For the drone revolution to really take off, the flying machines will have to fly longer than the half-hour-or-so that today's batteries allow.
By definition, flight autonomy is the amount of time an UAV can flight without landing due to lack of power. There is a compromise between flight autonomy and load capacity; the greater the load the UAV is supporting, the less time it can fly.
To calculate the flight autonomy, it is necessary to consider different factors such as the type of engine, aerodynamics, weight, wind, and the kind of shunting the UAV has to do. Hence, UAV flight autonomy is very limited, rarely getting flight times longer than 60 minutes.
To increase flight autonomy, it is necessary to consider the battery. There are basically two groups of batteries, commercial and military types.
One of the more common batteries available for commercial UAVs is the Lithium Polymer (LiPo) battery which provides around 2Ah of service to the UAV. The LiPo battery is favored as it light (130gr.) and small (72x36x27mm). The LiPo battery is capable of producing one hour of flight autonomy with a 2A current. If we consider regular conditions (5mph wind with no load capacity), flight autonomy may be approximately 25 minutes.
Another type of battery for commercial applications is Lithium Sulphide battery. The nominal capacity for this type of battery is about 2.2Ah, while it is lighter (15gr.) and smaller (55x37x11mm) than the LiPo battery. It is possible to get a little more flight autonomy (between 25 and 30 minutes) than the LiPo Battery.
On the other hand, one of the challenges in the military field is to reduce the battery weight and size. Compared to the commercial batteries, the military invested in developing a higher density battery, which resulted in a smaller battery while increasing power. This helps the soldier to be more agile and go further in the field, as well as allowing the soldier to carry other equipment or systems that was not possible before.
The two most popular types of batteries used in military applications today are Lithium/Sulfur Dioxide (Li/SO2) and Lithium/Manganese Dioxide (Li/MnO2). The life expectancies for these batteries are between 30 minutes and 2 hours, depending on motor use, control of the UAV, the use of the radio and other equipment.
Increasing battery density results in increasing battery life. Battery density is measured in either watt-hours per kilogram or watt-hours per liter. Military research attained 7.5Ah of service with the LiSO2 battery, then improved upon that figure with about 11.5Ah of service with a the Li/MnO2. Meanwhile, the military is studying other battery materials such as Lithium/Polycarbon Monofluoride (Li/(CF)x) that is a potential next-generation
improvement for the battery life time.
Available Battery Types
Drones can already do a many tasks, and will do more when equipped with artificial intelligence. However, short battery life is a major issue to be resolved. Here are 6 known ways to power a drone.
Most of the drones we see are powered by Lithium-Polymer batteries (LiPo) which can only power a drone for about 20 minutes, depending on the load. Using this battery means your drone will have to come down to replace a battery or recharge a battery quite often. LiPo batteries work on the principle of intercalation and de-intercalation of lithium ions from a positive electrode material and a negative electrode material, with the liquid electrolyte providing a conductive medium. To prevent the electrodes from touching each other directly, a microporous separator is in between which allows only the ions and not the electrode particles to migrate from one side to another.
Most of the drones we see are powered by Lithium-Polymer battery which only powers drone for about 20 minutes, depending on your load. Using this battery means your drone will have to come down and replace the battery or recharge battery quite often. LiPos work on the principle of intercalation and de-intercalation of lithium-ions from a positive electrode material and a negative electrode material, with the liquid electrolyte providing a conductive medium. To prevent the electrodes from touching each other directly, a microporous separator is in between which allows only the ions and not the electrode particles to migrate from one side to another.
2. Solar Power
Drones powered with solar power usually have solar cells attached on its wings. They utilize solar power to fly when the sun is up while simultaneously storing power to the battery for flying when there is no sun in the sky, more like a backup power. This power source is ideal if your drone is meant to stay on the air indefinitely. The most recent breakthrough is an 81 hours flight by Atlantik Solar!
3. Hydrogen Fuel Cell
Intelligent Energy has been researching and developing a hydrogen fuel cell for use in the aerospace, automotive, consumer electronics and distributed power & generation markets. Last March, they successfully demonstrated their hydrogen-powered drone. This fuel cell can take your drone for a spin for about two hours while traditional Li-Po battery can only last for about 20 minutes. They also claim that the refueling process is done almost instantly while Li-Po battery takes a relatively long time to bring itself to full charge.
4. Combustion Engine
Yeair! started a kickstarter project for their drone powered by combustion engine. The drone is capable to stay for about an hour in the air with max speed 100km/h. It maybe a bit louder than your average drone with two-stroke 10cc gasoline engines and quite dangerous because the drone flies with a full tank of flammable gas but still, combustion engine offer more power than the usual Li-Po Batteries and it may come in handy for a power user.
A drone that fly with a cable tethered to a power supply is capable of staying in the air “forever”. If the drone’s controls also work by the tether line control and data transmission will be faster. Of course the drawback of a tethered system is that the drone can only go as far as the tethered cable allows. Some drones services tether a drone’s flight, allowing the drone to cover more ground.
6. Laser Transmitter
Lasermotive introduced a technology called The Power Link. This method sends a beam of light from a ground station to a receiver on a UAV, where the light is converted into electricity. With this technology, drones can fly outside of the zone of the light beam until its power runs down. The, this drone can fly back to the power link range and recharge its power.