Delfi-C³ Electrical Power Subsystem
The Electrical Power Subsystem (EPS) is generating electrical power and supplying it to the various loads in an appropriate form. The solar panels are produced by Dutch Space and the circuitry of the general power supply is developed by SystematIC BV.
Power generation is accomplished by using four solar arrays. Every array consists of a single string of 5 TEC1 triple junction gallium arsenide (GaAs) cells in series, which are provided by Dutch Space. The panels are deployed to an angle of 35 degrees with respect to the body to ensure sufficient power production at every attitude. One of the most striking characteristics of the Delfi-C³ spacecraft is the absence of energy storage. All required power at a particular instance has to be generated by the solar cells. Therefore, the Delfi-C³ spacecraft is not operational in eclipse. During eclipse the spacecraft will shut down due to an inability to maintain the required bus voltage, and during the sunlit part of the orbit the computer will commence a new boot sequence for powering up the spacecraft.
As the electrical characteristics of the solar arrays are dependent on temperature and level of incident radiation, power conditioning is applied to produce a stable bus voltage. Step-up converters are used for generating 12V on the bus. Every individual solar array is equipped with its own converter to ensure redundancy in the system. With respect to power conditioning, no specific provisions are made. This means that only the required electrical power is removed from the solar array, with the remaining power staying at the array. As the minimum required power is far less than the maximum generated power, the operating point of the solar cells will move along a large part of the IV-curve of the solar cells.
Because every individual load aboard the spacecraft makes use of a characteristic input voltage, the bus voltage is converted down to the needed voltage locally (3.3 V, 5V, etcetera). In order to waste as little power as possible, high efficiency step-down converters are applied, which are able to yield efficiencies of approximately 85%. Power supply to the individual printed circuit boards is controlled by a local microcontroller. This microcontroller is able to switch subsystem on and off when it receives a command from the onboard computer. .