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Solar Powered Charging Station: Mid-Term Presentation. Sponsors: Conn Center for Renewable Energy Dr. James Graham, PhD Dr. Chris Foreman, PhD. Design Team: Ben Hemp Jahmai Turner Rob Wolf, PE. Revision A, 10/3/11. Background.
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Solar Powered Charging Station:Mid-Term Presentation Sponsors: Conn Center for Renewable Energy Dr. James Graham, PhD Dr. Chris Foreman, PhD Design Team: Ben Hemp Jahmai Turner Rob Wolf, PE Revision A, 10/3/11
Background • The design, fabrication, assembly and integration / testing of a solar powered charging station • 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
Solar Data for Louisville, KY Source: PVWatts
Electric Vehicle SpecificationsNoGas Vintage Scooter • 50 MPH Top Speed • 50 Mile Range • 72 VDC, 40 Ah Lithium-Ion Batteries with BMS • Regenerative Braking • 340 lb. capacity • Built-in Charger • 110V Charging with 1-8 hr. max charge time • regenerative braking • Front and rear hydraulic disk brakes • Hydraulic shocks front and rear
Charging Requirements • Fundementals AH = Power / Battery Voltage Power = Vehicle Efficiency * Range • Scooter • 72 VDC, 40 Ah Batteries Power = AH * Battery Voltage = 40 Ah * 72 VDC = 2.88 kW Efficiency = Power / Range = 2.88 kW / 50 miles = 57.6 W / mile
Charging Requirements (Cont.) • Assume Driven 20 Miles Per Day: Power = Efficiency * Range = (57.6 W/mile) * (20 miles) = 1152 W AH Required to Charge = Power / Battery Voltage = (1152 W) / (72 V) = 16 Ah • Assume 8 Hour Charging / Day Requires 2Ah to Batteries
Charging Requirements (Cont.) • Requirements Based on Solar Study DC Rating: 500W AC to DC Derate Factor: 77% AC Rating: 385W Solar Hours / Day: 2.96 (December) & 4.71 (Average for Year) December Output 500W System = 385W * 2.96 Hours = 1140 Wh / Day Yearly Average Output 500W System = 385W * 4.71 Hours = 1813 Wh / Day
Charging Station Components • Solar Panels • Inverter • Battery Bank • Charging Station • Remote Monitoring and Control • Data Logging
Solar Panel Technologies • Solar Panels (SP’s) convert photons (light) into DC current. This technology is called photovoltaic (PV). • Maximum efficiencies for most commercial SP’s is around ~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 high efficiency SP. • Common output powers for large SP’s are 50-300W 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 *Values determined using Voc and Isc temperature coefficients from manufacturers
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 would power building and charging station would be powered by building) • Need instrumentation to compare power into building versus power supplied to charging station
Comparison of Inverter Technologies Microinverters Centralized Inverters DC Voltages Up to 600 V Not Easily Expanded Higher Initial Cost Lowest Output Panel is Weakest Link of System Standard Wiring Methods Typically Requires More Integration for SCADA • Lower DC Voltages (30-50V) • Modular & Expandable • Lower Initial Cost • Compensates for Shading • Connectorized Cables • Remote SCADA Interface
What to Do with Excess Power Grid-tied Off-grid Using Batteries Limited by Battery capacity Only requires DC to DC battery charger Batteries Need Conditioned Room, which will require building wiring • More efficient use of power • Requires two branch circuits • No Additional Space Required
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