This paper was authored by researchers from the Tsinghua University in Beijing China were they looked into using a graphene supercapacitors for power based supply needed for a separation of a QSat.
Firstly the paper started with looking at Proba-1 satellite that was the first in-orbit successful demonstration of lithium-ion batteries (LIB) on a satellite this launched happened in 2001. This satellite used lithium based batteries as its main energy storage system which was due to the high specific energy it can give and also the long life span it offers. There was a limitation to small satellite in this case which is their limited ability to support high power consumption payloads due to the constraints on the allowable mass and volume of the batteries, not to forget that lithium ion battery also could have thermal run-away.
After careful consideration of the various effects and limitations, the next big idea that was brought forward by the researchers, were the use of supercapacitors also known as ultra-capacitors or electric Double layer capacitors (ELDC), they are said to overcome the disadvantages of the LIBs. These supercapacitors have capacitance and internal resistance that change little with time, which makes it have very high charging and discharging life cycle. Also has a wide range of operating temperature of about -30⁰C to +60⁰C.
The paper did not only talk about using a supercapacitor which had various advantages, but also was looking for how to make it even better, then they introduced the graphene supercapacitors where graphene is the main material and thus adds its uniqueness and advantages to the already set down ones that the supercapacitors gives which are its large surface area, excellent electrical conductivity and good mechanical properties. Although the usage of graphene supercapacitors (GSC) has not been widely accepted in the aerospace industry, the feasibility needs to be proven and this was done in this paper when it was incorporated with a Q-Sat.
In this paper, the power supply talks about providing instantaneous high power driving current for the separation system of the Q-Sat. The key of the separation for the Q-SAT is a simply locking and release mechanism. The current/power for the satellite is provided by the rocket but the electromagnet which has a certain level of inductance can cause accidents. This brought the researchers to using the rocket current/power as a trigger signal and use a self-providing power supply to output the high-power current required by the electromagnet. The GSC was the best, most preferred choice since it has an excellent power density of about 92-260KW/Kg and a long life span of about 2000cycles up to 200000cycles. Not to forget that the compatibility of the GSC since it’s a small satellite.
The supercapacitors also undertook various tests to be sure that it can handle the launch and the space environment and it passed the tests and thus was proven adequate for missions that involved small satellite that need a prolonged life span and more energy for its operation.
Conclusion: GSC is an ideal solution to issues that have such requirements listed above due to its advantage in power density and environmental adaptability. The method can be used as an auxiliary power supply or main power supply for satellite and spacecraft with high-power requirements. The GSC are highly safe and has little to no risk of explosion and combustion making it suitable for needs of manned space projects.
Sources: Yunhan He, Zhaokui Wang, Yulin Zhang. The design, test and application on the satellite separation system of space power supply based on graphene supercapacitors. (2021). https://doi.org/10.1016/j.actaastro.2021.04.034