Energy development
The global energy infrastructure is shifting dramatically from carbon-based fossil fuels to solar energy (photovoltaic, wind, and hydropower are all forms of solar energy, collectively referred to as solar energy hereafter). As the foundation of our energy supply changes, nearly every industry will experience a revolution. In the era of fossil fuel-based energy, we witnessed the birth of steam engines, internal combustion engines, jet engines, and gas turbines. These devices are essentially heat engines that convert chemical energy into mechanical energy. Throughout centuries of industrial revolution, we have established a comprehensive system for the extraction, processing, transportation, and distribution of fossil fuels, spanning the globe with extensive connections.
Fossil fuel-based energy systems may appear perfect in terms of stable supply, reasonable efficiency, and a robust industry chain. However, they have one fatal flaw: carbon emissions. As the global consensus on carbon neutrality forms, it becomes clear that fossil fuel-based energy systems can no longer support sustainable human development. Solar energy emerges as the best choice for decarbonization, theoretically achieving a carbon-free process throughout the entire supply chain (solar for solar). The downside of solar energy, however, is its intermittency. The Earth’s rotation and revolution around the Sun inevitably lead to short-term energy fluctuations on a daily basis and medium to long-term fluctuations on an annual basis.
Energy storage has been a pressing concern since the development of solar energy. Conventional fossil fuel storage is well-established, with coal transported by train, gasoline stored in tanks, and natural gas piped through extensive networks. These infrastructures still operate efficiently today. Various mobile transportation modes essentially comprise a heat engine and a carbon storage container (e.g., fuel tanks, gas cylinders, storage tanks).
In the era of solar energy, storing sunlight becomes a complex challenge. The most straightforward solution is generating electricity, which can be seamlessly integrated into the existing large-scale power grid developed during the fossil fuel era. Thus, solar power has experienced rapid growth in Europe and America for decades. As the 21st century progresses and China joins the solar industry, the pace of solar energy expansion accelerates dramatically. As the proportion of solar power in the grid increases, it begins to strain the power grid, which was designed for fossil fuel-based energy. This system is inherently suited to that era, with fossil fuels combusting to boil water, which then drives electricity generation through cutting magnetic flux lines. The grid is resilient but lacks flexibility, struggling to cope with the variable nature of solar energy.
The fundamental need for an “energy storage industry” arises. Whether for frequency regulation or peak shaving, the primary goal is to increase the flexibility of the inflexible grid and make it more “elastic.” Electrochemical batteries, represented by lithium-ion batteries, emerge as a viable energy storage solution.
Electrochemical energy storage
Undoubtedly, electrochemical energy storage is one of the most outstanding energy storage methods, favored by both industry and capital. As the world transitions from fossil fuels to renewable energy sources, such as solar power, the need for efficient energy storage methods is becoming increasingly important.
The Growing Importance of Solar Energy and the Need for Storage
Undoubtedly, electrochemical energy storage is one of the most outstanding energy storage methods, favored by both industry and capital. As the world transitions from fossil fuels to renewable energy sources, such as solar power, the need for efficient energy storage methods is becoming increasingly important. This article will explore the role of batteries and hydrogen in the transition to a renewable energy future.
In recent years, the solar energy industry has grown rapidly, reaching a 20% or higher share in many countries’ energy grids. This growth has led to a shift in the requirements for energy storage, with large-scale, long-cycle storage becoming increasingly necessary. If not addressed, the rapid expansion of solar energy could lead to a bottleneck in the energy sector.
Electrochemical Energy Storage and the Rise of Electric Vehicles
The rise of electrochemical energy storage has brought about the emergence of lithium-ion battery-powered electric vehicles (EVs). As EVs become more popular, their carbon emissions will decrease as the electricity grid becomes more decarbonized. In fact, according to the concept of a flexible electricity grid, the batteries in EVs could become an important energy storage device for future power grids.
Hydrogen: A Key Player in Long-cycle Energy Storage
As the need for large-scale, long-cycle energy storage grows, the industry is turning to hydrogen. While hydrogen is not a new discovery, the increased demand for carbon neutrality and energy storage has brought it back to the forefront of the industry. Essentially, hydrogen energy is a branch of the energy storage market, with short-term, small-scale frequency regulation and peak shaving storage (electrochemical) coexisting with large-scale, long-cycle storage (hydrogen).
The Future of Hydrogen Energy: Production, Storage, and Application
The hydrogen energy industry will likely see substantial growth in the coming years, with hydrogen production, storage, and application technologies becoming increasingly important. At present, the most visible application is fuel cell technology, which essentially combines a hydrogen generator, a hydrogen storage tank, and an electric motor. However, fuel cells are just one part of the hydrogen energy value chain.
Green Hydrogen: A Sustainable Alternative for Energy Storage
Green hydrogen, produced through the electrolysis of water using renewable energy sources, offers a sustainable alternative to traditional hydrogen production methods. Proton exchange membrane (PEM) water electrolysis is a promising technology for producing high-purity hydrogen from water, with no corrosion or pollution and a rapid startup and shutdown time. This technology is well-suited to integrate with wind and solar power generation.
