1. Estimating solar energy requirements to meet U.S. energy needs: an outreach event Daniel Esposito, 1 Vernon Alt 2 1 Columbia University 2 Northrup Grumman Corporation

2. 20 mW 60 W 1.2 kW 1 GW An Introduction to Energy and Power Energy is the capacity to do work and has the unit of Joules (J) Power is the rate of energy consumption or generation and has the unit of Watts (W), equal to one Joule/second.

3. 3,500,000,000,000 W = 3.5 TW = 3.5x10 12 TW Primary Power Use in the U.S.

4. Today’s Question: How Many Solar Panels are Needed to Power the U.S.? B.) Virginia 102,000 km 2 A.) Connecticut 13,000 km 2 D.) Alaska 1,507,000 km 2 C.) Texas 684,000 km 2 (40,000 mi 2 ) (5,000 mi 2 ) (267,000 mi 2 ) (588,000 mi 2 )

5. Photovoltaic Energy Conversion Electricity Light Load U.S. Energy consumption = 3.5 TW Solar Panel Area?

6. Why Solar Energy? 1.Solar is abundant 130,000 TW

7. Why Solar Energy? 1.Solar is abundant 2.Solar is widely available across the globe

8. Why Solar Energy? 1.Solar is abundant 2.Solar is widely available across the globe 3.Solar is a renewable resource

9. Why Solar Energy? 1.Solar is abundant 2.Solar is widely available across the globe 3.Solar is a renewable resource 4.Solar is environmentally friendly. It does not emit green house gases or other pollutants while operating

10. Description of a Solar Cell 4 main components of a solar cell: Sun light 3. back contact2. front contact 1. Semiconductor 4. wires (+) (-) Electricity

11. Leads Measuring electrical power produced by a a solar cell 1.Voltage (units: Volts) 2.Current (units: Amps) 3.Area (units: cm 2 ) Multimeter Quantities to be measured Power = (Voltage) x (Current) [=] Watts

12. Calculating Required Area of Solar Panels: 1.Find electrical power from a single solar panel (P s ) : (unit: Watt) 2.Find number of Solar Panels required to get 3.5 TW: Number of Panels = 3,500,000,000,000 Watts (Power from 1 panel)x(6/24) 3. Find total area occupied by solar panels Total Area = (Number of panels) x (Area of 1 Panel) P s = (Voltage) x (Current)

13. Virginia 102,000 km 2 Connecticut 13,000 km 2 Alaska 1,507,000 km 2 Texas 684,000 km 2 (40,000 mi 2 ) (5,000 mi 2 ) (267,000 mi 2 ) (588,000 mi 2 ) How did you do???

14. Why Isn’t Solar Energy More Prevalent?

15. 1.$$$$$$$$$$ 2.Solar Intermittency Why Isn’t Solar Energy More Prevalent? Price trends in U.S., 1976-2009^ ^ J. Newman, J. Electrochem. Soc., 2012. 3. Efficiency

16. Final Questions?

17. Extra Slides

18. What is Electricity, and how do we quantify the energy/power in electricity? Electricity is the flow of negatively charged electrons Three major metrics to describe electricity: 1. Voltage (V)2. Current (I)3. Power (P) electron (-) (+) V Power= Current x Voltage Unit: Watt Unit: Volt Unit: Amp (-) (+)

19. Light is made of photons The more photons being emitted by a light source, the brighter the light source appears, and the more power being released by the light source Power low high What is Light?

20. How do we measure the power contained by Light? 1. Brightness (B) Flux meter 2. Power, also known as Irradiance (P L ) unit: lux unit: mW / cm 2 Detector P L = B/1,000

21. =60 billion light bulbs =3 billion toasters =4 thousand nuclear plants 3,500,000,000,000 W

22. Technology (Math & Science) PolicyBusiness Politicians Psychologists Sociologists Urban planners Economists Bankers Marketing Engineers (Chemical Electrical, Mechanical, Civil) Scientists (Chemists, Physicists, Biologists) Technicians & skilled workers How do we make Solar Panels more common Sustainable Energy Future

23. Where does Energy Come From? (Oil)

24. 2 MAJOR Problems with fossil fuels 1. Fossil fuels are non-renewable

25. 2 MAJOR Problems with fossil fuels 2. Global Warming / Pollution Fossil Fuels (Coal, oil, natural gas) Energy

26. 2 MAJOR Problems with fossil fuels Fossil Fuels (Coal, oil, natural gas) Energy 2. Global Warming / Pollution

27. Some outgoing light is trapped by the earth’s atmosphere and warms turns it into heat Some light is radiated back into space by earth Much of the sun’s radiation is absorbed by the Earth Greenhouse Gas Effect

28. One More Important Metric: Efficiency Electricity Light PLPL P PV

29. One More Important Metric: Efficiency Power produced by the solar panel Power from the sun or light Conversion efficiency= Electricity Light PLPL P PV P L =

30. Electrical Loads 2 Amps 20 mA small lights Refrigerator 80 mA Radio