Electrical Power System (EPS)

Our EPS (Electrical Power System) consists of three main elements: solar panels, ESS (Energy Storage Systems) and PMS (Power Management System).

Photo: CubeSat solar panels configuration (from Multidisciplinary Engineering RIT - Senior Design Program)

Solar panels:

The easiest way to mount solar panels is to simply put them on the sides of a CubeSat.

However, usually, a CubeSat needs at least one side with no solar panels for a camera, antennas, or some other specific payload. It is problematic because when the satellite is facing the Sun directly with only one of its sides, it is at its lowest solar power production moment. When the side happens to have no solar panels on it, the situation could become even dangerous, because the CubeSat is completely cut off from power.

To avoid such situations, our CubeSat will have deployable two-sided solar panels. Our panel configuration has to be optimized for a tumbling satellite, in order to have some sort of solar power at any moment. Therefore our panel configuration will be similar to the one presented in the picture on the left.

Photo: CubeSat battery pack example (from GOMspace NanoPower BP4)

ESS (Energy Storage Systems):

Why do we need ESS instead of simply relying on our solar panels?

For starters, when the CubeSat is on the opposite side of Earth to Sun, it doesn’t have access to solar power, and it would be simply turned off. In addition, transmitting data drains lots of power, which is why ESS complements solar panels in moments of the highest demand for power.  

Usually, CubeSat’s ESS consists of just Li-ion UL-listed batteries. The batteries cannot be exposed to very low temperatures, which is why in space they have to be heated by coils wrapped around them.

However, in our CubeSat, we have to consider other ESS options too.

Firstly, batteries take lots of space inside of a 1U CubeSat. They also have to be charged and heated, which drains extra power. Our CubeSat’s size doesn’t allow us to have a big solar panels’ surface area, which limits our solar power production capabilities.

On the other hand, batteries have a high flight heritage and can be considered the most reliable.

Secondly, we could rid off of batteries and many problems which come along with them by using supercapacitors as our ESS. We would not have to heat them, charging wouldn’t be much less problematic and they could potentially take less space. However, our data transmission would have to be pulsating.

Thirdly, we have to consider the option of having no ESS at all. Our CubeSat would be completely cut off from power while being on the Earth’s dark side for about half of its orbital period. That would be about 45 minutes in the dark, and the same amount of time in the light. We would have no contact with our CubeSat about 50% of the time, which could be risky.

Photo: PMS example (from CubeStar Electronic Power System)

PMS (Power Management System):

The main task of PMS is to make sure that the EPS is safe and efficient. Is a PCB with a separate microcontroller, which for example, could have special circuits for managing solar power, charging batteries, regulating the voltage and current, separating power buses between different devices, or acting in emergencies. The conditions in space are harsh, so electronic components can get damaged and fail to cause damage to the CubeSat. For example, if power consumption is larger than power production capacity, load shedding is used to avoid a blackout.

Mr Fahrenheit

Mr Fahrenheit is a CubeSat satellite project entirely managed by high-school students attending IB World School 1531 from Warsaw, Poland.

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