The Global Push for Green Hydrogen
Both Europe and China are investing heavily in green hydrogen production. Europe’s 2×40 GW Green Hydrogen Plan aims to mature the hydrogen economy by 2030-2040 and apply it to sectors that are difficult to decarbonize through electrification, such as aviation and heavy machinery. The recent conflict between Russia and Ukraine and the European Union’s sanctions against Russia have accelerated Europe’s efforts to reduce its dependence on Russian natural gas.
China, the world leader in installed wind and solar capacity, also has a bright future in hydrogen energy. The large amount of wind and solar power in China’s grid has created a significant burden, leading to instances of curtailed electricity. By using rapidly responsive PEM electrolysis to produce hydrogen from excess wind and solar power, a practical and cost-effective energy storage solution can be developed.
In recent years, the solar energy industry has grown rapidly, reaching a 20% or higher share in many countries’ energy grids. This growth has led to a shift in the requirements for energy storage, with large-scale, long-cycle storage becoming increasingly necessary. If not addressed, the rapid expansion of solar energy could lead to a bottleneck in the energy sector.
Hydrogen Storage, Transportation, and Applications in a Low-Carbon Era
Compared to hydrogen production, hydrogen storage is relatively more difficult. Hydrogen, being the lightest element in the periodic table with the lowest density, means that even storing a small amount of hydrogen requires a large volume. At a standard atmospheric pressure (1 atm, or 1.013 bar, or 0.1 Mpa), one cubic meter of hydrogen gas weighs only 0.09 kg. Such low transport efficiency necessitates converting hydrogen into a denser form for storage and transportation.
Conventional storage methods, such as high-pressure gas storage, are widely used. We often see tube trailers on highways, which typically operate at pressures between 35-70 Mpa (350-700 atmospheres). At 350 atmospheres, 1 cubic meter of hydrogen weighs about 23 kg.
By cooling hydrogen gas to extremely low temperatures (-252.8°C), it can be liquefied with a density of 70 kg/cubic meter. However, cooling gas to such low temperatures requires specialized equipment and high energy consumption, making it only widely used in the aerospace industry. Applications in other fields are still in their early stages.
In addition to storing hydrogen as a single element, it can also be combined with other substances to form hydrogen-containing compounds. Metal hydride materials and liquid organic hydrogen carriers are two promising storage methods. Some metals or organic materials can form stable hydrogen-containing compounds at room temperature, allowing for safe storage and transportation. When heated, these hydrides can decompose and release hydrogen again, making them a potential hydrogen storage system.
Ammonia, alcohols, and hydrocarbons, all of which contain significant amounts of hydrogen, have potential as hydrogen storage materials. These substances can be produced in large quantities using electrolytic hydrogen production, and existing infrastructure can be utilized for storage and transportation.
In the era of zero-carbon and low-carbon energy, hydrogen has a wide range of applications beyond traditional industrial uses, such as transportation and energy storage. In urban transportation and light-duty commercial vehicles, lithium-ion battery electric vehicles have shown considerable advantages. However, for long-haul, heavy-duty commercial vehicles, battery-powered vehicles struggle due to the large power consumption and battery weight, affecting the vehicle’s payload.
For electric vehicles, energy replenishment is a critical issue. Even for home users, charging an electric vehicle is time-consuming, and for heavy-duty commercial vehicles with a 300 kWh battery pack, each charge takes at least two hours, impacting the vehicle’s economic efficiency.
Currently, hydrogen fuel cells or hydrogen-based synthetic fuels are the only effective solutions for long-haul, heavy-duty logistics. Not to mention aviation, inland and ocean shipping, there are no mature alternatives to hydrogen fuel in the zero-carbon, low-carbon era.
One of hydrogen’s most extensive uses is energy storage. As wind and solar power continue to develop, energy storage equipment is needed to balance peaks and troughs and ensure a continuous energy supply during windless and sunless periods. Large-scale, long-cycle energy storage systems must be used.
Besides traditional physical energy storage (such as pumped hydroelectric storage and compressed air energy storage) and electrochemical energy storage (lithium-ion batteries, sodium-ion batteries, vanadium redox batteries), hydrogen has the potential to become one of the pillars of energy storage.
As a stable chemical substance, hydrogen can be stored safely for extended periods and can serve as a long-term energy reserve. Hydrogen can be transported through pipelines to remote areas, and while pipeline construction takes time, its operational costs are incredibly low. According to a European Union study, a 48-inch diameter hydrogen transportation pipeline can deliver 17 GW of energy, equivalent to 4-5 800 kV DC transmission lines, but at a much lower cost than building 4-5 DC transmission lines.
In the long run, in a zero-carbon era, hydrogen can completely replace natural gas as a fuel for power generation through direct combustion or fuel cell systems. It can provide distributed power generation for communities or other mobile power-consuming devices.
Lastly, using hydrogen and capturing carbon dioxide from the atmosphere or other carbon sinks can produce hydrocarbons through the Fischer-Tropsch process. After refining, these hydrocarbons can be used as synthetic fuels for existing aircraft, making it the only viable zero-carbon aviation fuel solution currently available.
With breakthroughs in photovoltaic power generation and PEM hydrogen production entering large-scale operation, hydrogen can replace fossil fuels in various application scenarios, enabling a genuine industrial application of a zero-carbon, low-carbon economy.
