1. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Lecture Notes Renewable & Clean Energy, Transportation Solar Powered Airplanes

2. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Question If we were to coat a Boeing 747 jumbo jet with solar panels, is it possible to fly it using only the energy generated by these solar panels? Solar Powered Airplanes

3. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Power of a 747 The amount of power needed for a 747 during flight will vary depending on: o Whether the plane is rising, falling, or cruising at a constant altitude, o The air density at the altitude it’s flying o The mass of its payload o Prevailing winds Solar Powered Airplanes

4. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Estimations We don’t want to deal with any of these complications, so we’ll make a very rough estimate of the amount of power needed to keep a modern passenger 747 flying. o Maximum range = 15,000 km o Consumes 200,000 L of jet fuel o Cruising speed = Mach 0.8, 800 km/h, or 0.22 km/s o Specific energy of jet fuel is 36 MJ/L Solar Powered Airplanes

5. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Power of a 747: Total energy used in flight: Total time over which the energy is used: Average Power: Solar Powered Airplanes

6. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Solar Power The sun radiates power toward us (sunlight) - this power is what drives everything from the water cycle to plant growth (and the creation of fossil fuels). The power from the sun given to an area of 1 m 2, assuming the sun is directly above us, is 1365 W/m 2 (called “flux”) The goal of solar power generation is to turn this incident sunlight into usable power i.e. mechanical or electrical power. Solar Powered Airplanes

7. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Extracting Power A number of methods exist for extracting power from the sun, including: o Solar thermal power - using sunlight for cooking, or for heating water to run a turbine o Growing of food and biofuel Solar Powered Airplanes

8. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Solar Panels Solar panels are slabs of photovoltaic cells, and use the photoelectric effect to generate electricity from sunlight o Sunlight hits the photovoltaic cell. o Energy is transferred to electrons of the cell, raising them to an “excited state” o Excited electrons are free to travel through the cell, but only in one direction o This travel is a (DC) electric current, which can be attached to a load, such as a light bulb or motor. Solar Powered Airplanes

9. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Efficiency Now we have to worry about efficiency, define to be the ratio between the power output and the power input. The efficiency limit for solar panels is ~ 30% Concentrators may increase this to ~ 60% Common photovoltaics have efficiencies of ~10%, but we can assume 20%, which can be reached by the most expensive photovoltaics available today Solar Powered Airplanes

10. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Boeing 747-8 The schematics of a Boeing 747-8 Solar Powered Airplanes Boeing. 747 Schematic (online). http://www.boeing.com/commercial/747family/pf/pf_exterior.htmlhttp://www.boeing.com/commercial/747family/pf/pf_exterior.html [27 May 2010].

11. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Using Solar Panels We will cover the top surface of the wings of a 747 with solar panels. The wing area is 525 m 2 This gives a power of: This is less than 1% of the needed power for the plane to take flight. Solar Powered Airplanes

12. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Using Solar Panels To power an airplane, we would need solar panels covering an area: This is about the footprint of BC Place in Vancouver, which doesn’t sound too bad until we consider that at any given moment tens of thousands of planes are aloft in North America alone. Solar Powered Airplanes

13. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Solar Panel Area A to-scale comparison of a Boeing 747-8 to the area (in blue) solar panels would need to cover in order to power a 747's flight (270 m) 2. Solar Powered Airplanes

14. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Complications The angle of incoming solar radiation depends not only on latitude but also on the time of day and the season. An airplane flying level to the ground at high latitudes will get much less than 1365 W/m 2. Simple trigonometry shows that the flux from the Sun at latitude θ should be 1365 x cos θ where θ is the angle between the normal to the plane of the solar panel and the direction of the solar flux. Solar Powered Airplanes

15. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Complications Flying any solar-powered airplane at night is impossible, since the flux from the Moon is orders of magnitude smaller than the flux from the sun. Flying below clouds is also problematic, since clouds reduce the power from the Sun by a factor of 10 6. Solar Powered Airplanes

16. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Complications If we decided instead to use ground-based solar power to fuel our airplanes, there are other forms of solar power generation, such as the Stirling engines mentioned earlier, that potentially have higher efficiencies than photovoltaics. Solar Powered Airplanes

17. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Bibliography 1.Boeing. 747-8 Technical Characteristics (online). http://www.boeing.com/commercial/747family/747- 8_fact_sheet.htmlhttp://www.boeing.com/commercial/747family/747- 8_fact_sheet.html [27 May 2010]. 2.Wikipedia. Speed of Sound (online). http://en.wikipedia.org/wiki/Speed_of_soundhttp://en.wikipedia.org/wiki/Speed_of_sound [27 May 2010]. 3.U.S. Department of Energy. Heat Content for Various Fuels (online). http://cta.ornl.gov/data/tedb28/Spreadsheets/TableB_ 04.xls [27 May 2010].http://cta.ornl.gov/data/tedb28/Spreadsheets/TableB_ 04.xls 4.Ostlie, Dale A & Caroll, Bradley W. An Introduction to Modern Stellar Astrophysics. 5.MacKay DJC. Sustainable Energy Without the Hot Air. Solar (online). http://www.withouthotair.com/ [27 May 2010].http://www.withouthotair.com/ 6.Wikipedia. Solar Cell (online). http://en.wikipedia.org/wiki/Solar_cellhttp://en.wikipedia.org/wiki/Solar_cell [27 May 2010]. 7.Boeing. 747 Schematic (online). http://www.boeing.com/commercial/747family/pf/pf_exterior.htmlhttp://www.boeing.com/commercial/747family/pf/pf_exterior.html [27 May 2010]. Solar Powered Airplanes

18. Physics and Astronomy Outreach Program at the University of British Columbia Physics and Astronomy Outreach Program at the University of British Columbia Bibliography 8.Top Speed. 2011 Boeing 747-8 (online). http://www.topspeed.com/aviation/aviation-reviews/boeing/2011- boeing-747-8-ar86257.htmlhttp://www.topspeed.com/aviation/aviation-reviews/boeing/2011- boeing-747-8-ar86257.html [1 June 2010]. 9.Google Earth’s ruler function 10.McKay, DJC. Sustainable Energy Without the Hot Air. Planes (online). http://www.withouthotair.com/ [27 May 2010].http://www.withouthotair.com/ Solar Powered Airplanes