Advanced CHHP: Integration, Heat Management and Strategies

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A proposed Combined Hydrogen, Heating, and Power (CHHP) system integrating photovoltaic (PV) power supply, alkaline water electrolysis (AWE), metal hydride (MH) hydrogen storage, and proton exchange membrane fuel cells (PEMFCs) aims to address the volatility and intermittency of renewable energy sources. Here is a detailed overview of the system and its energy management strategies, emphasising the thermal scheduling aspect:

CHHP System Overview

Integration Components:

    • Alkaline Water Electrolysis (AWE): Utilises electricity generated from PV panels to produce hydrogen through water electrolysis.
    • Metal Hydride (MH) Hydrogen Storage: Stores hydrogen produced by AWE, providing a stable supply of hydrogen that can be used as needed.
    • Proton Exchange Membrane Fuel Cells (PEMFCs): Convert stored hydrogen into electricity and heat, offering a high-efficiency energy conversion process.

    Heat Generation and Utilisation:

      • The processes of water electrolysis, hydrogen adsorption/desorption, and PEMFC operation all generate heat. Efficient utilisation of this heat is crucial for enhancing the overall energy efficiency of the CHHP system.
      • The system aims for the cascade utilisation of heat, where different grades of heat are used sequentially to maximise energy utilisation.

      Energy Management Strategies

      Peak-Valley Strategy:

        • Designed for on-grid operation, this strategy focuses on matching the energy production and consumption with the electricity grid’s peak and off-peak periods.
        • Benefits include better grid stability and efficient energy utilisation during periods of high and low electricity demand.

        Heat Priority Strategy:

          • Prioritises the use of waste heat for thermal applications. This strategy aims to minimise residual electricity and heat, thus maximising the thermal efficiency of the system.
          • Particularly suitable for scenarios where heating demand is high, ensuring that the waste heat from PEMFCs and other processes is fully utilised.

          Peak Clipping Strategy:

            • This strategy aims to reduce the peak demand by managing the operation of the CHHP system during high load periods. It ensures that the current density of the PEMFC fluctuates the least, maintaining a steady performance.
            • Suitable for applications where avoiding peak load penalties and maintaining system stability is critical.

            Load Reduction Strategy:

              • Focuses on reducing the system’s electric power during specific periods (e.g., from 5:00 p.m. to 6:00 a.m.) when the demand is lower. This strategy ensures the system electric power is lower than the power load for the shortest duration, accounting for 23.93% of this operating period.
              • Ideal for off-grid scenarios where reducing energy consumption during low-demand periods can enhance system efficiency and prolong operational life.

              Benefits of the Proposed CHHP System

              Efficient Renewable Energy Utilisation:

                • The integration of PV, AWE, MH, and PEMFCs allows for the stable absorption and conversion of intermittent renewable energy into hydrogen, which can be stored and used as needed, smoothing out energy supply fluctuations.

                Cascade Heat Utilisation:

                  • By utilising the heat generated at various stages of the energy conversion processes, the system achieves higher overall energy efficiency. This cascade utilisation ensures minimal heat loss and optimal energy use.

                  Versatile Application Scenarios:

                    • The four proposed energy management strategies provide flexibility, making the system suitable for different application scenarios, including both on-grid and off-grid operations.
                    • Each strategy is tailored to specific operational needs, whether it’s prioritising heat usage, managing peak loads, or reducing energy consumption during low-demand periods.

                    The CHHP system proposed by Zhao et al. addresses the challenges of renewable energy volatility by integrating advanced components and proposing effective energy management strategies. The efficient use of waste heat through cascade utilisation and tailored scheduling schemes enhances the overall system efficiency, making it a promising solution for future energy systems that aim to maximise renewable energy utilisation and improve energy reliability .

                    Source

                    Energy management strategy for accurate thermal scheduling of the combined hydrogen, heating, and power system based on PV power supply, International Journal of Hydrogen Energy, 2024-08-12

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