Transcript Sustainable Energy Systems Engineering

Sustainable Energy Systems Engineering
Peter Gevorkian
Ch 2: Solar Power Generation Design
Brevard Community College
EST1830
Bruce Hesher
Other References
Photovoltaic systems is only a topic for this text. If you
want more info try:
Photovoltaic Systems by Jim Dunlop. This is the text for
ETPC2410 Photovoltaic Technology.
Section 690 of the National Electrical Code (NEC)
www.enphaseenergy.com
www.fsec.ucf.edu/en/consumer/solar_electricity/basics/types_of_pv.htm
Photovoltaic System Types
Utility Interactive (Grid-Tied): Most common type for
residential. Only works when sun is up. Uses the grid to
store energy. Used to lower the electric bill.
Stand-alone: Provides power when grid is down. Uses
batteries to store energy. Has high cost and maintenance.
Bi-Modal: has features of both Grid-Tied and Stand-alone.
More equipment but provides power when utility is out.
Hybrid: Has more than just solar modules as an energy
source (wind turbine, generator, etc). Google HOMER.
Dedicated: Used as power source for a specific system. ex:
road signs, electric car recharging stations, communications
repeaters, water pumping.
Design Skills
Solar power design essentially consists
of electronics and power systems
engineering, which requires a thorough
understanding of the electrical
engineering discipline and the prevailing
standards outlined in Article 690 of the
National Electrical Code (NEC).
Designers are only one part of the
workforce needed for the PV
industry. Installers, Energy Auditors,
System Integrators (wholesale and
retail outlets), manufacturing staff to
build equipment, and others are also
needed.
Functions Systems Perform
Not every system type performs every function. Utility
Interactive systems do not have batteries; a hybrid
system will have multiple energy sources.
Solar Power System
Components and Materials
note: The text’s use of terminology on p26 is poor.
Sample PV System Diagrams
Utility Interactive systems with battery backup
Sample PV System Diagrams
Utility Interactive system
Wiring Diagram
(Enphase D380 Utility Interactive System)
Batteries
Not used for most residential grid-tied systems. Used in
stand-alone systems. Required if power needed when grid
is down.
Batteries are expensive and high maintenance. May have
significant permitting requirements. Can also be
dangerous.
Solar batteries are not car batteries. Car battereis are
designed for fast discahrge and slow recharge. Solar
battereis are designed for slow discharge and recharge.
Special Solar batteries or deep cycle marine
batteries are sometimes used.
Solar batteries often have gel electrolyte.
Some PV Terminology
MPPT: Maximum Power Pont Tracking. Automatically adjusting the load
on the array to get the most power out of it. Done by Charge Controller
or Inverter.
Net Metering: Metering power taken from and sent to the utility company
and being charged or paid for the difference.
Inversion: changing DC to AC.
Rectification: Changing AC to DC.
String: modules connected in series.
Islanding: unintentional energizing of a local section of the grid.
Azimuth: Angle off from due south.
Tilt Angle: the degree the modules are raised up (lattitude for fixed array.
Sun Hours: Average annual KWH per day that strike a particular location.
AWG: American Wire Guage. Standard table for wire guages, types, and
ratings
Derating: Adjust design parameters to account for temperature or other
factors.
Components of a PV System
Array: Modules are made of cells connected in series. Stings are made
of modules connected in series. Arrays are made of strings connected
in parallel in a fuse combiner box.
Fuse Combiner box: A weather proof box on the roof with the array
that individually fuses each string and combines the wires into a +, - ,
and ground.
DC Disconnect: A DC rated switch between the array and rest of
system.
PCU: Power Conditioning Unit. Unit that does all or most of the
following; MPPT, DC to AC inversion, DC to DC conversion. May
include a charge controller.
Charge Controller: Unit that uses power from the array to charge the
batteries, may also do MPPT.
AC Disconnect: Switch between distribution panel and utility meter.
BOS: Balance of System. Parts of a PV system other than the major
components.
Solar Power System Wiring
Starts with the array and the nameplate on the modules.
The nameplate gives several important parameters:
Voc: Open Circuit Voltage. The highest voltage the
module can produce.
Vmp: Max Power Voltage
Isc: Short Circuit Current. The maximum current the
module can deliver.
Imp: Max Power Current
Component Connection
The Series/Parallel arrangement of the modules and
strings determines the voltage and current of the array.
The voltage of the array must meet the input requirements
of the PCU/Charge controller.
For best performance the arravoltage should be in the
MPPT range of the Charge controller or PCU.
For safety of people and equipment; all component
connections need to be done while the system in NOT
energized. Turn off all component and shade the
array!
System Monitoring
Most Charge
Controllers and
PCU’s have
monitoring ability.
It may be a front
panel display and it
may be on-line
graphical display.
“Theres an app for
that.”
See http://www.enphaseenergy.com/products/products/enlighten.cfm
System that needs attention?