Technology: 

• Solar Impulse is the first solar-powered airplane that can fly day and night, powered entirely by the sun. 
• Thousands of solar cells power its four electric motors with clean renewable energy.  
• Solar energy is stored in batteries during the day and power the airplane at night. Ten hours of continuous bright sunlight is needed per day in order to charge the batteries and power the plane through the night. 

Sustainability problem:

Airplanes use conventional fuels and emit carbon dioxide and other greenhouse gases, thus contributing to global warming. Most airplanes today fly using conventional fuels. 

Stakeholders:

• Small  Airline companies
• Air Force Engineers and Pilots
• Solar companies
• Investors

Implementation: 

1.  Test flights were done in order to see the potential of the solar-powered experimental aircraft in flying both days and nights. Solar Impulse is a one-pilot plane and started with day flights before its first night flight in 2010. Inter-continental flights followed in 2012. Solar Impulse made its first cross-country flight in 2013. It started from NASA Ames Research Center in California, and made stops in five states before finally landing at New York’s JFK Airport. The flights took a total of 105 hours and 41 minutes.
2. On June 20, 2016, the longest day of the year, Solar Impulse 2, a slightly bigger plane with 5,000 more solar panels than SI, make its trans-Atlantic flight to Europe. The flight from New York to Madrid is a continuous ninety-hour trip. 
3. As of now, Solar Impulse is a one-pilot plane which has proved to fly with clean energy for very long hours. More experiments and further research should be done in order to improve this very exciting technology on a larger scale: as a two-pilot plane, an Air Force plane, a cargo plane, or as a small passenger-carrier plane. It will take many years for it to be on a commercial scale so accelerated research is needed to be done in order to reduce carbon emissions from aircraft. 

Sources:

http://inhabitat.com/solar-impulse-airplane-to-complete-cross-country-flight-in-new-york-tonight/

http://inhabitat.com/solar-impulse-2-begins-4-day-nonstop-flight-across-the-atlantic-on-longest-day-of-the-year/

http://inhabitat.com/meet-the-solar-impulse-2-the-first-plane-to-attempt-a-round-the-world-solar-powered-flight/