Glass sphere concentrator offers creative solution to improving solar PV efficiency

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 rightRawLemon Beta-ey solar sphere) 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

© 2014 Solar Choice Pty Ltd

James Martin II

Contributor at Solar Choice
James was Solar Choice's primary writer & researcher between 2010 and 2018.

He is now the communications manager for energy technology startup SwitchDin, but remains an occasional contributor to the Solar Choice blog.

James lives in Newcastle in a house with a weird solar system.
James Martin II

Comments

  1. The problem faced by this model is the high temperature obtained in the panel
    So as we know the efficiency decreases with increase in temperature…
    So can u suggest a possible solution for this…
    Like a photovoltaic which is efficient enough to sustain under high temperatures more than 100deggres

  2. I am very interested in knowing more and a possible installation. But I am in Canada. Do you have anything set up in Canada yet? Would you like too? Solar energy is taking off here!!!!

    Thank you and have a GRRRRRREAT day! …Owen

    1. Hi Owen,

      Thanks for the comment. The fact is, though, that we’re only reporting on this invention–we’re not distributors, or affiliated with Rawlemon in any way. I’d recommend connecting with the company directly, but even then it looks like at this juncture they only have small-scale versions of the solar sphere technology in commercial production.

  3. In this article they say “it’s only more efficient if it is cheaper than the current PV flat panel system….” Not true AT ALL. This method is more efficient regardless of cost. The cost factor is not the issue. The issue is that flat panel farms are inefficient and have to take up a wide range of flat space. But these spheres can be STACKED (so a very small amount of land is used instead of the “flat farm” method), or put into windows of buildings, or even in windows in a cell method, and even work at night and on very stormy days. When did initial cost become the only determination on efficiency? These spheres are FAR more efficient than flat panels in terms of land usage and long-term energy storage

    1. Hi Andrew,

      Thanks for commenting. The article doesn’t contain the statement you quoted. You’re absolutely right that cost has nothing to do with efficiency, but the comments on the article focus on the cost-effectiveness of the sphere technology relative to flat panels.

      While it is true that the solar sphere approach likely increases efficiency (in that more power can be produced using the same amount of PV material because the sunlight is highly concentrated), you still need a larger area of glass sphere surface to capture that sunlight, which will be projected onto a small piece of PV material. Then there’s the heat factor–the efficiency of solar cells decreases as temperature increases, and having multiple suns concentrated a small area of PV substrate will result a drop in efficiency. So unless there’s more R&D done into reducing the impact of high temperatures (which results in a solution that doesn’t significantly increase the cost of the cell in question), it doesn’t seem that this technology would necessarily be the superior choice when compared to a conventional solar farm (with tracking) in terms of economic competitiveness.

      This could change in the future if the technology is refined; there is certainly promise in the fact that these units could be mass-produced and sold as off-the-shelf electricity generators that simply need to be placed on your lawn. And as you point out there is certainly potential for other interesting applications of the solar sphere technology–but because of their weight & relative complexity, replacing flat panels on roofs is definitely not one of them.

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