Supercapacitors are finding an increasing number of applications in the civil aviation, automotive, defence, and telecommunication industries. On municipal buses, for example, they are charged during braking, and supply electricity to open and close the doors when the vehicle stops, also helping the vehicle accelerate when it starts moving again. On the new Airbus A380, supercapacitors help open and close the aircraft's heavy doors; in an emergency, they can even do this independently of the aircraft's central power system. In short, supercapacitors are now part of daily life.
Do supercapacitors also have applications in telecommunications satellites? To find out, ESA recently funded a study under ARTES 5.1 in which researchers from ESA/ESTEC (NL), Eggo (CZ), Airbus Defense and Space (FR), and Brno University of Technology (CZ) examined their potential.
How electrical energy is stored on satellites is crucial. During the times when the sun is eclipsed, solar panels stop generating electricity and a spacecraft needs to rely on stored energy. The commonly-used satellite batteries, based on Li-Ion technology, can store a large amount of electric energy with a relatively low battery mass for those long, dark moments in space. Supercapacitors do not store as much energy, but what makes them really useful is their ability to deliver very high bursts of electricity for a few seconds.
While a typical space battery can deliver around 200 W/kg, banks of supercapacitors can deliver up to a 10 kW/kg for short durations.
A bank of supercapacitors (housing not shown)
The researchers have found that one potential application for supercapacitors in telecommunications is to keep a satellite’s power supply from fluctuating as loads change. Another promising application is to drive pyrotechnic separation mechanisms. In addition to telecommunications, there are potential applications in other areas, such as high-power radar for earth observation.
One particularly favourable characteristic of commercially-manufactured supercapacitors is their very long lifecycle. In the laboratory, the team subjected supercapacitor banks to more than 1.7 million charge/discharge cycles at 45°C, and the results showed capacity fade of only 11%, with internal resistance rising to just 18%. For telecommunication payloads, it is critical that components are durable. They need to last the life of the spacecraft's mission, which is normally fifteen years.
“Our work on supercapacitors reflects ESA's commitment to ensuring that the European and Canadian space industries remain at the very forefront of developments in electric energy storage systems,” says Brandon Buergler, Energy Storage Engineer at ESA.