Sebastian Hämmerle received his MSc degree in mechatronics in 2013 and his MSc degree in Energy Economics in 2017 from the University of Applied Sciences in Vorarlberg. He worked at Hirschmann Automotive GmbH as an engineer from 2011 to 2013. Then he worked at Photinus GmbH & Ko KG as an engineer from 2013 to 2015. The main topic there was the development of autarkic street lighting. Afterwards, he started to work at LEDON Lamp GmbH as the Chief Technology Officer. His development focuses on retrofit lamps and indoor luminaires.
Lifetime- and Economic Efficiency Simulation of LED Luminaires
This paper introduces a new open-source Modelica library for dynamic simulation of LEDs: The DynaLed library. The aim of the work was to evaluate the lifetime and the corresponding economic efficiency of LEDs in dynamic operation by means of the LM-80 report and according to the TM-21 calculation method. Furthermore, it should be possible to use the library for component dimensioning, e.g. the heatsink. The primary task was to develop simulation models which can be parametrized with manufacturer information, e.g. the datasheet, but still provide sufficient accuracy.
As an application example an LED louvre luminaire from the company LEDON Lamp GmbH was simulated utilizing the developed library. At the end, results from the lifetime- and the economic efficiency simulation are discussed.
The lifetime of an LED system is specified by the manufacturer. In general this value is based on the LM-80 report and is calculated with the TM-21 method. The result is transferred into the manufacture’s datasheet. Unfortunately, this value is solely valid for one specific application. Moreover, this application is not regulated by law and can be defined by the manufacturer. A common application is for example to use an ambient temperature of 25°C, a continuous full load operation and a specified maximum allowed decline of luminous flux of 30 %. In further consequence the specified lifetime will be used to calculate the economic efficiency of a lighting installation to compare the costs and benefits of the investment.
However, this practice raises a number of delicate questions, particularly regarded to comparability and accuracy:
- How to compare two lighting products with different lifetime information?
- What is the lifetime if a dynamic operating cycle is used?
- What is the lifetime if a dynamic ambient temperature is given?
To answer these questions sufficiently accurate, an LED model has to meet the following requirements: The electric- and thermal behavior has to be described properly. Aging, i.e. the decline of luminous flux for different operating cycles, e.g. full load, office or industry has to be modeled. Finally, by utilizing the results from the aging model the economic efficiency has to be calculated.
Since currently no model is available in the literature that meets the requirements mentioned above, this paper is intended to present a dynamic model of an LED which can be used for lifetime simulations and economic efficiency calculations of dynamic operating cycles. Furthermore, the model can be parametrized with parameters specified in the datasheet and in the LM-80 report or with parameters that can be measured easily by the user.
After the modeling approach is briefly described, the models of the Modelica library DynaLed are introduced. After explaining how a simulation has to be set-up, an application example is shown and the simulation results are discussed. At the end the most important results will be summarized.