Power Systems Design -II Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems or EPS Power Systems Design II 2 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II 3 Introduction to Space Systems and Spacecraft Design Space Systems Design

Look at the parts of the EPS Power Systems Design II Look at the parts of the EPS 4 Introduction to Space Systems and Spacecraft Design Space Systems Design

Take Solar Panel Power Systems Design II 5 Introduction to Space Systems and Spacecraft Design Space Systems Design

5. 6. 1350 Power Systems Design II 6 Introduction to Space Systems and Spacecraft Design Space Systems Design

What do we need from the solar panel? Power Systems Design II What do we need from the solar panel? What are the attributes of a solar panel? Total output power of solar panel. Voltage of solar panel. Maximum packing factor. Efficiency of the solar cells. Operating temperature of the panels. Lets go back and look at the solar cell. 7 Introduction to Space Systems and Spacecraft Design Space Systems Design

Lets go back and look at the solar cell. Power Systems Design II Lets go back and look at the solar cell. This dual junction cell Has an efficiency of ~ 22% Open circuit voltage ~ 2.2v Size – 76 x 37 mm 8 Introduction to Space Systems and Spacecraft Design Space Systems Design

Solar cell has an I-V curve like this Power Systems Design II Solar cell has an I-V curve like this This dual junction cell Has an efficiency of ~ 22% Open circuit voltage ~ 2.2v Size – 76 x 37 mm 9 Introduction to Space Systems and Spacecraft Design Space Systems Design

Looked at the solar cell. Power Systems Design II Looked at the solar cell. This dual junction cell Has an efficiency of ~ 22% Open circuit voltage ~ 2.2v Size – 76 x 37 mm What are the attributes of a solar panel? Total output power of solar panel. Voltage of solar panel. Maximum packing factor. Efficiency of the solar cells. Operating temperature of the panels. 10 Introduction to Space Systems and Spacecraft Design Space Systems Design

Need to select a battery to design for solar panel voltage Power Systems Design II Need to select a battery to design for solar panel voltage What are the attributes of a solar panel? Total output power of solar panel. Voltage of solar panel. Maximum packing factor. Efficiency of the solar cells. Operating temperature of the panels. 11 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II Rechargeable 12 Introduction to Space Systems and Spacecraft Design Space Systems Design

Use a lithium ion battery Power Systems Design II Use a lithium ion battery Li Ion batteries = 3.6 v nominal Design Criteria for charging Li Ion battery: Need 10-15% more voltage to charge than the nominal voltage. Here we would need solar panel voltage of ~ 4.0 – 4.2v to charge this battery. Design Criteria solar panel: Number of cells = Max voltage/cell voltage. Take minimum number of whole cells. # cells = (4.2v/string)/(2.2v/cell) = 1.9 or 2 cell for a string voltage of 4.4v 13 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II 14 Introduction to Space Systems and Spacecraft Design Space Systems Design

Use two lithium ion batteries Power Systems Design II Use two lithium ion batteries Li Ion batteries = 7.2 v nominal Design Criteria for charging Li Ion battery: Need 10-15% more voltage to charge than the nominal voltage. Here we would need solar panel voltage of ~ 8.0 – 8.3v to charge this battery. Design Criteria solar panel: Number of cells = Max voltage/cell voltage. Take minimum number of whole cells. # cells = (8.3v/string)/(2.2v/cell) = 3.77 or 4 cell for a string voltage of 8.8v Lets be conservative and use 5 cells for 11v. 15 Introduction to Space Systems and Spacecraft Design Space Systems Design

Now we have: Two Li Ion batteries = 7.2 v nominal Power Systems Design II Now we have: Two Li Ion batteries = 7.2 v nominal 5 cells for 11v to charge with. 16 Introduction to Space Systems and Spacecraft Design Space Systems Design

What is packing factor? What are the attributes of a solar panel? Power Systems Design II What is packing factor? What are the attributes of a solar panel? Total output power of solar panel. Voltage of solar panel. Maximum packing factor. Efficiency of the solar cells. Operating temperature of the panels. Got Got 17 Introduction to Space Systems and Spacecraft Design Space Systems Design

Packing Factor Packing Factor = Total Cell Area/ Total Panel Area Power Systems Design II Packing Factor Total Cell Area Total Panel Area Packing Factor = Total Cell Area/ Total Panel Area 18 Introduction to Space Systems and Spacecraft Design Space Systems Design

Cell type 2 Fixed solar panel size Cell type 3 Power Systems Design II Packing Factor Cell type 1 Cell type 2 Fixed solar panel size Cell type 3 What do you do if given a fixed size panel on which to put solar cells and you have these different size solar cells? 19 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II Packing Factor What do you do if given a fixed size panel on which to put solar cells and you have these different size solar cells? 20 Introduction to Space Systems and Spacecraft Design Space Systems Design

How do you mount these 5 cells on this panel? Power Systems Design II 11v Now we have: 5 cells for 11v where the string has all of the cells hooked in series Total Panel Area How do you mount these 5 cells on this panel? 21 Introduction to Space Systems and Spacecraft Design Space Systems Design

