LEDs have already attracted entrepreneurs and designers and are starting to be more and more applied in the lighting fixture design with heterogeneous results in terms of lighting features and performances. LED Lighting is transforming not only the industrial strategies and the lighting designer attitude toward lighting projects but also the design of lighting fixture.
LEDs are generating a new radical transformation in the lighting sector from an operational and cultural point of view: it is undoubted that LED lighting projects require a deeper and spread knowledge from other sectors and a wider collaboration between different stakeholders in all the phases of the R&D process.
“SSL technology gives lighting designers and industry an almost unlimited freedom to develop new lighting concepts and design parameters. It enables new forms of luminaires and lighting systems including their full integration into building elements (walls, ceilings, windows)”.
In this, outdoor LED applications have already seen and are expected to see a fast growth in market share up to 70 percent or more by 2020, utilizing the advantages of LED. The major technology shifts in outdoor lighting are towards both HID and LED lighting, increasing their share within white-colour preference for street application. LEDs lighting fixture shows two competitive advantages: a potentially longer lifetime (if designed properly), higher efficiency and the lighting management (dynamics and interactivity). Yet, the rapid evolution of LED technology presents a challenge to manufacturers in creating and maintaining complete product lines.
Research aim and focus
To study this phenomena and also providing some solutions, in 2011 I was involved in the development of a project of LEDs based lighting fixture for outdoor application. The driving idea was to provide a compact solution in form of modules or light engine in order to ensure performance and product continuity. The same module, thought as a bi-dimensional geometry with reduces materials, volumes and components, could be equipped with different technologies meanwhile the Leds were upgraded. Other features of the system would be energy efficiency (in terms of luminous efficacy, DLOR, Utilization coefficient CU and also in terms of controls). More than this, it would have been developed with low cost techniques as an open source lighting (patent free).
Building on the modular fixture idea, in 2011 an experimental lighting device was developed in the framework of the research project funded by ENEA at the Politecnico di Milano (Laboratorio Luce) and it was aimed at developing high-efficiency intelligent lighting systems at low production costs to provide illumination of “Smart Street”.
Plus, Public Lighting Unit System, is also scalable and can be configured in several configuration in relation to different application: two or four modules equipped with different free form lenses by LEDIL with the aim of obtaining diverse photometric distribution to implement S and CE categories of street lighting.
The Power LEDs were selected, after a background research and consequent measurements and comparison, for the wide availability of lenses available and also because of high efficiency (about 80-85%) . The combination of free-form asymmetrical lenses for street lighting by LEDIL (TDW and TDN) characterized by different emission allows the creation of modules that realize complex photometric distribution such as those required by street lighting applications. It allows obtaining good photometric distribution which does not require expensive investments on the customization and production of lenses. More than this, Plus was developed by deeply studying the optical and thermal interfaces in order to determine the best geometrical shape for efficiency and lighting performance. The final design was a compromise between lowering the shading between lenses and the optical support and containing the device dimensions. Virtual simulation via CFD software (for fluid-dynamic calculation) about thermal performance of the lighting fixture allows reducing the number of prototypes giving a wider degree of freedom to the design in defining both innovative and functional heat sink in term of shapes and geometry. The behavior of the dissipation system was simulated since the initial phase of the product design in order to reach a fair compromise between freedom of design, dissipation efficiency of heat produced by LED sources while containing production costs.
The basic idea was not only to give complete information about the methodology of research and design, about critical issues and lesson learned during the research process but also to customize the modularity concept with several different concept of design that let every designer or producer to define its own aesthetics of the entire lighting fixture. Some visualization as examples were provided.
Finally, the prototypes were realized by CrossPoint S.r.l. in order to be validated and tested in terms of thermal and optical performances.
More details are in the following presentation (italian language): design_PLUS_ENEA
A shorter and revised version in english (part of a Lecture presented at the Politecnico di Milano, Laboratorio Luce – LIGHTING PRODUCT DESIGN Introductory course on lighting fixture design) can be found here: LECTURE_PART1_DARIACASCIANI_PLUS
 GREEN PAPER (2011) Lighting the Future. Accelerating the deployment of innovative lighting technologies. European Community (December 2011)
 McKinsey & Company, “Lighting the way: Perspectives on the global lighting market”, http://img.ledsmagazine.com/pdf/LightingtheWay.pdf, accessed the 30 September, 2011.
 Mikhail A. Moiseev, Leonid L. Doskolovich and Nikolay L. Kazanskiy, “Design of high efficient freeform LED lens for illumination of elongated rectangular regions,” Opt. Express 19, A225-A233 (2011).
Design & Engineering by Daria Casciani in collaboration with Eng. Fulvio Musante
Publish report about the research and design
Rossi M., Musante F., Casciani D. (2011) Ricerca di sistema elettrico. Relazione relativa all’attività A: Contributo allo sviluppo di sistemi di illuminazione intelligenti per la gestione della “Smart Street” Parte seconda: Concept – P.L.U.S. (Public Lighting Unit System) Report RdS/2011/181 September 2011, accessed the 08/09/2014 http://www.enea.it/it/Ricerca_sviluppo/documenti/ricerca-disistema-elettrico/illuminazione-pubblica/rds-181.pdf
Rossi, M.; Casciani, D.; Musante, F. (2012) Report Ricerca di Sistema Elettrico. Advance LED Lighting design nell’illuminazione pubblica. Relazione tecnica Attività C.3: Ricerca e Misure su sorgenti e prototipi. Report RdS 2012-276. September 2012, accessed the 08/09/2014 http://openarchive.enea.it/handle/10840/4607
Published paper about this research
M. Rossi, Musante F., Casciani D., Fumagalli S. (2013) PLUS, Public Lighting Unit System, Lux Europa, Polski Komitet Oswietleniowy SEP Krakòw
Casciani D., Musante F., Paleari D., Rossi M. (2012), Analysis of Three Projects to Optimize the Design of Street Lights, p. 156-167, LED Lighting Technologies – Winning Approaches ISBN 978 –3 – 9503209 – 4 – 7 Luger Research e. U. presented during the LED professional Symposium + Expo 2012, Bregenz, 25 – 27 Sept. – 2012