Analyze the nine power systems of uav

If drones are to continue to improve flight performance, batteries must become smaller and lighter. When it comes to power density, we can see that we have reached a certain limit. Li-po and li-ion batteries have become small and affordable, largely as a result of the mobile phone industry. As a result, such batteries are widely used, and it is fair to say that the vast majority (96%) of drones today use batteries as a source of power.

Simply adding batteries to a drone system will not extend its flight time or its payload capacity. Given the state of the art for specific energy sources, achieving higher payloads and longer flight times requires a number of considerations: mass specific energy (energy per unit of mass) and volume specific energy (energy per unit of volume).

Just thinking about the energy source is not the right way, because the whole system (energy + propulsion system) affects flight performance. If the propulsion system, such as a turbine or a fuel cell, is very heavy, a source with a very high energy density, such as kerosene or H2, will do little good.

Propulsion efficiency factors also vary widely: battery-powered systems convert 73 percent of their energy to power, fuel cells 44 percent, and combustion engines only 39 percent.

Another factor affecting energy use is its expected mission. Should drones fly longer or carry higher loads? Should drones fly within a limited radius or above distant clouds? These problems have a great impact on the use of energy, different operation scheme to choose different energy sources.

When we consider propulsion systems, missions, and the need to increase energy density, we go back to the source. The figure below shows the specific energy density of each source on a log-log scale:

A, battery

Yes, batteries again. Batteries have many advantages: they can be charged anywhere, can be transported without restrictions in most cases, and can be easily replenished by replacing the battery block without overflows or heat.

Li-po and li-ion are the most common sources for drones, but that doesn't mean the end. Compared with li-po batteries, li-socl2 batteries have more than twice the energy density per kilogram, while li-air batteries have more than seven times the energy density per kilogram. Both batteries are not widely used, partly because they are too expensive. Li-s batteries could be replaced by li-ion batteries because of their high energy density and the reduced cost of sulphur.

Hydrogen fuel cell

Fuel cells have many advantages: no direct pollution, no sound, and they are powered by a very powerful source, H2. Compare the energy density of liquid H2 to that of a lithium-ion battery, and the coefficient between them is 150! That alone is enough to bring hydrogen drones to market.

Protonex, a unit of fuel cell developer ballard power systems, wants to take advantage of these opportunities. Insitu, a division of U.S.special giant Boeing, recently put its proton exchange membrane (PEM) fuel cells on display. Boeing makes military-grade and industrial-grade long-endurance fixed-wing drones, such as PhantomEye and ScanEagle.

FSTDSingapore has already achieved breakthroughs in the field of solid hydrogen demand power systems. Robotics developer H3Dynamics has also unveiled its hand-launched fixed-wing drone, Hywings, which can fly for up to 10 hours with a range of up to 500km.

The Hycopter drone launched by HorizonUnmannedSystem can fly for up to four hours with zero load and 2.5 hours with two pounds of load. The drone eliminates energy storage by using its "hollow" structure to store energy as hydrogen instead of air.

MicroMulticopterAeroTechnology company (MMC) for unmanned aerial vehicle (uav) launched commercial hydrogen fuel cells "fuel cell" H - 1. In addition, MMC designed and manufactured the world's first hydrogen-powered drone, the "" HyDrone1550" ".

KoreanHyliumIndustries company is developing a flight time can be up to 4 hours of unmanned aerial vehicle (uav); Montreal's EnergyOr h2quad-1000 can fly for two hours with a payload of one kilogram.

It has been claimed that IntelligentEnergy's air-cooled fuel cell system, which is based on hydrogen and ambient air, has been used to generate clean direct current power supply, and the battery itself is simple in structure, light in weight, strong and cost-effective. It has a higher energy to mass ratio than battery-based systems and can be fully charged in minutes.

Metroskyways, a subsidiary of UrbanAeronautics, announced in April 2017 that the company was developing a CityHawk, a hydrogen-powered vertical take-off and landing flight vehicle that can be used by up to four people.

