Hydrogen fuel cells and lithium batteries

Aug 23, 2019   Pageview:157

For every successful energy revolution in human history, there has been a clear main line of logic, which is that there has been an order of magnitude jump in energy density. For example, coal is 160 times more expensive than wood, and oil is twice as expensive. Only when new energy has the advantage of crushing energy density, can it be able to subvert the perfect basic network and industrial supporting facilities established by the long-term development of traditional energy and reverse its huge inertia in use. This is similar to the 10-fold speed principle put forward by grove, the founder of Intel, in the field of IT. The new technology that can be successfully subverted once appears is basically catching fire and overwhelming. For example, gasoline cars appeared 20 years later than electric cars, and the early technology was also more immature, but with the advantage of high energy density, they replaced electric cars like devastating.

Hydrogen fuel cell and lithium battery analysis

In recent decades, countries have been vigorously promoting electric vehicles, but the proportion of electric vehicles is still very low, less than 1%. Even the latest generation of lithium battery car, the extreme value of its energy density is only 1/40 of gasoline, the industry has been slow to appear 10 times the speed of improvement. But fuel cells have changed all that. Its hydrogen as raw material, the basic energy density is three times that of gasoline, the motor's work efficiency is two times that of the internal combustion engine, the actual density is six times that of gasoline, the advantages are obvious. And energy from the past one hundred years of human evolution, its essence is the history of hydrocarbon ratio adjustment, the higher the hydrogen content, the higher energy density, the future from carbon energy to hydrogen energy is the trend of The Times, so the hydrogen fuel cell is more representative of the historical development direction, and the most expected to become the foundation of the next generation of energy.

Vehicle performance mainly includes endurance, charging/hydrogen charging time, output power and safety, etc. Fuel cell energy density is much higher than lithium battery, corresponding battery capacity, quick charging capacity and range have natural advantages, even compared with the top luxury car Tesla lithium battery is also a substantial lead. But its power density is not high, the maximum output power depends on the auxiliary power battery system, the corresponding maximum speed and 100km acceleration index and lithium battery is not different. In order to facilitate the comparison, we select the current mainstream 2L gas displacement gasoline vehicle, corresponding to the 45-degree lithium battery vehicle and the output power of 100KW fuel cell vehicle as the analysis benchmark.

Energy density comparison

As a kind of battery, lithium battery is a closed system. The battery is only a carrier of energy, and it can only run after being charged in advance. Its energy density depends on the energy density of the electrode material. Since the current energy density of anode materials is much higher than that of anode materials, increasing the energy density requires the continuous upgrading of anode materials, such as lead acid, nickel series and lithium batteries. But lithium is already the smallest metallic element in terms of atomic weight. A better anode material than lithium ion is only pure lithium electrode in theory, but its energy density is actually only a quarter of that of gasoline, and it is extremely difficult to commercialize and will not be able to break through for decades. Therefore, the improvement of energy density of lithium battery is subject to the theoretical bottleneck, and the space is very limited, that is, from the current 160Wh/KG to 300Wh/KG at most, even if it reaches only 1/120 of the fuel cell, it may be said to be at the starting line.

Volume energy density comparison

The main disadvantage of raw hydrogen in fuel cells is its low volume and energy density. According to the current pressurization model of 700 atmospheres, its volume energy density is 1/3 that of gasoline. The fuel cell hydrogen storage tank is 100L in volume and 30KG in weight, corresponding to 30L in gasoline car fuel tank. However, the motor is 80L smaller than the internal combustion engine, and the overall volume difference is not significant. Lithium battery car is divided into three yuan and lithium iron phosphate two mainstream technology routes, representative enterprises for Tesla and byd. Ternary energy density is higher, but the safety is poor, which requires auxiliary safety protection equipment. The two types of batteries required for 300km are 140L and 220L in volume and 0.4t and 0.6t in weight, both much higher than fuel cells. Looking ahead, if hydrogen storage alloys and cryogenic liquid hydrogen storage technologies can be breakthrough, fuel cell volume and energy density will increase by 1.5 times and 2 times respectively, and the advantages will be more obvious.

