MMC released a new drone, which surprises people for its 4-hour for UAV flight time. In the end of last month, Intelligent Energy, a British company, announced that they had developed a method enabling drones to fly two hours. Now, the lipo battery has been developed to the upper limit. Since most of the consuming-level drones have the flight time no more than half an hour, what makes the drones have ultra-long flight time?
The answer is simple-change the battery!
Both the MMC and the Intelligent Energy take a new type of battery-hydrogen fuel cell-as the core “weapon” in developing the ultra-long flight time.
The production and principle of fuel cells
Fuel cells has been applied in several fields. Although we call it as “new type cell”, it has appeared in 1839. At that time, William Rogoff, a British physicist, has made the fist fuel cell in the world. In the 60s of last century, fuel cell has contributed to the space exploration.
Not as the internal combustion engine, generate energy by firing the fuels, the fuel cells make the oxidation-reduction reaction between the fuel inside and the oxygen or catalyst, turning the chemical energy to the electric energy. The fuels include hydrogen, the most common one, natural gas, alcohol, methane etc. Though the fuels are different, most of the fuel cells have similar operation principle and mode.
Fuel cells are composed of three adjacent zones: anode, cathode and electrolyte. Two chemical reactions happen among three different zones. (Fuels react with oxygen and produce water, carbon dioxide and electric energy.)
In the anode, it is common to use catalyst to oxidize the fuel, turning the fuel into an electron with positive charge and an electron with negative charge. Then, electron and ion are separated by the electrolyte or membrane, with the ion going through electrolyte and preventing from electron. For the next step, the released electron passes a wire and generate current. Ion goes from electrolyte to cathode, and once it reaches to the cathode and gets together with electron, it will react with oxygen and produce water and carbon dioxide.
The classification and application of fuel cells
Now, the mainstream of fuel cells can be divided into five types: alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), solid oxide fuel cell (SOFC), proton exchange membrane fuel cell (PEMFC). Besides, there are some less popular fuel cells such as regeneration fuel cell (RFC), direct alcohol fuel cell (DAFC), ect.
To be insightful, the PEMFC and MCFC have the best prospective. To make a reactive fragment, PEMFC needs the graphene to be dielectric film and expensive metal, processed by nanometer technology, to be catalyst. Every reactive fragment can generate 0.7-0.9V, and you can combine the reactive fragments to become a hydrogen fuel pile for high-power. The operation temperature of PEMFC is less than 100 degree centigrade and have comparatively low output power, which is most suitable for consuming-level battery from motor vehicles, drones to PC, mobiles.
The advantages and disadvantages of fuel cells
1. The fuel cells is of superior quality.
2. The hydrogen fuel cell can offer stable power continuously unless the fuel depletes. And after depletion, it can replenish fuel fast and charge again so as to improve the working efficiency.
3. Compared with lipo battery, hydrogen fuel cells can adapt to the environment better and there would not be cutoff under the extremely low temperature as the lipo battery.
4. It has tens of times lifespan than the lipo battery.
5. The hydrogen fuel cells are eco-friendly. The resultant is just the water, carbon and so forth. After the cells scrap, the membrane and catalyst can be recycled.
Although the hydrogen fuel has more strength compared with other power sources, it has some weaknesses.
1. High cost. The graphene, used for membrane, has price of 1000 dollar for one gram. Besides, the catalyst composes some rare noble metals which are expensive and need further nanometer technology.
2. The hydrogen fuel source is hard to get. Now, the hydrogen refueling station is initially developing. Though there are some ways to but the hydrogen on the market, a special pressure device is required, which has not been spread widely.
3. It is inconvenient to move and carry, since the standard of delivering is very high.
4. Some professional people have questioned the safety. The inflammability, explosion hazard and the high temperature while the battery operates all result in the probability of accident.
Generally, the hydrogen fuel cell has not developed completely. Many professional drone practitioners still hold the negative attitude and reckon that the hydrogen fuel cells are the trend but are not suitable for the power of drones till now. Therefore, we should keep paying attention to the hydrogen fuel cells.