New hydrogen energy technology could represent a commercial breakthrough for unmanned aerial vehicles, paving the way for the development of mobile robots with extended range and load capacity. Doosan Mobility Innovation (DMI) announced that it has successfully used hydrogen-powered drones to deliver humanitarian aid to remote locations. With two hours of flight time (longer than most battery-powered drones), hydrogen drones flew masks and emergency supplies between the US Virgin Islands and delivered medical supplies to the summit of Mt. Hallasan, South Korea’s highest mountain, located on Jeju Island. DMI has accumulated many years of knowledge in materials and systems related to phosphoric acid fuel cells (PAFCs) and proton exchange membrane fuel cells (PEMFC), also known as electrolyte polymer membrane fuel cells (PEM). PEMFC generates electricity and operates on the opposite principle of electrolysis, which consumes electricity. Thanks to this experience, Doosan is developing the PEMFC Mobile Power Package for UAVs. In an interview with EE Times, Jiwon-Yeo, Doosan Mobility Innovation Sales Representative, highlighted how long-distance use of hydrogen-powered drones also allows commercial surveillance of large areas such as Korea’s largest solar power plant in Solasido, Haenam. . “When performing the same task with a battery powered drone, it was necessary to replace more than six batteries. Due to the high energy density of the hydrogen fuel cell, which is 3 to 4 times more than conventional batteries, the hydrogen fuel cell is a more efficient and effective energy source, Jeon Yu said. The development of hydrogen energy solutions includes a range of technologies from materials engineering to improving the powertrain of the drone. Being able to fly for up to two hours on a single charge, these long-range fuel cell-powered drones can cover even large sites in a single flight, rather than having to use multiple batteries and multiple launch points. Drones also provide benefits in personnel safety and accident prevention, as aerial surveying eliminates the need to climb structures on site. Figure 1: An example of solar panel screening (Source: Doosan Mobility Innovation) Hydrogen Fuel Cell Technology Science Hydrogen is the lightest component on Earth. When hydrogen is combined with air in the atmosphere, water is formed, which makes hydrogen a gas free of pollution. Efforts to reduce particulate matter and the risks of nuclear energy and greenhouse gases around the world are also increasing the demand for the use of renewable energy. So hydrogen appears as the most promising alternative energy. A fuel cell is a device that converts the chemical energy of a fuel into electricity and heat without using thermal cycles. Hydrogen (H2) fuel cells produce electricity and hot water from hydrogen and oxygen. This process is the exact opposite of electrolysis: when dividing water (H2O) into H2 and O, it is necessary to supply current, and the reverse process produces current and water. The drone is powered by the electricity generated in the stack using hydrogen and oxygen, as shown in Figure 2. As demonstrated by Jiwon-Yeo, the stack consists of several cells formed from a polymer electrolyte (PEM) membrane and two electrodes, generating ions and electrons through hydrogen reaction and reaction Oxygen. Hydrogen is first compressed under high pressure before being used in the cell, thus ensuring a high supply period. “DMI provides a complete hydrogen system in which the packaged hydrogen cylinders are shipped to customer sites. Users will only need to replace the hydrogen cylinders, which takes about a minute,” said Jiwon Yu. “Our tanks have not only passed the tests required to obtain the hydrogen tank certification but also a variety of safety tests that are very similar to drone flights,” she added. Cells with a polymer membrane provide high conductivity and operate at temperatures between 70 and 100 ° C. It is mainly used for traction and generation / cogeneration in small scale (1 – 250 kW). Combustion cells provide high electrical efficiency, and their values range from 40 to 60 percent, depending on the temperatures used. The modularity of the system makes it possible to increase the installed power. The cells can be arranged in series to form a “stack”, which can be grouped into modules to obtain the required power generators. One of the biggest challenges will be the lack of hydrogen infrastructure. We believe the increased mobility of hydrogen fuel cells such as drones will stimulate the market. Through local partnerships, we have completed the hydrogen supply chain in Korea, China and the USA. We are cooperating with local gas companies to charge our hydrogen cylinder, which has been certified with DOT, TPED and KGS label, ”said Jiwon-Yeo. Figure 2: How energy is generated from fuel cells (Source: DMI) Figure 3: Energy Density Comparison: Hydrogen fuel cell versus lithium power (source: DMI) Hydrogen increases drone flight time The 48-volt system deals with energy management of hydrogen A cell-powered UAV similar to tethered UAVs by implementing a Power Distribution Network (PDN). Energy, PDN is one of the most important due to several factors that have a major influence on design options. These factors are market driven before they are driven by technology. Optimization of a power supply in PCB design is a system-wide problem. PDN is designed to provide specific levels of Voltage and current for different loads within a system that is derived from large power source (s). As system power requirements increase, traditional PDNs are subjected to tremendous pressure to provide adequate performance. PDNs based on a new standard such as 48V, are appearing in many applications. The 2.6 kW DP30 power supply used by DMI on two main packages provides power to the drones’ rotors and control modules for the two stackers. Due to the wide range and variable output voltages of the DP30 power supply, from 40 to 74 volts, the output power units operate at 48 volts and 12 amps for the motors and 12 volts and 8 amps for the control circuits and fans. The chassis is supported by the Vicor PRM ™ buck boosters and the ZVS buck regulator. “ The wide range of fuel cell voltage and hybrid connection to a conventional Li-Po battery is the basic configuration of our energy management system. By doing this, it allows lithium batteries to be charged automatically by the fuel cell when needed, or discharged when the fuel cells need additional power when the aircraft is in operation. Unmanned. Thermal management is important for a hydrogen fuel cell, and we have an internal cooling fan to regulate the thermostat, ”said Jiwon-Yeo DMI, which plans to diversify its production lines according to energy capacity. Jiwon-Yeo indicated that the company will soon develop products with various capacities, ranging from the 1.5 kW hydrogen fuel cell power package which is scheduled to be launched next year to the 10 kW power package, and will launch matching drones for each power package. Increased flight time, along with rapid refueling, opens up a wide range of new business possibilities for companies that use drones for offshore platform screening, search and rescue operations, high-quality aerial photography, precision agriculture, delivery and more. Google, Amazon and Alibaba are testing plans to launch a drone delivery service. If fuel cell-powered drones succeed, optimists say they could create a low-carbon delivery system worldwide, reduce air pollution and emissions, and replace road transport. The construction of these aircraft must be subject to air traffic regulations that need to be revised and adapted to new mobility scenarios. Indeed, safety must be ensured before the countless buzzing robots cross the skyscrapers of major cities. The scenario in the 2015 movie Back to the Future is not far away, then!