Energy Power System

1. Energy Power System

2. Electricity • Electricity is the flow of electrons through a conductor • Electricity will only move through a closed circuit, if the circuit is broken the flow of electrons stops

3. Electricity (cont.) • Voltage - Electric potential or potential difference, provided by the battery, expressed in volts • Amperage - The strength of an electric current, flows through the conductors to the load, expressed in amperes • Resistance - Is present in any load, expressed in ohms

4. Light to Power • Solar Panels collect sunlight and convert them into electrical power • For maximum power solar arrays need to be perpendicular to the light rays hitting them.

5. Orbit Cycle • During the 30 minute eclipse period the batteries supply power • While in insolation period the solar arrays provide power while the batteries charge for the next eclipse period

6. Primary and Secondary power • Primary power is high voltage power generated at a centralized source • Before power is delivered to users it is stepped down by a transformer to a set voltage (secondary power) • Secondary power is then delivered to the user

7. System Overview • Internal and external systems • Internal system distributes secondary power • External distributes primary power • 8 identical channels of power (1A-4B) • Each channel supplies 160 volts

8. Internal EPS • Loads, RPDA, SPDA, DDCU, MBSU Converts primary power to secondary power • Routes secondary power to any internal systems

9. Loads • A load is anything that needs electricity to function. • Computers, Lights, Pumps, etc. • Each load requires a certain current (amps) which is specific to that device • All loads are designed to use 124 volts • Not all loads are physically inside the station, but all are supplied by the same internal distribution network

10. MBSU/DDCU • Main Buss Switching Unit • Each support 2 channels of primary power • Power can be cross-strapped between channels if needed • Routes power through DDCUs to SPDAs • Direct current to Direct current Converter • Converts primary power (~160 dc) to secondary power (~124 dc)

11. SPDA/RPDA • Secondary Power Distribution Assembly • Multiple SPDAs per power channel • Routes power to RPDAs and multiple loads • Remote Power Distribution Assembly • Routes power to six loads Only difference between SPDA and RPDA is that RPDAs are always downstream of SPDAs

12. External EPS • PVA, BGA, SSU, ECU, BCDU, DCSU, PVCU, SARJ • Produces primary power from the solar arrays, and stores power in batteries for eclipse phase

13. BGA/PVA • Photovoltaic Array • Collects sunlight and converts it into electrical power • Two PV blankets composed 1 PVA • Beta Gimbal Assembly • BGA attached to a single set of PV Blankets • Controls rotation perpendicular to the main station truss

14. ECU/SSU • Sequential Shunt Unit • Shunts any excess power generated as heat • Regulates primary voltage to 160 volts • Electronic Control Unit • Controls BGA rotation, PVA deployment, SSU output voltage • Runs on secondary power from DDCU on IEA

15. IEA • Direct Current Switching Unit (DCSU) • Routes power from BGA to batteries, other EPS components, and MBSU • Direct current to Direct current Converter Unit (DDCU) • Provides Secondary power for BGA, ECU, PVA deployment motor, and PFCS.

16. IEA • Integrated Equipment Assembly • Contains EPS components for two power channels • Battery Charge Discharge Unit (BCDU) • Regulates charging or discharging of batteries, controlled by PVCU • Three per power channel • Batteries (BAT) • Batteries store power for use during the eclipse phase of the station’s orbit • Six per power channel

17. PVCU • Photovoltaic Control Unit • Controls all IEA components for a single channel, other than those controlled by ECU • Controls BCDUs, PFCS, DDCU, etc. • Runs on primary power from both power channels for redundancy • Controlled by PMCU on station

18. SARJ • Solar Alpha Rotary Joint • Rotates 4 channels of power at one time • Controls rotation parallel to the main station truss • Allows power and data to transfer

19. IEA Thermal control system • IEA has a self contained thermal control system for each channel • Small radiators under each IEA dissipate heat from the SSU as well as batteries and other IEA components • This system functions in the same manner as the main TCS for the station • Pump and Flow Control Subassembly (PFCS) and Photovoltaic Radiator (PVR)

20. Grounding • To prevent electricity from arcing across the station all electrical devices are grounded to the main truss. • Plasma Contractor Unit (PCU) • Emits a stream of plasma to ground the space station’s main truss to space • Prevents arcing to any external spacecraft during docking or EVA

21. Warning Signs of a SOBE • Red indicator light on the system wall • Loss of Power (I.e. lights or computer unexpectedly shut down) • Warning through HAL or other system • Contingency of another SOBE

22. Things to check during a SOBE • For maximum power the panels must be perpendicular to the sunlight, if misaligned they may not produce enough power • There are many points where power can be stopped, be sure to check them all