Solar-Powered Boat

California Solar Regatta 2022

Team Name: Applied Engineering

Institution: Arcadia High School

Project Duration: April-June 2023

Role Roject Description: Sized propellor for and helped program motor controller for our boat

Team achievements: Placed 3rd overall at the California Solar Regatta 2022

Competition Results

The California Solar Regatta races built-from-scratch solar powered boats. Boats are judged on the below 3 races, design, and a technical presentation.

Placed 3rd overall (out of 10 schools).

Sprint Race (100 yards dash, solar)

Sprint 1: 1:04 min
Sprint 2: 0:59.3 secs

Endurance (Boats take as many laps around 200 yd track in 25 min, battery):

8.75 laps

Slalom Race (Boats manuever around bouys for 150 yards round trip, solar)

2:38 min

Drone footage of our boat on competition day

Technical presentation (From our team's instagram)

My Role

Team secretary 2020-2021
- Sent forms to apply to the competition
- Filed paperwork to keep our nonprofit going
- Helped advertise our team and interview/recruit new members
Electrical team member, technical details below
- Selected propellor and motor combination to optimize boat speed
- Programmed maximum power point tracking (MPPT) algorithm for running off solar
- Presented for the electrical team during technical presentation at competition

2022: Propellor Thrust Test

Goal: Measure propellor thrust to validate calculations (see "choosing a propellor")

Method:

Put the motor on a scale. Stick propellor in pool and turn on the motor. Then measure weight "lost" on scale to see upward thrust

Results:

Couldn't get a good reading on the scale and it was hard to hold the propellor in such a way to not fall in the water/put external force on the scale. It was also very hard to gather people to bring everything to the pool several meetings in a row.

In the future I would design a better mechanical setup for the test, and recruit more help from mechanical team members since things like thrust are probably more up their alley.

Testing propellor thrust in a pool

2021: Choosing a propellor

Goal: Pick one out of the two available propellors to optimize our boat for all 3 races, or determine if it was necessary to purchase a new propellor

Method:

Calculated effect of propellor, boat drag, and power supply conditions on boat speed
Created a spreadsheet to test different combinations of battery/solar panel/propellor conditions
Converted spreadsheet to the calculator below
Used the below calculator + consideration of the materials we already had to choose the following operating point:
- Motor: MANTA DC Brushed Motor (one of the motors we already had)
- Battery: 24V LiPo pack (welded by another team member)
- Propellor: Radius 5.5 in, pitch 13 in (one of two propellors we already had)
- Expected boat speed: 9 m/s battery, 6 m/s solar

Results: Using the above operating point, boat traveled about one fourth the expected speed. I likely simplified the propellor drag calculations too much. Still, the boat traveled fast enough for us to be competitive. This was a big improvement over the previous year where the operating point was so far out of range the boat could barely move.

Also, during the battery endurance race, we didn't calculate use the battery very well. We drove the boat way too slowly and ended the race with over half of the battery capacity left.

Top layer of my tachometer board

2021: Motor RPM measurement

Goal: Measure RPM of our brushed DC motor

Method:

Build a light-based tachometer using an online design as inspiration
- Designed and fabricated board with the help of team leads, but ended up frying the LM358 by misconnecting things. Due to slow shipping of materials over COVID, decided to try something simpler instead.
Stick a magnet on the shaft and measure RPM with a hall sensor
- Wrote a simple Arduino script to count the number of magnets sensed within a given period of time, and then convert to RPM
- Test of measured vs actual RPM showed this method was inaccurate at high RPMs (See below image)

Result: Decided not to include RPM sensor on boat, and refer to datasheet for RPM at various torques instead of manual testing

Testing my hall sensor RPM calculator by waving a magnet in front of it to the beat of a metronome (that way, I could see the difference between expected and measured RPM). As RPM increased this method of measuring became too inaccurate to use.

2020: MPPT (Maximum Power Point Tracking) First Implementation

Goal: Get motor to spin fast on solar

Method:

Change duty cycle of PWM signal to help motor draw optimal amount of power from controller based on amount of sunlight
- Measure change in power compared to previous measurement. If power increased, keep pushing the duty cycle in the same direction it was before. Otherwise, push duty cycle in the opposite direction

Result: Motor ran off solar panels without getting stuck at 100% or 0% duty cycle. Passed onto software team for refinement.

Testing MPPT in full sunlight

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