Iluminación eficiente. Tecnologías y Prácticas

Efficient lighting has undergone the greatest technological revolution of all active building systems over the past two decades. Luminous efficacy — the ratio between luminous flux emitted and electrical power consumed — has risen from 10-15 lumens per watt (lm/W) in incandescent lamps (Edison, 1879), to 50-80 lm/W in T5 linear fluorescents with electronic ballast, up to 100-200 lm/W in today's commercially available LEDs (Light Emitting Diodes), with laboratory records exceeding 280 lm/W (Cree, 2014). This 10-15 fold increase in luminous efficacy means the same quantity of light (measured in lumens) is obtained with 85-93% less electricity. LED dominates the global lighting market with a 52% share in 2022 (compared to 5% in 2012), and is projected to reach 75-80% by 2030 according to the IEA (Global Lighting Sales Report, 2023), rendering discharge and halogen technologies residual.

Efficient lighting practices go beyond lamp replacement: they integrate the complete system design — source, luminaire, optics, controls and daylight harvesting — to minimise energy consumption while maximising luminous quality. Lighting accounts for 15% to 30% of electricity consumption in commercial buildings and 10% to 15% in residential buildings (Eurostat, 2021), making its optimisation one of the savings strategies with the best cost-benefit ratio: the full replacement of a fluorescent lighting installation with LED incorporating DALI controls and sensors delivers payback periods of 2-5 years with savings of 50-70% on lighting consumption. Standard UNE-EN 12464-1:2022 establishes lighting requirements for indoor workplaces — minimum maintained illuminance levels (Em), uniformity (Uo), glare (UGR) and colour rendering index (Ra) — which define the quality benchmark that efficient technologies must guarantee.

Today's high-power LEDs based on indium gallium phosphide (InGaN) chips with phosphor conversion achieve efficacies of 150-200 lm/W in commercial modules, with colour rendering indices (CRI/Ra) of 80-97 that make them suitable for any application, from hospitals (Ra >= 90 required by UNE-EN 12464-1) to retail and museums. The service life of LED modules is specified as L70B50 (the point at which 50% of modules retain at least 70% of their initial luminous flux), with typical values of 50,000-100,000 hours compared to 10,000-15,000 hours for T5 fluorescents, reducing replacement and maintenance costs by 60-80%. LED COB (Chip-on-Board) technology integrates multiple chips on a single substrate, enabling compact luminaires of 10,000-50,000 lumens for large-space lighting (industrial halls, sports facilities) with efficacies of 140-170 lm/W.

OLEDs (Organic LEDs) represent the technological frontier of architectural lighting: surface-emitting panels (not point-source like LEDs) with thicknesses under 2 mm, flexible and transparent, with current efficacies of 60-90 lm/W (lower than LEDs but rapidly improving). LG Display produces OLED lighting panels of 320x110 mm with a service life of 40,000 hours and CRI > 90. The current cost (200-500 EUR/panel) limits their use to high-value design applications, but projections by McKinsey (2021) estimate a price reduction of 70-80% by 2030 through large-scale roll-to-roll manufacturing. Emerging applications include Human Centric Lighting (HCL) — lighting that adapts colour temperature (2,700-6,500 K) and intensity according to the human circadian rhythm, with studies by the Fraunhofer IAO (2018) documenting productivity improvements of 10-15% and error reductions of 20-30% in work environments with HCL compared to static lighting.

Control technologies transform an efficient lighting installation into an intelligent system that adapts light to actual need. The DALI (Digital Addressable Lighting Interface, IEC 62386) protocol allows individual addressing of each luminaire (up to 64 devices per line, expandable to 128 with DALI-2), grouping them into zones with programmable scenes and continuous dimming from 0.1% to 100% of luminous flux. A properly commissioned DALI system reduces lighting consumption by 30-50% compared to a manual on/off installation, by adjusting light levels to the actual task and to the available daylight contribution. The additional cost of a DALI system over conventional on/off is 5-15 EUR/m2, with payback periods of 2-4 years in commercial buildings with operating hours exceeding 2,500 hours/year.

Occupancy and absence sensors eliminate lighting consumption in unoccupied spaces — which represent 20% to 50% of the time in typical open-plan offices according to measurements by CIBSE (Chartered Institution of Building Services Engineers, 2019). Occupancy sensors (automatic on and off) save 20-35% of consumption, while absence sensors (manual on, automatic off) save 30-45%, by avoiding unnecessary switch-ons when daylight is sufficient. Daylight harvesting sensors regulate artificial lighting proportionally to the daylight contribution, maintaining a constant target illuminance level (e.g. 500 lux on the working plane): in perimeter zones (< 5-6 m from the facade), these sensors reduce lighting consumption by 40-60% in climates with high solar availability. The combination of high-efficacy LEDs, DALI controls, occupancy sensors and daylight regulation enables lighting energy numeric indicator (LENI) densities of 5-10 kWh/m2/year compared to the 25-40 kWh/m2/year of conventional installations — a reduction of 60-80%.

Efficient lighting reaches its full potential when it is integrated with daylight harvesting from the architectural design stage. Light shelves — horizontal reflective surfaces positioned at the window lintel height — redirect direct sunlight onto the interior ceiling, distributing it up to 6-8 m deep with a 40-60% reduction in artificial lighting in the affected zone. Light pipes (solatubes) channel natural daylight from the roof into interior spaces without facade access, delivering 3,000-10,000 lumens per tube of 350-530 mm diameter, equivalent to 2-6 fluorescent luminaires. A study by the University of Nottingham (Mayhoub and Carter, 2012) documented that light pipes reduce lighting electricity consumption in interior zones by 40-75% during daylight hours, with an investment of 400-1,200 EUR per unit and payback periods of 3-7 years.

Integrated luminous design simultaneously considers daylight (orientation, size and type of openings, solar shading), artificial lighting (source type, luminaire layout, optics, wattage) and the control system (DALI, sensors, time scheduling) as a single optimised system. Standard UNE-EN 15193-1:2017 establishes the calculation method for the LENI indicator (Lighting Energy Numeric Indicator, in kWh/m2/year), which enables comparison of the energy performance of different lighting designs. Design best practices include: localised task lighting (300-500 lux on the working plane) combined with reduced ambient lighting (100-200 lux in circulation areas), reducing installed power by 20-30% compared to uniform lighting; selection of luminaires with downward light output ratio (LOR) exceeding 80%; and high interior reflectances (ceiling >= 0.7, walls >= 0.5, floor >= 0.2) that maximise the utilisation of emitted luminous flux. Efficient lighting is not about installing LEDs and considering the project finished: it is a comprehensive design exercise that combines advanced technologies with luminous design practice and intelligent control to deliver the right quantity and quality of light with the lowest possible energy consumption.