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, PhD Dr. Chris Foreman, PhD Revision D, 10/17/11

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 7

Charging Requirements Scooter 72 VDC, 40 Ah Batteries Power = 2.9 kW Charging station should be able to supply approximately 3 kW-h 375W-h over 8 hours 8

Charging Requirements (Cont.) Requirements Based on Solar Study (6 Panels) DC Rating: 1500W AC to DC De-rate Factor: 77% AC Rating: 1200W 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: 9

Charging Requirements (Cont.) Requirements Based on Solar Study (2 Panels) DC Rating: 500W AC to DC De-rate Factor: 77% AC Rating: 385W 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: 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, poly- crystalline, 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 W per panel. SP’s may be combined in series to increase voltage, or parallel to increase current. 14

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. 15

Solar Panel Technologies Alternative Energies (Danville, KY) Received (2) 230 W poly-crystalline panels via Conn Center. Panels built in-house at Alternative Energies. 230W Panel Specifications 60 cells (Enphase compatible) V max (1000W/m 2, 25°C, AM 1.5) = 29.7VDC I max (1000W/m 2, 25°C, AM 1.5) = 7.5A ~18% efficient ” (~3.25’) x 65.5” (~5.5’) 16

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 (16-50V) Modular & Expandable Lower Initial Cost Compensates for Shading Plug-and-Play Cables Available Remote 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 More efficient use of power (ie – only limited by building energy consumption) Requires a branch circuit No additional space required Off-grid Using Batteries 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 240VAC inverters? 24

Power Converter 25

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

Charging Station 27

Charging Station Provides 120 VAC Interface to Scooter Either NEMA 5-15R receptacle or NEMA 5-15P 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 Indicates whether panels are providing adequate energy or if energy is being provided from building 30

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

Next Steps Select Final Location for Charging Station Order Materials Build Station Test Final Product 32

Questions? 33