Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Reexamination Certificate
1997-04-23
2001-04-17
Robinson, Ellis (Department: 1772)
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
C136S291000, C136S292000, C136S245000, C244S173300, C323S906000
Reexamination Certificate
active
06218605
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to optimizing power output of satellite solar arrays and more particularly relates to a method and apparatus to optimize solar array performance with passive diode switching of different states of a satellite mission.
BACKGROUND OF THE INVENTION
Satellites are usually launched with their solar arrays stowed against the spacecraft sidewalls to fit within the launch vehicle. In this configuration, most of the power from the solar array is not available because there is no exposure to the sun. However, usually an outboard portion of the solar array is stored so that it's outward facing end produces some power from whatever sunlight reaches it during the initial phase, also known as “transfer orbit” (i.e., transfer from the as-launched orbit to the preferred mission orbit).
Solar arrays on satellites generally have three phases of operation. The first phase is the stowed configuration, in which the solar panels of the array are folded, concealed and compacted into a small area that accommodates fitting the satellite into the launch vehicle's cargo space. For maneuvering purposes, the solar panels are maintained in a stowed position until the satellite is properly placed in its final orbit. The time between launch of the satellite and it reaching its final orbit is generally referred to as “transfer orbit.” The second phase of operation is deployment of the solar panels once the satellite is comfortably situated in it's destination orbit. The last and third phase constitutes the deployed panels at the end of the satellite's useful life.
Typically, the size of solar arrays are designed for their end-of-life (EOL) voltage and power requirements to meet the minimum voltage and power requirements of the satellite's electrical operation bus. That is, the maximum EOL power output of the solar array should meet the minimum power requirements of the satellite's electrical operation bus. The present method of meeting this EOL requirement necessarily means some degree of over-design at the BOL (beginning-of-life). Therefore, to provide sufficient EOL voltage the design will produce as much as twenty-five percent (25%) excessive voltage output at the BOL. Since standard satellite power regulation electronics operate at a constant voltage, the excessive voltage differential is wasted during BOL operation.
Solar cells are also temperature dependent devices and their running temperature depends on satellite orbit location and solar array geometry. At EOL, a deployed solar array operates at about 50° C. which goes into the design analysis to meet the satellite minimum voltage requirement. Thus, during transfer orbit with the solar array not yet deployed and held tightly against the spinning satellite, as described above (typical stowed configuration) the solar array operates at about −20° C. This 70° C. temperature difference (−20° C. to +50° C.) further exacerbates the voltage differential noted above. The BOL voltage can be as much as sixty percent (60%) above the constant operating voltage required. This effectively amplifies the mismatch between the satellite constant voltage required and the voltage supplied leaving as much as a third or more of the voltage that cannot be traversed.
Therefore, one object of the present invention is to optimize solar array performance throughout the life of a satellite mission.
Another object of the present invention is to optimize solar array performance so as to provide maximum power output that matches the satellite's operation bus voltage during transfer orbit operation.
An object is also to optimize solar array power performance by selectively isolating non-contributing sections of a solar array to maintain the maximum power output of the stowed, BOL solar array.
A solar array power output is optimized as another object of the present invention by isolating a subsection of the solar array during transfer orbit operation and then connecting the subsection in series with another section to provide maximum power output that matches the power of the satellite operating bus at deployed EOL.
The solar array power output is optimized by connecting a subsection of the solar array through a switching device that automatically connects the subsection to the full array upon deployment of the solar panel of a satellite. Preferably, the switching devices are passive elements such as bypass diodes connecting sections of a solar array to the satellite's operating bus.
BRIEF DESCRIPTION OF THE INVENTION
The purpose of the present invention is to provide a method and apparatus to optimize the performance and power output of solar arrays on panels through all phases of the satellite mission from launch transfer orbit and final destination orbit of a satellite.
The solar arrays, on the solar panels of a satellite, produce power commensurate with the three phases of operation described hereinabove as transfer orbit operation, deployed operation at BOL and deployed operation at EOL. The power produced during transfer orbit is severely restricted due to the limited area exposed to the sun. Only the outermost panels will be exposed to the sun, while the other panels that are stowed are hidden from the sun (shaded by the outermost panels). Furthermore, the exposed solar panel is generally not normal to the sun and experiences a cosine angle related loss of power. Further, the satellite is often spinning during transfer orbit, which further reduces the power output from the solar array (called a one-over Pi loss). The satellite is usually maneuvering itself into its destination orbit during this transfer period, which generally precludes the outermost solar panel from tracking the sun.
During the second phase, the satellite is now in its final destination orbit, and the solar panels are fully deployed and tracking the sun so they produce maximum solar array power. In nearly all cases, the power produced in this phase is excessive and only a portion of the array's power is gathered. The deployment stage is often referred to as “beginning of-life” (BOL) stage.
The third phase, or “end-of-life” (EOL) stage is the stage at which the solar arrays have been degraded in power as the result of their useful operation in the space environment due to radiation. Generally, the solar arrays are sized such that the EOL power is just enough to power the satellite's load requirements. This power is generally equivalent to the partially utilized power in the BOL stage.
Critical factors in the analysis of power are the operating voltage of the satellite and the maximum power voltage of the solar arrays. Generally, the solar arrays are designed to have an EOL maximum power voltage that matches the satellite's operating bus voltage. The EOL maximum power voltage of the solar array is a function of the solar cells'maximum power voltage, the degradation factors associated with the satellite orbit and the EOL phase, the operating temperature of the solar cells at EOL and thus, the number of solar cells in series. A problem that is often encountered is that the solar arrays' BOL maximum power voltage is much higher than the satellite's bus voltage due to the non-degradation state of the solar. Cells and due to the more efficient cold operating temperature of the solar arrays (caused by spinning and off angle cosine).
A solution to this problem is to isolate sections of the solar array and then bring them on-line or switch them into the circuit when they are needed to maintain the maximum power output matching the operating bus voltage of the satellite. Thus, by using switching devices, a subsection of a solar array can be kept in the circuit to provide maximum power voltage that matches the satellite's operating bus voltage through all phases of operation. This solution involves populating the solar panels of a solar array with the number of solar cells needed to maintain the maximum power output at the operating voltage of the satellite's operating bus, and co
Dally Robert B.
Jones P. Alan
Lyon & Lyon LLP
Miggins Michael C
Robinson Ellis
LandOfFree
Performance optimizing system for a satellite solar array does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Performance optimizing system for a satellite solar array, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Performance optimizing system for a satellite solar array will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2483914