Since the end of last century, all countries and major automobile companies in the world, as well as major domestic scientific research institutions and universities have devoted themselves to developing clean and energy-saving vehicles, and new energy vehicles have made great progress. Gasoline and diesel are the energy sources of traditional internal combustion engine vehicles, and vehicles that use other energy sources to provide steam power can all be called new energy vehicles. The new energy currently being developed includes natural gas, liquefied petroleum gas, alcohols, dimethyl ether, hydrogen, synthetic fuel, biogas, air and rechargeable fuel cells.
This paper introduces the general development situation of new energy vehicle technology, and puts forward some views on its development prospect.
1 Types and characteristics of new energy vehicles
1. 1 natural gas vehicles and liquefied petroleum gas vehicles
Natural gas vehicles, also known as "blue power" vehicles, mainly use compressed natural gas (CNG), liquefied natural gas (LNG) and adsorbed natural gas (ANG) as fuels, and the common one is compressed natural gas vehicles (CNGV). Liquefied petroleum gas vehicles use liquefied petroleum gas as fuel. CNG and LPG are ideal ignition engine fuels, which have the advantages of single composition, high purity, uniform mixing with air, complete combustion, low emission of CO and particulate matter, low combustion temperature, less emission of nitrogen oxides, good lean combustion characteristics, good low-temperature starting and low-temperature operation performance, etc. Its disadvantages are that the storage and transportation performance is worse than that of liquid fuel, the volumetric efficiency of the engine is low and the ignition delay period is long. Most of these two types of vehicles use dual fuel systems, namely, gasoline or diesel fuel systems and compressed natural gas or liquefied petroleum gas systems. The vehicle can be driven by any system and can be easily switched from one system to another. Cummins and the U.S. Department of Energy are cooperating to develop a new generation of natural gas engines called Advanced Reciprocating Engine System (ARES). According to the development goal, the thermal efficiency of the engine is 50% (more than 80% of cogeneration), the emission of nitrogen oxides is less than 0. 1g/km, the manufacturing cost is 400,450 USD /kW, and the maintenance cost is less than 0.065,438 USD +0//kwh.
1.2 alcohol car
Alcohol car is a car that uses methanol, ethanol and other alcohol substances as fuel. Ethanol has a wide range of uses and sources, and its preparation technology is mature. The latest technology of producing ethanol from cellulose raw materials includes almost all agricultural and forestry wastes, urban organic wastes and industrial organic wastes. At present, alcohol vehicles are mostly driven by flexible fuel mixed with ethanol, gasoline or diesel in any proportion, and there is no need to modify the engine, which also has good energy saving and emission reduction effects. However, in order to obtain the power equivalent to gasoline or diesel, the fuel injection quantity must be increased. When the alcohol blending ratio is greater than 15%-20%, the compression ratio and ignition advance angle of the engine should be changed. Ethanol fuel has low theoretical air-fuel ratio, low requirements for engine intake system, poor self-ignition performance, high octane number, high antiknock performance, good volatility, uniform distribution of mixed gas and high thermal efficiency, and automobile exhaust pollution can be reduced by more than 30%. This kind of car was originally developed by Ford in the mid-1980s. By the end of 2003, there were more than 2.3 million ethanol vehicles in the United States, most of which were dodge and Chrysler vans-233,466 vehicles were sold in 2003.
1.3 hydrogen fuel vehicle
Hydrogen is a clean fuel. Using hydrogen as fuel, the traditional spark plug ignition engine only needs a little modification. Its combustion efficiency is higher than that of gasoline, and the mixture can be diluted to a great extent, which is beneficial to saving fuel. Hydrogen can also be added to other fuels (such as CNG) to improve efficiency and reduce NO2 emission. The mass energy density of hydrogen is the highest among all fuels, but the volume energy density is the lowest, and the biggest obstacle to its use is storage and safety. BMW has been committed to the research and development of hydrogen engines and developed a variety of hydrogen engine cars. Its 7-Series car equipped with V 12 hydrogen engine is the first batch of hydrogen engines in the world, which can use both hydrogen and gasoline.
