, for the first time, operation and investment timescales are considered while covering both the local district and national level infrastructures. This model is applied to optimize decarbonization strategies of the U.K. integrated electricity and heat system, while quantifying the benefits of the interactions across the whole multi-energy system and revealing the trade-offs between portfolios of: 1) low carbon generation technologies (renewable energy, nuclear, and CCS) and 2) district heating systems based on heat networks and distributed heating based on end-use heating technologies. Overall, the proposed modeling demonstrates that the integration of the heat and electricity system (when compared with the decoupled approach) can bring significant benefits by increasing the investment in the heating infrastructure in order to enhance the system flexibility that in turn can deliver larger cost savings in the electricity system, thus meeting the carbon target at a lower whole-system cost.