Greater sunlight-to-energy conversion efficiency is something that solar photovoltaic technology manufacturers and researchers alike strive for, and cost-effective efficiency improvements are something of a Holy Grail in the PV industry. Approaches vary widely: Improvements in materials, components and manufacturing methods are some of the most common methods for raising efficiency. Solar tracking systems are another economical and popular way to extract more power from the sun throughout the day. Concentrated solar PV, meanwhile, while less common and not as cost-effective, combines tracking the sun with the added bonus of focusing its energy to yield more electricity with less PV material.
Occasionally, however, we hear about ‘outside the box’ approaches that are more radical in the way that they look at the problem and the technologies that they use. US-based Solyndra for example, now infamous for its bankruptcy, found a way to track the sun by revolutionising how solar panels are constructed–with PV tubes instead of flat panels, so that the sun’s rays would naturally fall in a straight line on its surface, regardless of its angle in the sky throughout the day. Other interesting approaches have included spinning solar tripods (which purportedly cool the solar cell through spinning) and even ‘solar robots’ which do things like adjust panel tilt & orientation throughout the day for optimal exposure, or which work to keep panels clean.
One of the latest innovations to appear comes from a German Architect named André Broessel, whose idea earned him a finalist spot for the World Technology Network Award last year and whose company is currently running a fundraising campaign on Indiegogo. What he has designed is a kind of concentrating solar PV (CPV) device, but instead of using mirrors to reflect and focus sunlight on a photovoltaic cell or cells, his approach takes advantage of the simple geometry of a glass sphere. Rather than moving a heavy piece of equipment to track the sun as it moves through the sky (as most sun-tracking CPV technologies do), a much lighter kind of rounded arm containing PV cells revolves around a water-filled glass globe. Thanks to the properties of spheres, the sun’s rays are automatically captured and concentrated directly on the opposite side in line with the sun–without complex tracking machinery. The sphere can even take advantage of the weaker, diffuse solar radiation available on cloudier days. Some are saying that the technology could improve the yield of a solar cell by up to 35% compared to an similarly sized solar cell without the concentrator.
Although it’s apparent from the Indiegogo campaign that Mr Broessel’s company, Rawlemon, is seeking to commercialise the technology and disseminate it to the masses (initially in the form of a solar phone charger much smaller than the monument-style device pictured to the right) it is questionable whether the solar sphere solution is more economical and practical than conventional flat panel PV. First of all, the units are only more cost-effective if their total production cost is less than that of a conventional panel with the same rated power output–the devices may use a smaller area of PV cell, but their overall size and weight are still greater (and good luck mounting them on your roof). On top of this is the possibility that the added heat that results from the increased concentration of sunlight could be counterproductive in terms of increasing power yields–a hurdle that CPV technology developers have worked hard to find ways around.
Nevertheless, it’s hard to argue that there isn’t a great deal of appeal in the ‘cool factor’ of Rawlemon’s invention. Given the aesthetics and applications, it would not be surprising to see the company’s solar spheres becoming common as decorative yet practical ornaments in yards and gardens around the world.
Images via Rawlemon
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