The Solar Scholars Program and Fundamentals of PV Design

1. The Solar Scholars Program and Fundamentals of PV Design Prepared by: Colin Davies & Eric Fournier Sept 2007

2. Outline • Renewable vs. non-renewable energy • The science of photovoltaics • Principle design elements • System configurations • The Solar Scholars program at Bucknell

3. What’s wrong with this picture? • Pollution from burning fossil fuels leads to an increase in greenhouse gases, acid rain, and the degradation of public health. • In 2005, the U.S. emitted 2,513,609 metric tons of carbon dioxide, 10,340 metric tons of sulfur dioxide, and 3,961 metric tons of nitrogen oxides from its power plants.

4. Making the Change to Renewable Energy • Solar • Geothermal • Wind • Hydroelectric

5. Harnessing the Sun • Commonly known as solar cells, photovoltaic (PV) devices convert light energy into electrical energy • PV cells are constructed with semiconductor materials, usually silicon-based • The photovoltaic effect is the basic physical process by which a PV cell converts sunlight into electricity • When light shines on a PV cell, it may be reflected, absorbed, or pass right through. But only the absorbed light generates electricity.

6. The Science of Photovoltaics http://www1.eere.energy.gov/solar/video/solarcell1.mpg Source: Olympus Microscopy Resource Center

7. Crystalline Structure • Single Crystal Silicon – Very efficient but expensive manufacturing process - A single seed crystal is place atop a crucible of molten silicon. As this seed crystal is slowly raised a large single crystal ingot is formed. This ingot is then sliced into several sheets for solar panel manufacturing. Source: U.S. Dept of Energy

8. Other options • Multicrystalline Silicon – Less efficient than single crystalline silicon but also less expensive to produce • Amorphous Silicon – Non-crystalline structure (even less efficient); very inexpensive depositional manufacturing process

9. Electricity Basics • The power produced by solar arrays is in the form of direct current or DC power. • The outlets in our homes provide alternating current (AC). • Questions?

10. Design Elements: Going from DC to AC power… • The DC power generated by the array must first be converted to AC before it can be used in the home or sold back to the utility • An Inverter converts DC power to AC power

11. Wiring • Efficiency penalty associated with DC power over long distances • AC line losses are minimal • Resistance depends on conductor: gauge, length, material, and temperature

12. Getting Desired Voltage and Amperage • Series: Voltages are additive, current is equal • Parallel: Currents are additive, voltage remains the same

13. Power (Watts) = Current (Amps) X Voltage (Volts) IV Curve - MPP

14. IV Curve – Cell Temp & Irradiance Response

15. Site Selection - Shading • Shading effects important to site selection • Orientation of shaded region on module is critical to output

16. Site Selection – Panel Direction • Face south • Correct for magnetic declination

17. Site Selection – Tilt Angle Year round tilt = latitude Winter + 15 lat. Summer – 15 lat. Max performance is achieved when panels are perpendicular to the sun’s rays

18. Mounting Options • Fixed • Roof, ground, pole • Integrated • Tracking • Pole (active & passive)

19. Configurations • Grid-tied • Grid-tied with battery backup • Stand-alone

20. Grid-tied • When grid goes down, you also lose power • Excess power can be sold to grid • Electricity can be bought from grid at night or on cloudy days

21. Grid-tied with battery backup • More independence • Batteries add complexity and cost

22. Stand-alone • Remote locations • Road-side

23. Energy Consumption • Air conditioner (1 ton) …………………… 1500W • Blow dryer ……………………………....... 1000W • Refrigerator/freezer (22 ft3) …………….. 540W • Washing Machine ……………………...... 1450W • Incandescent light (75W) ……………….. 75W • Compact fluorescent (75W equiv.) …….. 20W • Cell phone charger …………………….... 24W Avg U.S. home = 25 – 30 kWh per day

24. Energy Efficiency • Home energy audit • Insulation, windows • Compact fluorescent lights • Appliances • Phantom loads • $45 billion kWh annually • $3.5 billion per year • 10 power plants • 18,000,000 tons of CO2 • More pollution than 6 million cars • TVs and VCRs alone cost the US $1 billion per year in lost electricity

25. Solar Scholars Overview • Solar Scholars is an innovative, solar-energy education program for university students throughout Pennsylvania, created by The Sustainable Energy Fund of Central-Eastern Pennsylvania (The SEF-CEPA). • Its goal is cultivating the “solar and renewable energy leaders, policy-makers and entrepreneurs of tomorrow.”

26. Solar Scholars Workshop

27. BUEC Installation • Twelve 200 W GE panels (2.4kW) • Ground mounted • Fronius Inverter with Datalogger • Grid-tied

28. Mod Installation • Two pole mounted arrays: Eight 200 W GE panels per pole (3.2kW total) • Fixed • Passive tracker • Two Fronius Inverters • Grid-tied

29. Mod Installation (cont) All in a good days work…

30. Ready for a field tour? • Questions? If you are interested in anything you have seen today and would like to get involved, please contact any member of the Solar Scholars team: Colin Davies, Eric Fournier, or Jess Scott (cjdavies, efournie, jpscott)