OK! NO! How do you mount these 5 cells on this panel? Power Systems Design II How do you mount these 5 cells on this panel? OK! NO! Visually we can see a very poor packing factor. 22 Introduction to Space Systems and Spacecraft Design Space Systems Design

Oh Oh! What if the cells were bigger? Power Systems Design II What if the cells were bigger? Oh Oh! Now you have only 4.4v in the string. 23 Introduction to Space Systems and Spacecraft Design Space Systems Design

Got a cube? Put other cells on another face? Power Systems Design II Got a cube? Put other cells on another face? Can’t do. All cells for a single string must be on same face. 24 Introduction to Space Systems and Spacecraft Design Space Systems Design

Where are we now in the solar panel design? Power Systems Design II Where are we now in the solar panel design? What are the attributes of a solar panel? Total output power of solar panel. Voltage of solar panel. Maximum packing factor. Efficiency of the solar cells. Operating temperature of the panels. Got Not got, but understand Got Assume we could mount the 5 cells on a panel, what is total power for the cells selected? 25 Introduction to Space Systems and Spacecraft Design Space Systems Design

How much power from these cells? Power Systems Design II How much power from these cells? 5 cells for 11v One cell area = 76 x 37 mm = 2812 mm^2 Total cell area = 8*2812 = 22496 mm^2 = 2.25 x10-2 m^2 We have 1350 watts/m^2 from the sun in space Direct power = (1350 w/m^2) x (2.25 x10-2 m^2) = 34.4 watts Converted power = direct power x cell efficiency = 34.4 w x 0.22 eff = 7.5 watts 11v For this dual junction cell Has an efficiency of ~ 22% Open circuit voltage ~ 2.2v Size – 76 x 37 mm 26 Introduction to Space Systems and Spacecraft Design Space Systems Design

Where are we now in the solar panel design? Power Systems Design II Where are we now in the solar panel design? What are the attributes of a solar panel? Total output power of solar panel. Voltage of solar panel. Maximum packing factor. Efficiency of the solar cells. Operating temperature of the panels. Got Got Not got, but understand Got Now we can assume to start: panel is at 90 degrees with sun – max power operating temperature 20 degrees.. Centigrade – 22% eff Don’t forget, temperature counts a lot. 27 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II Start here Tuesday for Idaho 28 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II Now that we have beat our way through the solar panel design ----- lets go look at the some more parts of the EPS. 29 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems or EPS What is this? Power Systems Design II 30 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems or EPS Back bias diode Panel 1 Power Systems Design II Power Systems or EPS Back bias diode When panel 1 is shaded, the back bias diode keeps the current from flowing backwards through panel 1, when panel 2 is generating a voltage across it. Panel 1 Panel 2 31 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems or EPS What is this? R V Power Systems Design II 32 Measure current by measuring voltage across a low resistance precision resistor 32 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems or EPS Power Systems Design II 33 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems or EPS Power Systems Design II 34 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II 35 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II 36 Introduction to Space Systems and Spacecraft Design Space Systems Design

Expanded subsystem control Power Systems Design II Expanded subsystem control 37 Introduction to Space Systems and Spacecraft Design Space Systems Design

Expanded subsystem control Power Systems Design II Expanded subsystem control 38 Introduction to Space Systems and Spacecraft Design Space Systems Design

What does a charge regulator do? Power Systems Design II What does a charge regulator do? Controls voltage from PV to battery Controls rate of charge Prevents overcharging Can “boost” or “buck” PV voltage to match battery needs. 39 Introduction to Space Systems and Spacecraft Design Space Systems Design

Expanded subsystem control Power Systems Design II Expanded subsystem control 40 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II Consider: When high current occurs in a subsystem, it could be from latch-up. What to do? Cycle power. Where do you do this – hardware controlled in the EPS. 41 Introduction to Space Systems and Spacecraft Design Space Systems Design

Consider the satellite’s attitude control for solar power generation. Power Systems Design II Consider the satellite’s attitude control for solar power generation. 42 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II Satellite Orbit Parallel Sun Rays Eclipse Sun Earth 43 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II Gravity Gradient Stabilized Introduction to Space Systems and Spacecraft Design Space Systems Design

N Power Systems Design II Passive Magnetic Stabilized S N S N S N S N 45 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II Inertially Stabilized 46 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II 47 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II 48 Introduction to Space Systems and Spacecraft Design Space Systems Design

Some Solar Notes Power from sun in orbit ~ 1350 watts/meter2 Power Systems Design II Some Solar Notes Power from sun in orbit ~ 1350 watts/meter2 Power from cells on ground ~ 35% less than in space Can get some power form albedo – earth shine ~ 35% 49 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II 50 Introduction to Space Systems and Spacecraft Design Space Systems Design

Power Systems Design II Need to consider the power requirements of all of the subsystems and when they are used to build a power budget. 51 Introduction to Space Systems and Spacecraft Design Space Systems Design

Questions? Power Systems Design II 52 Introduction to Space Systems and Spacecraft Design Space Systems Design