Sustainable Energy Systems Engineering Peter Gevorkian Ch 2: Solar Power Generation Design

1. Sustainable Energy Systems EngineeringPeter GevorkianCh 2: Solar Power Generation Design Brevard Community College EST1830 Bruce Hesher

2. 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

3. 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.

4. 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.

5. 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.

6. Solar Power System Components and Materials note: The text’s use of terminology on p26 is poor.

7. Sample PV System DiagramsUtility Interactive systems with battery backup

8. Sample PV System DiagramsUtility Interactive system

9. Wiring Diagram(Enphase D380 Utility Interactive System)

10. 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.

11. 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.

12. 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.

13. 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

14. 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!

15. 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

16. System that needs attention?