Monday, October 15, 2007

Spherical Solar Cell Production Breakthrough

With a diameter of a mere 1 to 1.5mm, Sphelar can be connected either in parallel or in series. This enables diverse spherical products to be created, such as dome-shaped solar cells and "flexible" solar cells aligned on soft film substrates. It is also possible to create "power-generating window glass" while maintaining a certain level of transparency. Caption & Image Credit: Kyosemi Corporation

Spherical Solar Cell Production Breakthrough

Traditional solar cell production techniques require the use of more silicon and are inflexible as to the shape the cell arrays can be made into.

Solar cells use the property of semiconductors, which generate an internal charge when they receive light. Currently the mainstream "silicon solar cells" comprise two types of semiconductors with different electrical properties - n-type and p-type - connected to one another (see diagram). When the surface where p-type and n-type semiconductors are joined receives light energy, free electrons (negative) and holes (positive) are generated, and the internal electrical field at the pn junction causes the electrons to move to the n-type semiconductor, and the holes to move to the P-type semiconductor. If the electrodes on the two types of semiconductor are connected by an external wire (see diagram), electrons move along the wire, i.e. current is generated. Caption & Image Credit: Kyosemi Corporation

This breakthrough in the way solar cells are created utilizes gravity to form the crystallized silicon into energy converting spheres. The spherical shape allows the silicon cell to grab and convert light from any direction … even light that bounces off of our Oblate Spheroid.

The reason why a room does not become dark even if it does not receive direct sunlight is a variety of reflected and diffused light. However, conventional flat solar cells were unable to effectively harness this indirect light. In addition, the sun takes on a many different positions according to the season and time of day, so in order to obtain a stable supply of power, there was a need to change the orientation of the solar cell by constantly following the sun. Sphelar® captures light from all directions, which means it can catch reflected light and diffused light. In addition, there is no need for the superfluous operation of tracking the sun. The spherical light-receiving surfaces achieve unprecedented high generation efficiency. Caption & Image Credit: Kyosemi Corporation

This edited from Digital World (Tokyo) via SlashDot -

1mm diameter solar cell spheres formed in freefall by gravity
By J Mark Lytle - Digital World (Tokyo) October 12th, 2007

The traditional flat
solar panel looks like becoming a thing of the past now that a Japanese company has developed a spherical equivalent that is both more efficient and far cheaper to make.

Conventional flat solar cells are produced by slicing crystalline silicon ingots, generating a large quantity of "Kerf loss" in the production process. In contrast, Sphelar is produced using a unique process whereby melted silicon is subjected to free fall, and spheres are formed naturally by the microgravity conditions, so there is hardly any waste of raw materials at all. This results of course in a dramatic reduction in costs, and helps ensure the efficient use of silicon, a finite resource. Sphelar is an environmentally-friendly product, not only in terms of performance but also during the production phase. Caption & Image Credit: Kyosemi Corporation

The Sphelar, which is the brainchild of Kyoto-based Kyosemi, is a perfectly round solar cell that can be made as small as 1mm in diameter. In serial or parallel, hundreds or thousands of the devices can be used to form a solar panel of any shape.

While it may not seem like a major difference, the practical effect of making a non-flat solar panel is that it doesn’t have to precisely face the sun to capture energy. In fact, Sphelar cells can generate electricity from both direct and indirect sunshine; effectively soaking up available light whatever direction it comes from.

Construction methods are also efficient - less silicon is needed to make a Sphelar than a conventional solar cell as the spheres are crystallized out of molten silicon by gravity during freefall from 14m. Standard cell manufacturing results in half as much silicon being wasted as is actually used.

Perhaps the most flexible aspect of the new cells is their ability to be molded into any shape needed and placed in any location. Possibilities include solar panels in awkward places or even windows that generate electricity through Sphelar cells embedded in the glass.

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