Transcript Solar Powered Charging Station: Progress Report

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 B, 10/16/11
Agenda
• Background
• System Requirements
• Scooter Specification & Charging
Requirements
• Block Diagram
• System Components
• Questions
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Background
• To 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
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System Requirements
• 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
• Inverter: Converts DC power into AC power
– Determine inverter type (Centralized or
Distributed)
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System Requirements (cont.)
• Battery Bank: Originally required to store
energy when scooter is charged or not
plugged in, or to charge scooter when panels
are unable to provide enough energy
• Grid-Tied System: Alternate means of energy
storage
– Scooter charged or not plugged in: Building
consumes energy
– Cloudy Day: Building assists in charging
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System Requirements (cont.)
• Charging Station: Provides 120 VAC, 60 Hz
interface to scooter
• 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
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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 kW
– Charging station should be able to supply approximately 3
kW-h
• 375W-h over 8 hours
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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: http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/code/pvwattsv1.cgi
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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: http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/code/pvwattsv1.cgi
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Block Diagram
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Charging Station Components
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Solar Panels
Inverter
Building Connection
Transformer
Charging Station
Instrumentation
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Solar Panel Technologies
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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.
Inverters
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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
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Distributed Inverters / Microinverters
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Centralized Inverters
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Comparison of Inverter Technologies
Microinverters
• Lower DC Voltages (30-50V)
• Modular & Expandable
• Lower Initial Cost
• Compensates for Shading
• Connectorized Cables
• Remote SCADA Interface
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
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Energy Storage
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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
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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
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Power Converter
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Power Converter
• 120 – 240V transformer
• 1500 VA
• Cost ~300
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Charging Station
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Charging Station
• Provides 120 VAC Interface to Scooter
• Either NEMA 5-15R receptacle or NEMA 5-15P
cord-connected plug on a reel.
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Instrumentation
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Instrumentation
• Smart meters with embedded web interface
to allow user to connect from web brpwser at
computer
• Monitor power flow to scooter and power
flow from inverter
– Difference is that either consumed or provided
from building
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Current Status
• System has been designed and waiting for
Sponsor approval
• Ready to order components and build
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Next Steps
• Order Materials
• Build Station
• Test Final Product
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Questions?
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