Power density comparison

In essence, fuel cell can be understood as a chemical power generation system with hydrogen as the raw material, so the output power is relatively stable. In order to maximize the discharge power, the power battery system must be added. For example, Toyota Mirai is a supporting nimh battery. However, as an open power system, its energy comes from external input. The addition of nimh battery does not need to consider the problem of energy storage. As long as 5-8 degrees, it can meet the demand and has low requirements for battery life. Although the theoretical discharge efficiency of lithium battery is very high, but in order not to harm the battery life, the use of a lot of restrictions. In the case of full charge can not be large rate discharge, rapid discharge only applies to 0-80% of the range. Even so, the battery cycle life in the laboratory will be shortened to only 600 times when discharging at 5C multiplier, and further reduced to 400 times under real working conditions. For example, even though the maximum power of Telsa can reach 310KW, the actual discharge multiplier is only 4C. Moreover, as a closed energy storage system with low energy density, lithium battery is difficult to be compatible with high power discharge and high range unless the battery weight is greatly increased. Even though Tesla USES the best ternary battery with the highest energy density, its battery components weigh nearly half a ton.

Safety comparison

In addition to the above indicators, safety is undoubtedly also very critical for motor vehicles. As a closed energy system, lithium battery is difficult to be compatible with high energy density and safety in principle, otherwise it is equivalent to bomb. Therefore, in the current mainstream process, lithium iron phosphate with low energy density is relatively safe. The battery does not start to decompose until the battery temperature reaches 500-600 degrees, which basically does not require too much protective auxiliary equipment. The ternary battery used by Telsa has a high energy density, but it is not resistant to high temperature. It will decompose at 250-350 degrees and has poor safety. The solution is to connect more than 7,000 batteries in parallel, dramatically reducing the risk of a single battery leaking or exploding, and even then combining a complex battery protection system. In addition, although the safety design of Telsa did not result in any casualties in the previous accidents, they were actually very minor collisions in terms of the accidents themselves, and the car body did not suffer any injuries. However, the battery caught on fire, which also reflected its natural disadvantages in safety.

Because hydrogen is flammable and explosive, there are widespread concerns about the safety of fuel cells. But according to the data in the table below, compared with gasoline steam and natural gas, two common combustible gases for vehicles, hydrogen is not worse or even slightly better. Today's hydrogen storage units in cars are made of carbon fiber and can survive a crash test at 80KM/h at multiple angles. Even if the accident results in a leak, hydrogen explosions, because of the high concentration required, usually start burning before the explosion, but it is difficult to explode. And the hydrogen is light, overflow system hydrogen will quickly rise after the fire, but to a certain extent to protect the car body and passengers. The gasoline is liquid, the lithium battery is solid, it's hard to rise in the atmosphere, the combustion is in the bottom of the car cabin, the whole car will quickly fire scrap. The hydrogen storage and transportation link is actually very similar to LNG, but it requires more pressure. With the promotion of commercialization, its overall safety is controllable.

The cost of battery car is mainly divided into vehicle cost, raw material cost and supporting cost. At present, fuel cells are mostly criticized for their high cost. However, from the perspective of development, with the progress of technology and the improvement of commercialization, there is a lot of room for cost reduction. Considering the cost of power grid expansion, the comprehensive supporting cost of lithium battery is actually higher than that of fuel cell. The specific calculation is as follows:

Vehicle cost comparison

The cost difference between lithium battery, fuel cell and traditional gasoline vehicle is mainly reflected in the engine cost, while the other components are not too different. The engine cost of 2L gasoline car is about 30,000 yuan, and it is difficult to have much change in the future. The cost per kilowatt hour of existing lithium battery is 1200 yuan /kWh, which is expected to be reduced to 1000 yuan /kWh in the future. The battery cost of 45 degree electric vehicle is 45,000 yuan. The cost of fuel cell is mainly battery pack and high-pressure hydrogen storage tank. Now the cost of 100kw battery pack is 100,000 yuan. It is predicted that after the annual production of 500,000 sets, the unit cost will be reduced to 30 dollars /KW, namely 20,000 yuan. The existing hydrogen storage tank costs 60,000 yuan, which is expected to be reduced to 35,000 yuan in the future, with a total cost of 55,000 yuan. In the long run, the cost of the three power systems does not differ much, so the cost of the vehicle is not the core issue.

Raw material cost comparison

A 2L gasoline car consumes 10 liters of fuel per 100 kilometers. The price of gasoline is 5.8 yuan /L and the cost is 58 yuan. The 100km power consumption of lithium battery vehicle is 17 degrees, 0.65 yuan/KWH, and the cost is 11 yuan. Fuel cells consume 9 cubic meters of hydrogen per 100 kilometers. Hydrogen production methods are mainly divided into electrolysis of water or chemical reactions, such as coal to hydrogen and natural gas to hydrogen. The cost of water electrolysis is mainly electricity, with an average of 5 KWH and 1 cubic meter of hydrogen. The cost is about 3.8 yuan/cubic meter, but it can be directly electrolyzed in the hydrogenation station, saving the transportation cost. If large-scale and centralized production of fossil energy is adopted, the lowest cost in China is to produce hydrogen from coal, which is about 1.4 yuan per square meter, while the cheap natural gas in North America can be utilized at 0.9 yuan per square meter. If we take the cost of coal-to-gas as the standard, the raw material cost of 100 kilometers is 12.6 yuan, which is not much different from lithium battery.

