Featured Research

from universities, journals, and other organizations

Solar energy: Solar concentrator increases collection with less loss

Date:
November 4, 2011
Source:
Penn State
Summary:
Converting sunlight into electricity is not economically attractive because of the high cost of solar cells, but a recent, purely optical approach to improving luminescent solar concentrators may ease the problem, according to researchers.

An LSC is illuminated by a laser beam (central spot) resulting in luminescence that is emitted from the edges and projected onto a white business card. The faintly visible concentric rings and different colors of light on the business card result from microcavity effects.
Credit: Image courtesy of Penn State

Converting sunlight into electricity is not economically attractive because of the high cost of solar cells, but a recent, purely optical approach to improving luminescent solar concentrators (LSCs) may ease the problem, according to researchers at Argonne National Laboratories and Penn State.

Using concentrated sunlight reduces the cost of solar power by requiring fewer solar cells to generate a given amount of electricity. LSCs concentrate light by absorbing and re-emiting it at lower frequency within the confines of a transparent slab of material. They can not only collect direct sunlight, but on cloudy days, can collect diffuse light as well. The material then guides the light to the slab's edges, where photovoltaic cells convert the energy to electricity.

"Currently, solar concentrators use expensive tracking systems that need to follow the sun," said Chris Giebink, assistant professor of electrical engineering, Penn State, formerly of Argonne National Laboratory. "If they are a few tenths of a degree off from perfection, the power output of the system drops drastically. If they could maintain high concentration without tracking the sun, they could create electricity more cheaply."

LSCs can do this, potentially concentrating light to the equivalent of more than 100 suns but, in practice, their output has been limited. While LSCs work well when small, their performance deteriorates with increasing size because much of the energy is reabsorbed before reaching the photovoltaics.

Typically, a little bit of light is reabsorbed each time it bounces around in the slab and, because this happens hundreds of times, it adds up to a big problem. The researchers, who included Giebink and Gary Widerrecht and Michael Wasielewski, Argonne-Northwestern Solar Energy Research Center and Northwestern University, note in the current issue of Nature Photonics that "we demonstrate near-lossless propagation for several different chromophores, which ultimately enables a more than twofold increase in concentration ratio over that of the corresponding conventional LSC."

The key to decreasing absorption is microcavity effects that occur when light travels through a small structure with a size comparable to the light's wavelength. These LSCs are made of two thin films on a piece of glass. The first thin film is a luminescent layer that contains a fluorescent dye capable of absorbing and re-emitting sunlight. This sits on a low refractive index layer that looks like air from the light's point of view. This combination makes the microcavity and changing the luminescent layer's thickness across the surface changes the microcavity's resonance. This means that light emitted from one location in the concentrator does not fit back into the luminescent film anywhere else, preventing it from being reabsorbed.

"We were looking for some way to admit the light, but keep it from being absorbed," said Giebink. "One of the things we could change was the shape and thickness of the luminescent layer."

The researchers tried an ordered stair step approach to the surface of the dye layer. They looked at the light output from this new configuration by placing a photovoltaic cell at one edge of the collector and found a 15 percent improvement compared to conventional LSCs.

"Experimentally we are working with devices the size of microscope slides, but we modeled the output for larger, more practical sizes," said Giebink. "Extending out results with the model predicts intensification to 25 suns for a window pane sized collector. This is about two and a half times higher than a conventional LSC."

The researchers do not believe that the stair step approach is the optimal design for these LSCs. A more complicated surface variation is probably even better, but designing that will take more modeling. Other approaches may also include varying the shape of the glass substrate, which would produce a similar effect and potentially be simpler to make.

"We need to find the optimum way to structure this new type of LSC so that it is more efficient but also very inexpensive to make," said Giebink.

The U.S. Department of Energy supported this work. Argonne National Laboratory has filed for a patent on this application.


Story Source:

The above story is based on materials provided by Penn State. Note: Materials may be edited for content and length.


Cite This Page:

Penn State. "Solar energy: Solar concentrator increases collection with less loss." ScienceDaily. ScienceDaily, 4 November 2011. <www.sciencedaily.com/releases/2011/11/111102125549.htm>.
Penn State. (2011, November 4). Solar energy: Solar concentrator increases collection with less loss. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2011/11/111102125549.htm
Penn State. "Solar energy: Solar concentrator increases collection with less loss." ScienceDaily. www.sciencedaily.com/releases/2011/11/111102125549.htm (accessed July 31, 2014).

Share This




More Matter & Energy News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
Amid Drought, UCLA Sees Only Water

Amid Drought, UCLA Sees Only Water

AP (July 30, 2014) A ruptured 93-year-old water main left the UCLA campus awash in 8 million gallons of water in the middle of California's worst drought in decades. (July 30) Video provided by AP
Powered by NewsLook.com
Smartphone Powered Paper Plane Debuts at Airshow

Smartphone Powered Paper Plane Debuts at Airshow

AP (July 30, 2014) Smartphone powered paper airplane that was popular on crowdfunding website KickStarter makes its debut at Wisconsin airshow (July 30) Video provided by AP
Powered by NewsLook.com
U.K. To Allow Driverless Cars On Public Roads

U.K. To Allow Driverless Cars On Public Roads

Newsy (July 30, 2014) Driverless cars could soon become a staple on U.K. city streets, as they're set to be introduced to a few cities in 2015. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins