Solar arrays, composed of photovoltaic cells, are the most common power generation method for satellites. These cells convert photons from sunlight into electrical current. The output voltage and current are dependent on factors like solar intensity, temperature, and the array's orientation. For missions operating beyond the inner solar system, radioisotope thermoelectric generators (RTGs) may be used, which convert heat from radioactive decay into electricity.

Batteries serve as energy storage devices, accumulating excess power generated by solar arrays during sunlight periods and discharging it when solar power is insufficient. Common battery chemistries for spacecraft include Nickel-Cadmium (NiCd), Nickel-Hydrogen (NiH2), and Lithium-ion (Li-ion), each offering different energy densities, cycle lives, and temperature tolerances. The battery management system (BMS) is crucial for monitoring and controlling charging and discharging to prevent damage and maximize lifespan.

The Power Conditioning and Distribution Unit (PCDU) acts as the central hub for managing and distributing electrical power. It takes the raw power from the solar arrays and batteries, converts it to the required voltage levels for different satellite components (e.g., 5V, 12V, 28V), and distributes it through a network of power buses. The PCDU also incorporates protection mechanisms like circuit breakers, fuses, and voltage regulators to safeguard the satellite's electronics from power anomalies.

Load shedding is a crucial power management technique employed when the available power is insufficient to meet the demands of all active subsystems. The satellite's onboard computer, often part of the PCDU or a dedicated power management controller, identifies and deactivates non-essential loads (e.g., scientific instruments, high-power transmitters) in a predefined order. This ensures that essential systems, such as the command and data handling unit, attitude determination and control system, and basic communication links, continue to function, preserving the satellite's core capabilities.

Maximum Power Point Tracking (MPPT) is an electronic charge controller technology that optimizes the power output from solar arrays. Solar arrays have a specific operating point (voltage and current) where they produce the maximum power. This point changes with factors like solar irradiance and temperature. MPPT controllers continuously monitor the array's output and adjust the load impedance to maintain operation at this maximum power point, thereby increasing the efficiency of power generation.

Space is filled with energetic particles (protons, electrons, heavy ions) that can penetrate satellite components and cause 'single-event effects' (like bit flips) or cumulative damage leading to device failure. Power system components, particularly sensitive microcontrollers within PCDUs and battery management systems, must be radiation-hardened or shielded to ensure reliable operation over the mission lifetime. This often involves using specialized semiconductor manufacturing processes or adding physical shielding.

The extreme temperature fluctuations experienced in orbit, from direct sunlight to deep shadow, pose a significant challenge for thermal management. Solar arrays can overheat, reducing their efficiency, while batteries must be kept within a specific temperature range to prevent damage and ensure optimal performance. The PCDU also generates heat during operation. Therefore, sophisticated thermal control systems, including radiators, heaters, and insulation, are integrated to maintain component temperatures within acceptable limits.