In theory this is possible, but in reality it is not yet possible to use this technology in production.
First of all: the production of hydrogen gas by water electrolysis is itself an energy conversion process (conversion of electrical energy into chemical energy). We know that energy itself is conserved in this conversion process. some conversion efficiency problem. For example, during the process of electrolysis of water, the current will heat the water and vaporize part of it, which requires a certain amount of energy, which makes the chemical energy (hydrogen and oxygen) obtained lower than the previous electrical energy. When used in cars to convert it into kinetic energy, there is a certain conversion efficiency problem. At the current price of electricity, this cost is too high.
In addition, hydrogen itself is difficult to store. To achieve a certain densityenergy, a certain pressure and adsorption materials are necessary. Currently manufactured hydrogen storage tanks and hydrogen absorption materials cannot achieve greater energy density. . You can't just let a car pull a big tank and drive down the road like a tanker truck, can you?
So not yet.
Why can't we use hydroelectric power generation and water electrolysis to produce hydrogen as a fuel?
So, can hydrogen really be produced from water? What are the ways to produce hydrogen and what is the cost?
It is clear that hydrogen can be produced from water. There are two main ways: electrolysis of water and reaction of active metals with water to replace hydrogen.
Electrolysis of water
Direct current passes into a reserveElectrolytic glass filled with electrolyte, and the water molecules undergo an electrochemical reaction on the electrodes and decompose into hydrogen and oxygen. Since the ionization degree of pure water is very low and the conductivity is low, electrolysis is difficult or very slow. Therefore, electrolytes such as sulfuric acid, sodium hydroxide and potassium hydroxide are usually added to increase the conductivity of the solution and allow. Water flows easily and quickly electrolyzes into hydrogen and oxygen. The chemical formula of electrolyzed water is:
At the current technical level, electrolyzing water to produce 1 cubic meter of hydrogen at standard atmospheric pressure requires 5 kWh of electricity at atmospheric pressure standard, the mass of. 1 cubic meter of hydrogen is approximately 0.089286 kilograms, so electrolysis of water to produce 1 kilogram of hydrogen requiresapproximately 60 kilowatt hours of electricity. If we add the cost of storing hydrogen, the cost of electrolysis of water to produce 1 kilogram of hydrogen is about 50. yuan. For a car using hydrogen fuel cells, each kilogram of hydrogen can provide a range of around 100 kilometers, which is equivalent to consuming 60 kilowatt hours of electricity per 100 kilometers. Compared with the current level of energy consumption of most pure electric vehicles, i.e. 20 kWh per 100 kilometers, it can be seen that the cost of producing hydrogen by water electrolysis is high. It is certainly not possible to use electrolyzed water to produce hydrogen to drive a vehicle. car.
Active metals react with water to displace hydrogen
Metals that are more mobile than hydrogen ions can react with water to displace hydrogen ions in the water to form hydrogen. For example, potassium and sodium, which are very reactive metals, can react quickly with cold water to generate hydrogen. The chemical formula of the reaction is:
According to the chemical formula above, 1 kilogram of. nanometal can only displace 0.0435 kilograms of hydrogen, while 1 kilogram of goldThe starting cost of sodium is at least several tens of yuan. If you want to use sodium metal to produce 1 kg of hydrogen, the cost will be at least several hundred yuan, and the cost is even higher. Additionally, sodium is an extremely reactive metal, very dangerous and extremely difficult to preserve. It is therefore impossible to use the reaction of reactive metals and water to produce hydrogen as a routine method and it is generally only used in laboratories.
We can see that the above two methods of producing hydrogen from water arerelatively expensive. If hydrogen is produced in this way to drive a car, the gains exceed the losses and there is virtually no prospect of application.
Due to the high demand for industrial hydrogen, hydrocarbon cracking, steam reforming, soda water and other processes are generally used to produce hydrogen. The production cost is relatively lower than the above methods.
Hydrogen fuel cells have the advantages of high energy density, high energy conversion efficiency and no pollutant emissions. At present, hydrogen fuel cells also provide a path for the development of new energy. by the high cost of producing and storing hydrogen, transportation risks are high and hydrogen fuel cells are still at the research and experimentation stage.tion.
Basically, hydrogen is not the primary form of energy in modern society, and there aren't many places to use it. When the cost is high, few people naturally use it. is concerned, on the one hand, the method of electricity transmission is relatively mature and inexpensive, on the other hand, hydroelectric plants have more efficient energy storage measures in case of peak: when the consumption of energy is low, just use the remaining electricity to. pump water. But this does not mean that there are no applications for the production of hydrogen by electrolysis of water: substances with high energy density like oil can be used as clean energy to replace oil in places where electricity is not suitable, such as rockets. , planes, ships, etc. In addition, as an intermediate substance for energy storage, wind energyand photovoltaic energy can be used to electrolyze water to produce hydrogen, and then generate electricity through gas turbines, which can effectively solve the problem of the new. connection to the energy network. The problem with liquid hydrogen is that there is currently no particularly efficient and safe storage method. Large-scale storage still relies on low temperature and high pressure, which are not only expensive but also dangerous. This is still acceptable, but not acceptable for civil and commercial use. As a solution, solid-state storage of metal hydrides has sweet dreams and a cruel reality. It still belongs to the category of rare metals, and it is far from possible to have safe and efficient storage in the future, combined with wind energy. photovoltaic and Electrical energy provided by nuclear energy has considerably diminishedinué, and it is quite possible that hydrogen energy will replace oil energy in certain regions.