Hydrogen energy storage system is a technology that achieves long-term and large-scale energy storage through bidirectional conversion of electrical and chemical energy, and has important strategic value in new energy systems. The following analysis will focus on technical details, application scenarios, advantages, and challenges:

1、 System composition and core technology

1. Hydrogen production system

-Technical route: Mainly using electrolysis of water to produce hydrogen, including alkaline electrolysis (AE), proton exchange membrane electrolysis (PEM), high-temperature solid oxide electrolysis (SOEC) and other technologies. Among them, alkaline electrolysis technology is mature and cost-effective, but its efficiency (about 60%) and dynamic response capability are limited; PEM electrolysis has high efficiency (about 80%) and small volume, but relies on precious metal catalysts; The theoretical efficiency of SOEC exceeds 90%, but it requires high temperature (800-950 ° C) operation and is still in the research and development stage.

-Efficiency and Cost: The current electrolytic cell efficiency is 65% -85%, and the system cost is approximately $855/kW (2020). It is expected to decrease to $305/kW by 2030 (learning curve rate of 20%).

2. Hydrogen storage system

-Storage method:

-High pressure gaseous hydrogen storage: mainstream technology, with a mass density of about 5% at 35MPa and 38kg/m ³ at 70MPa, but high compression energy consumption (accounting for one-third of liquefaction energy).

-Low temperature liquid hydrogen storage: The volumetric density is increased to 800 times that of the gaseous state, but liquefaction energy consumption accounts for one-third of the combustion heat of hydrogen gas, and the evaporation loss rate is 1% -2%/day.

-Solid state hydrogen storage: using metal hydrides (such as LaNi5H6, MgH2) for storage, with high safety and no evaporation loss, but low mass density (about 5-10 kWh/kg)

-Hydrogen storage materials: Carbon fiber composite storage tanks are widely used, and large-scale hydrogen storage solutions such as underground salt caverns and abandoned oil and gas fields are being demonstrated.

3. Hydrogen power generation system

-Fuel cell technology: Proton exchange membrane fuel cells (PEMFC) are suitable for distributed power generation, with an efficiency of 50% -60% and high power density, but rely on platinum catalysts; Solid oxide fuel cells (SOFCs) have an efficiency of 65% and high waste heat utilization, making them suitable for combined heat and power generation.

-Power generation efficiency: The overall efficiency of fuel cells is affected by factors such as hydrogen purity and temperature management, and the current system efficiency is about 35% -50%.

2、 Application scenarios and typical cases

1. Peak shaving and frequency regulation of power system

-Mechanism of action: Utilize surplus electricity to produce hydrogen, generate electricity through fuel cells during peak electricity consumption, or directly participate in grid peak shaving. For example, Xizang, Qinghai and other areas with serious wind and light abandonment (the light abandonment rate will exceed 8% in 2022) can absorb fluctuating power through hydrogen storage.

-Case: Zhangjiakou Renewable Energy Hydrogen Production Project (200MW wind power+10MW hydrogen production) achieves cross seasonal peak shaving through hydrogen storage.

2. User side demand response and combined cooling, heating, and power supply

-Valley electricity hydrogen production: The user side uses low-priced electricity at night to produce hydrogen, and uses fuel cells to supply heat during the day, achieving peak valley arbitrage. For example, industrial parks can build hydrogen storage microgrids to reduce electricity costs.

-Combined heat and power supply: The waste heat from fuel cells can meet the heating needs of buildings, with a comprehensive energy efficiency of over 80%.

3. Cross regional energy allocation

-Hydrogen production from offshore wind power: Far reaching offshore wind power breaks through transmission limitations by electrolyzing water to produce hydrogen. For example, the European North Sea wind power hydrogen production project (1GW wind power+annual production of 1 million tons of hydrogen) utilizes salt cavern hydrogen storage to achieve seasonal regulation.

-Transformation of oil and gas fields: Exhausted oil and gas fields can be transformed into "hydrogen gas fields" and transported through pipelines mixed with hydrogen (<15%) to reduce transportation costs.

3、 Advantages and Challenges

1. Core advantages

-Long term energy storage: suitable for storing energy for more than 4 hours to a quarterly scale, which can smooth out seasonal fluctuations in wind and solar power.

-Large scale and cross regional: With a storage capacity of 100 GWh, hydrogen can be transported through pipelines and tanks to achieve remote allocation, breaking through geographical limitations.

-Environmental friendliness: The entire cycle of "electricity hydrogen electricity" only produces water. If renewable energy is used to produce hydrogen, zero carbon emissions can be achieved.

2. Main challenges

-Efficiency and Cost: Currently, the total efficiency of "electricity hydrogen electricity" is about 30% -40%, and the cost per kilowatt hour is 1.8 yuan (2020), far higher than lithium energy storage (0.5 yuan) and pumped storage (<0.25 yuan).

-Technical bottleneck: Hydrogen storage materials and key components of fuel cells (such as membrane electrodes and bipolar plates) rely on imports, and the localization rate needs to be improved.

-Safety: Hydrogen is flammable and explosive, and tank design, transportation management, and leak monitoring technology need to be optimized.