SHADOW EFFECT ON PHOTOVOLTAIC POTENTIALITY ANALYSIS 
USING 3D CITY MODELS 
    
  
  
N. Alam® *, V. Coors? S. Zlatanova®, P. J. M. Oosterom 
2 Faculty of Surveying, Computer Science and Mathematics, Stuttgart University of Applied Sciences, Schellingstr. 24, 
70174 Stuttgart, Germany - (nazmul.alam, Volker.coors)@hft-stuttgart.de 
b OTB, GIS-technology, Delft University of Technology, Jaffalaan 9, 2628 BX Delft, The Netherlands — (S.Zlatanova, 
P.J.M.vanOosterom)@tudelft.nl 
KEY WORDS: Shadow Detection, Solar Energy, Photovoltaic System, 3D City Models, Potentiality Analysis, 3D GIS 
ABSTRACT: 
Due to global warming, green-house effect and various other drawbacks of existing energy sources, renewable energy like 
Photovoltaic system is being popular for energy production. The result of photovoltaic potentiality analysis depends on data quality 
and parameters. Shadow rapidly decreases performance of the Photovoltaic system and it always changes due to the movement of the 
sun. Solar radiation incident on earth’s atmosphere is relatively constant but the radiation at earth’s surface varies due to absorption, 
scattering, reflection, change in spectral content, diffuse component, water vapor, clouds and pollution etc. In this research, it is 
being investigated that how efficiently real-time shadow can be detected for both direct and diffuse radiation considering reflection 
and other factors in contrast with the existing shadow detection methods using latest technologies and what is the minimum quality 
of data required for this purpose. Of course, geometric details of the building geometry and surroundings directly affect the 
calculation of shadows. In principle, 3D city models or point clouds, which contain roof structure, vegetation, thematically 
differentiated surface and texture, are suitable to simulate exact real-time shadow. This research would develop an automated 
procedure to measure exact shadow effect from the 3D city models and a long-term simulation model to determine the produced 
energy from the photovoltaic system. In this paper, a developed method for detecting shadow for direct radiation has been discussed 
with its result using a 3D city model to perform a solar energy potentiality analysis. 
1. INTRODUCTION 
Photovoltaic potentiality analysis is very complex and important 
task, since this expensive technology has become an essential 
part of urban planning. Even governments in some countries are 
also boosting and supporting photovoltaic energy production by 
involving private households through various strategies. China 
is fuelling the solar companies with cheap loans amounting 21 
billion euros which lowers price 30 percent below the 
production cost. Germany has also been supporting solar 
industry with subsidies, incentives and feed-in tariffs 
(Wasserrab, 2011). But before installing it is essential to know 
how much energy will be produced and how long will it take to 
recover the cost. Photovoltaic cells are expensive and if it is 
placed at a wrong place where due to shadow, the production is 
much lower than it was measured from potentiality analysis, 
they will lose money. Therefore it must be investigated to 
measure exact shadow effect and sunlight intensity on each 
surface. Energy production from photovoltaic system depends 
of incident solar energy and photovoltaic efficiency. Efficiency 
of photovoltaic cell depends on spectrum and intensity of 
incident light and temperature of the cell. Solar energy incident 
upon a surface depends on longitude, latitude, sun angles, 
surface tilt, surface orientation, contribution of direct and 
diffuse radiation, absorption, reflectance, shadow caused by 
surrounding objects etc. 3D models are most realistic options 
for detecting shadow and other parameters. Advancement in 
geo-information is producing high quality and realistic 3D 
urban models including high geometric details which are being 
used for urban planning, cultural heritage, navigation, gaming, 
disaster management, architecture and other purposes. A good 
  
* Corresponding author. 
basis for automatic detection of best fitting roof and facade 
surface for photovoltaic cells in terms of energy performance 
and integration possibilities are 3D city models. Buildings are 
the largest consumers of energy in cities. For large scale 
implementation in the urban areas building integrated 
photovoltaic system is an appropriate option. A calculation 
procedure of shading factor under complex boundary condition 
can be found in Cascone et al. (2011), which introduced an 
external shading reduction coefficient of the incident solar 
radiation based on simplified hypothesis. Baum (2009) has 
developed shadow analyzer tool for the analysis of the shadow 
from external objects as well as sun tracking solar collector for 
very small area, which gives an approximate result by 
considering default monthly probabilities of clear sky. Joachem 
et al. (2009) considered shadowing effects by calculating the 
horizon of each point, which used full 3D information based on 
input LIDAR point clouds where small objects are not 
considered and excluded from the profile line. Hofierka & 
Kaiüuk (2009) presents a methodology for photovoltaic potential 
which includes a shadowing algorithm which was unable to be 
used with vertical facades. Izquierdo et al. (2008) described a 
method for estimating the potential roof surface for large-scale 
evaluations excluding fagades. Here the influences of hourly 
shadow on monthly values and spacing needed between 
modules to avoid shadowing are taken into account. 
The paper has been organized with a brief introduction at the 
beginning explaining background of photovoltaic energy and 
motivation for this research in section 1. Then some related 
researches have been mentioned to find out the gap in literature.