Power Selection process
Table of Contents
Solar Power System Selection process
Solar Power Functional Decomposition
The functional decomposition of the solar power system is shown below.
Solar Panels Benchmark
From benchmarking, the options for solar panels has been narrowed down to two solar panels shown below. They are the highest power solar panel that fits the size and weight constraints of our system. They are both designed for RVs and boats so they are built to be rugged. Options for structural supports and mounting will need to be looked at to determine which solar panel is the better choice.
Solar Panel Options
MPPT Controller and Battery Charger Benchmark
It was decided to use an off the shelf controller for ease of design and to reduce room for errors. The senior design team, P12408 used the GV-5-Li-12.5V, 5 AMP in their design. This MPPT or the equivalent version that is rated for higher will be used. Using the higher power (120W) MPPT would allow for room to add more solar panels in parallel if more power was needed for the design in the future.
MPPT Controller and Battery Charger Options
A link to the full document can be found here: Systems Level Design Documents/Solar/Solar Power Benchmarking.xlsx
Feasibility: Prototyping, Analysis, Simulation
Power NeededPreliminary power estimates for each system indicate that around 17.7W of power will be used during normal operation. A sleep mode will be used for all the systems on the platform overnight when no sunlight is available. Not enough is known about the power that will be needed in sleep mode yet. This will be examined further during the next phase of MSD.
Solar Panel Output PowerIn March-April, when the balloon will be launched, there is approximately 12-13 hours of daylight and 11-12 hours of darkness. The batteries will need to support the power needs during the dark time.
If a 30W solar panels is not sufficient for the burst balloon, not rechargeable batteries can be used. This is also an option if we exceed our max weight. Since the burst balloon flight is only approximately 3 hours, it is not needed to recharge the batteries during this launch.
If a 30W solar panels is not sufficient for the lab test and zero pressure balloon, a second solar panel could be added in parallel to produce twice the power if the chosen MPPT is capable of this power input.
Battery Capacity NeededCalculations were done in MathCAD so that they are easily update-able as we have a better power needed estimate. The batteries will need to be sized to sustain the power for the system overnight. A sample calculation is shown below
Some potential batteries have been benchmarked but the final batteries to be used will be selected after sleep mode power consumption is finalized.
Morphological Chart and Concept Selection
A link to the full document can be found here: Systems Level Design Documents/Solar/Solar Morphological Chart.xlsx
Two previous projects that designed similar solar power systems for high altitude balloon platforms were researched. The previous senior design team P12408 is very similar to the application needed for this project. Their system was not capable of the power needed for the project though. MPPTs from the same company they used will be used for this design as well as similar battery packs. The Fox-1 MPPT was also researched but is far too complex for the needed application.
Solar Power Concept Selection
Solar Power Pugh Chart
A link to the full document can be found here: Systems Level Design Documents/Solar/Solar Concept Selection.xlsx
Designs and Flowcharts
In the next phase of development, the functionality of the microcontroller will be examined further to determine if a separate microcontroller is needed for the solar power system or if the Master board can handle the solar power system's needs.