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Esquivias, P.M.; Moreno, D.; Fernández-Expósito, M. (2015, 25 de Mayo). Dynamic daylight simulation: new technics and metrics to study strategies to reduce lighting energy consumption

CONGRESO: Book of Abstracts of the II International Congress on Sustainable Construction and Eco-Efficient Solutions

PÁGINAS: 726-752

CIUDAD: Sevilla (España)

ABSTRACT:

After the energy crisis of 1973, the control of the thermal conditions in buildings has exponentially increased and new technologies have been developed forward greater energy efficiency in buildings, including artificial lighting between them.
As a proper thermal conditioning reduces energy consumption by reducing energy demand, an adequate daylighting will reduce the lighting energy consumption, increasing thereby the energy efficiency by taking advantage of a natural and free CO2 emissions source.
However, while there is a long history to predict the temperature and humidity conditions, the prediction of daylighting conditions is based, for more than 50 years ago, in the calculation of Daylight Factor.
This factor, despite its great international expansion and recognition, for example in LEED or BREEAM accreditation systems, is not considering the light from the Sun, so the only possible real sky conditions where there is no presence of the Sun is under a completely overcast sky, but considering this sky condition, Daylight Factor is insensitive to orientation.
In addition, due to the low frequency of cloudy skies in the sunnier climates in southern Europe, daylighting studies have fallen into disuse, considering the Daylight Factor distribution, at best, as representing the worst daylighting conditions. So, artificial lighting is usually designed independently to daylighting.
However, the recent emergence of Dynamic Daylight Simulation makes possible to obtain daylighting levels throughout the year due to local climatic conditions, considering, therefore, the presence and action of the Sun.
The statistical analysis of these results has led to the birth of new Daylighting Metrics that predict, for example, the amount of hours in which daylight is sufficient or the amount of hours when the use of electric lighting is really needed for visual comfort.
The analysis of these new metrics allows us to obtain a better comprehension of daylighting performance of a space, letting us making certain decisions that directly affect to comfort and energy consumption.
In this paper, the importance of these new daylight metrics is highlighted but also their relationship with lighting energy use. Considering these new metrics, a better lighting system design and a better adequacy of its regulation and control devices can be reached, giving energy savings up to approximately 30%.