Unmanned Systems Technology 022 | XOcean XO-450 l Radar systems l Space vehicles insight l Small Robot l BMPower FCPS l Prismatic HALE UAV l InterDrone 2018 show report l UpVision l Navigation systems

62 Dossier | BMPower fuel cell power system BMPower has a buffer battery in its FCPS to assist vehicle launch and for ‘peak shaving’ during high climb rates. The level of battery charging is controlled during the flight. Ivanenko notes that the control system allows the user to combine several fuel cell modules and a buffer battery into one system, whose operation is automatically synchronised. The control system takes readings from all key operating parameters: power, current, voltage, device temperature, residual pressure in the cylinder and at the fuel cell module input. All this data can be transmitted to the ground control station via a radio link. The control unit governs the two valves that determine the supply of hydrogen, the discharge of ‘ballast gases’ and the speed of the four fans that supply cooling air. The speed control is set to maintain the cell working temperature of about 50 C. Also, the unit, in response to the measurement of the volts and amps created by each cell in the main unit, converts the output voltage to the required level. Ivanenko explains, “The control system automatically regulates the power produced by the fuel cell module depending on the power consumption of the vehicle. At the same time, the voltage for its motors remains stable during the flight, irrespective of the power consumption, because we have developed a lightweight automatic voltage regulator [DC-DC converter].” The control system maintains the buffer battery charge at the necessary level and provides customers with any necessary information about the system’s status, including the current and voltage in the battery and the fuel cell module, and calculates the time remaining until the hydrogen in the cylinder will be depleted. If the fuel cell is producing a surplus of power – say when the aircraft is in a descent – the control system will use that excess energy to charge the battery. If the battery is fully charged, the control system does not dissipate excess energy; instead it reduces the amount of energy produced by the cells. “This approach increases the effectiveness of the whole system”, says Ivanenko. “The efficiency of the fuel cell module is increased, and that allows fuel saving for a longer flight duration. The efficiency of our system can now reach 60% during a flight.” Hydrogen supply Any hydrogen source can be used by the BMPower FCPS, provided the gas has a purity of at least 99.99%. Ivanenko remarks that an agreement with Linde Gas, a multinational company, makes getting the necessary hydrogen supply straightforward in whatever country the FCPS is operated. The tie-up with Linde Gas sees that company offer three dedicated carbon fibre composite hydrogen cylinders, respectively of capacities of 7, 10 and 25 litres and all capable of storing gas compressed to 350 bar. These are included in the current Linde catalogue, notes Ivanenko. The cylinder has a simple on/off switch, and is attached to the BMPower pressure regulator, which controls its outflow, reducing the supply pressure from 350 bar to the working pressure of the system, which is no more than 1 bar. The cell needs a hydrogen pressure of only 0.5 bar to operate, so the cylinder can be allowed to run down to only 1 bar before it needs to be changed. The DC-DC converter for the BMPower 1000 FCPS The efficiency of the fuel cell allows fuel saving for a longer flight duration. The efficiency can now reach 60% during a flight October/November 2018 | Unmanned Systems Technology