The New Shape of Solar?

Imagine if the earth were flat.

Not only would ships hurtle off its edges into the void; due to the limited angle-of-solar-incidence, days would most likely be shorter, darker and colder. Because less surface area would be directly exposed to the sun, less solar radiation would be absorbed by the earth.

The same principle applies to solar panels. The flat shape of the typical photovoltaic cell requires that, in order to maximize its efficiency, its position be adjusted to correspond to the shifting sun throughout the day. Solyndra, a California-based company that specializes in the design and manufacture of pV systems, is now applying this simple geometric principle to create cheaper and more efficient solar arrays.

Solyndra’s cells resemble the ubiquitous fluorescent lighting tubes found in many homes and apartments and consist of one smaller glass tube encased within another. The inner tube is coated with a compound known as CIGS (for copper, indium, gallium and selenide), which is used to make thin-film photovoltaics. The outer tube serves to keep moisture out and act as a solar concentrator, focusing photons onto the compound coating. Though thin-film systems are currently less efficient than traditional silicon-based systems, thin-film offers many advantages in that it is cheaper to produce, uses less material and can be deposited on a wider variety of surfaces. Many companies therefore are banking that thin-film solar will be the future of renewable energy. As Solyndra has discovered, its ability to be shaped into this tubular design makes the case for thin-film even stronger.

First of all, the tubular arrays can collect sunlight from any direction, even from below, so most cylindrical systems are placed on white-painted substrates in order to reflect light back up into the tube, as well as absorbing it directly from above. This allows these arrays to collect 20% more sunlight than standard flat systems, according to Solyndra’s estimates. In addition, the cylinders are easier to install and maintain, thereby reducing labor costs; traditional flat panels need to be carefully arranged so that they don’t shade each other, a time-consuming and labor-intensive process, and they also need to be tilted to follow the sun’s trajectory. This means that, not only can cylindrical arrays do away with automatic tracking systems that are expensive and can limit the system’s efficiency, but they are also less prone to damage caused by wind and exposure to other elements. This helps to alleviate one of the other drawbacks of flat-panel systems – maintenance and replacement costs associated with hurricanes and other storms.

Solyndra is currently targeting only commercial rooftops, but with improved efficiency and incentive policies, that will hopefully change; their systems are popular in Germany and Spain, both countries with progressive feed-in tariffs that help mitigate the start-up costs for solar installation. Their largest customer is Phoenix Solar, a German company that has contracts with Solyndra worth $1.2 billion. Among Phoenix Solar’s Solyndra-designed arrays are five prototype systems here in the U.S., including in California, Utah and Florida. If these tubes prove they can overcome the obstacles associated with traditional arrays, the iconic flat panel may soon be replaced by an altogether different shape.

Sources: “Cylindrical Solar Cells Give Whole New Meaning to Sunroof”, Scientific American;“Tubular Sunshine”, The Economist;“Solyndra, with over $600M in funding, finally shows its solar hand”, The New York Times; “Better Solar For Big Buildings”, MIT Technology Review; “Inside Secretive New Solar-Tech Factory”, Wired; “Measuring Solar Spectral and Angle-of-Incidence Effects on Photovoltaic Modules and Solar Irradiance Sensors”, Sandia National Laboratories; “”Effect of sun angle on climate”, Wikipedia; “Shading: Solar Incidence”, squ1.org/wiki/Solar_Incidence; “Earth-Sun relationships and insolation”, www.eoearth.org; www.solyndra.com; www.phoenixsolar.com.


Posted on Wednesday, November 12th, 2008 at 1:39 pm | Tagged in Energy, Energy Efficiency, Green Building, Photovoltaics, Renewables, Sustainability, Technology | posted by Jamie

AddThis Social Bookmark Button