Increasing percentages of Distributed Generators (DGs) in active distribution networks (ADNs) have increased the concern on excess generations in the medium and low voltage levels. High capacities of excess power are mainly from intermittent wind, solar power, and restricted power generations of combined heat and power (CHP) plants, which are determined by the heat demand. Turning excess power to hydrogen (P2H) has been recognized as a promising method to meet potential hydrogen demand from the traffic sectors. Nevertheless, it suffers from a low power-to-hydrogen efficiency, which is usually below 70% for commercialized electrolysis. By introducing in the heat recovery at the system level, we propose an integrated solution to supply heat to district heating networks (DHNs) while producing hydrogen, i.e., a power-to-hydrogen-and-heat scheme (P2HH). The extra benefit of P2HH resulting from heat supply is the reduction in the output of CHP, which reduces the excess energy in ADNs. This paper establishes a detailed "T-H-H" model to couple the power-to-heat and power-to-hydrogen processes. Then, a simplified P2HH dispatch model is proposed for the electricity-heat-hydrogen dispatch coordinated with ADN and DHN. Finally, the overall benefits of P2HH via improving the system economy and security are demonstrated with a modified IEEE 33-node system.

Most industrial practices for turning power into hydrogen face a similar challenge, i.e., hydrogen consumption. One solution is injecting hydrogen into the existing natural gas (NG) infrastructure, so as to enter the market without expensive investments. However, a major concern regarding HCNG (Hydrogen enriched compressed natural gas) is the amount of hydrogen that can be added to the natural gas infrastructure without any modification. The current studies have focused on the modeling of HCNG components under various H2 fractions, but there is a lack of research on the system operation of HCNG, especially when incorporated with dispersed renewables and CHP plants. To fill in the gaps from the component to the system level, this paper proposes a comprehensive HCNG operation model coupled with the operations of an electrical and heating network. Via this model, the system performance incorporated with HCNG distribution networks could be studied under various H2 fractions and HCNG load portfolios (HLP). The numerical studies demonstrate the benefits of integrating the HCNG distribution network, especially in terms of local balancing of distributed generators and minimizing the operational costs.

Converting renewable energy into ammonia has been recognized as a promising way to realize “green hydrogen substitution” in the chemical industry. However, renewable power to ammonia (RePtA) requires an essential investment in facilities to provide a buffer against the strong volatility of renewable energy and the limited flexibility of ammonia synthesis, which involves the three main stakeholders, namely, power, hydrogen, and ammonia. Therefore, the sizing and pricing of RePtA play a core role in balancing the interest demands of investors. This article proposes an optimal sizing and pricing method for grid-connected RePtA systems planning. First, power to ammonia (P2A) is modeled as a flexible load, especially considering the limited flexibility of ammonia synthesis, which has been verified using real dynamic regulation data. Second, the multi-investor economic (MIE) model is established considering both external and internal trading modes. Then, a two-stage decomposed sizing and pricing method is proposed to solve the problem caused by the strong coupling of planning, operation, and trading. The information gap decision theory (IGDT) method is utilized to handle the uncertainty of renewable generation. Finally, real data from a real-life system in Inner Mongolia are utilized to verify the proposed approach. The results show that the system proposed has an internal rate of return (IRR) of 8.55%, which indicates the practical feasibility of the proposed planning method.

Converting wind energy into ammonia (WtA) has been recognized as a promising pathway to produce “green” ammonia compared with traditional coal-based technologies. As the key part of WtA, Power-to-Ammonia (PtA) has great potential to facilitate the usage of wind generation. This paper proposes a co-planning approach for regional wind resources-based ammonia industry and the electric network (EN). To this end, PtA is first modeled as a flexible power load of power systems with spatial and temporal constraints on hydrogen supply chains (HSC). Then a novel co-planning model of WtA and EN is established to optimize the WtA configuration and the EN expansion. An alternating direction method of multipliers (ADMM) based algorithm is introduced to effectively solve this model. Real data of Inner Mongolia Province in China is adopted to verify the effectiveness and significance of the proposed approach. It is shown that the siting and operation flexibility of PtA with HSC can reduce the expansion burden of EN. The co-planning of WtA and EN can significantly enhance wind power utilization and reduce total investment costs. Furthermore, feasibility analysis on WtA in comparison with coal-to-ammonia (CtA) and ultra-high voltage transmission (UHV) provides helpful guidelines for the realization of WtA.