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ISSUE

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All you need to know about solar Aircrafts

June 2013

Solar Aircrafts The future of transportation

Time Line

Introduction to Solar aircrafts P.1

Nov 1974 – Sunrise I, the worlds first solar airplane takes off.

Solar plane statistics P.2

Jan1975 – the new and improved

Conclusions P.3

Sunrise II was built

Questions and Answers P.4

Aug 1976 – the Solaris completed three flights Dec 1978 – the Solar I was created to be the first manned solar plane using Ni Cd batteries to store energy May 1980 – the Gossamer Penguin took flight and was considered the first solar powered flight

Introduction Solar energy is one of the most known renew-

1974 from bicycle lake and was destroyed on

able resource. One of the most innovative

the 28 by turbulence.

uses for it, would be taking someone into the

The most recent flight mission is by the plane

July 1981 – The Solar Challenger

skies. This is where the million dollar solar

flew from Paris to London covering

airplanes come in. Although the technology is

262.3km in 5h 23min

new, solar airplanes may one day be the new

22min. The Solar Impulse project started De-

Aug 1990 – Sunseeker flies 121h

mode of air transportation.

cember 3rd 2009 . It holds the record for the

in the air in 21 flights 1994 – The Pathfinder by NASA flies at an altitude of 15,392m Aug 1998 – The new and improved Pathfinder Plus sets the national altitude record of 24,445m Aug 2001 – Nasa’s Helios beats the altitude record once again by flying at 29,863m July 2010 – the Qinetiq Zephyr holds the endurance record of unmanned flight of 2 weeks

Solar Impulse going from Dallas and it landed on June 4th and the flight lasted for 21h

manned flight. The Zephyr built by QinetQ In this report, we will be discussing about the

has been able to fly for 14 days, 22 minutes,

most technological advancement of solar

8 seconds, in 2010 holding the record for the

aircrafts as well as the specifications of an

longest unmanned flight. This makes these

few solar aircrafts and compared it with tradi-

unmanned very useful for surveillance, or for

tional airplanes. Along with calculations of

disaster response.

energy consumption, efficiency, we can about learn about the future modes of transporta-

What engineers designed for a special flight

tion. To conclude, you will answer the ques-

path of the solar airplane in order to achieve

tion about whether the technology is ready to

maximum flight time and using less energy

be commercialized and the technological re-

from the battery.

strictions of the aircraft.

May 2013 – The Solar Impulse sets the world distance of 1,514km beating its previous record of 1,116km. It also holds the longest duration in a solar airplane (manned) of 26 hours

Starting from the 1970s the solar cells have become more affordable and a considered source of energy. The earliest recorded official solar airplane was called the Astrofight sunrise. It took flight in the 4th of November

technology


Solar Panels The solar panels used by the Solar Impules is made by Sunpower. Although Solar panels is a good method of flying

The solar panel uses solar cells or Photovoltaic cells. They have the ability to convert light energy into electricity. This is renewable source since the sun is always available. It uses semi conductors to absorb the sun’s energy and generating electricity. On the solar airplane, unlike house hold solar panels, the Solar airplane uses panels that are only millimeters thick.

The problem with solar panels is that with each square feet of

Technical Specifications of a solar airplane Solar aircrafts utilize solar energy as the energy source to power many electric motors. It requires a lightweight body but have enough solar panels to provide energy to fly the plane. Solar airplanes face the limitations of high turbulence and the lack of solar energy at night. Here’s how Solar airplanes are built to face these challenges Wingspan The wingspan of the solar aircraft is very flimsy. Engineers try to maximize the surface area of the solar panels to absorb solar energy. Therefore one can imagine a solar aircraft looking like a flying ruler. The wingspan of the solar airplane would parallel the ones on a commercial airplane but weigh less. For example, the wingspan of the Helio is 75 meters. Flight path What the Solar impulse has done for their flight path is use a special flight cycle that minimizes energy consumption. What they do is they ascend 8000m by day, obtaining the most solar energy from the sun and avoiding turbulence. At night, the Solar impulse descends 1000-1500m converting its potential gravitational energy to kinetic letting it glide for 4-5m without consuming much electrical energy. Then in the morning it ascends. Electric engines The electric engine is one of the most important thing. It requires a battery to store electricity and enough power to keep it running through the night. It also needs to produce enough horsepower to lift off and keep it flying. For the Solar Impulse, it contains 4 x 10hp electric engines, and it can travel at an average speed of 70km/h. Compared to the

solar cells, the maximum efficiency is 21% as stated from Sun power. Generally in a day, the average irradiance that hits the earth is 250W/m2 . Therefore a 1 x 1 solar panel would produce 52.5 Watts.

Weight The weigh of the solar aircraft must be light. Most of the recent solar airplanes are made out of lightweight carbon fibre materials. Engineers try to get rid of as much weight as possible, therefore when looking at solar airplanes, some of them do not even have landing wheels. When taking off, the plane takes off at bicycle speeds . When landing, the propellers are turned off and glide to the ground. Limitations There are many limitations that causes the solar airplane stops the Solar airplane from flying. First of all, the ground winds should not exceed a speed of 16 kilometres per hour. Also, Solar airplanes can’t handle high wind speeds and turbulence. This is because the planes are very lightweight, they are very fragile. Going down 50 meters in a short period of time causes the plane reach its maximum speed and going up 50 meters causes the plane to reach its maximum stall speed. Altitude For the commercial airplanes, the altitude for cruising would be 35,000ft(10.6km). This is the turbulent layer. In this layer, there are jetstreams and turbulence that may sweep away and destroy the solar aircrafts. Above the jetstream, there are clouds that block the the sun light. Then the plane needs to pass the stratosphere(40,000ft—20km) which has icy cirrus clouds. Finally the perfect altitude of 65,000ft which there is no practically no wind resistance and has a good angle of sunlight.