1.4 DME car
Dimethyl ether (DME) is a colorless and odorless gas with excellent combustion performance, cleanliness, high cetane number, good power performance and little pollution. When slightly pressurized, it is liquid, which is very suitable as an alternative energy source for compression ignition engines. Vehicles using this fuel can meet California's ultra-low emission standards. NKK Company of Japan successfully developed the equipment for producing dimethyl ether from inferior coal, and completed the experiment of dimethyl ether as automobile fuel with Sumitomo Metal Industry Company in 1998. Dimethyl ether vehicles (DMEV) will not emit black gas to pollute the environment, and produce 20% less NOX than diesel.
1.5 pneumatic car
Cars that use compressed air, liquid air, liquid nitrogen, etc. As a medium and provides driving energy through heat absorption and expansion, it is called a pneumatic car. The pneumatic engine has no combustion or other chemical reactions, but emits air or nitrogen, and there is no pollutant radiation, thus realizing zero pollution. At present, the compressed air powered vehicle (APV) has been successfully developed, and its working principle is similar to that of the traditional internal combustion engine vehicle, except that the energy for driving the piston-connecting rod mechanism comes from high-pressure air. APV media sources are convenient and clean, and the cost of social infrastructure construction is not high, so it is easy to build. Fuel-free combustion process has low requirements for engine materials and simple structure, and can learn from the existing internal combustion engine technology, so the research and development cycle is short and the design and manufacture are easy. But at present, the energy density and energy conversion rate of APV are not high enough, and the driving range is short. 199 1 year, French engineer guy Negre obtained the patent of compressed air power engine and joined MDI company. In 2000, MDI Company introduced the APV named "evolution", with a mass of only 700kg, an engine mass of only 35kg, a speed of 120km/h/h, and a driving speed of 2000km/h with full compressed air. The inflation cost is only $0.30, and it can be driven in the city for about 10h, and it can be completed in a compressed air station for 2 minutes and an air pump for 3 hours.
1.6 electric vehicle
The first electric car in the world was made by Americans in the 1990s. Electric vehicles can be roughly divided into battery electric vehicles (BEV), fuel cell electric vehicles (FCEV) and hybrid electric vehicles (HEV). A common feature of electric vehicles is that they can achieve low and zero emissions by driving the motor completely or partially by electricity.
Battery electric vehicle is the earliest electric vehicle. There is a big gap between the power and driving range of vehicles using lead-acid batteries and traditional diesel locomotives. Using high-performance nickel-hydrogen batteries or lithium batteries will greatly increase the cost. However, JtBEV needs a certain charging time and corresponding charging equipment, so its use is limited. Fuel cells have an energy utilization rate of nearly 65%, and can achieve zero emission and low noise. The newly developed high-performance fuel cell abroad has been able to achieve almost the same power performance as the traditional internal combustion engine vehicle, which has a good development prospect, but the cost is the bottleneck restricting its industrialization. The demonstration test in Canada shows that the manufacturing cost of fuel-powered cars is 6.5438+200,000 Canadian dollars, while the manufacturing cost of diesel-powered cars is only 275,000 Canadian dollars.
Hybrid electric vehicle combines the advantages of traditional internal combustion engine vehicle and electric vehicle, and overcomes their disadvantages. In recent years, they have developed rapidly and have been industrialized and commercialized. The success of Prius and INSIGHT hybrid cars shows people the charm and huge market potential of hybrid technology.
