Solar Powered Charging Station: Final Presentation

1. Solar Powered Charging Station:Final Presentation Design Team: Ben Hemp Jahmai Turner Rob Wolf, PE Sponsors: Conn Center for Renewable Energy Dr. James Graham, PhD Dr. Chris Foreman, PhD Revision A, 11/27/11

2. Agenda • Project Overview • System Requirements • Detailed Design • Trade Studies and Research • Test Results

3. Project Overview Original System Goals • Charge an electric vehicle (EV) from a charging station using 110 VAC, 60 Hz, 1ø as the charging source • Use power created by solar panels (SP’s) for the EV charging • For periods when an EV is not plugged into the charging station, store energy created by SP’s into a battery bank • If the battery bank is depleted, use grid-tied energy to make the charging times more predictable • Use instrumentation to detail the detail energy created by charging station and energy used by electrical grid • This semester’s team is expected to design the complete system, but is only expected to implement the solar charging aspect due to planning with subcontractors

4. Project Overview The Test Subject • Manufactured by NoGas LLC in Nashville, TN • 50 MPH top speed/50 mile range • 72 VDC, 40 AH Lithium batteries with Battery Management System (BMS) • Regenerative braking • Built-in charger • 340 lbcarrying capacity • 120 VAC charging with 1 to 8 hr. max charge time • Front and rear hydraulic disk brakes • Hydraulic shocks front and rear

5. System Requirements

6. System Requirements First Requirement- Solar Array • A solar array of multiple SP’s for solar charging • A solar study should be conducted to determine the number and size of SP’s needed to charge the scooter • Solar study determined seven solar panels are needed to reach 3.5 kW/day for worst case month • Conn Center funded two panels by vendor of choice • Decisions regarding fabrication technology and make/buy • Funded SP’s are poly-crystalline • Mounting location and attachment techniques must be determined (W.S. building, build structure, etc.) • “Cart-style” structure chosen for mobility

7. System Requirements Alternative Energies (Danville, KY) • Received two 230W poly-crystalline panels from the Conn Center • Alternative Energies fabricates the panels • A preferred vendor 230 W Panel Specifications • Each panel has 60 cells • Vmax (1000W/m2, 25°C, AM 1.5) = 29.7 VDC • Imax (1000W/m2, 25°C, AM 1.5) = 7.5A • ~18% efficient • Size = 39.375” (~3.25’) x 65.5” (~5.5’) • ~ 2.0 yards2or 1.9 m2

8. System Requirements

9. System Requirements Second Requirement- Inverter • Component is needed to convert DC power from SP’s to AC power for charging station • Determine between distributed vs. centralized • Distributed chosen due to: • Work at low DC voltages (150+ VDC at input required for most centralized inverters). Shut off at ~16 VDC. • Higher efficiency (compensates for shading, independent panel operation) • Expandability, can add a panel and inverter at a time. Centralized inverters are not flexible with expandibility. • Greater safety (low DC voltages) • Choose an inverter capable of supporting off-grid battery bank and future grid-tie • Distributed inverters must be grid-tied to function • Grid-tie circuit must be implemented this semester • Battery banks are not compatible with distributed inverters

10. System Requirements Enphase M215 Distributed Inverter • Maximum input power: 260W • Output power: 215W • DC operation range: 16V – 36V • Maximum modules for 240VAC 20A branch circuit: 17 • Inverters operate independently • Low-voltage operation • 96% efficiency • Works with 60-cell SP’s • Plug-and-play cabling • No high voltage DC wiring

11. System Requirements

12. System Requirements Third Requirement– Charging Station • Charging Station provides interface to EV • 120 VAC receptacle and long cord is provided • Provides instrumentation for system requirements • All instrumentation located in enclosure with clear door

14. System Requirements Fourth Requirement– Transformer • Converts 120 VAC, 1ɸ from W.S. Speed grid to the 240 VAC, 1ɸ required for the M215 distributed to be grid-tied • 2kVA power rating

15. System Requirements Fifth Requirement– Gateway

16. System Requirements Sixth Requirement – Energy Meters • Two Eaton IQ150 energy meters. Takes measurements from two of 3 braches of the circuit. • Capable of measuring: • Voltage • Amperage • kW • kVAR • Frequency • Gathered information is sent to Gateway via RS-485

17. System Requirements Seventh Requirement – Current Transformers (CT’s) • Measure current at specific branches in the circuit • Wires are wrapped once around the CT’s. CT’s measure the inside magnetic field. • Ratio used to compare current through the CT (branch circuit) vs. current output to the energy meters

18. Detailed Design Seventh Requirement – Current Transformers (CT’s) • Measure current at specific branches in the circuit • Wires are wrapped once around the CT’s. CT’s measure the inside magnetic field. • Ratio used to compare current through the CT (branch circuit) vs. current output to the energy meters

19. Questions?