Scientists predict that hydrogen energy could become an important secondary energy source in the 21st century. The calorific value of hydrogen reaches 1.2×10^6 J/kg, or 24 times that of gasoline. When liquid hydrogen is burned, it can produce a high temperature of around 1700°C, which can be used to cut metal. As a fuel for gas turbines, hydrogen can not only generate electricity, but also generate high-pressure steam for heating. As a general fuel for internal combustion engine or urban civil gas, it is even more superior. Once the hydrogen is burned, it returns to the water. Water is the raw material for the production of hydrogen, it can be recycled several times and constitutes a non-polluting source of energy.
Hydrogen energy has abundant reserves. There are 1,000 grams of hydrogen for every 9,000 grams of water on earth.The source is stable and inexhaustible. It is easy to store and transport and can be bottled or piped. It reacts with certain active metals and can temporarily become solid to facilitate transport.
Methods for producing hydrogen from water include pyrolysis, electrolysis and photolysis. The hydrogen present in ammonia produced from coal or coke is obtained by breaking down water vapor through a hot layer of carbon. This is a typical pyrolysis method for hydrogen production. When salt is electrolyzed to produce caustic soda, hydrogen is released from the cathode of the electrolytic cell. Additionally, there is also a hydrogen production method that directly electrolyzes water. Another method is to mimic the photolysis of water to produce hydrogen that some natural plants possess. Scientists are considering consbuild special nuclear power plants to produce hydrogen for water electrolysis. For example, it is economical and safe to build artificial islands and to build nuclear power plants on artificial islands. Water for electrolysis and cooling is easily accessible and away from residential areas. The produced hydrogen and oxygen are transported to land using gas pipelines laid underwater, and then special underground gas storages are dug on land to store the hydrogen using the natural gas storage method .
Hydrogen is a secondary energy source. Because it is produced using other energy sources by certain methods, unlike coal, oil and natural gas, which can be extracted directly from the ground and rely almost entirely on fossil fuels. Hydrogen energy is considered the clean energy with the greatestnd development potential in the 21st century.
Primary energy refers to energy resources that exist in nature in their original form and have not been processed or converted. Also known as natural energy. Including fossil fuels (such as raw coal, oil, crude oil, natural gas, etc.), nuclear fuel, biomass energy, hydropower, wind power, solar energy, geothermal energy, ocean energy, tidal energy, etc.
Secondary energy refers to the energy obtained after processing and converting primary energy, including electric energy, gasoline, diesel, liquefied petroleum gas and hydrogen energy. Secondary energy can be divided into "processing energy" and "energy energy". Electric power is the most widely used processing energy, while gasoline and diesel are acurrently the most used energy source. Secondary energy can also be explained as energy that is reused from primary energy. For example, burning coal to produce steam can power a generator, and the electricity produced can be called secondary energy. Or, once the electrical energy is used, it is converted into wind energy via an electric fan. At this point, wind energy can also be called secondary energy. There must be some degree of loss between the secondary energy and the primary energy. Secondary energy is different from primary energy. It does not come directly from nature and can only be added by primary energy. It is obtained after energy conversion, so it is not strictly speaking an "energy", but rather a “secondary energy”. The energy crisis, renewable energies, etc. do not involve the enesecondary management.