Power Density Targets for Efficient Lighting of Interior Task Areas

This paper concentrates on the formulation of a general criterium for the assessment of the power installed for lighting in order to achieve proper illumination under night-time conditions. Actual efficiency criteria are formulated in terms of the normalized power density. Target values are based on current good practice, assuming a standard task area more or less equal to the floor area of the room. The publication of the European Standard EN12464 Lighting of Work Places however, defines specific task areas and task illuminances. A general criterium for the assessment of the energy efficiency of a lighting installation which is broadly applicable and easy-to-use is developed, taking into account lighting comfort requirements. An analytic expression for the utilance target value is presented.