Effect of supercapacitors on the operation of an air-cooled hydrogen fuel cell

摘要

One of the greatest challenges associated with efficient energy use in unmanned aerial vehicles (drones) is that of the energy storage systems – more specifically it's weight and capacity. Current hydrogen fuel cell drones have very promising flight durations, but have a low power density thus performing poorly at peak power demands. Supercapacitors are known to have high power densities and respond significantly well to peak power demands. For this research it is desired to evaluate how supercapacitors can affect the operation of an existing hydrogen fuel cell system, when combined. This study will include the evaluation of the viability of a DC-DC converter used to reduce the size (and subsequently, weight) of a supercapacitor bank. It also evaluates whether specified switching of the sources has an effect. Using data generated from the experiment it was determined that the DC-DC converter (with efficiency >94%) reduced the efficiency (by 0.5%) and duration (by 3.8%) of the supercapacitor bank whilst increasing the weight (by 16.7%). It was also seen that the method of selective switching offered no benefit over that of a self-selecting system, where the former obtained 223 s of usability and the latter 365 s. However, comparing all the results it was observed that the addition of a supercapacitor bank allowed for an improvement in energy- and power density, of the hydrogen fuel cell system, from 0.65 Wh/kg to 1.19 Wh/kg and from 69.7 W/kg to 125.7 W/kg, respectively.