From solar energy and photovoltaics to hydrogen energy civilization - a new outlet for power electronics

When it comes to hydrogen, children all know it.

It's light, and the hydrogen balloon is fun.

Accidentally flew into the sky.

Hydrogen is easy to obtain. You can use metals with stronger activity than hydrogen to react with acids to displace hydrogen. In middle school experiments, zinc is used to react with dilute sulfuric acid to produce hydrogen, Zn+H2SO4=ZnSO4+H2. Of course, you can also use potassium, calcium, sodium and other metals to react with dilute acids, but you may not be able to handle the intensity of the reaction.

In commercial applications, aluminum is reacted with sodium hydroxide solution to produce:

2Al+2NaOH+6H2O=2Na[Al(OH)4]+3H2↑

The zero-pressure hydrogen machine used to sell balloons on the roadside is based on the reaction of aluminum and sodium hydroxide to produce hydrogen to fill the balloons. Because it is open, it fills the balloons while discharging materials, and there is no air pressure inside the machine, so the safety factor is relatively high.

Hydrogen is easy to obtain. It is produced in the production of steel, chemical industry, etc., as a byproduct of chlorine-alkali and light hydrocarbon cracking. These hydrogen may be mixed with city gas and burned. Is it a pity? Hydrogen is a very good fuel with a calorific value of up to 1.4*108J/kg, while natural gas is 8.5*107J/kg. Moreover, burning hydrogen is the most environmentally friendly, producing only water and zero carbon emissions.

The torch for our Winter Games is fueled by zero-emission hydrogen.

So how much of our heat comes from hydrogen?

Let's start with the starry sky~

Looking at the night sky, the stars are twinkling, that is they are transmuting hydrogen into helium. Our sun consumes 600 million tons of hydrogen every second day and night, converting it into 596 million tons of helium. After hydrogen turns into helium, where does the 4 million tons of matter go? According to Einstein's formula E=mc², it turns into energy, of which about 1.5kg of the heat generated by hydrogen comes to our earth, giving us light and energy. All things grow by the sun and hydrogen nuclear fusion.

Hydrogen is a green fuel, but there is only a very rare free hydrogen on the earth and in the earth's atmosphere. In the earth's crust, if calculated by mass, hydrogen accounts for 1% of the total mass, and if calculated by atomic percentage, it accounts for 17%. Hydrogen is widely distributed in nature. Water is the "warehouse" of hydrogen - the mass fraction of hydrogen in water is 11%. Oil, natural gas, animals and plants also contain hydrogen. In the air, there is not much hydrogen, accounting for about 5/10 million of the total volume. In the entire universe, hydrogen is the most abundant element in terms of atomic percentage. According to research, in the atmosphere of the sun, hydrogen accounts for 81.75% in terms of atomic percentage. In the universe, the number of hydrogen atoms is about 100 times greater than the sum of atoms of all other elements.

Although hydrogen is present in very small amounts in nature,

But you can ask water for hydrogen.

Water Gas Method

Water gas is a gas produced when water vapor passes through red-hot coke. Its main components are carbon monoxide and hydrogen.

C+H2O(g)=(high temperature)CO+H2↑

If a catalyst is added, one part of coal can produce double the amount of hydrogen.

C+2H2O(g)=(high temperature)CO2+2H2↑

It is very convenient to produce hydrogen from coal, and the cost is not high, but it consumes fossil energy coal and produces carbon dioxide. This type of hydrogen now has a new name - gray hydrogen.

Because hydrogen is very environmentally friendly, it only produces water after combustion and has zero carbon emissions. If the process of manufacturing hydrogen does not produce carbon dioxide, the entire ecological process will be perfect.

We can also "clean" hydrogen**, capture, store and utilize the generated carbon dioxide, which we call clean hydrogen. The captured carbon dioxide can be used to charge Coke, synthesize biodegradable plastics...

Our goal is to develop green hydrogen,

Use new energy to generate electricity and produce hydrogen.

New energy power generation refers to wind power generation, photovoltaic power generation and hydropower generation. The process does not consume coal and oil and does not produce carbon dioxide.

Electrolysis of hydrogen only requires water. Electricity breaks water down into hydrogen and oxygen. That is to say, we store electrical energy in the form of hydrogen and turn it into hydrogen energy.

2H2O=2H2↑+O2↑

We have hydrogen, but what is the use of hydrogen?

Chemical raw materials

At present, the four major single uses of hydrogen are: oil refining, synthetic ammonia, synthetic methanol and direct reduction of iron ore to produce steel. There are countless other uses. China consumes 20 million tons of hydrogen a year.

Hydrogen, as a clean new energy carrier, can be used in fuel cells. Renewable energy such as solar energy and wind energy can be stored in hydrogen and used in fuel cell electric vehicles, airplanes and ships.

Fuel Cells

Fuel cells are the reverse process of hydrogen electrolysis. The power generation process only produces pure water, which is very environmentally friendly. Moreover, hydrogen refueling can be as quick and convenient as refueling.

H2+1/2O2==H2O

Fuel cells are not a new technology, and the principle is not too complicated. They are already part of middle school classroom teaching and experiment content. When a fuel cell is working, the hydrogen at the anode is decomposed into hydrogen ions and electrons under the action of a catalyst. The hydrogen ions pass through the proton exchange membrane to the cathode, and the electrons follow the external circuit to the cathode (positive electrode) to generate current. At the cathode, oxygen in the air reacts with hydrogen ions and electrons to generate water.

Fuel cells can be made into power banks, just like batteries. You can also produce hydrogen at home by electrolysis and fill hydrogen tanks. The electricity can come from solar energy, which seems very convenient.

Fuel cell power bank, output power 2 watts

Household hydrogen electrolysis machine, 23W, produces 3 liters of hydrogen per hour

But the high-power fuel cell system for vehicles is not that simple, it is a complex power generation system that requires air compressors, hydrogen pumps, fans, water pumps, etc. The system requires motor drivers and various sensors.

Fuel cell power generation is not limited by the engine's Carnot cycle. In theory, its power generation efficiency can reach 85% to 90%, but due to the power consumption of the system's auxiliary system, the current energy conversion efficiency of fuel cells is about 40% to 60%. If combined heat and power is achieved, the total fuel utilization rate can be as high as 85% or more. This system has been industrialized for use in Japanese households. As of the first half of 2019, Japan has sold more than 300,000 ENE FARM household fuel cell systems.

Combined heat and power fuel cells are an effective way to use gas efficiently. The figure below shows that of 1,000 cubic meters of natural gas, 27GJ is used for thermal power generation, with an efficiency of 58.5%. However, if 40.6GJ of natural gas is used as fuel cells, 15.8GJ of electricity is generated, 22.8GJ of heat is generated, and only 2GJ is not used, with an efficiency of up to 95%.

Hydrogen into every household is the development direction of a high-efficiency society.

Hydrogen is a green energy and also a carrier of green energy. From new energy power generation, electrolysis to hydrogen production to fuel cell power generation, it constitutes the green energy chain of the new world.

We look forward to hydrogen fuel cell cars, airplanes, ships, household cogeneration... the era of hydrogen energy civilization is just around the corner.