Facilities: Lighting - Energy Conversion and Management - page 244

(c) The lumen output as at step (b) must be reduced by introducing the lamp and
luminaire depreciation factors as given by the manufacturers (after a reference
life period of the lighting system).
(d) The ratio between the value of the total luminous flux (lm) required as at step
(a) and the value of lumen per lamp as at step (c) gives a preliminary evaluation
of the number of lamps and luminaires required and then of the cost of the
lighting system.
(e) The electric power required is then equal to the product of the single lamp
power (or lamp with ballast, if necessary) multiplied by the number of lamps as
at step (d). Knowing the working hours per year allows to calculate the energy
consumption.
A more detailed knowledge of the lamp and luminaire space distribution
diagram will place luminaires to ensure the task-surface level in all the working
area while providing lower lighting levels in surrounding zones. In this way,
capital and operating costs are reduced while the illumination requirements
are satisfied.
As with any other investment in energy saving, economic analysis must take into
account many aspects of the operating (energy and others) and capital costs.
A worksheet showing the main technical parameters together with capital and
operating costs is given in Table 14.6 as a suggested guideline for evaluation.

14.5 Energy-Saving Opportunities

The foregoing considerations show that the energy-saving opportunities in lighting
systems are as follows:
• A proper selection of lamps and luminaires to provide the task surface with the
maximum efficiency (lm/W). This opportunity can be exploited both in new
installations and in retrofitting.
• A planned maintenance program for replacing lamps, cleaning luminaires,
replacing defective components, and cleaning surrounding surfaces in order to
achieve the maximum exploitation at any time.
• A periodical checkup of the task surface.
• A control of lighting at a degree of complexity determined by the incidence of
lighting costs on the energy bill: This control system may interact with other
building or factory subsystems, in particular with the HVAC, because of the heat
that lamps dissipate in surrounding areas.

14.6 Practical Examples

Example 1 Replacement of standard fluorescent lamps and luminaires by high-
frequency ones (HF fluorescent lamps and electronic ballast).
In a shopping center with a shopping surface of 5,000 m 2

replace standard

fluorescent lamps and luminaires with HF ones.