Luminescent Solar Concentrators (LSCs) are composed of coloured panels of plastic material that have a special characteristic: they can capture sunlight and concentrate it along their edges, where it is intercepted by small photovoltaic cells and converted into electricity. Developed in collaboration with MIT in Boston, the key advantage of these LSCs is that they can produce electricity even in low light conditions, and can be incorporated into architectural structures as transparent elements.

Current photovoltaic technologies rely on panels that are more or less opaque, and perform best in direct light conditions; as such, the only way to integrate these into buildings and architectural structures is to fix them at a certain angle on walls and roofs, avoiding windows and any other element that must remain transparent. The characteristics of our Luminescent Solar Concentrators mean that they can produce electricity even in low light conditions , and can also be used where transparent surfaces are required.

The goal we set ourselves when we started developing LSCs was to create a system that could produce electricity in an efficient manner, even in conditions characterised by diffuse and low light. We were also looking for a material that was light and photostable, and perhaps also easy to produce in various forms, so that we could integrate the technology directly into architectural elements. We obtained these characteristics by adding special luminescent pigments developed in our laboratories to sheets of transparent plastic. When added to the material during the production phase, these photoactive substances can absorb part of the solar radiation and convert it to higher wavelengths: from the band between ultraviolet and visible light to the band between visible and infra-red light. At the same time, the light is transported inside the plastic sheet and concentrated in the edges, via an internal reflection mechanism. Here, we have added rows of small photovoltaic cells that intercept the solar radiation which in turn have been intercepted by the pigments and concentrated inside the plastic plates, transforming this into electricity. We have developed Luminescent Solar Concentrators in a range of colours, but the most efficient of these - now ready for industrial development - have proved to be yellow and red. Meanwhile, we are also working on a range of neutral colour versions.

As a technology, Luminescent Solar Concentrators have been conceived, designed and developed to be installed with ease within other structures, particularly in the construction sector. The sector of reference is BIPV (Building Integrated PhotoVoltaics), which includes all the photovoltaic systems that can be considered an integral part of the building envelope. Specifically, LSCs can be used to create transparent surfaces with photovoltaic properties. This principle has been applied in the Eni Ray Plus® technology that is at the heart of Domal smart windows - presented at Milan Design Week 2018 - which use the sun's rays to power an automatic temperature control system. Consisting of a sheet of "double glazing" composed of two LSCs, these windows feature a Venetian blind inside them, which automatically adjusts according to the response provided by the internal and external light and heat sensors, reducing or increasing sun exposure in response to variations in temperature. The entire system is connected to a battery which is powered by the electricity generated by the LSCs, with no need to be connected to the mains power. Other interesting areas of application within the construction sector include motorway and railway anti-noise barriers and public transport shelters. Elsewhere, greenhouses for flower growing, nurseries and agriculture represent another promising sector - in this instance, panels with pigments that absorb only the solar radiation not used by plants for photosynthesis (for example, green) can be used.

Luminescent Solar Concentrators belong to the category of technologies that boast more than one advantage at the same time. Due to their characteristics and their versatility, LSCs can be used to increase the energy savings of buildings, whilst simultaneously improving their habitability. The use of this solution in intelligent windows through Eni's Ray Plus® technology can reduce energy consumption by 50 to 75%. The yellow colour of these mean that they also improve luminous efficiency , by converting the light spectrum into wavelengths that are more agreeable to the human eye, increasing visual comfort. A key aspect to be taken into consideration is that these improvements can be achieved simply by replacing the old windows, with no need to resort to major building work, and without requiring a connection to the electrical grid.