Matching cost comparison

The costs of refueling stations, gas stations and charging stations are mainly divided into land costs, equipment costs and construction costs, and the differences are mainly reflected in equipment costs. The gas station is basically 3 million yuan, the charging station is 4.3 million yuan, the refueling station is estimated to be 15 million yuan according to the current Japanese standard, and the total cost of the refueling station is about 10 million yuan higher. According to 15 years of depreciation, the annual sales volume is 10 million cubic meters, so the depreciation cost is 0.1 yuan/cubic meter. In a small scale, hydrogen is generally transported by tank trucks, and the estimated freight is 0.44 yuan/square meter. After the scale is expanded, it can be transported by pipe network, and the cost will be reduced to 0.23 yuan/square meter.

Although lithium batteries currently rely on off-the-shelf grid systems, the cost of supporting them is low. But if large-scale expansion, existing grid capacity redundancy will be basically exhausted, must be large-scale expansion in the future. Therefore, the charging station essentially externalizes the supporting costs to the power grid. Therefore, when calculating the cost of the whole industrial chain, the cost of the power grid should be added. Generally, commercial operation of charging stations should meet the standard of one-hour quick charging at least, and the power of each charging station composed of 10 charging piles should reach 600 kilowatts, which is equivalent to the power load of hundreds of households and has a great impact on the load of the power grid. The corresponding power grid needs an additional investment of 1.2 million yuan to expand the load, but the annual increase in electricity sales is only 930,000 KWH. According to the calculation of 0.65 yuan/KWH purchase cost and the recovery of investment by the power grid end in 15 years, the selling price shall increase by 0.18 yuan/KWH on the basis of the cost.

Sales-side cost measurement

The sales network of petrol stations is very mature, and the profit level per hour can be used as a benchmark for calculating the reasonable return of refueling stations. The price difference is 0.51 yuan per square meter for a hydrogen station and 4.9 yuan per kilowatt hour for a lithium battery. Under this electricity price, the lithium battery vehicle is basically unable to promote. At present, the national regulation caps the service fee of charging stations at 0.4 yuan/KWH, but the background is that they are heavily subsidized. However, no industry can rely on subsidies to develop for a long time. If the charging efficiency of lithium battery is not significantly improved in the future, the profitability of the enterprise in the filling station will be significantly lower than that of petrol stations and hydrogen stations. Without reasonable returns, investors have no incentive to promote charging stations in big cities where land is currently scarce, and the industry cannot develop naturally. However, the low energy density of lithium battery is too low. If high charging efficiency is forced, the engineering challenge of battery cycle life will be huge. Moreover, even if the 3-minute quick charging can be realized, the power of a single charging pile should be up to 1200 kw, and each charging station should be equipped with a 110 kv substation. Its investment is as high as 50 million yuan, covering an area of 5,000 square meters, and around 300 meters can not have residential buildings, for now coastal cities in the operational level of the challenge is also very big.

Total cost

Taking all the above costs into account, the cost of gasoline vehicles, lithium battery vehicles, and fuel cell vehicles at this stage and after full commercialization is 58 yuan, 83 yuan, 23 yuan and 20 yuan. Since the price difference accounts for a high proportion of the cost of lithium battery, considering that the investment of charging pile equipment is 1/3 of that of the refueling station, the hourly profit is reduced to 1.4 yuan, and the comprehensive cost is still 37 yuan, the long-term cost advantage of fuel cell vehicle is still very obvious. In fact, the root of all this is that fuel cells have the highest energy density. When commercialized, the cost is naturally advantageous.

