PROFESSOR JOHN MO and GANESH SEN share the results and lessons learnt from RMIT’s recent research into the commercial application of solid-state technology lighting.
RMIT University’s strategic research and innovation plan encourages staff and students to participate in collaborative practical research and development projects with industry and technology partners with a focus on the commercial application of research using proven and developing technologies.
In 2010/2011 RMIT’s Research Lounge, which is located in Building 28 (B28) of the university’s Melbourne CBD campus was developed as a pilot site to investigate how new solid state lighting (LED) technologies could be used to provide a cost-effective sustainable solution for retrofitting buildings. Technology partners of the project included ABB, CREE and Reiz, and the industry and project management partner was Eco Refurbishment. Unlike conventional light-for-light replacement, the B28 project adopted an innovative approach in the design and engineering of a retrofit solution. The specifically designed DC electronics provided better illumination distribution than the previous CFL and T5 luminaires.
THE DIFFERENCE DC MAKES
In order to maximise energy utilisation efficiency and to eliminate the need of rewiring during retrofitting, the lighting circuit in the Research Lounge was reticulated in DC mode and specially designed LED luminaires. The entire installation, encompassing some 100 luminaires, with preassembled DC switching gear, line protection and distribution enclosure, was installed within two days.
Since this was a pilot study, prior to the change, the research team measured the energy utilisation pattern of the lounge over a period of two weeks. Using this pattern, the research team estimated the energy consumption after change was only 35 percent of the original level; however, after retrofitting the circuit with smart electronics and DC reticulated circuitry, a saving of 65 percent was realised.
DC is the native environment of LED. Failure mode and effect analyses (FMEA) based on test data from CREE’s LM79 and LM80 laboratory show that the life cycle of a suitably designed LED system can exceed 10 years. The longevity of a DC reticulated LED lighting system will significantly reduce maintenance and facilities management services costs.
TESTING IN A COMMERCIAL ENVIRONMENT
The B28 system design has been further exploited in a commercial environment recently. Sofitel Melbourne on Collins (SMOC), one of the flagship five-star properties of Accor group of hotels in Australia, was presented with the B28 lighting technology and system design developed by RMIT University. At the time, SMOC was investigating appropriate lighting technology available to enhance the existing lighting of 14 floors of the hotel’s guestroom corridors. The existing lighting along the corridor did not provide adequate lighting for guest comfort and safety.
A lighting specification and design criteria were developed by Eco Refurbishment based on RMIT’s B28 lighting application and customised in consultation with the hotel management, with particular importance placed on lighting levels, lighting colour and the overall lighting system effectiveness to blend in with the hotel’s existing interior façade of the corridors.
Emphasis was also placed on the importance of lighting system design for ease of installation without significant disturbance to the hotel’s patrons. The lighting system design also accounted for durability of the lighting system and ease of maintenance in case the lights failed prematurely.
A lighting concept design was established using Cree’s MLB LED diodes, ABB’s 480-watt high powered primary AC-DC switch mode power supplies (SMPS) integrated in control panel with lighting timers and DC protection switch gear.
The lighting fixture was designed using a 1.5-millimetre gauge aluminium formed into a half ‘Y’ symmetrically that housed the custom-made high-powered 2800 K (Kelvin) lighting strip modules with a four-millimetre twin core cable harness.
The cable harness was powered from the service zones of each floor via two power SMPS, one SMPS driving 45 metres of LED lighting strip modules designed in segments of 1.1-metre to 2.1-metre lengths. A second SMPS was used to power the balance of the 45 metres of lighting from the opposite entry of corridor from the service zone.
Each light module was powered via a miniature 3M insulation displacement connector (IDC) tapping between the strip lighting cable tail and main power supply cable harness. This module lighting design using a tap connection into a harness system ensured that replacement of lighting was contained in 1.1-metre and 2.1-metre lengths, rather than having to uplift an entire 45 metres of continuous strip lighting, which was initially being considered.
The aluminium lighting fixture was fixed to the exiting ceiling-wall balustrade along the entire guestroom corridor spanning 90 metres per floor elevating from level 36 to level 49. Level 36 was used for prototyping the design concept for approval from the hotel management, after which the lighting concept design was rolled out to all the guestroom floors.
DESIRED OUTCOMES ACHIEVED
Adoption of RMIT’s B28 system design has achieved the desired outcome from the client’s perspective:
- better lighting luminous levels without compromising energy efficiency
- consistent lighting colour aesthetics
- improved reliability and reduced maintenance costs, and
- guaranteed LED performance over five years of continuous usage by selection of LED based on scientific data.
NO GRID POWER REQUIRED
The DC circuit unlocks the option for direct renewable energy feeds from either solar or wind. These renewable power sources are best used to operate the DC reticulated lighting system. B28 lighting control system has been designed with a smart controller capable of auto detecting power feeds from renewable source, otherwise, power is supplied by the battery bank.
With a significant reduction in energy usage, a compact battery bank can be used and still maintain up to four hours of continuous usage. This means if the system is operated carefully, no grid power is required. Hence, by the same argument, SMOC has the potential of using renewable energy sources, thereby achieving zero net energy use.
More details on this research can be found from this research paper: John PT Mo, Syed A Ehsan and Ganesh Sen (2012) Sustainable Lighting System Design for Retrofitting, Advanced Materials Research, Vols 347-353, pp 3999-4002.
Professor John Mo is the discipline head of manufacturing and materials engineering for RMIT’s School of Aerospace, Mechanical and Manufacturing Engineering. Ganesh Sen is the business development director of Eco Refurbishment.