Check out this slideshow from Computer Weekly featuring the recently-unveiled Solar Impulse (registration HB-SIA), "the world's first aircraft the first aircraft designed to fly around the
clock without using fossil fuel or polluting the planet."
From a post on our Future Proof blog from earlier this year:
The Solar Impulse HB-SIA, the first prototype of a Solar aircraft has aAnd from a Flight International report a while back in '07:
wingspan of 12m, wing area of 200m2, and weighs 1500kg. It
will fly during the day propelled only by solar energy and will glide
at night using energy stored during the day. The pilot will also wear a
symbiotic garment, which allows him to sleep but wakes him up to make
any necessary flight adjustments.
With 200m² of solar cells on the wing and horizontal tail, 400kg of lithium-based batteries and four electric motors driving propellers, HB-SIA is intended to make a 36h flight to demonstrate the ability to operate through a complete day-night-day cycle without fuel.
The single-pilot aircraft will take off with its batteries fully charged, climb to 8,500m (28,000ft) during the day under solar power and descend to 1,000m during night under battery power. The goal is to have enough power remaining to begin the cycle again the next day, says Solar Impulse chief executive André Borschberg.
HB-SIA will be powered by four electric motors each producing a maximum of 10hp (7.5kW), but averging only 2.5hp, he says. This will be sufficient for a flying speed of around 45km/h (25kt).