(156c) Optimal Design and Operation of a Hydrogen Generation and Storage System for Utilization in the Peaker Plant

There are considerable efforts worldwide for reducing the use of fossil fuel for energy production. While renewable energy sources are being increasingly used, fossil fuel still contribute about 80% of the energy used worldwide. As a result, the level of CO₂ is still increasing fast in the atmosphere currently exceeding about 410 ppm. Various research efforts are ongoing to reduce CO₂ build up in the atmosphere. One approach is utilization of hydrogen as a fuel in power plants, and this can reduce CO₂ emission by 30-40% [1]. Hydrogen can be used as an energy storage medium producing it during the time when electricity is in excess while utilizing it later when needed. There are different options for hydrogen storage, among them storing it as a compressed gas is currently the cheapest and most practical option especially for distributed storage. [2]. However, capacity and maximum operating pressure of storage must be optimal for cost-efficient storage of hydrogen [3,4]. There are three leading approaches for utilization of stored H₂ for power generation- co-injection with natural gas in an existing natural gas combined cycle (NGCC) power plant, firing of H₂ by itself in a turbine, and use it in a fuel cell. Co-injection of H₂ with natural gas facilitates use of existing gas turbines in NGCC plants and peaker plants. Peaker plants are generally operated when the electricity is in high demand and therefore plays a key role in maintaining the resiliency and reliability of the electric grid. Currently no studies on optimal design and operation of hydrogen generation and storage facilities integrated with peaker plants could be found in the literature.

This research presents an integrated model of hydrogen production, storage and utilization for the peaker plants. The system includes electrolyzers for producing hydrogen, hydrogen compression and cooling system, hydrogen storage, hydrogen expansion and heating system and an aeroderivative gas turbine for power generation. Two types of electrolyzers, namely alkaline and proton exchange membrane (PEM) electrolyzers, are evaluated. To store hydrogen as a compressed gas, an optimum storage vessel is designed. A model of the vessel is developed by considering geometry of the vessel that takes into account the design thickness of the wall by considering the stress and corrosion allowance. A cost model of the hydrogen storage vessel is developed and compared with the in-house data. Optimal design and operation of the hydrogen storage system and the peaker plant are done by maximizing the net present value (NPV) of the integrated system. Due to the dynamics of the storage and generation systems, a dynamic optimization problem ensues that is solved using Python/PYOMO. The NPV optimization problem is solved for 14 regions by considering their respective locational marginal price (LMP) of electricity [5] with varying carbon taxes. A clustering algorithm [6] is used to reduce the number of representative days to be considered for optimization for a year-long optimization. Results show that the optimal size and design pressures of the hydrogen storage vessels and the design and operating conditions of the peaker plant differ not only from region to region based on the LMP profile, but also can differ for the same region due to the difference in carbon tax.

Bibliography

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