New Solar Concentrators advance Solar Power Possibilities

Marc Baldo
Research Laboratory of Electronics

Organic solar concentrators developed in the laboratory of EECS Prof. Marc Baldo. (photo: Donna Coveney, MIT News Office).

Organic solar concentrators developed in the laboratory of EECS Prof. Marc Baldo. (photo: Donna Coveney, MIT News Office).

Solar cells remain an expensive source of electrical power. Our work addresses the cost of solar electricity. We follow the example of the dominant solar energy system on earth – photosynthesis, which has evolved separate structures to perform the two functions of a solar cell: absorbing light and generating charge. Adopting the same architecture in synthetic solar cells allows us to improve efficiency and potentially to lower costs. For example, it is wasteful to employ large areas of crystalline silicon merely to absorb light. A solar concentrator, which collects light for a small solar cell, promises to be cheaper and more efficient.

We have developed new technologies that address the weaknesses of traditional solar concentrators. Conventional concentrators track the sun to generate high optical intensities, often by using large mobile mirrors that are expensive to deploy and maintain. They require direct sunlight, solar cells at the focal point of the mirrors must be cooled, and the entire assembly wastes space around the perimeter to avoid shadowing neighboring concentrators.

Marc Baldo, EECS associate professor (left) and Shalom Goffri, postdoc in MIT’s Research Laboratory of Electronics (right) hold examples of organic solar concentrators. (photo: Donna Coveney, MIT News Office).

Marc Baldo, EECS associate professor (left) and Shalom Goffri, postdoc in MIT’s Research Laboratory of Electronics (right) hold examples of organic solar concentrators. (photo: Donna Coveney, MIT News Office).

High optical concentration from diffuse light without excess heating in a stationary system can be achieved with a luminescent solar concentrator (LSC). [A. Goetzberger, W. Greubel, Applied Physics 14, 123 (1977)]. LSCs consist of a dye dispersed in a transparent waveguide. Incident light is absorbed by the dye and then re-emitted into a waveguide mode. The energy difference between absorption and emission prevents re-absorption of light by the dye, isolating the concentrated photon population in the waveguide. In this way, LSCs can achieve high optical concentrations without solar tracking. Unfortunately, the performance of LSCs has been limited by self-absorption losses that restrict the maximum possible concentration factor.

Our work has demonstrated an efficient variant of an LSC that exhibits optical concentrations suitable for practical applications. [ M. J. Currie, J. K. Mapel, T. D. Heidel, S. Goffri, M. A. Baldo, Science 321, 226 (July 11th, 2008)]. The concentrated light increases the electrical power obtained from each solar cell by a factor of over 40. The system is simple to manufacture, and could be added onto existing solar-panel systems, increasing their efficiency by 50% for minimal additional cost, substantially reducing the cost of solar electricity.

Schematic illustrating the concept of the Baldo solar concentrators coutesy of the National Science Foundation.

Schematic illustrating the concept of the Baldo solar concentrators coutesy of the National Science Foundation.

4 Responses to “New Solar Concentrators advance Solar Power Possibilities”

  1. Jonno says:

    Excellent article, we have to take a look at solar energy as the real answer to the globes environmental crisis, after all it makes perfect sense, its already produced, and it’s renewable and green.

  2. Diy says:

    The possibilities are huge for residential solar energy. With the rising cost of energy solar power will only become more attractive in the future.Solar power is important to the evolution of the society.

  3. Now you just have to make one small enough for residential use :) I’d love to use solar power to reduce my dependence on the grid but living in the UK where we rarely see the sun makes it difficult.

    Even wind turbines although we get plenty of wind getting planning permission is difficult or impossible. I look forward to the day when solar panels are efficient enough to make it worthwhile installing them in this country.

  4. John says:

    Solar panels ARE efficient enough to make it worthwhile installing them in the UK and indeed many other temperate climates AS LONG AS they are south facing, that’s from what I can gather. I wonder if these luminescent solar concentrators still have to be south facing? Increasing solar efficiency by 50% would certainly mean more people would go solar.

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