Minimizing energy consumption for artificial lighting in a typical classroom of a Hellenic public school aiming for near Zero Energy Building using LED DC luminaires and daylight harvesting systems

•Examination of a typical classroom in Greece and its installed power for an artificial lighting profile from 1970 until today (type and number of luminaires, installed power per classroom, consumed annual energy kWh/m2).•Calculation of potential energy savings for customizing installed power LED with AC and DC supply aiming for the illuminance target values from the European Norm 12464–1, 2011.•Measurements of dimming curves of LED luminaires with AC and DC supply (consumed energy versus lighting output) and measurements of power of typical photosensors.•Estimated energy savings, CO2 reduction and cost optimal analysis due to various scenarios (different luminaire technologies and daylight harvesting techniques).•Calculation of the final energy consumption for potential power supply from renewable energy sources using DC LED luminaires and photosensors. The energy consumption for the artificial lighting in school buildings is one of the main consumers of electricity. In Greece, there is a large number of school buildings with quite old lighting systems using luminaires with T8 and sometimes T12 fluorescent lamps and degradated translucent diffusers. Due to the economic crisis, the public sector failed to invest in LEDs and although daylight is adequate during the year, the adoption of control technology is rather slow. The paper, using a typical classroom of a Greek public school, examines a number of lighting technologies (with AC and DC supply) together with two daylight harvesting systems. The first one uses one stand-alone photosensor per luminaire while the second one sensor per control zone, in an effort to calculate energy savings and light adequacy. The dimming curves of the DC LEDs were measured along with the installed power of the photosensors. The results show that the existing 90.5 kWhp/m2 of annual lighting primary energy consumption can be reduced to 0.55 kWhp/m2. The maximum annual reduction of CO2 emissions was 32.44 kgr/m2 for classroom areas, which is translated to 201929 tn for the whole country. It is evident that the path to Zero Energy School Buildings goes through the mandatory use of daylight controls. [Display omitted]