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Proposal for a Luminaire Specific Index for the Description of Photometric Properties of Interior Luminaires Taking into Account the Efficient Use of Energy
Axel Stockmar
LCI Light Consult International
Lindenallee 21 a, D-29227 Celle
Abstract
The ratio between the achievable illumination level, expressed in terms of average horizontal illuminance on the utilisation plane, and the necessary electric power depends on the selection of lamps, ballasts, and luminaires, as well as on the appearance of the interior, expressed in terms of average reflectances of all interior surfaces. For lamps and ballasts it is common practice to use energy-dependent quantities, such as luminous efficacy or ballast-lumen-factors, which could be classified easily. However, for luminaires the obvious measure, the light output ratio, is not a suitable quantity, as there exists no relationship to the achievable illumination level.
For general lighting in interiors only an index based on utilisation factors could describe photometric properties while taking into account the necessary electric energy, as the utilisation factor is in proportion with the light output ratio and is dependent on the luminaire flux distribution for given standard conditions. Therefore a standard room has been defined concerning dimensions, luminaire layout, and reflectances. For a larger number of different luminaire types for direct illumination the utilisation factors have been calculated for the defined standard room alongside with the glare rating. The glare limitation has been checked using the tables of unified glare ratings which will be a standard part of oncoming luminaire documentations. On the basis of calculated utilisation factors and glare ratings a classification system will be proposed which could be used to describe the photometric properties of interior luminaires for direct illumination taking into account the efficient use of energy.
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