Luminescent solar concentrators (LSC) are a promising technology for building integrated photovoltaics (BIPV) given the wide variety of forms and colours that can be realised. Given the flexibility of the technology, the use of ray-trace modelling is indispensable in the design, performance evaluation, and optimisation of LSCs. This work begins by comparing a threedimensional (3D) ray-trace model of an LSC with experimental results. The study includes 70 samplesboth square and circular LSCs, containing five different fluorescent organic dyes (BASF Lumogen) each at seven different concentrations. The figure-of-merit used for performance evaluation was the average power density determined at the LSC edge sheet, measured using an optical fibre connected to a spectrometer. The results demonstrate that 3D ray-trace results gives good agreement with the experimental measurements, to within around ±5% within a wide concentration range (optical density = 0.05-8) and a maximum difference of ±13%. The wide range of colours achieved is presented in a CIE chart. Overall, the validated experimental results give confidence in the use of modelling for future larger LSCs for BIPV. Therefore, based on these results and the colours achievable, a model of a stained-glass window is constructed and its performance throughout a solar day is simulated.

Increasing colour variety in photovoltaics can improve the uptake of this renewable technology, which is vital to the creation of sustainable architecture. However, the introduction of colour into photovoltaics often involves increased cost and decreased efficiency. A method was found to add colour to photovoltaics, using luminescent materials: fluorescent organic dyes (BASF Lumogen). These selectively absorb and emit light, giving a good balance between colour addition and electricity production from underlying photovoltaic cells. Very small amounts of Lumogen dye were added to a silicone encapsulant (Dow Corning Sylgard 184), which was then used hold photovoltaic cells in place between sheets of painted glass. When making sufficient quantities of dyed encapsulant for a 600 x 450 mm testpiece, the dye colours faded, with low levels of fluorescence, although some colour was retained. Improvement of the method, including testing of alternative encapsulant materials, is required, to ensure that the dyes continue to fluoresce within the encapsulant. Although the Lumogen dyes are quite stable when compared to other dye molecules, in general organic dyes are not yet sufficiently durable to make this technology viable for installations that are to last for more than 20 years: the guaranteed lifetime of standard photovoltaic modules. Dye replenishment, or replacement of materials, will be required; or a product with a shorter 'useful' lifetime identified. This method opens up a wide variety of architectural glass design opportunities that incorporate photovoltaics, providing an example of one new medium to make eco-architecture more aesthetically pleasing, whilst generating electricity.

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