1.7 cars using vegetable oil
In order to find a new energy source that can replace oil, scientists have also turned their attention to vegetable oil, and are developing internal combustion engine oil from vegetable oils such as soybean oil, corn oil and sunflower oil. Scientists are still studying biodiesel, a fuel based on vegetable oil, which can be used as a substitute for truck and ship diesel in the future. Biodiesel does not contain sulfur, so it will not pose a threat of acid rain to the environment. In order to produce biodiesel, chemists are esterifying vegetable oil and converting it into methyl ester compounds, which burn cleaner and have less residue in engines.
2 the development of new energy vehicles in China
China is rich in natural gas resources and widely distributed. Hainan, Beijing, Shanghai, Chongqing and other provinces and cities are listed as national key demonstration cities of gas vehicles. Compressed natural gas vehicles and liquefied petroleum gas vehicles are developed and modified on the basis of fuel vehicles in various places, which are mainly used in taxis, buses, large vehicles and engineering facilities. FAW-Volkswagen developed Jetta LPG, Shanghai Jiaotong University developed LPG cars and jointly developed and modified LPG city buses with Shenwo Bus, and Beijing developed CNG city buses.
Shanxi is a big coal-producing province. The methanol vehicle project has been going on for many years, and now it has reached the stage of commercial operation. The methanol car used adopts a flexible fuel system, which can use both methanol and gasoline, and use ethanol as aerobic fuel. Now it is popularized in Hebei and Heilongjiang. At the same time, the state has formulated the relevant standards for ethanol gasoline fuel. Datong Automobile Factory of Yungang Automobile Company in China has developed a methanol minibus.
China is rich in coal resources, and the government supports the project of making vehicle fuel from coal. The project of producing vehicle fuel by direct liquefaction and indirect liquefaction of coal is being actively carried out. During the Tenth Five-Year Plan period, demonstration plants for direct coal liquefaction were established in Yunnan and Shaanxi to synthesize automobile fuels such as petroleum or dimethyl ether from coal. After five years of cooperative research, Xi Jiaotong University and the Institute of Coal Chemical Industry of China Academy of Sciences developed the "ultra-low emission dimethyl ether vehicle" in 2000. Through the test of burning dimethyl ether on TYll00 single-cylinder diesel engine produced by Dalian Diesel Engine Factory and van equipped with CA498 diesel engine, it is found that the engine power can be increased by 10%- 15%, the thermal efficiency can be increased by 2-3 percentage points, and the noise can be reduced by 65438.
There are more than 20 companies engaged in fuel cell research in China, and proton exchange membrane (PEM) fuel cell technology has made great progress, but there is still a big gap with foreign countries. For example, the PEM fuel cell with power of 50-80 kW is used in foreign cars, while the power of the largest PEM fuel cell in China is 5kW, which is far from the automobile use. China's metal fuel cell technology has reached the advanced level in the world.
The technical level of Ni-MH battery and lithium battery in China has also reached the international advanced level, and the E 1 electric vehicle exhibited by BYD at the Shanghai Auto Show in 2005 already has good vehicle dynamic performance.
At present, Zhejiang University reports the most about compressed air powered vehicles in China. They have developed a research platform for compressed air powered motorcycles and explored many useful conclusions, which are being further studied. In addition, Chongqing University and Tongji University have also done some exploratory research. It should be said that the development of APV in China has just started.
3 Development prospects of alternative fuel vehicles
Among all kinds of alternative fuels for automobiles, LPG and CNG are the most convenient to put into use, and they already have good supporting infrastructure. It has a good application prospect in the field of public transportation with high emission and economic performance but general dynamic performance. In recent years, natural gas vehicles have occupied a large proportion in new buses in the United States. In a big agricultural country like China, especially some big agricultural provinces, ethanol resources are abundant, and ethanol vehicles have a good application prospect. Synthetic fuels such as dimethyl ether have good emission characteristics and will have a good application prospect, especially as a substitute for diesel for hybrid vehicles. Hybrid electric vehicle is undoubtedly the main form of the next generation automobile power system.