An important logic of the development of new energy vehicles is energy saving and environmental protection, which is undoubtedly more important to China. At present, China's air pollution is not only serious, but also depends on oil imports up to 60%, 85% of which also through the us-controlled malacca strait, energy security has become the biggest weakness of our national security. Therefore, the state gives huge subsidies to new energy vehicles, an important reason is to ease the dependence on oil imports. In the following paragraphs, we will compare the two from the aspects of energy conservation, environmental protection and resource constraint, as follows:

Comparison of energy saving and environmental protection

At present, the most economical means of fuel cell raw hydrogen in China is to produce hydrogen from coal, and the raw power of lithium battery in China also mainly comes from coal power generation. Therefore, both of them are essentially energy from coal, and carbon emissions are just transferred to the upstream. Therefore, whether energy conservation is achieved depends mainly on the energy conversion efficiency. At present, the lithium battery car consumes 17 degrees of electricity per 100 kilometers, corresponding to 6.8 kilograms of coal. The fuel cell consumes 9 cubic meters of hydrogen per 100 kilometers, with a loss of 20% in the storage and transportation link, corresponding to 7.3 kilograms of coal. A petrol car consumes 10L of petrol per 100km and emits 10kg of coal. In fact, the energy-saving effect of new energy vehicles is not obvious, its core value lies in the primary energy consumption from oil to China's abundant reserves of coal, to alleviate the problem of energy security. From the perspective of environmental protection, fuel cells have almost no exhaust emissions, lithium batteries have only a small amount of emissions, the pollution of the whole industry is mainly concentrated in the upstream. But compared with dealing with the scattered gasoline vehicle exhaust emissions, the upstream centralized pollution control is undoubtedly much less difficult. Overall, the fuel cell industry chain has the lowest pollution, which can be considered as the best green vehicle energy.

Resource constraint comparison

Fuel cell catalysts use the precious metal platinum, and there is widespread concern about resource constraints. In 2015, the global total demand for platinum was 270 tons, and the main downstream products were automobile exhaust cleaning catalyst, jewelry and industry, accounting for 44%, 34% and 22%. Mirai USES about 20g of platinum per vehicle, 10-15g more than a petrol car. Assuming that fuel-cell vehicles account for 5% of global annual production, with an average annual increase in consumption of around 56 tonnes, that seems a big shock. But under the same assumption, the annual increase in consumption of lithium resources is 80,000 tons, which corresponds to the output of 40,000 tons per year. In fact, the impact is greater, which has been proved by the soaring price of lithium ore this year. In addition, Toyota's medium-term optimization goal is to reduce the platinum unit consumption by 75% and realize the platinum recovery of the catalyst. If any of the above objectives are achieved, the platinum resource constraint is basically solved.

Comparison of commercialization degree

In terms of commercialization, the fuel cell and the lithium battery vehicle are about five years apart. They are still on the eve of commercialization, and the explosion point is expected to be around 2020. At present, Japan and the United States are the world's leading countries in terms of technology, especially in the field of passenger cars. In 2015, the mass production of Mirai basically reached the entry standard of commercialization. By contrast, China has made few achievements in the field of fuel cell industrialization. Only baic foton and saic motor have produced fuel cell buses for the 2008 Olympic Games and the 2010 world expo, and they are still in the stage of technology demonstration. However, China's advantage is its large economic size, and with the maturity of fuel cell technology, it has the ability to catch up quickly.

The future of energy and the restructuring of industry

At present, the whole global energy still comes from the edge energy generated by solar nuclear fusion, with a total output power of 1.8*1013. According to the kardashev index, it is still in the stage of planetary civilization. In the future, if we want to continue to make breakthroughs, we must achieve controllable nuclear fusion. Only in this way can we achieve the starting conditions of 1016 star civilization. One kilogram of hydrogen isotopes could generate hundreds of millions of kilowatts of electricity, equivalent to one kilogram of sea water equivalent to 300 liters of gasoline. Electrolysis of water to hydrogen will be extremely low-cost, controllable nuclear fusion + hydrogen energy will become the ultimate combination of energy structure. Oil can be completely freed from the low-end field of fuel, and the cost of various petroleum-based raw materials will be reduced to an extent that can be imagined, which also brings infinite possibilities for the reconstruction of human industrial system in the future. That will be a very beautiful era!

Throughout human history, every energy revolution has resulted in the restructuring of entire industrial systems and even the change of global leadership. The first industrial revolution made Britain and the second industrial revolution made America. If fuel cell vehicles can completely replace petroleum vehicles in the future, the entire industrial system supporting petroleum will be subverted, and the value of the technological advantages accumulated by developed countries in the era of internal combustion engine in the past 200 years will be greatly reduced, which also gives our country a chance to overtake on a curve. If we can seize this historic opportunity, we have every chance to become the leader of the next generation of industrial systems. Japan, as the first country to develop lithium battery, has basically abandoned the research and development of lithium battery vehicle and vigorously attacked the fuel cell. The logic behind it is worth thinking deeply.

The page contains the contents of the machine translation.

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