Tethys Tower Off-Grid Rainwater Distribution System P roject T eam M - PowerPoint PPT Presentation

Tethys Tower Off-Grid Rainwater Distribution System P roject T eam M embers : J ason H elle & Q uae A twood

BACKGROUND • CORDATA COMMUNITY GARDEN LOCATED AT THE NORTH END OF CORDATA PARKWAY IN BELLINGHAM, WA • FOUNDED IN 2008 • 14,500 SQ. FT. LAND PLOT WITH 50, 4’ X 16’ RAISED-BED GARDEN PLOTS • HOSTED BY CORDATA NEIGHBORHOOD ASSOCIATION • GROW LOCAL, ORGANIC FRUITS AND VEGETABLES FOR SURROUNDING COMMUNITY AND LOCAL FOOD BANKS

PROBLEM STATEMENT The utility cost and environmental footprint of the Cordata Community Garden is too high. An alternative source of cheaper water that also promotes the utilization of sustainable and renewable resources is desirable.

CONCEPT SELECTION: Gravity-Fed Drip Irrigation

CONCEPT SELECTION • Components • 100W Monocrystalline PV Array mounted in ATaL configuration • MCU (see next slide) • 2,500 gallon Polyethylene (PE) water tank • Net Positive Suction Head Available = 30.5 ft. at minimum water level (static head = 2in.) • Polyethylene piping → absolute roughness 5 E-6 ft. • 15 ft. head loss due to friction per 100 ft. length • BLDC DC50B-12100 pump • Max head 30 ft. (limited to 93% total output) • 54W at 4.5A • 5 ft. high 30 gal. drum • Adjustable drip emitters

Electrical Hardware: MPPT and Pump Control System ● Application-specific electronic system PV ○ MPPT via synchronous buck-converter ○ Pump dry-run and fault protection ○ Basin overflow protection Indicator LEDs ○ LED indication of error states and critical water level conditions ○ Power and water throughput logging onto Float external memory card Pump Switches ● Low power electronic float switches

Development Tools: Software Dev. Tools: Simulation: • • IDE: Kinetis Design Studio Multisim • Rev. Control: EGit • Datalogging Verification: MATLAB Debug Tools: • FRDM-KV10Z Dev. Board • P&E Micro USB Multilink Universal • Tektronix MDO3024 Mixed O-scope • Keithley DC 2231A Power Supply

MCU Resources MKV10Z128VLF7 • • 75MHz bus frequency 24 ADC Channels (3 used) • • 16MB SRAM (>4MB) 1 SPI Module (1 used) • • 128MB Total Flash (>30MB) 40 GPIO (9 used) • 4 DMA Channels (3 used) • 20 16-bit PWM Channels (1 external, 2 internal used)

Kernel uC/OS-III • Preemptive task scheduler implements priority and minimizes CPU load • Implements software timers, message queues, semaphores and more • Contains performance metrics (i.e. CPU load measurements)

Tasks and ISRs ADC0IRQ_Handler - Controls the SMPS by reading the signaled 12-5V bus voltage value and setting the PWM value appropriately, considering the desired voltage value. • Execution period: 400us • Execution time: <50us (CPU Load: 12.5%) DMA0IRQ_Handler - Signals to DataAcqTask that ADC data is ready for processing. • Execution period: 100ms • Execution time: <5us (CPU Load: 0.005%)

Tasks and ISRs Cont’d DataAcqTask - Processes sample tables filled by the DMA with CMSIS functions and produces global voltage, current and power values for use in MPPT and for logging purposes. (Priority: 0) • Execution period: 100ms • Execution time: <5ms (CPU load: 5%) MPPTTask - Implements MPPT algorithm by reading the acquired voltage and current values and updates the desired voltage value appropriately. (Priority: 1) • Execution period: 100ms • Execution time: <100us (CPU load: 0.1%)

Tasks and ISRs Cont’d DispTask - Applies the appropriate values to the LED display to indicate error states. (Priority: 2) • Execution period: >500ms • Execution time: <10us (CPU load: 0.002%) DataLogTask - Writes the average voltage, current and power values for the hour to the memory card via SPI. (Priority: 3) • Execution period: 1 hour • Execution time: <10ms (CPU load: ~0%)

Tasks and ISRs Cont’d PTD6IRQ_Handler and PTD7IRQ_Handler - These ISRs control the pump, turning off the pump either when the holding tank is empty or when the elevated basin is full. • Minimum time between execution: 10s • Execution time: <10us (CPU load: ~0%) Total CPU load: ~17.6%

Modules Module Details Pre-written main.c Init. Functions: AppStartTask(), main() no Control.c Init. Functions: FTMInit() no Recurring Functions: MPPTTask(), PTD6IRQ_Handler(), PTD7IRQ_Handler(), ADC0IRQ_Handler() Public Variables: ErrState Data.c Init. Functions: ADCInit(), DataInit() no Recurring Functions: DataAcqTask(), DMA0IRQ_Handler(), DataLogTask() Public Variables: PwrData Disp.c Init. Functions: LEDInit() no Recurring Functions: DispTask() CMSIS DSP arm_mult_q15(), arm_rms_q15() yes Library

Testing/Verification Plan 1. Display LEDs. 2. Data acquisition. a. ADC and DMA interfacing b. Flow control c. Table filling and emptying 3. SMPS MPPT implementation. a. Variable load, fixed input b. Variable load and input 4. Shutoff conditions (i.e. float switch interface) 5. Data logging

QUESTIONS?