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 (1-4 A/B) –Each channel supplies 100 amps of current

8. Internal EPS Loads, RPDA, SPDA, DDCU, MBSU, ICC 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 Not all loads are physically inside the station, but all are supplied by the same internal distribution network

10. SPDA/RPDA/DDCU Secondary Power Distribution Assembly –Supports a single channel of power A is even channel B is odd channel –Routes power to one RPDA and six loads Remote Power Distribution Assembly –Routes power to six loads Direct current to Direct current Converter Unit –This is the unit that converts primary power (~160 V dc) to secondary power (~124 V dc)

11. MBSU/ICC Main Buss Switching Unit –Each support 2 channels of power with a total of 200 amps –Routes power to two SPDAs Interconnecting Cables –Create a bridge for two or more MBSUs to share power across them

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

13. SARJ Solar Alpha Rotary Joint Rotates 4 channels of power at one time –Controls rotation parallel to the main station truss

14. IEA Integrated Equipment Assembly Battery Charge Discharge Unit (BCDU) –When signaled by the ECU the BCDU begins charging or discharging the batteries Batteries (BAT) –Batteries store power for use during the eclipse phase of the station’s orbit

15. IEA (continued) Direct Current Switching Unit (DCSU) –Routes power from BGA to batteries, IEA, and Internal system Direct current to Direct current Converter Unit (DDCU) –Provides Secondary power for all components.

16. 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)

17. ECU/SSU Electronic Control Unit –Manages when to charge and discharge the batteries Sequential Shunt Unit –Shunts any excess power generated as heat –Small radiator beneath each PVA radiates heat

18. 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

19. BGA/PVA Beta Gimbal Assembly –Rotates one channel of power per BGA –Controls rotation perpendicular to the main station truss Photovoltaic Array –Collects sunlight and converts it into electrical power

20. 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

21. 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 were power can be stopped, be sure to check them all