insulation of the gondolas . Although the Mission Team was monitoring the flight closely , there was no way to decrease the temperature for the remaining duration as each daily cycle requires an ascent to 28,000 feet and descent for optimal energy management .
The damage to the batteries was not a technical failure or a weakness in the technology but rather an evaluation error in terms of the profile of the mission and the cooling design specifications of the batteries . The temperature of the batteries in a quick ascent / descent in tropical climates was not properly anticipated .
To avoid the batteries overheating again , engineers upgraded the whole battery system and integrated a cooling system .
Flying over 35,000 km The Solar Impulse ’ s motors have an average power over 24 hours of a small motorbike ( 15 hp ) with a maximum power of 70 hp ( four 17.5 hp engines ).
Four brushless , sensorless motors , each generating 17.4 hp , were mounted below the wings , and fitted with a reduction gear limiting the rotation speed of a 4m diameter , two-bladed propeller to 525 rpm . The entire system is 94 % efficient , setting a record for energy efficiency .
Solar Impulse can fly at the same speed as a car , between 36 km / h ( 20 Kts ) and 140 km / h ( 77 Kts ). At sea level , minimum speed is 45 km / h ( 20 Kts ) and maximum speed 90 km / h ( 49 Kts ). At maximum altitude , speed can pick up to between 57 km / h ( 31.5 Kts ) and 140 km / h ( 77 Kts ).
Being as a light as a feather … or a car The engineering team managed to build the entire structure proportionately 10 times lighter than that of the best glider . Every gram added had to be deducted somewhere else , to make room for enough batteries on board , and provide a cockpit in which a pilot can live for a week . In the end , it had the weight of a small van or 2,300kg , using a combination of ultralight materials : carbon fibre weighing 25 g / m2 ( three times lighter than paper ) and alveolate foam in the form of a honeycomb . These two materials , assembled in a sandwich , are used in the whole frame of the plane : fuselage ( body of the plane ), cockpit and spars ( central beam representing the spinal column of the wings ).
Robustness The upper wing surface of the plane is covered by a skin consisting of encapsulated solar cells , and the lower surface by a high strength , flexible skin . A total of 140 carbon fibre ribs spaced at 50 cm intervals give the wing its aerodynamic crosssection , and also maintain its rigidity .
To be resistant to wind , water , mold and large temperature variations , chemists and engineers invented especially light insulating materials . These included a rigid polyurethane foam ( insulation made of alveolate foam ) for protecting the cockpit and the pods housing the motors and batteries ; high performance polycarbonate sheets ( derived from plastic ) for the windows , and an ultrathin polymer film ( a kind of resin ) to protect the photovoltaic cells from water and UV radiation , and allow them to adopt the curvature of the wings without breaking .
Energy efficiency The systems on the airplane for collecting and storing energy were designed to minimise energy loss . The solar cells , batteries and motors have record beating energy efficiency : 23 % for the solar cells , and 97 % for the motors , which only lose 3 % of energy against 70 % for standard thermal motors .
With so many technical innovations on board , Borschberg described the Solar Impulse as “ a flying laboratory full of clean technologies ”. These technologies are now opening up new industrial markets and offering an opportunity for economic development and job creation . ( see Table 3 ).
Many hearts and minds have been captivated by Solar Impulse ’ s flight around the world this year . Although commercial aviation powered by the sun is still far way , the plane has inspired innovations and pushed the limits of solar energy and energy efficiency . “ If an airplane can fly several days and nights in a row with no fuel , then clean technologies can be used on the ground to reduce our energy consumption , “ Borschberg explains . He believes that clean technologies , such as the ones developed and tested for Solar Impulse , could cut energy consumed on a daily basis by 50 %. – Inforeach
REFERENCE
www . solarimpulse . com Wikipedia
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