Increasing Solar Efficiency through Luminescent Solar Concentrators
For years, scientists have sought to harness energy from the sun, using lenses and mirrors to focus and track sunlight, or photovoltaic cells to absorb and convert sunlight to electricity. Their goal is for solar energy to reach “grid parity”—that is, for its cost to become comparable to that of more traditional sources of energy like coal, oil, natural gas and nuclear power. Thus far, however, converting sunlight into electric power has proved to be prohibitively expensive.
Scientists from Northwestern University and Argonne National Laboratory have developed an inexpensive alternative to traditional methods of collecting solar energy. Their innovation, a luminescent solar concentrator (LSC), captures sunlight without the need for tracking the sun, while significantly reducing absorption losses that have plagued previous LSC designs. The discovery offers a path to a lower-cost, efficient way to harness the power of sunlight, even in regions with fewer sunny days.Description
The LSC consists of two thin layers of fluorescent-plastic film on glass. The top layer is imbued with a fluorescent dye and also structured with different thicknesses across the concentrator surface. The concentrator captures light rays, changes them to a different wavelength and re-directs the photons to photovoltaic cells at the outer edges of the concentrator, where they are converted into electricity.
The technology works through a “resonance-shifting” phenomenon, in which light fails to recognize the environment from which it is emitted, drastically reducing its reabsorption. This is accomplished through the use of two thin layers that act as a bilayer waveguide, with the resonance of the cavity dependent upon the thickness of the top layer. Since the thickness alters the resonance, the light waves experience a kind of “amnesia.” When the photons fail to recognize where they entered the LSC, they are less likely to be reabsorbed or scattered.
A path toward use of this technology is to choose a color of emitted light that can best be absorbed by the photovoltaic material. The total system can efficiently convert sunlight into electricity without requiring costly tracking machinery. A stack of properly designed LSCs, coupled to appropriate photovoltaic cells, would allow a broader portion of the spectrum of sunlight to be absorbed, re-emitted and converted into electricity.Benefits
- Will facilitate more affordable collection of solar power, leading to more cost-effective use of solar energy; and
- Does not require machinery for tracking the sun.
- Used for both commercial and residential purposes; and
- Can operate in regions where there is indirect illumination from the sun (e.g., it can work with scattered light).
This technology currently works with light that propagates in one direction. In order to fully realize the benefits of this technology, it will need to work for light traveling in two dimensions in the concentrator. This requires further modeling and fabrication efforts.
The resonance-shifted LSC for light that propagates in one dimension has been developed. Argonne is seeking collaborators to develop and/or license this technology for commercial uses.Patents and Patent Applications
|Title and Abstract||
Resonance-shifting luminescent solar concentrators
An optical system and method to overcome luminescent solar concentrator inefficiencies by resonance-shifting, in which sharply directed emission from a bi-layer cavity into a glass substrate returns to interact with the cavity off-resonance at each subsequent reflection, significantly reducing reabsorption loss en route to the edges. In one embodiment, the system comprises a luminescent solar concentrator comprising a transparent substrate, a luminescent film having a variable thickness; and a low refractive index layer disposed between the transparent substrate and the luminescent film.
|Technology ID||Development Stage||Availability||Published||Last Updated|