Solar Powered Charging Station MidTerm Presentation Design Team

Solar Powered Charging Station: Mid-Term Presentation Design Team: Ben Hemp Jahmai Turner Rob Wolf, PE Sponsors: Conn Center for Renewable Energy Dr. James Graham, Ph. D Dr. Chris Foreman, Ph. D Revision C, 10/16/11

Agenda • • • Background Information System Requirements Scooter Specification & Charging Requirements Block Diagram System Components Questions 2

Background Information • Design, fabricate, assemble and test of solar powered charging station for a plug-in electric scooter • Our Tasks: • Size and Specify Panels Supplied By the Conn Center • Research Various Technologies (panel, inverters, etc. ) • Work with Sponsors to Select Final Design Criteria 3

System Requirements 1) Solar Array: Converts solar energy into electrical energy • Perform solar study to determine what size array and panel technology will be required to charge the scooter in a normal workday in Louisville, KY 2) Inverter: Converts DC power into AC power • Determine inverter type (Centralized or Distributed) 4

System Requirements (cont. ) 3) Battery Bank Originally required to: • Store energy when scooter is charged or not plugged in • Charge scooter when panels are unable to provide enough energy 4) Grid-Tied System Alternate means of energy storage: • Scooter charged or not plugged in: Building consumes energy • Cloudy Day: Building assists in charging 5

System Requirements (cont. ) 5) Charging Station • Provides 120 VAC, 60 Hz interface to scooter 6) Instrumentation • Verify how much energy is generated by charging station and how much is consumed by scooter • Determines net load flow between charging station, scooter, and building 6

Electric Vehicle Specification • The test vehicle for the charging station will be a NOGAS Vintage pluggable electric motor scooter: • 50 MPH top speed/50 mile range • 72 VDC, 40 AH Lithium batteries • • • with Battery Management System (BMS) Regenerative braking Built-in charger 340 lb carrying capacity 120 VAC charging with 1 to 8 hr. max charge time Front and rear hydraulic disk brakes Hydraulic shocks front and rear

Charging Requirements • Scooter • 72 VDC, 40 Ah Batteries Power = 2. 9 k. W • Charging station should be able to supply approximately 3 k. W-h • 375 W-h over 8 hours 8

Charging Requirements (Cont. ) • Requirements Based on Solar Study (6 Panels) • DC Rating: 1500 W • AC to DC De-rate Factor: 77% • AC Rating: 1200 W • Average Solar Hours / Day: 2. 96 (December) & 4. 71 (Average for Year) • December 22, 1980: 3449 W • 1004 W from Noon to 1: 00 FROM: http: //rredc. nrel. gov/solar/calculators/PVWATTS/version 1/US/code/pvwattsv 1. cgi 9

Charging Requirements (Cont. ) • Requirements Based on Solar Study (2 Panels) • DC Rating: 500 W • AC to DC De-rate Factor: 77% • AC Rating: 385 W • Average Solar Hours / Day: 2. 96 (December) & 4. 71 (Average for Year) • December 22, 1980: 1150 W • 335 W from Noon to 1: 00 FROM: http: //rredc. nrel. gov/solar/calculators/PVWATTS/version 1/US/code/pvwattsv 1. cgi 10

Block Diagram 11

Charging Station Components • • • Solar Panels Inverter Building Connection Power Converter Charging Station Instrumentation 12

Solar Panel Technologies 13

Solar Panel Technologies • Solar Panels (SP’s) convert photons (light) into DC current. • Maximum efficiencies for most commercial SP’s is ~20%. • Three major types of PV technology: mono-crystalline, polycrystalline, and thin-films. These are listed in order from most to least efficient. • To create equivalent power, a lower efficiency SP needs more surface area than a higher efficiency SP. • Common output powers for large SP’s are 50 -300 W per panel. • SP’s may be combined in series to increase voltage, or parallel to increase current.

Solar Panel Technologies Mono-crystalline • Most efficient style (least surface area needed) • Best performance during low light and shading • Usually most expensive $/watt Poly-crystalline • Mid-grade efficiency • Tend to be less expensive than mono-crystalline for $/watt Thin-Film • Least efficient style • May be the least expensive, or similar to others for $/watt. • Styles capable of roll-up panel mats and artificial shingles.

Solar Panel Technologies Alternative Energies (Danville, KY) • Received (2) 230 W poly-crystalline panels via Conn Center. • Panels built in-house at Alternative Energies. 230 W Panel Specifications • 60 cells (Enphase compatible) • Vmax (1000 W/m 2, 25°C, AM 1. 5) = 29. 7 VDC • Imax (1000 W/m 2, 25°C, AM 1. 5) = 7. 5 A • ~18% efficient • 39. 375” (~3. 25’) x 65. 5” (~5. 5’)

Inverters 17

Inverters • Centralized versus Distributed • Grid-tied versus Off-grid • Off-grid means batteries required • Grid-tied: Requirements for net-metering • This project would be tied in W. S. Speed Hall building infrastructure (i. e. – solar panels will power building and charging station will power building) • Need instrumentation to compare power into building versus power supplied to charging station 18

Distributed Inverters / Microinverters 19

Centralized Inverters 20

Comparison of Inverter Technologies Microinverters • Operate at lower DC Voltages (16 -50 V) • Modular & Expandable • Lower Initial Cost • Compensates for Shading • Plug-and-Play Cables • Remote SCADA Interface Centralized Inverters • Operate at Higher DC Voltages (150+ V) • Not Easily Expanded • Higher Initial Cost • Lowest Output Panel is Weakest Link of System • Standard Wiring Methods • Typically Requires More Integration for SCADA 21

Energy Storage 22

What to Do with Excess Power? Grid-tied Off-grid Using Batteries • More efficient use of power (ie – only limited by building energy consumption) • Requires a branch circuit • No additional space required • Limited by Battery capacity • Only requires battery charger for regulation • Batteries need conditioned room, which will require additional building penetration for wiring • Maintenance Headache 23

Grid-tied System • Must comply with UL-1741 and IEEE-1547 Anti-Islanding standards • Loss of grid causes inverter to de-energize • This is a safety standard • Cost ~$1000 to run a 120 VAC circuit to charging station • How do we connect a 120 VAC circuit to our 240 VAC inverters? 24

Power Converter 25

Power Converter • 120 – 240 V transformer • 1500 VA • Cost ~$300 26

Charging Station 27

Charging Station • Provides 120 VAC Interface to Scooter • Either NEMA 5 -15 R receptacle or NEMA 5 -15 P cord-connected plug on a reel. 28

Instrumentation 29

Instrumentation • Smart meters with embedded web interface to allow user to connect from web browser at computer • Monitor power flow to scooter and power flow from inverters • Difference in power consumed or provided from building 30

Current Status • System has been designed and waiting for sponsor approval • Ready to order components and build 31

Next Steps • Order Materials • Build Station • Test Final Product 32

Questions? 33