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 E, 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 to be supplied by the Conn Center • Research various technologies for component selection • 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 vs. 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 • Monitor 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. All have similar life expectancies. • 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 • 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 is Net Metering? • Renewable energy generated is compared to the energy consumed from the power grid. • Energy flowing from Utility means not enough renewable generation • Energy flow to Utility means excess renewable generation • Our system is much too small to flow into Utility, however, net metering will be used to indicate whether the system is generating enough to charge scooter and to offset building energy usage. • NOTE: LGE-KU does not purchase power, rather offers credits when onsite generation is in excess of facility usage. 23

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 24

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? 25

Power Converter 26

Power Converter • 120 – 240 V transformer • 1500 VA • Cost ~$300 27

Charging Station 28

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. 29

Instrumentation 30

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 31

Current Status • System has been designed and waiting for sponsor approval • Ready to order components and build 32

Next Steps • • Select Final Location for Charging Station Order Materials Build Station Test Final Product 33

Questions? 34