Luminescent Solar Concentrators (LSC)
Luminescent Solar Concentrators (LSCs) are composed of coloured panels of plastic material that can capture sunlight and concentrate it along their edges, where it can be converted into electricity by small photovoltaic cells. They capture solar radiation over a large area and then convert this radiation into luminescence and direct it to a smaller target with a photovoltaic receiver.
In 2013, researchers at Michigan State University demonstrated the first visibly transparent LSCs with a power conversion efficiency of close to 0.5%, efficiencies of over 10% are possible. In 2021, they would makeover their Biomedical and Physical Sciences Building with fully transparent 'solar windows' made of LSCs. More here.
LSCs are transparent active 'photographic plates' made from plastics to which 'special luminescent pigments' or dyes have been added during the production phase. These photoactive substances can absorb light from a wide spectrum of solar radiation and they convert it to higher wavelengths: from between ultraviolet and visible light to between visible light and infra-red light.
With the help of an internal reflection mechanism, the light is transported inside the plastic sheet and concentrated in the edges where rows of small photovoltaic cells have been added to intercept the solar radiation which in turn have been intercepted by the pigments and concentrated inside the plastic plates and transformed into electricity.
LSCs have been developed in a range of colours but the most efficient of these have proved to be yellow and red. Work continues on the development of a range of neutral colour version.
LSC panels are cheaper than classic photovoltaic panels. In fact, they are made of plastic or glass plates on which the luminescent molecules are deposited. Also, the heating of silicon cells which often leads to reduced efficiency and energy losses is reduced.
The key advantage, however, is that they can produce electricity even in low light conditions, and can be incorporated into architectural structures as transparent elements. Efforts are solar windows depend on this technology. Currently, photovoltaic technologies use panels that are mostly opaque and work best when receiving direct light. This means that the only way to incorporate these panels into buildings and structures is to attach them to walls and roofs at a specific angle, avoiding windows or any other transparent elements.
LSCs are generally less efficient than conventional solar cells. The reason is that some of the re-emitted light escapes the volume of the waveguide and can no longer be converted into electrical energy.
LSCs were created as a technology that can easily be integrated into other structures, especially in the construction industry. The primary application of LSCs is in Building Integrated PhotoVoltaics (BIPV), which refers to photovoltaic systems that can be incorporated into a building's envelope. One unique feature of LSCs is their ability to transform transparent surfaces into ones with photovoltaic properties.
Their characteristics mean that they can be used to increase the energy savings of buildings while at the same time, improving their habitability. The yellow color of LSCs enhances luminous efficiency by converting the light spectrum into wavelengths that are more pleasing to the human eye, leading to increased visual comfort. One of the advantages of LSCs is that they can be easily implemented by replacing old windows, without the need for extensive construction work or a connection to the electrical grid.
Also, they can be used in mobile electronic devices and fabrics (e.g., backpacks).
Other potential applications for LSCs in the construction industry include motorway and railway noise barriers and public transportation shelters. LSCs are also well-suited for use in greenhouses, nurseries, and agriculture. In these settings, panels with pigments that only absorb solar radiation not used by plants for photosynthesis (e.g., green light) can be utilized.
The production costs of traditional solar cells are still relatively high. The low conversion efficiency of silicon cells cannot increase without a simultaneous increase in production and retail costs. LSCs is one of the many attempts to solve these problems and create new and economical possibilities.