1 minute, improve your understanding of green hydrogen!
Time：2022/8/25 Tag：Electrolytic cell, electrolytic water, water electrolysis
As an energy source, the earliest application of green hydrogen can be traced back to a village at the end of 19th century. Danish scientist Paul La Kuhl electrolyzes water with the electricity generated by a fan in Skov, where he teaches. It is located in the electrolytic basement under the wind turbine building, with a total of 10 electrolyzers. On windy days, as much as 1000 liters (1m) of hydrogen is produced per hour.
A hundred years later, in the face of "environmental crisis" and "energy transformation", the technology of producing, storing, transporting and using hydrogen has become the most noticeable focus in the 21st century.
- |01 What resources are needed to produce green hydrogen?
The raw materials for producing hydrogen by electrolysis of water are mainly "green electricity" and "pure water".
Green electricity is clean electricity produced by renewable energy sources such as wind and light. It takes about 56 kWh to produce 1kg of hydrogen.
Pure water, also known as "raw water", needs to meet the relevant domestic water quality requirements for hydrogen production, that is, the provisions in GB/T 37562—2019 "Technical Conditions for Pressure Water Electrolysis Hydrogen Production System"—the conductivity is ≤1mS/m (alkaline electrolyzed water hydrogen production system).
According to the reaction formula, in theory, it takes 9kg of water to make 1kg of hydrogen, but considering the consumption of pure water and other consumption, it actually takes 15-18kg of water to make 1kg of hydrogen.
Equipment, mainly photovoltaic modules and hydrogen production equipment, as well as equipment installation sites.
- |02 What are the main ways to store hydrogen?
Hydrogen is the simplest and lightest element in the universe. Usually, we use high-pressure gas storage tanks/underground space for storage, but it will occupy a lot of space.
For example, high-pressure gaseous hydrogen storage, the common high-pressure hydrogen storage bottles have two specifications, 35MPa and 70MPa, which correspond to the hydrogen density of 25g/L and 41g/L respectively, and the gas storage capacity is small.
Compressed into liquid hydrogen, the corresponding liquid hydrogen density is about 70 kg/m at normal temperature and pressure, but it is technically difficult and is mainly used in aerospace field.
In addition, there are solid hydrogen storage and organic liquid hydrogen storage methods, which are difficult to achieve large-scale application at this stage.
The market is also optimistic about the way compounds store hydrogen, that is, combining hydrogen with other elements to make compounds that are easier to store and transport, such as synthetic ammonia.
- |03 What can we do with green hydrogen?
The calorific value of hydrogen is as high as 142MJ/kg, which is 3-4 times that of fossil fuels such as coal and gasoline. It can provide power and electricity through direct combustion of hydrogen internal combustion engine and hydrogen gas turbine, and can also provide heat and power through electrochemical reaction of hydrogen fuel cell.
When hydrogen is used as power by fuel cell, the efficiency of fuel cell system is 50%, gasoline engine position is 28%, diesel engine position is 38%, and lithium battery system efficiency is 90%. When hydrogen is used in fuel cell vehicles, it is equivalent to 6.9L gasoline, 45L diesel oil or 18.6k lithium battery.
Most importantly, the product of green hydrogen combustion is only water, which does not produce carbon emissions.
Green hydrogen can replace part of gray hydrogen, blue hydrogen and even kerosene gas, which is of great significance for reducing carbon emissions in industries such as steel, housing, cement, industry, automobile, commerce, petrochemical industry, light trucks, buses and shipping railways.
- Write it at the end
Power demand has obvious seasonal characteristics. In cold winter or hot summer, the power grid is bound to bear greater pressure than in spring and autumn.
If hydrogen and electricity are combined, on the one hand, it can calm the intermittent fluctuation of renewable energy generation, and at the same time, it can be used as a seasonal reserve of energy to form a powerful coupled energy network.
At the same time, hydrogen has a wide range of applications, and it can be traded flexibly. Some people think that hydrogen will be the "new oil" in the future energy industry.
Here, jules verne's idea of hydrogen energy in the novel Mysterious Island in 1874 is quoted: "One day, water can be electrolyzed into hydrogen and oxygen and used as fuel, and the hydrogen and oxygen that make up water ... will become infinite energy for heating and lighting."
Hydrogen energy drives the future.
Source of data in this paper:
(1) Machinery Industry Press [Italy] Mark Albela's Hydrogen Energy Revolution;
(2) China Electric Power Press, National Power Investment Group, compiled "Hundred Questions on Hydrogen Energy" in the innovation of hydrogen energy industry.