The performance of battery electric vehicles is not as good as that of hybrid electric vehicles and fuel cell vehicles, and the cost is high. The energy utilization rate of hydrogen fuel engine is not as good as that of hydrogen-oxygen fuel cell. Therefore, the development prospects of battery electric vehicles and hydrogen engine vehicles are not very optimistic. Of course, with the development and breakthrough of solar cell technology, perhaps pure electric vehicles can usher in a good development situation. Although the compressed air-powered vehicle has achieved zero pollution, its overall performance is far from that of traditional vehicles, and it can only be used in a small range of specific occasions.
Fuel cell is the automobile energy with the highest energy utilization rate under the current technical conditions. The specific energy of fuel cells can reach 200-350 Wh/kg, which is 2-3 times that of lithium-ion batteries. The energy conversion efficiency is as high as 60% ~ 80%, which is 1.5 ~ 2 times that of gasoline engine or diesel engine. It can achieve ultra-low pollution or even zero pollution, and the hydrogen energy used in fuel cells is renewable. At present, methanol fuel cell technology is the most mature. Major foreign oil companies and automobile companies are committed to the research and development of fuel cell vehicles in order to seize the beachhead position in the future automobile development. 1993-2000, Daimler-Benz automobile company successively launched Necari-Necarⅳ Ⅳ and Nebas series FCEVs. In May, 200 1 year, Necar4 was tested in the United States, with a power of 55kW, a maximum speed of 145km/h and a full-load stroke of 450km. The latest Necar V-FCEV uses methanol fuel cells. 1997 Ballard Power Company and Ford Motor Company set up Xcellsis Company to develop fuel cell vehicles, and American oil companies such as AR-CO, Shell and Texaco and California CARB joined in succession, forming the most powerful fuel cell vehicle development alliance in the world. Japan Electric Power Central Research Institute is fully developing fuel cells using heat-resistant ceramics. When the battery works at the high temperature of 1000℃, the power generation efficiency is very high, and the output power of electrolyte reaches 1w/cm2, which is five times that of traditional fuel cells. EvomR company is committed to the development of aluminum-zinc fuel cells, which has reached a considerable level.
In a word, the comprehensive evaluation of alternative fuels should consider the following factors: fuel cost; Vehicle cost; Dependence on imported oil; Effective energy utilization rate; Greenhouse effect; Discharge pollution; Production, storage and transportation, distribution and filling facilities; Loading mileage and filling time; Safe. Based on these factors, CNG and LPG are the easiest alternative fuels to use at present. The comprehensive evaluation indexes of electricity, methanol and ethanol are all lower than gasoline. It can be predicted that the market share of liquefied petroleum gas, compressed natural gas and ethanol will continue to increase. The market share of dimethyl ether and synthetic diesel will increase rapidly and steadily in ten years. Hybrid electric vehicles will further develop and rapidly increase their market share. Fuel cell vehicles will be industrialized within 20 years and gradually increase their market share. After 20 years, the market share of traditional gasoline engine vehicles will begin to decline obviously, but diesel vehicles will continue to maintain a high market share in the field of heavy vehicles.
4 conclusion
In the next 20 years, gasoline and diesel are still the main energy sources of automobiles, but the quality requirements of gasoline and diesel are getting higher and higher, and engine technology will develop rapidly to improve energy utilization. Alternative fuels will be used quickly, natural gas vehicles and ethanol vehicles will take the lead in large-scale use, and dimethyl ether and synthetic fuels will gradually expand their application scope.
Hybrid power system will be developed and applied rapidly, and hybrid vehicle will be the most feasible way to solve the energy and pollution problems of automobile industry in at least 30 years. Therefore, we should integrate resources, accelerate the development of hybrid electric vehicles, and seize the new highland of automobile technology development.
Fuel cell is the most promising energy source for automobiles and the main energy source for automobiles in the future. The domestic oil industry should jointly develop advanced fuel cell technology with the automobile industry to seize the forefront of advanced automobile technology in the future!