DAYLIGHT AVAILABILITY IN AN EASTERN MEDITERRANEAN CLIMATE

PROF. ELIYAHU NE’EMAN

Technion – Israel Institute of Technology, Haifa

Daylight can be efficiently utilized for the illumination of building interiors. Israel and the whole East Mediterranean region are characterized by a temperate climate, and thus enjoy high values of solar radiation through most seasons of the year. Therefore daylight admitting strategies have a great potential of energy saving. Surveys show that in modern work places, electric lighting consumes 30% to 50% of the total energy consumed. Furthermore, the application of daylight can be saved also on the load of the airconditioning systems. It has been shown that up to 50% of this energy can be saved by efficient use of daylight.

Well-being is another important benefit of the daylighting. Most people prefer daylight during daytime in their workplace.

On the other hand, the proper architectural design for daylight admission requires sophisticated design tools and accurate data on the local daylight availability. Regretfully, both are not readily available to the practicing architects and designers.

The creation of a data base for daylight availability has been made possible by a measurement program sponsored by the Ministry of Energy and Infrastructure of Israel. Systematic measurements of daylight are being carried out for several years at the Israeli Meteorological Service at Beit Dagan, about 10 km east of the Mediterranean coast, near Tel Aviv

(32’N and 34’49’E). Height of the sensors above sea level is 50 meters. The measurement program is part of the International Daylight Measurement Program – IDMP sponsored by the Commission Internationale de L’Eclairage – CIE and the World Meteorological Organization – WMO.

The measured results are processed later and compared to the full solar radiation which is simultaneously measured at the same site.

The daylight availability data base is essential for many other applications, like aviation, road traffic, agriculture. photovoltaic research and development and defence.

Based on these measurements, guidelines for the efficient design of daylight admission into buildings for use by architects and daylight designers, will be written at a later stage.