Calculations

For Solar Impulse, the number of solar cells it has 11,628 photovoltaic cells (solar cells). This means that it has approximately 200m2 of solar panels. Each solar panel would have approximately absorb 250W/m2 . So how much Watts does it create with an efficiency of 12% 200m2 x 250W/m2 = 50000W 50000W x 12% = 6000W Therefore, the solar airplane would only run on 6000W (or J/s) of electricity. Gravitation energy needed to have the solar plane lifted up at service ceiling (see chart below) 8500m = mgh = 1600kg x 9.8m/s2 x 8500m = 133,280,000J Kinetic energy needed to have the solar plane flying at the cruising speed (see chart below) 70km/h Speed conversion: 70km/h=70x1000/3600 m/s = 19.4 m/s

Recall kinetic energy =

1 mv 2 2

= 0.5 x 1600kg x (19.4m/s)2= 301088J Total energy = (133280000+301088)J = 133,581,088J Therefore, time needed for the solar plane (with all solar panels) to store that much energy = (133,581,088J)÷(6000J/s) = 6.2 hrs Conclusion: not very efficient, this is one of the reasons why solar planes are not readily available for public use. However, this is calculated under the assumption that each solar panel has the ability to absorb 250W/m 2, and have an efficiency of 12% (data obtained from commercially available company). Solar panels used for Solar Impulse could be more efficient. Boeing 747-B calculations Energy needed to fly @11000m =214503kg x 9.8 x 11000 + 0.5 x 214503 x 253.6^2 =3.002x10^10J So how much more energy does the Boeing need ? =3.002x1010 J / 133581088J =224.7 TIMES higher the requirement Meaning you need 244.7 TIMES MORE PANELS!!!!! That is another reason why it’s not feasible to fly boeing 747 w ONLY solar energy…

Comparison between a Boeing 747-B and the Solar Impulse HB-SIA Measurement Seating Length

Solar Impulse HB-SIA 1

Boeing 747- 8 467

21.85m

76.3m

63.4

68.5

Weight empty)

1600kg

214,503 kg

Maximum takeoff weight

2000kg

442,253 kg

4 x electric motors using 7.5Kw each

4 x GEnx-2B67 using 90Kw each

Cruising speed

70km/h

913 km/h

Service ceiling

8,500m

11,000m

Wingspan

Engine


Questions and Answers • Why aren’t solar aircrafts feasible as a method of transportation today As researched in this matrix, the solar aircrafts are very inefficient. It is not ready for commercialization because to hold hundreds of people and still be able to keep the airplane flying using electricity generated by solar panels is not enough to keep it up. Also there are restrictions to flying this solar airplane. Today, the solar aircrafts are very fragile and in turbulence and high wind speeds, these solar airplanes cannot be flown. One of the more important factors to keep in mind is the available sun energy. The day cannot be cloudy and if it is, not enough electricity will be generated to make long distance flights in the aircraft.

• So what can the solar airplane do? As of this moment, the military and research facilities like NASA have planned to utilize these long term flying planes as a method of surveillance. Since they can fly for up to weeks before landing, makes it very useful to gather data in the stratosphere or track natural disasters. For the military, they can be used as spy planes since they have the ability to reach very high altitudes without the use of people. Another use for it could be for replacing satellites. Since solar aircrafts have the ability to take cameras up to the skies, this makes it a very useful method. They are easier to maintain and can be easily moved

What good can come from solar aircrafts First of all, this is a renewable source of energy. Unlike commercial planes, the electric aircraft produces no CO2 emissions. Commercial airplanes emit 0.5 billion tons of CO2 or 2% of human CO2 emissions in the 1992. This is a huge amounts and some emissions from the planes impact our health in addition to the major air pollution problem.

Citations

Noth, Andre. History of Solar Flight. Zurich: Autonomous Systems Lab, Swiss Federal Institute of Technology Zürich, 2008. Http:// www.asl.ethz.ch/research/asl/skysailor/History_of_Solar_Flight.pdf. Gindroz, Alexandra. "Solar Impulse HB-SIA." SOLAR IMPULSE. SOLAR IMPULSE, 2013. Web. 07 June 2013. <http:// www.solarimpulse.com/en/airplane/hb-sia/>. Archangel, Amber. "CleanTechnica." CleanTechnica. N.p., 23 May 2013. Web. 07 June 2013. <http://cleantechnica.com/2013/05/24/newsolar-aviation-world-distance-record-set-by-solar-impulse/>. Bhatia, Aatish. "Solar Planes Are Cool, but They’re Not the Future of Flight." Empirical Zeal. N.p., 6 Apr. 2013. Web. 07 June 2013. <http:// .empiricalzeal.com/2013/04/06/solar-planes-are-cool-but-theyre-not-the-future-of-flight/>. Toothman, Jessica, and Scot Aldous. "How Solar Cells Work." HowStuffWorks. How Stuff Works Inc, n.d. Web. 07 June 2013. <http:// science.howstuffworks.com/environmental/energy/solar-cell.htm>. Nasr, Susan L. "How Solar Aircraft Work." HowStuffWorks. N.p., n.d. Web. 07 June 2013. <http://science.howstuffworks.com/ environmental/green-tech/sustainable/solar-aircraft.htm>. Curry, Marty. "NASA - Helios." NASA - Helios. N.p., 27 Oct. 2007. Web. 07 June 2013. <http://www.nasa.gov/centers/dryden/news/ ResearchUpdate/Helios/>. "NASA - National Aeronautics and Space Administration." NASA. N.p., 12 Dec. 2009. Web. 07 June 2013. <http://www.nasa.gov/centers/ dryden/news/FactSheets/FS-054-DFRC.html>.

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