Gasoline, kerosene, methanol, ethanol, liquefied petroleum gas propane

There are a number of mature gasoline-powered solutions available, some of which have excellent flight performance. UAVFactory's penguins inc. Fixed-wing drones can fly for more than 20 hours when the tank is full, and Siebel's CAMCOPTERS 100 can fly for six hours when the tank is full.

The advantage of this energy source is the combination of high mass specific energy [Wh/kg] and volume specific energy [Wh/l]. Compared with li-po batteries, gasoline has a mass density of 48 times and a volume density of 13X. In addition, the internal combustion engine is strong, compact, light weight, with good fuel consumption rate.

When it comes to endurance, another advantage of gasoline-powered drones is that, over time, the stronger weight makes the platform lighter, increasing the range.

Gas and electricity mixture

Products from Waterloo, Ontario - based PegasusAeronautics and YEAIR Berlin are prime examples of hybrid engines. The companies combine the quick response of electric motors with the benefits of gasoline-powered flying.

V. solar energy

In the past few years, the efficiency of solar cells has increased from 10% to nearly 46%, reaching a power ratio of about 175W/m2. Obviously, this requires the entire wing surface to be covered with a large area of solar panels, so that it can work like a multi-rotor drone.

Silicon valley tech companies are also exploring the potential of solar-powered drones: Facebook hopes to bring wireless networks to remote corners of the world with its Aquila (high-altitude, long-endurance) solar-powered drones, and Google X's now defunct Titan project.

Airbus's zephyr is a high-altitude pseudosatellite (HAPS) designed to bridge the capability gap betweenspecials and drones. Powered by solar energy, the zephyr can fly above the weather and commercial air traffic at an altitude of 70,000 feet. Boeing's solar hawk program was canceled in 2012.

OpenRobotixLabs is developing the Mars xsol-e1, a solar-powered quadcopter. A company spokesperson outlined that flight time depends on a number of factors, but in general, we can extend the 15-minute flight to 40 to 45 minutes with solar assist technology.

Vi. Solar energy mixture

The endurance of the solar hybrid (solar + cell) is amazing. AltaDevices and PowerOasis have announced that they are teaming up to develop the world's first small drone that integrates solar and li-ion battery powered systems. The uav's reference frame is 2-4 meters and USES 5s-7s lithium ion battery. Plans for the drone will be released in late 2017.

Seven, mooring

The mooring system can fly indefinitely within a small radius, making it a perfect choice for surveillance andspecial. MMC's T1 moorings support most drones, such as MMC's TDrone1200, DJI Matrice600, DJI S1000, Yuneec TyphoonH, Intel Falcon8+, and Microdrones md4-1000. Bluevigil, Elistair, DroneAviationCorp and SPHEngineering have similar projects.

Super capacitors

Could graphite's monatomic layers take ultracapacitors to new heights? In February 2015, ge sponsored research on ultracapacitors. Primary energy sources such as internal combustion engines, fuel cells, and batteries work well as low-power continuous sources, but do not efficiently handle peak power or recycled energy because they discharge and recharge very slowly. Supercapacitors can provide a quick burst of energy at peak power demand, then quickly store the energy and capture any residual power that might be lost.

Capacitors may seem like a long way behind the battery's energy density, but they seem to be a great vehicle for improving agile hybrid configurations.

Nine, laser

LaserMotive has developed drone powerchain technology, a power-beam drone with a laser receiver. In 2012, lockheed Martin, with LaserMotive's assistance, unveiled its "Stalker" drone, which flew for 48 hours on top of a laser-charging system. "Surface-to-air systems like this allow us to provide Stalker with almost unlimited flight endurance, extending the mission profile that Stalker can accomplish," said TomKoonce, Stalker's project manager.

AscendingTechnologies of Germany and LaserMotive demonstrated its efficiency in 2010 with a small drone that flew for 12 hours on a quad.

At the end

All drone power sources have their own advantages in specific missions. Hybrid solutions (source and propulsion systems) meet the needs of the transition to clean energy. Now, because mixtures can be a separate technique that balances the pros and cons, combining the best of both worlds seems like a smart choice. It is also a smart move to look at other leading sectors, such as cars, especially when it comes to reducing future costs of mass production and infrastructure.

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