reLight app: easier and faster to inspect lighting systems

Research in focus October 2013

In Europe, lighting systems account for some ten percent of overall electricity demand. The majority of this power is consumed by old systems. Renovating these systems would yield huge energy savings of two thirds or more in many cases. What energy and lighting consultants do is sniff out this kind of savings potential. The concepts they devise make sense from lighting engineering, design, and energy perspectives. But the bigger the building, the more laborious and time-consuming the analysis phase. “Unlike heating systems, for which the technology is generally centralized, with lighting you have to go into and study every single room,” explains Berat Aktuna, a scientist in the Lighting Technology and Passive Solar Systems working group at the Fraunhofer Institute for Building Physics IBP. “So lighting experts have often had to carry lots of printouts of checklists with them and painstakingly fill them out by hand on site. This is precisely why people often don’t bother to have existing lighting systems inspected properly.” The new reLight app for mobile devices such as tablet computers and smartphones makes this analysis work easier for lighting experts when inspecting buildings. It also offers other useful energy consultancy functions, such as creating cost comparisons over several years. It was Berat Aktuna himself who developed this practical, innovative application.

“Not only is the reLight app fast and easy to operate, it also does away with the need for time-consuming, error-prone tasks such as typing up data originally recorded by hand,” says Aktuna. “Graphics, pictures, and explanations support users and guide them intuitively through the program.” A logical, cascading structure enables users to learn the different functionalities quickly and intuitively. And the app also has a special added-value feature that is particularly convenient: effectively at the push of a button, it generates not only an energy analysis of the existing lighting system, but at the same time suitable renovation suggestions, including a separate statement of costs for each of the different proposals. This gives consultants very useful data on which to base their decisions. “However,” says Aktuna to nip any misconceptions in the bud, “reLight cannot and should not replace a professional lighting consultant.” The app was developed first and foremost for professionals, and a certain amount of prior lighting engineering knowledge is a prerequisite for using the tool effectively. But technically savvy laypeople can also get useful results from the app after a little practice and with the aid of the detailed descriptions and help menus. reLight is available for free download on the android app market.
So how does the app work? There are two main aspects to the data acquisition system: first, an assessment of the existing lighting system by means of a visual comparison; and second, a simple qualitative description of the room proportions and façade type. Users define only the main, quickly assessable parameters and then select what the room is used for (office, production, warehouse, etc.). Pre-parameterization and verification logic ensure that no invalid data sets are created and that results can be viewed right from the start.
Relevant system components such as lamps, control equipment, and luminaires are stored in a database together with their characteristic values for energy and efficiency. Also recorded is data such as the typical service life of lamps or the illumination needed for different types of room. This data is supplemented by descriptive image and text documentation. If enough data is recognized for comparison with related energy and cost-efficiency models, the app identifies various renovation options that are possible in the case at hand and costs them compared to continued operation of the existing system. The app features a multi-zone model that enables whole buildings to be assessed and managed. Where there are rooms of the same kind, only one of them has to be analyzed. This room serves as the model for the others, which are calculated via multipliers in the evaluation of the building as a whole. Depending on the user’s interests, different renovation options per zone can ultimately be combined into an overall renovation, in order to obtain optimum energy and/or cost-efficiency results and view them in a graphical display.
The development of the app was sponsored under the German Federal Institute for Research on Building, Urban Affairs and Spatial Development‘s ”Future Building” research initiative (only German) with support from the companies TRILUX and EnBW.


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