this is the Technology Report.In 2012, a team of pilots and engineersfrom Switzerland successfully flew a planepowered by sun light from Spain to Morocco.The same team flew the aircraftacross the United States in 2013.Now, the Swiss team is preparingfor a flight around the world in 2015.The new, improved version of the plane,named Solar Impulse 2,was recently shown in Switzerland.Solar Impulse 2 is a very light,single-seat airplane.Its wings are 63 meters across.This large wingspan provides 200 square meters of spacefor energy cells that charge lithium-ion batteries.These special batteries are neededto keep the plane flying at night.Four electric motors permit the plane to cruiseat a speed of up to 140 kilometers per hour,at an average height of 8,500 meters above sea level.The longest flight of Solar Impulse 1 was made in May 2013.The plane flew from Phoenix, Arizona to Dallas, Texas,a distance of just over 1,500 kilometers.Pilot Andre Borschberg says Solar Impulse 2will be able to fly much longer distances between stops."When we leave the coast of China,we don't know what the weather looks likeon the side of the ocean.So these are big question marks," said Borschberg.12 years of research and testing went into building Solar Impulse 2.The researchers and testers believe the aircraftwill be able to fly around the world in 20 to 25 days and nights.Andre Borschberg once flew jets for the Swiss Air Force.He says every detail on the airplane is designed to save energy."This airplane is an example of energy efficiency,how we save the energy,and how the energy from the sun is enoughto keep the airplane in the air day and night," said Borschberg.Mr. Borschberg will be able to sleep or even exercisewhen using the autopilot, a flight assistance device.Bertrand Piccard is the Chairman of the Solar Impulse project.He says the goal of the flight around worldis to support energy efficiency."It is to bring products to their clientswhich are more energy efficient:in home buildings, in the transportation,in appliances, it can be lighting," Piccard said.Solar Impulse 2 begins test flights in May.The flight around the world is planned to start next Marchfrom an airport somewhere along the Persian Gulf.And that's the VOA Learning English Technology Report.For more technology stories, go to our website 51voa.com.更多听力请访问51voa.com