* Astronomy

A solar-powered bicycle which allows riders to go faster and use less leg power has been invented.
The bright yellow device, named "Cycle Sol", operates like a normal pedal cycle but has a canopy lined with solar cells overhead.
When the user pedals in the sunshine the rays charge a battery that powers an electric motor in the back wheel, propelling the bike at speeds up to 15mph.

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Silicon as smooth as glass
Every irregularity no matter how small must disappear: Polishing silicon wafers for solar cells and computer chips demands the greatest precision. Until now, wafers could only be inspected after polishing. A new polishing tool continuously monitors the process.
Without silicon there would be no computer industry since most computer chips consist of this semiconductor material. The same is true for solar cells: They too are predominantly silicon-based. The monocrystals are cut in round slices approximately one millimetre thick, which experts call wafers. Their surfaces must be as smooth as glass; irregularities may only be a few nanometers wide, i.e. less than one ten thousandth of a hair. Therefore, after they have been cut out of a large silicon monocrystal, the wafers must be ground and polished. Until now, whether a surface had become sufficiently smooth was only apparent after polishing. If not, the tool had to be reattached and the process repeated a time-consuming procedure. Moreover, the tool can easily nick the silicon when it is being attached. When that happens, the expensive material of the entire wafer must be machined until the surface is even again.
Researchers at the Fraunhofer Institute for Factory Operation and Automation IFF in Magdeburg have developed a polishing tool that can constantly control the pressure on a wafer even during polishing. Its revolutionary feature: Several piezosensors and piezoactors are integrated in the tool. If it comes across an impurity or a material defect during polishing, it intensifies the tools pressure on the surface of the material. The piezosensor compresses somewhat and converts this mechanical pressure into electrical voltage. This in turn signals the actor to change the tools pressure on the silicon and remove the uneven spot.

The primary challenge was integrating the sensors and actors in such a way that the tools surface is unaffected and the sensor is nevertheless close enough to the surface being machined - Susan Gronwald, project manager at the Fraunhofer IFF.

Another advantage: The polishing tool consists of three rings lying inside one another so that a wafers edge can be ground with a different pressure than the inside.
The new tool shortens machining time and simplifies the polishing process even for optical glass lenses.

The pressure with which material is machined could not be measured here until now. Hence, the lenses had to be taken out of the polishing process again and again to inspect the surface with a laser. The final finish grinding was done manually.

The sensor-aided grinding system has been in industrial use for a short time.

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Using a novel technology that adds multiple innovations to a very high-performance crystalline silicon solar cell platform, a consortium led by the University of Delaware has achieved a record-breaking combined solar cell efficiency of 42.8 percent from sunlight at standard terrestrial conditions.
That number is a significant advance from the current record of 40.7 percent announced in December and demonstrates an important milestone on the path to the 50 percent efficiency goal set by the Defense Advanced Research Projects Agency (DARPA). In November 2005, the UD-led consortium received approximately $13 million in funding for the initial phases of the DARPA Very High Efficiency Solar Cell (VHESC) program to develop affordable portable solar cell battery chargers.

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The global search for a sustainable energy supply is making significant strides at Wake Forest University as researchers at the universitys Centre for Nanotechnology and Molecular Materials have announced that they have pushed the efficiency of plastic solar cells to more than 6 percent.
In a paper to be published in an upcoming issue of the journal Applied Physics Letters, Wake Forest researchers describe how they have achieved record efficiency for organic or flexible, plastic solar cells by creating nano-filaments within light absorbing plastic, similar to the veins in tree leaves. This allows for the use of thicker absorbing layers in the devices, which capture more of the suns light.
Efficient plastic solar cells are extremely desirable because they are inexpensive and light weight, especially in comparison to traditional silicon solar panels. Traditional solar panels are heavy and bulky and convert about 12 percent of the light that hits them to useful electrical power. Researchers have worked for years to create flexible, or conformal, organic solar cells that can be wrapped around surfaces, rolled up or even painted onto structures.

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