Dyson Spheres and Ring Worlds

From the Guardian:

"[Scientists] identified sunshine as a "tantalizing source of environmentally friendly power, bathing the Earth with more energy each hour than the planet's population consumes in a year." ... "We only need to capture one part in 10,000 of the sunlight that falls on the Earth to meet 100% of our energy needs," futurologist Ray Kurzweil, a member of the NAE group, told the AAAS. "This will become feasible with nanoengineered solar panels and nanoengineered fuel cells.'"

While all that sounds very well and good, but whatever happened to the Dyson Sphere? Basically the idea is to create a sphere that completely encompasses the star, like an egg around a yolk. No solar energy is wasted. Variants include a Dyson Swarm and a Ringworld, as seen here:


A ringworld is basically a man-made structure with walls 1000 miles tall to maintain an atmosphere, with a circumference of over 600 million miles. It was made popular in the Halo series, according to the folks at Wikipedia. Its surface area is something like four hundred times that of Earth. Obviously, these are developments that are only possible once all the nano-solar machinery is created and becomes cost-effective, but it's something to shoot for.