Solar plane finishes historic flight around entire world

After flying across four continents, three seas, two oceans and covering 26,098 miles, Solar Impulse 2 finished its trip around the world on July 26 in Abu Dhabi, the same city where the journey began on March 9, 2015. Bertrand Piccard, who has alternated piloting duties with Andre Borschberg, made the landing.

The Solar Impulse 2, as its name implies, is a solar-powered plane. Its wings, which stretch 236 feet tip to tip, are covered by 17,000 solar cells that provide energy for the plane’s four electric motors. The plane no heavier than a car, but has the wingspan of a Boeing 747, according to the BBC. The global flight was intended to highlight how clean energy can work as a power source for transportation needs, a goal largely proven by the nearly five-day flight across the Pacific Ocean from Nagoya, Japan, to Kalaeloa, Hawaii. That leg netted Borschberg the world record for the longest uninterrupted solo flight.

As for what’s next for Solar Impulse 2, Borschberg wrote that the plane was designed to travel 2,000 hours but has only flown for 700, so it still has plenty of time left in the air. To that end, Borschberg sees the plane contributing to more solar energy testing and to the development of unmanned solar-powered vehicles, including drones.

credit: Noel Kirkpatrick

Solar Sunflower harnesses power of many suns

The latest in solar power comes to us from Swiss inventors working for Airlight Energy, Dsolar (a subsidiary of Airlight), and IBM Research in Zurich, reports Ars Technica. It’s called the Solar Sunflower, and like its namesake, it tracks the sun and cools itself by pumping water through its veins like a plant.

Aside from its aesthetically-pleasing design, the Solar Sunflower also makes use of some innovative technology. It uses something called HCPVT (Highly Efficient Concentrated PhotoVoltaic/Thermal) to generate electricity and hot water from solar power. Basically, this method entails using reflectors to concentrate the sun, as well as highly efficient photovoltaic cells (known as gallium-arsenide photovoltaic cells) to convert that concentrated solar energy into electricity.

Though concentrated solar thermal power and PVs are nothing new to the solar power industry, the Solar Sunflower incorporates these technologies in a novel way that represents a few ingenious engineering breakthroughs.

According to Gianluca Ambrosetti, Airlight’s head of research, the Solar Sunflower’s reflectors concentrate the sun “to about 5,000 suns.” In other words, the difference between this technology being classified as a death ray as opposed to a solar array is merely a matter of how the reflectors are angled. For instance, during one test, Airlight used the reflectors to melt a hole in a lump of iron. It gets extremely hot, and dealing with those high temperatures is how the Solar Sunflower really sets itself apart.

Photovoltaic cells used by the Sunflower have a max operating temperature of around 105 degrees Celsius, which is significantly less than the melting temperature of iron, let alone the heat of 5,000 suns. To counteract this, the Sunflower makes use of a hot water cooling system invented by the project’s IBM collaborators. Basically, this consists of pieces of silicon packed with microfluidic channels that are stuck to the backside of the PV cells. Water pumps through these highly efficient microfluidic channels to absorb all that heat.

Here’s where things get really efficient and innovative, though: rather than piping all that scorching-hot water through a radiator to dissipate the heat (and thus waste it), the team instead uses that hot water as a power source itself, to heat homes or drive industrial processes. The end result is a device that produces about 12kW of electricity, along with 21kW of thermal energy.

Even though that doesn’t amount to a huge amount of energy (the 12kW of electricity is only enough to power a few homes, for instance), it is nonetheless highly efficient. The real obstacle to the implementation of the Solar Sunflower is its cost. Its gallium-arsenide photovoltaic cells, though more efficient than standard PV cells, are not cheap. Add up construction costs and the costs of the fancy cooling system, and the design isn’t going to be able to financially compete with less innovative but sure-fire solar energy harvesters already on the market.

It does have an aesthetic appeal, however. And the innovation at the heart of the design could lead to future advances that might eventually lower the costs. At the very least, the Solar Sunflower adds to the list of highly-efficient alternatives to non-renewables now available to consumers.

credit: Bryan Nelson