Solar energy for the built environment
Harnessing the Sun's radiation to produce electricity is an extremely sustainable way to power human activities. Technology that concentrates solar energy can increase efficiency significantly. LSCs could substantially reduce costs compared to large-area silicon-based devices, and have the benefit of absorbing both direct and diffuse solar radiation so that Sun tracking is not required. However, low efficiency of LSCs represents a stumbling block to commercialisation of this technology. Scientists initiated the SOLAR-PLUS (Maximizing the efficiency of luminescent solar concentrators by implanting resonant plasmonic nanostructures (SOLAR-PLUS)) project to tackle this issue by combining theoretical, modelling and experimental activities. One project outcome was the fabrication of an LSC utilising silicon that absorbs the Sun's light and then fluoresces, creating a glow that propagates to solar cells. Scientists immersed metallic nanoparticles in a thin fluorophore layer to create surface plasmon resonance and thus boost energy conversion efficiency of LSCs that currently cannot exceed 8 %. The team devised the first-ever experimental method for simultaneously determining optical efficiency and loss mechanisms in LSCs such as reabsorption losses, escape-cone losses and quantum yield losses. In addition, a hybrid model was designed that couples nanoscale simulation methods with Monte Carlo path tracing methods, thereby allowing the simulation of large-scale LSCs that contain nanostructures. Results show that metallic absorption causes substantial optical losses that limit the applicability of plasmonics for LSCs. Other simulation activities included accurately describing fluorophore alignment and linking, and the Förster resonance energy transfer (FRET) mechanism. Homeotropic alignment improved the light trapping efficiency while linking induced FRET between the fluorophores to circumvent the reduced absorption of homeotropic alignment. Results show that both fluorophore alignment and FRET enhance LSC conversion efficiency. As a proof of concept, scientists developed an LSC with quantum dots linked to organic dye molecules, proving that quantum dots exhibit high quantum yield due to the high efficiency of the FRET mechanism. Optimising energy conversion efficiency while reducing LSC cost will encourage widespread uptake and help the EU limit its dependence on fossil fuels. SOLAR-PLUS' flexible LSC prototype can show the way to integrating LSCs into the built environment.
Keywords
Solar energy, luminescent solar concentrator, SOLAR-PLUS, plasmonic, metallic nanoparticles
