Energy Savings by Using Daylight for Basic Urban Shapes : With a Case Study of Three Different Street Types

Abstract: During winter the sun is in short supply. But research at KTH shows that solar radiation can be facilitated while energy consumption for lighting is reduced. This provided that the buildings are appropriately designed. But, unfortunately, the sunlight is often not taken into account and the results are the opposite.The energy savings depend on good town planning where the daylight is accessible for longer periods of time during the day, both indoors and outdoors. Then, the periods of use for electric light will decrease. This research is one of the first studies which evaluate the savings in energy with electric lighting due to the use of daylight in urban planning. Three different patterns for street layouts are evaluated and discussed in this report. For example, with straight streets it is possible to save approximately 11 % of the electric energy for the exterior lighting compared to a bending street during twilight. However, it is possible to improve the daylight distribution with geometrical adjustments even along bending streets. Varying the height of the building along the street front and adding openings between the buildings can make for good daylight distribution, like in the strategic straight line format. The energy efficiency of the bending streets can be improved so the loss in energy efficiency compared to a straight street can be reduced from 11 % to 4 %, in a specific case. The energy savings are not so great that they alone can justify a specific street type. A number of other factors must also be considered, such as architectural style, uniformity and the building system. A long-term goal is practical guidelines for “better” geometry in urban design, taking into consideration the sun and daylight. The construction cost is not higher in such geometries than in conventional designs, since daylight is free. Therefore daylight can open up for new types of settlements with advantages as more space with more outlooks.